Micronutrient deficiencies in critical illness

  • W.A.C. Koekkoek
    Affiliations
    Department of Intensive Care Medicine, Gelderse Vallei Hospital, Willy Brandtlaan 10, 6716 RP, Ede, the Netherlands
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  • K. Hettinga
    Affiliations
    Division of Human Nutrition and Health, Wageningen University & Research, HELIX (Building 124), Stippeneng 4, 6708 WE, Wageningen, the Netherlands
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  • J.H.M. de Vries
    Affiliations
    Division of Human Nutrition and Health, Wageningen University & Research, HELIX (Building 124), Stippeneng 4, 6708 WE, Wageningen, the Netherlands
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  • A.R.H. van Zanten
    Correspondence
    Corresponding author. Gelderse Vallei Hospital, Department of Intensive Care, Willy Brandtlaan 10, 6716 RP Ede, Division of Human Nutrition and Health, Wageningen University & Research, HELIX (Building 124), Stippeneng 4, 6708 WE, Wageningen, the Netherlands. Fax: +31 318 434116.
    Affiliations
    Department of Intensive Care Medicine, Gelderse Vallei Hospital, Willy Brandtlaan 10, 6716 RP, Ede, the Netherlands

    Division of Human Nutrition and Health, Wageningen University & Research, HELIX (Building 124), Stippeneng 4, 6708 WE, Wageningen, the Netherlands
    Search for articles by this author
Open AccessPublished:May 10, 2021DOI:https://doi.org/10.1016/j.clnu.2021.05.003

      Summary

      Background & aims

      Low micronutrient levels in critical illness have been reported in multiple studies. Because of the antioxidant properties of various micronutrients, micronutrient deficiency may augment oxidative stress in critical illness. However, it remains unclear whether micronutrient concentrations in ICU patients are different from those in healthy age-matched controls. It is also unclear whether micronutrient deficiency develops, worsens, or resolves during ICU admission without supplementation.

      Methods

      We prospectively studied a cohort of adult critically ill patients. Micronutrient levels, including selenium, β-carotene, vitamin C, E, B1 and B6 were measured repeatedly during the first week of ICU admission. We compared the micronutrient concentrations at ICU admission to those of healthy age-matched controls. In addition, associations between micronutrient concentrations with severity of illness, inflammation and micronutrient intake were investigated.

      Results

      Micronutrient blood concentrations were obtained from 24 critically ill adults and 21 age-matched healthy controls. The mean micronutrient levels at admission in the ICU patients were: selenium 0.52 μmol/l, β-carotene 0.17 μmol/l, vitamin C 21.5 μmol/l, vitamin E 20.3 μmol/l, vitamin B1 129.5 nmol/l and vitamin B6 41.0 nmol/l. In the healthy controls micronutrient levels of selenium (0.90 μmol/l), β-carotene (0.50 μmol/l), vitamin C (45 μmol/l) and vitamin E (35.5 μmol/l) were significantly higher, while vitamin B1 (122 nmol/l) and B6 (44 nmol/l) were not significantly different between patients and controls.
      Selenium, vitamin B1 and vitamin B6 levels remained stable during ICU admission. Vitamin C levels dropped significantly until day 5 (p < 0.01). Vitamin E and β-carotene levels increased significantly on days 5–7 and day 7, respectively (p < 0.01).
      Micronutrient levels were not associated with severity of illness, CRP or micronutrient intake during the admission.

      Conclusions

      At admission, ICU patients already had lower plasma levels of selenium, β-carotene, vitamin C and vitamin E than healthy controls. Vitamin C levels dropped significantly during the first days of ICU admission, while β-carotene and vitamin E levels increased after 5–7 days. No association between micronutrient levels and severity of illness, C-reactive protein (CRP) or micronutrient intake was found. Progressive enteral tube feeding containing vitamins and trace elements does not normalize plasma levels in the first week of ICU stay. This was a hypothesis generating study and more investigation in a larger more diverse sample is needed.

      Keywords

      1. Introduction

      Low blood micronutrient levels in critical illness have been reported in multiple studies, possibly indicating micronutrient deficiencies. Because of the antioxidant properties of various micronutrients, these micronutrient deficiencies may augment oxidative stress in critical illness. Over the past 20 years, oxidative stress-mediated cell damage has been recognised to play a fundamental role in the pathophysiology of various critical illnesses such as acute respiratory distress syndrome (ARDS), ischemia-reperfusion injury, and multiple organ dysfunction syndrome (MODS) [
      • Koekkoek W.A.C.
      • Zanten A.R.H.
      Antioxidant vitamins and trace elements in critical illness.
      ].
      If micronutrient deficiency worsens oxidative stress, micronutrient supplementation may be beneficial in critical illness. However, studies investigating micronutrient supplementation effects in intensive care unit (ICU) patients show conflicting results [
      • Manzanares W.
      • Dhaliwal R.
      • Jiang X.
      • Murch L.
      • Heyland D.K.
      Antioxidant micronutrients in the critically ill: a systematic review and meta-analysis.
      ,
      ]. This is further complicated because most studies evaluated micronutrient cocktails rather than the effect of a single nutrient. Aggregation of the results of these heterogeneous studies suggest a reduction of overall mortality [
      ]. Recent guidelines, therefore, recommend micronutrient supplementation in ICU patients up to 5–10 times the dietary recommended intake (DRI) in healthy adults [
      • Singer P.
      • Reintam Blaser A.
      • Berger M.M.
      • Alhazzani W.
      • Calder P.C.
      • Caesar M.P.
      • et al.
      ESPEN guideline on clinical nutrition in the intensive care unit.
      ], but the evidence is limited.
      In addition, it remains unclear 1) whether low micronutrient levels in critical illness are different from levels in healthy matched controls and 2) what the course of micronutrient levels is during ICU admission in the absence of supplementation. Due to the large differences in micronutrient levels that have been described in healthy people [
      • Stoffaneller R.
      • Morse N.L.
      A review of dietary selenium intake and selenium status in Europe and the Middle East.
      ], as well as decreasing micronutrient levels with increasing age [
      • Savarino L.
      • Granchi D.
      • Ciapetti G.
      • Cenni E.
      • Ravaglia G.
      • Forti P.
      • et al.
      Serum concentrations of zinc and selenium in elderly people: results in healthy nonagenarians/centenarians.
      ], it is essential to know whether micronutrient levels in critical illness correspond with micronutrient levels of healthy controls of the same age and population, to determine whether they are genuinely lower in patients. Furthermore, it is crucial to know the natural course of micronutrient levels in critically ill patients as this may guide the investigation and application of possible therapeutic interventions.
      We performed a prospective cohort study in critically ill patients before implementing the current nutrition guidelines [
      • Singer P.
      • Reintam Blaser A.
      • Berger M.M.
      • Alhazzani W.
      • Calder P.C.
      • Caesar M.P.
      • et al.
      ESPEN guideline on clinical nutrition in the intensive care unit.
      ,
      • McClave S.A.
      • Taylor B.E.
      • Martindale R.G.
      • Warren M.M.
      • Johnson D.R.
      • Braunschweig C.
      • et al.
      Guidelines for the provision and assessment of nutrition support therapy in the adult critically ill patient: society of Critical Care Medicine (SCCM) and American Society for Parenteral and Enteral Nutrition (ASPEN).
      ]. As active micronutrient supplementation was not the standard of care, patients only received micronutrients from the standard composition of enteral nutrition (EN). This study determined the serum micronutrient levels of selenium, β-carotene, vitamin C, vitamin E and blood levels of vitamin B1 and B6 during the first week of ICU admission and compared these with the micronutrient concentrations of healthy age-matched controls. We also quantified a possible association between micronutrient levels and severity of illness, inflammation and enteral micronutrient intake during ICU admission.

      2. Materials and methods

      We performed a prospective observational study in critically ill patients. This study was performed in the mixed medical-surgical adult ICU of Gelderse Vallei Hospital Ede, The Netherlands between July 1st, 2002 and December 1st,2002. Patients were included when they were admitted to the ICU and were >18 years of age. Exclusion criteria were chronic kidney failure (creatinine > 177 μmol/l, peritoneal or haemodialysis), chronic liver failure (portal hypertension, histologically proven hepatic cirrhosis or oesophageal varices), or receiving parenteral nutrition.
      We asked 21 volunteers to participate in the control group. To recruit a control group with a similar age and dietary pattern as the patient group, relatives of the patient were asked to participate. If no relatives were available or did not agree to participate, patients with a similar age admitted to the general hospital wards without an underlying illness confounding micronutrient status were recruited. Volunteers were excluded when they had taken fortified foods or supplements in the previous 14 days.
      The ethics committee of Gelderse Vallei Hospital (Ede, The Netherlands) and Wageningen University and Research (Wageningen, The Netherlands) approved the research protocol. All volunteers and patients, or in case of impaired consciousness, the patients' relatives, gave written informed consent.

      2.1 Clinical management

      Patients participating in the study received usual intensive care treatment. According to Gelderse Vallei Hospital-specific standard operational procedures and protocols, the team of physicians, ICU nurses and dieticians performed clinical management, including nutritional support. The Harris-Benedict formula was used to calculate daily energy requirements. No additional vitamins or trace elements supplementation other than enteral nutrition was performed. Our local protocol for enteral nutritional support included four types of standard enteral nutrition with a slightly different composition regarding proteins, fibers and micronutrients and total amount of energy. Changes from one type to another were never based on micronutrient concentrations in the patient nor on the amount of micronutrients in the enteral nutrition.

      2.2 Sample size

      The number of ICU patients needed to include in this pilot study was estimated at 21, based on a power calculation of the most variable vitamin, vitamin C (between-person-variation 15%; power 0.90; α 0.05) [
      • Schorah C.J.
      • Downing C.
      • Pirpitse A.
      • Gallivan L.
      • Al-Hazaa A.H.
      • Sanderson M.J.
      • et al.
      Total vitamin C, ascorbic acid, and dehydroascobric acid concentrations in plasma of critically ill patients.
      ].

      2.3 Data collection

      Baseline characteristics were obtained from a questionnaire (in both patients and volunteers) and the individual patient files. The characteristics assessed by questionnaire were medical history, weight, height, smoking status, alcohol consumption and use of medication and micronutrient supplementation. The patient characteristics obtained from the patient files included type and amount of feeding, daily fluid balance, transfusions (blood and plasma), Acute Physiology and Chronic Health Evaluation-II (APACHE-II) scores, Sequential Organ Failure Assessment (SOFA) scores, C reactive protein (CRP), medications and micronutrient supplementation calculated from nutrition intake. Collected data were de-identified and stored on a secure hospital computer.

      2.3.1 Laboratory tests

      In patients, blood was sampled at 0, 12, 24, 36, 48, 72, 96, 120 and 144 h after ICU admission. The micronutrients selenium, β-carotene and vitamins C and E were measured in serum on every interval. The vitamins B1 and B6 were determined in haemolysed EDTA blood at the first, fourth and seventh time point. Besides measurements of the micronutrients in blood in ICU patients, other laboratory measurements were determined. All measurements are shown in supplement A. In the control group, only one sample was drawn to assess micronutrient status.

      2.4 Data analysis and statistical considerations

      Descriptive data are reported as means and standard deviation (SD) or median and interquartile range (IQR) in case of skewed distributions, or as frequencies and percentages when appropriate. A p-value <0.01 was considered statistically significant.
      The primary analysis comparing patient baseline micronutrient levels to the controls was performed using an independent-samples t-test in case of a normal distribution and a Mann–Whitney U test in case of non-normality.
      The course of micronutrient levels during ICU admission was shown graphically. Differences between time points were analysed separately for each micronutrient through mixed model regression analysis, taking into account the within-subjects' correlation. An autoregressive covariance was used, and the model was adjusted for multiple comparisons by Bonferroni correction.
      We also evaluated the associations of SOFA-scores, CRP, and micronutrient intakes in the ICU on micronutrient levels during ICU admission. These associations were analysed separately for each micronutrient through mixed model regression analysis, taking into account the within-subjects’ correlations. The dependent variable was divided by median split.
      IBM SPSS Statistics for Windows, version 25.0 (IBM Corporation, released 2017, Armonk, New York, USA) was used to perform analyses.

      3. Results

      During the study period, 106 patients were admitted to the ICU, of whom 24 were included according to the in- and exclusion criteria. Besides, 21 volunteers were willing to participate in the control group; three were excluded because of vitamin supplement intake in the past 14 days.
      Baseline characteristics are shown in Table 1. Full baseline laboratory results are shown in supplement B. The median ages were 65.5 and 66.0 years in the patient and control groups, respectively. Most patients and controls were male (66.7% and 54.6%). In the ICU group, median SOFA and APACHE II scores were 7 and 20, respectively. Twelve patients were admitted because of medical reasons (50%) and twelve because of emergency or (complicated) elective surgery (50%). The in-hospital mortality was 37.5%.
      Table 1Baseline characteristics.
      ICU patients

      (n = 24)
      Controls

      (n = 18)
      Gender (female)N (%)8 (33.3)8 (44.4)
      Age (years)Median [IQR]65.5 [62.5–71.8]66 [61–72]
      BMI on admission (kg/m2)Median [IQR]25.1 [22.0–26.9]25.4 [24.1–29.3]
       Malnourished (<18.5)1 (4.2)0 (0)
       Normal (18.5–24.9)10 (41.7)7 (38.9)
       Overweight (25–29.9)11 (45.8)9 (50.0)
       Obese (30–34.9)2 (8.3)2 (11.1)
       Morbidly obese (>35)0 (0)0 (0)
      Admission type
       Medical12 (50.0)NA
      N (%)12 (50.0)NA
       SurgicalN (%)
      Smoking status (yes)N (%)10 (45.5)∗2 (11.1)
      Alcohol consumption (yes)N (%)13 (61.9)∗15 (83.3)
      Nutrition in ICU
       Enteral nutritionN (%)22 (91.7)NA
       Parenteral nutritionN (%)0 (0)NA
       No nutritionN (%)2 (8.3)NA
      SOFA score on admissionMedian [IQR]7 [4–9.75]NA
      APACHE II score on admissionMedian [IQR]20 [15.8–28.5]NA
      In-hospital mortalityN (%)9 (37.5)NA
      Mechanical ventilationN (%)24 (100)NA
      ICU length of stayMedian [IQR]5 [
      ,
      • Singer P.
      • Reintam Blaser A.
      • Berger M.M.
      • Alhazzani W.
      • Calder P.C.
      • Caesar M.P.
      • et al.
      ESPEN guideline on clinical nutrition in the intensive care unit.
      ,
      • Stoffaneller R.
      • Morse N.L.
      A review of dietary selenium intake and selenium status in Europe and the Middle East.
      ,
      • Savarino L.
      • Granchi D.
      • Ciapetti G.
      • Cenni E.
      • Ravaglia G.
      • Forti P.
      • et al.
      Serum concentrations of zinc and selenium in elderly people: results in healthy nonagenarians/centenarians.
      ,
      • McClave S.A.
      • Taylor B.E.
      • Martindale R.G.
      • Warren M.M.
      • Johnson D.R.
      • Braunschweig C.
      • et al.
      Guidelines for the provision and assessment of nutrition support therapy in the adult critically ill patient: society of Critical Care Medicine (SCCM) and American Society for Parenteral and Enteral Nutrition (ASPEN).
      ,
      • Schorah C.J.
      • Downing C.
      • Pirpitse A.
      • Gallivan L.
      • Al-Hazaa A.H.
      • Sanderson M.J.
      • et al.
      Total vitamin C, ascorbic acid, and dehydroascobric acid concentrations in plasma of critically ill patients.
      ,
      • Wesselink E.
      • Koekkoek W.A.C.
      • Grefte S.
      • Witkamp R.F.
      • van Zanten A.R.H.
      Feeding mitochondria: potential role of nutritional components to improve critical illness convalescence.
      ,
      • Hawker F.H.
      • Stewart P.M.
      • Snitch P.J.
      Effects of acute illness on selenium homeostasis.
      ,
      • Forceville X.
      • Vitoux D.
      • Gauzit R.
      • Combes A.
      • Lahilaire P.
      • Chappuis P.
      Selenium, systemic immune response syndrome, sepsis and outcome in critically ill patients.
      ,
      • Bloos F.
      • Trips E.
      • Nierhaus A.
      • Briegel J.
      • Heyland D.K.
      • Jacschinski U.
      • et al.
      Effect of sodium selenite administration and procalcitonin-guided therapy on mortality in patients with severe sepsis or septic shock: a randomized clinical trial.
      ,
      • Heyland D.K.
      • Muscedere J.
      • Wischmeyer P.
      • Cook D.
      • Jones D.
      • Albert M.
      • et al.
      Canadian Critical Care Trials Group. A randomized trial of glutamine and antioxidants in critically ill patients.
      ]
      NA
      Abbreviations: ICU: intensive care unit; IQR: interquartile range; n: number; SD: standard deviation; SOFA: sequential organ failure assessment; APACHE: Acute Physiology And Chronic Health Evaluation; NA: not applicable.

      3.1 Primary outcome

      Baseline micronutrient levels in ICU patients and controls are shown in Table 2. Selenium, β-carotene, vitamin C and vitamin E levels were significantly lower in ICU patients than in controls (p < 0.001). Vitamin B1 and B6 levels were not significantly different in ICU patients and controls.
      Table 2Baseline micronutrient levels in ICU patients and controls.
      MicronutrientICUControlsp-value
      Selenium (μmol/l)0.52 ± 0.200.90 ± 0.16<0.0001
      β-Carotene (μmol/l)0.17 [0.08–0.26]0.50 [0.25–0.57]<0.0001
      Vitamin C (μmol/l)21.5 [8.5–32.0]45 [28.8–64.8]0.001
      Vitamin E (μmol/l)20.3 ± 8.335.5 ± 8.3
      Vitamin B1 (nmol/l)130 [107–169]122 [105–132]0.383
      Vitamin B6 (nmol/l)41 [37–56]44 [41–61]0.497
      Abbreviations: ICU: intensive care unit.
      Note: Results are depicted as mean ± standard deviation or median [interquartile range] as appropriate.

      3.2 Course of micronutrient levels during ICU admission

      Micronutrient levels during the first week of ICU admission are shown in Fig. 1A and F. Selenium levels remained stable and low. β-carotene levels remained below normal values but increased significantly on day 7 (p < 0.01). Vitamin C levels remained below normal values and dropped significantly from day 1 until day 5 (p < 0.01) of ICU admission. Vitamin E levels remained within normal values and increased significantly on days 5–7 (p < 0.01). Vitamin B1 and vitamin B6 levels remain stable and within the normal range.
      Fig. 1
      Fig. 1Mean micronutrient levels during ICU admission. A. Mean selenium levels during ICU admission. B. Mean β-carotene levels during ICU admission. C. Mean vitamin C levels during ICU admission. D. Mean vitamin E levels during ICU admission. E. Mean vitamin B1 levels during ICU admission. F. Mean vitamin B6 levels during ICU admission. Abbreviations: ICU: intensive care unit. Note: error bars represent ± one standard deviation.

      3.3 Effect of severity of illness on micronutrient levels

      Severity of illness was assessed through daily SOFA scores (Fig. 2). No significant associations were found between micronutrient levels and SOFA scores (selenium p = 0.562, β-carotene p = 0.155, vitamin C p = 0.528, vitamin E p = 0.044).
      Fig. 2
      Fig. 2Mean SOFA scores during ICU admission. Abbreviations: SOFA: sequential organ failure assessment.

      3.4 Effect of CRP on micronutrient levels

      CRP levels during ICU admission are shown in Fig. 3. No significant associations between micronutrient levels and CRP were found (selenium p = 0.400, β-carotene p = 0.377, vitamin C p = 0.064, vitamin E p = 0.552).
      Fig. 3
      Fig. 3Mean CRP levels during ICU admission.

      3.5 Effect of micronutrient intake in the ICU on micronutrient levels

      Micronutrient intake during ICU admission is shown in fig. 4A and F. The micronutrients were part of standard enteral nutrition (no additional supplements were used during the study period). No associations between individual micronutrient intake and blood micronutrient concentrations were observed over time (selenium p = 0.621, β-carotene p = 0.708, vitamin C p = 0.255, vitamin E p = 0.792, vitamin B1 p = 0.694, vitamin B6 p = 0.964).
      Fig. 4
      Fig. 4Mean micronutrient intake during ICU admission. A. Mean selenium intake during ICU admission. B. Mean β-carotene intake during ICU admission. C. Mean vitamin C intake during ICU admission. D. Mean vitamin E intake during ICU admission. E. Mean vitamin B1 intake during ICU admission. F. Mean vitamin B6 intake during ICU admission. Abbreviations: DRI: dietary reference intake; ICU: intensive care unit.

      4. Discussion

      We prospectively studied micronutrient blood levels in 24 critically ill adults and compared those with micronutrient levels in 21 healthy age-matched controls (Table 2). The micronutrient levels of selenium, β-carotene, vitamin C and vitamin E were significantly lower in ICU patients than in healthy controls. Vitamin B1 and B6 levels were within normal range and not significantly different between the patient and control groups.
      Vitamins and trace-elements have numerous essential functions throughout the body, as described in our earlier reviews [
      • Koekkoek W.A.C.
      • Zanten A.R.H.
      Antioxidant vitamins and trace elements in critical illness.
      ,
      • Wesselink E.
      • Koekkoek W.A.C.
      • Grefte S.
      • Witkamp R.F.
      • van Zanten A.R.H.
      Feeding mitochondria: potential role of nutritional components to improve critical illness convalescence.
      ]. Therefore, low blood levels may manifest the critical illness (patho)physiology, rather than intake deficiency. Low micronutrient levels in critical illness may be caused by redistribution, altered protein binding, increased losses through bodily fluids (urine, blood, sweat, ascites, pleural fluid), increased metabolic use, and dilution secondary to fluid resuscitation [
      • Koekkoek W.A.C.
      • Zanten A.R.H.
      Antioxidant vitamins and trace elements in critical illness.
      ].

      4.1 Selenium

      Selenium levels on ICU admission were significantly lower than in healthy controls in this study. Other studies report similar findings [
      • Hawker F.H.
      • Stewart P.M.
      • Snitch P.J.
      Effects of acute illness on selenium homeostasis.
      ,
      • Forceville X.
      • Vitoux D.
      • Gauzit R.
      • Combes A.
      • Lahilaire P.
      • Chappuis P.
      Selenium, systemic immune response syndrome, sepsis and outcome in critically ill patients.
      ]. The low selenium levels are the result of changes in selenium metabolism in critical illness. Selenium and selenoproteins are redistributed to tissues involved in protein synthesis and immune cell proliferation. Capillary leakage and no urinary excretion reduction, despite low serum levels, lead to an additional loss of selenium [
      • Koekkoek W.A.C.
      • Zanten A.R.H.
      Antioxidant vitamins and trace elements in critical illness.
      ,
      • Hawker F.H.
      • Stewart P.M.
      • Snitch P.J.
      Effects of acute illness on selenium homeostasis.
      ]. Selenium supplementation, in low and high dosages, as monotherapy or part of a combination of micronutrients, has been studied in large randomized trials [
      • Bloos F.
      • Trips E.
      • Nierhaus A.
      • Briegel J.
      • Heyland D.K.
      • Jacschinski U.
      • et al.
      Effect of sodium selenite administration and procalcitonin-guided therapy on mortality in patients with severe sepsis or septic shock: a randomized clinical trial.
      ,
      • Heyland D.K.
      • Muscedere J.
      • Wischmeyer P.
      • Cook D.
      • Jones D.
      • Albert M.
      • et al.
      Canadian Critical Care Trials Group. A randomized trial of glutamine and antioxidants in critically ill patients.
      ]. However, no beneficial effects on mortality, ICU length of stay, ventilation duration or infectious complications have been found in these trials nor in a meta-analysis of 21 trials studying selenium supplementation in ICU [
      • Manzanares W.
      • Lemieux M.
      • Elke G.
      • Langlois P.L.
      • Bloos F.
      • Heyland D.K.
      High-dose intravenous selenium does not improve clinical outcomes in the critically ill: a systematic review and meta-analysis.
      ].
      Mean selenium levels in healthy controls in this study are also lower than the international reference range for selenium, and this is per other studies of selenium status in the Dutch population [
      • Stoffaneller R.
      • Morse N.L.
      A review of dietary selenium intake and selenium status in Europe and the Middle East.
      ].

      4.2 β-carotene

      β-Carotene levels were relatively low in this study with a mean of 0.17 μmol/l in critically ill patients and 0.50 μmol/l in healthy controls. The normal range of β-carotene serum levels has been reported to be 0.04–2.26 μmol/l [
      Institute of Medicine (US)
      Panel on dietary antioxidants and related compounds. Dietary reference intakes for vitamin C, vitamin E, selenium, and carotenoids.
      ].
      Low levels of β-carotene have been earlier reported in patients with ARDS (mean 0.08 μmol/l vs 1.22 μmol/l in healthy controls [
      • Metnitz P.G.
      • Bartens C.
      • Fischer M.
      • Fridrich P.
      • Steltzer H.
      • Druml W.
      Antioxidant status in patients with acute respiratory distress syndrome.
      ]). The conversion of carotenoids to retinol is increased in patients with vitamin A deficiency; so low plasma values may indicate real vitamin A deficiency [
      • Mecocci P.
      • Polidori C.
      • Troiano L.
      • Cherubini A.
      • Cecchetti R.
      • Pini G.
      • et al.
      Plasma antioxidants and longevity: a study of healthy centenarians.
      ]. In addition, vitamin A metabolism is altered in critical illness; significant amounts of retinol and retinol-binding protein are excreted in urine (while it usually is mainly excreted in bile) [
      • Koekkoek W.A.C.
      • Zanten A.R.H.
      Antioxidant vitamins and trace elements in critical illness.
      ]. Stephensen et al. reported 33% of patients with acute infection excreted >50% of the DRI of vitamin A [
      • Stephensen C.B.
      • Alvarez J.O.
      • Kohatsu J.
      • Hardmeier R.
      • Kennedy Jr., J.I.
      • Gammon Jr., R.B.
      Vitamin A is excreted in the urine during acute infection.
      ]. Few studies have been performed on vitamin A supplementation (monotherapy), one study by Matos et al. showed a reduction in mortality and ICU length of stay [
      • Matos A.C.
      • Souza G.G.
      • Moreira V.
      • Ramalho A.
      Effect of vitamin A supplementation on clinical evolution in patients undergoing coronary artery bypass grafting, according to serum levels of zinc.
      ].

      4.3 Vitamin C

      We found a significant decline in vitamin C levels during the first four days of ICU admission. This is in accordance with other studies reporting a rapid decline in vitamin C levels after initial injury [
      • Berger M.M.
      Vitamin C requirements in parenteral nutrition.
      ,
      • Carr A.C.
      • Rosengrave P.C.
      • Bayer S.
      • Chambers S.
      • Mehrtens J.
      • Shaw G.M.
      Hypovitaminosis C and vitamin C deficiency in critically ill patients despite recommended enteral and parenteral intakes.
      ].
      Vitamin C supplementation has been studied in large trials, both as single interventions and combined with other vitamins and steroids [
      • Fowler 3rd, A.A.
      • Truwit J.D.
      • Hite R.D.
      • Morris P.E.
      • DeWilde C.
      • Priday A.
      • et al.
      Effect of vitamin C infusion on organ failure and biomarkers of inflammation and vascular injury in patients with sepsis and severe acute respiratory failure: the CITRIS-ALI randomized clinical trial.
      ,
      • Zanten van A.R.
      • Sztark F.
      • Kaisers U.X.
      • Zielmann S.
      • Felbinger T.W.
      • Sablotzki A.R.
      • et al.
      High-protein enteral nutrition enriched with immune-modulating nutrients vs standard high-protein enteral nutrition and nosocomial infections in the ICU: a randomised clinical trial.
      ]. In the Metaplus trial, enteral supplementation of vitamin C did not lead to normalization of plasma levels [
      • Zanten van A.R.
      • Sztark F.
      • Kaisers U.X.
      • Zielmann S.
      • Felbinger T.W.
      • Sablotzki A.R.
      • et al.
      High-protein enteral nutrition enriched with immune-modulating nutrients vs standard high-protein enteral nutrition and nosocomial infections in the ICU: a randomised clinical trial.
      ]. However, high dose intravenous supplementation (up to 200 mg/kg/day) has shown to increase plasma levels to normal and supranormal levels in a small phase I trial [
      • Fowler 3rd, A.A.
      • Syed A.A.
      • Knowlson S.
      • Sculthorpe R.
      • Farthing D.
      • DeWilde C.
      • et al.
      Phase I safety trial of intravenous ascorbic acid in patients with severe sepsis.
      ]. . More importantly, no improvements in significant clinical endpoints have been reported in recent randomised trials [
      • Fowler 3rd, A.A.
      • Truwit J.D.
      • Hite R.D.
      • Morris P.E.
      • DeWilde C.
      • Priday A.
      • et al.
      Effect of vitamin C infusion on organ failure and biomarkers of inflammation and vascular injury in patients with sepsis and severe acute respiratory failure: the CITRIS-ALI randomized clinical trial.
      ,
      • Zanten van A.R.
      • Sztark F.
      • Kaisers U.X.
      • Zielmann S.
      • Felbinger T.W.
      • Sablotzki A.R.
      • et al.
      High-protein enteral nutrition enriched with immune-modulating nutrients vs standard high-protein enteral nutrition and nosocomial infections in the ICU: a randomised clinical trial.
      ,
      • Fowler 3rd, A.A.
      • Syed A.A.
      • Knowlson S.
      • Sculthorpe R.
      • Farthing D.
      • DeWilde C.
      • et al.
      Phase I safety trial of intravenous ascorbic acid in patients with severe sepsis.
      ,
      ].

      4.4 Vitamin E

      Vitamin E levels remain within normal range; however, are significantly lower than in healthy controls in this study. A decrease in vitamin E serum levels has been frequently reported in critically ill patients [
      • Koekkoek W.A.C.
      • Zanten A.R.H.
      Antioxidant vitamins and trace elements in critical illness.
      ,
      • Richard C.
      • Lemonnier F.
      • Thibault M.
      • Couturier M.
      • Auzepy P.
      Vitamin E deficiency and lipid peroxidation during adult respiratory distress syndrome.
      ]. However, when standardised for serum lipids changes, no decrease or even an increase in vitamin E levels was found [
      • Vasilaki A.T.
      • Leivaditi D.
      • Talwar D.
      • Kinsella J.
      • Duncan A.
      • O'Reilly D.
      • et al.
      Assessment of vitamin E status in patients with systemic inflammatory response syndrome: plasma, plasma corrected for lipids or red blood cell measurements?.
      ]. Concurrent with these findings, we observed an increase in vitamin E levels during the first week of ICU admission.

      4.5 Vitamin B1

      The incidence of thiamin deficiency in critically ill patients is supposedly 10–30% [
      • Wesselink E.
      • Koekkoek W.A.C.
      • Grefte S.
      • Witkamp R.F.
      • van Zanten A.R.H.
      Feeding mitochondria: potential role of nutritional components to improve critical illness convalescence.
      ,
      • Donnino M.W.
      • Carney E.
      • Cocchi M.N.
      • Barbash I.
      • Chase M.
      • Joyce N.
      • et al.
      Thiamine deficiency in critically ill patients with sepsis.
      ,
      • Cruickshank A.M.
      • Telfer A.B.
      • Shenkin A.
      Thiamine deficiency in the critically ill.
      ,
      • Manzanares W.
      • Hardy G.
      Thiamine supplementation in the critically ill.
      ]. However, none of the patients included in our study, nor the healthy controls, had any sample with a thiamin level below the normal value (<70 nmol/l). A lower mortality rate has been reported in ICU patients with severe thiamine deficiency (<7 nmol/l) receiving thiamin supplementation. In patients with no deficiency, no benefit of thiamin has been shown [
      • Donnino M.W.
      • Carney E.
      • Cocchi M.N.
      • Barbash I.
      • Chase M.
      • Joyce N.
      • et al.
      Thiamine deficiency in critically ill patients with sepsis.
      ].

      4.6 Vitamin B6

      Only one previous study has investigated vitamin B6 intake and status in critically ill patients [
      • Huang Y.C.
      • Lan P.H.
      • Cheng C.H.
      • Lee B.J.
      • Kan M.N.
      Vitamin B6 intakes and status of mechanically ventilated critically ill patients in Taiwan.
      ]. Vitamin B6 levels were measured prospectively in 94 critically ill patients on day 1 and 14 of ICU admission. In accordance with our findings, the authors of this study found vitamin B6 status to be within normal values on ICU admission (42 nmol/l). However, a significantly lower vitamin B6 level was found on day 14 than on day 1, although intake was high and even increased during ICU admission (>10× DRI). Also, urinary excretion of vitamin B6 was significantly higher on day 14, although blood levels were lower. We found no significant change in vitamin B6 levels during the first week of ICU admission in this study, but we have no measurements after 14 days. Our findings may thus not be contradictory, as vitamin B6 levels may decline only after the first week of ICU admission.

      4.7 Inflammation, the severity of illness and micronutrient levels

      We observed no associations between CRP nor SOFA scores and micronutrient levels in this study. However, previous studies on vitamin C supplementation show low plasma concentrations associated with severity of illness, inflammation and mortality [
      • Koekkoek W.A.C.
      • Zanten A.R.H.
      Antioxidant vitamins and trace elements in critical illness.
      ,
      • Carr A.C.
      • Rosengrave P.C.
      • Bayer S.
      • Chambers S.
      • Mehrtens J.
      • Shaw G.M.
      Hypovitaminosis C and vitamin C deficiency in critically ill patients despite recommended enteral and parenteral intakes.
      ]. Also, selenium levels were negatively correlated with CRP [
      • Ghashut R.A.
      • McMillan D.C.
      • Kinsella J.
      • Vasilaki A.T.
      • Talwar D.
      • Duncan A.
      The effect of the systemic inflammatory response on plasma zinc and selenium adjusted for albumin.
      ] and associated with mortality, organ failure and sepsis severity scores in other studies. Our measurements may have been too early to see an effect of declining inflammation (as CRP and SOFA scores were still high at the end of the study). In addition, our study was not primarily powered for these analyses. Therefore the study population may have been too small to observe such an effect.
      No previous studies have investigated the association between CRP nor severity of illness and vitamin E or β-carotene levels.

      4.8 Micronutrient intake and micronutrient levels

      We observed no associations between micronutrient intake and micronutrient levels during ICU admission. It is possible that the micronutrient intake from EN in this study was too limited to influence actual serum micronutrient levels in ICU patients (i.e., the daily dose of micronutrients is too low to normalise levels). However, multiple studies with high dose micronutrient supplementation have also been unable to normalise micronutrient blood levels [
      • Fowler 3rd, A.A.
      • Truwit J.D.
      • Hite R.D.
      • Morris P.E.
      • DeWilde C.
      • Priday A.
      • et al.
      Effect of vitamin C infusion on organ failure and biomarkers of inflammation and vascular injury in patients with sepsis and severe acute respiratory failure: the CITRIS-ALI randomized clinical trial.
      ,
      • Huang Y.C.
      • Lan P.H.
      • Cheng C.H.
      • Lee B.J.
      • Kan M.N.
      Vitamin B6 intakes and status of mechanically ventilated critically ill patients in Taiwan.
      ]. This may indicate that micronutrient blood levels are mainly influenced by other processes (i.e., increased metabolic use, redistribution, increased losses), and intake may play a minor role [
      • Koekkoek W.A.C.
      • Zanten A.R.H.
      Antioxidant vitamins and trace elements in critical illness.
      ].

      4.9 Strengths and weaknesses

      Micronutrient status of critically ill patients was compared with healthy age-matched controls from the same geographical area. As micronutrient levels in healthy adults decline with age and differ widely between geographical regions, matching patients accordingly reduces the risk of falsely interpreting micronutrient levels in ICU patients as (ab)normal.
      We were also able to show the course of micronutrient levels during the first week of ICU admission in the absence of supplementation. This “natural” course has not been extensively investigated before.
      However, our study has several limitations. The study population was small and from a single-centre, resulting in low statistical power for our secondary analysis. Therefore, this study should be seen as a hypothesis generating study. Secondly, vitamin E levels were not standardised for serum lipid status. As serum triglyceride levels were lower in patients on ICU admission than in controls, the significant difference between mean vitamin E levels may be (partially) explained by this. Finally, the study was performed in 2002 thus indicating a long delay in manuscript preparation. Recently, the relevance of the data was reconsidered as this study was performed without additional micronutrient supplements and therefore shows the “natural course” of micronutrient concentrations in ICU patients. Nowadays, as many ICUs use additional micronutrients this study would be hard to perform in 2021. We do not think the delay has influenced the validity of our results.

      5. Conclusion

      Patients already showed lower plasma levels of selenium, β-carotene, Vitamin C and Vitamin E than healthy controls on ICU admission. Vitamin C levels dropped significantly during the first days of ICU admission, while β-carotene and vitamin E levels increased after 5–7 days. Selenium levels remained stable. Vitamin B1 and B6 levels on ICU admission were comparable with healthy age-matched controls and remained stable. No associations between micronutrient levels and severity of illness, CRP or micronutrient intake were found. Progressive enteral tube feeding containing vitamins and trace elements does not normalize plasma levels in the first week of ICU stay. When treatment objectives are to normalise plasma concentrations of the studied micronutrients only tube feeding is not sufficient and pharmacological supplementation should be considered.

      Statement of authorship

      Dr. Van Zanten had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
      Study concept and designing: Van Zanten, Hettinga, de Vries.
      Acquisition of data: Hettinga.
      Statistical analysis and interpretation of data: Koekkoek, Van Zanten.
      Drafting the manuscript: Koekkoek.
      Critical revision of the manuscript for important intellectual content: Koekkoek, Van Zanten, Hettinga, De Vries.
      Study supervision: Van Zanten.

      Conflict of interest statement and funding sources

      Prof. Dr. Van Zanten reported having received honoraria for advisory board meetings, lectures, research, and travel expenses from Abbott, Baxter, BBraun, Cardinal Health, Danone-Nutricia, Fresenius Kabi, Mermaid, Lyric, and Nestlé-Novartis. Inclusion fees for patients in clinical trials were paid to the local ICU research foundation. The remaining authors have disclosed that they do not have any conflicts of interest. There was no funding source for this work.

      Acknowledgements

      Roel van Vugt, Olga Souverein (statistical considerations), Gerbrich Folkersma, Ben de Jong.

      Appendix A. Supplementary data

      The following are the Supplementary data to this article:

      References

        • Koekkoek W.A.C.
        • Zanten A.R.H.
        Antioxidant vitamins and trace elements in critical illness.
        Nutr Clin Pract. 2016; 31: 457-474
        • Manzanares W.
        • Dhaliwal R.
        • Jiang X.
        • Murch L.
        • Heyland D.K.
        Antioxidant micronutrients in the critically ill: a systematic review and meta-analysis.
        Crit Care. 2012; 12: R66
      1. Critical care nutrition: systematic reviews. Supplemental antioxidant nutrients: combined vitamins and trace elements. 2018 Dec ([cited 2020 October 23rd] Available from: https://www.criticalcarenutrition.com/docs/systematic_reviews_2018/11.1%20AOX%20Comb_2018.pdf)
        • Singer P.
        • Reintam Blaser A.
        • Berger M.M.
        • Alhazzani W.
        • Calder P.C.
        • Caesar M.P.
        • et al.
        ESPEN guideline on clinical nutrition in the intensive care unit.
        Clin Nutr. 2019 Feb; 38: 48-79
        • Stoffaneller R.
        • Morse N.L.
        A review of dietary selenium intake and selenium status in Europe and the Middle East.
        Nutrients. 2015; 27: 1494-1537
        • Savarino L.
        • Granchi D.
        • Ciapetti G.
        • Cenni E.
        • Ravaglia G.
        • Forti P.
        • et al.
        Serum concentrations of zinc and selenium in elderly people: results in healthy nonagenarians/centenarians.
        Exp Gerontol. 2001; 36: 327-339
        • McClave S.A.
        • Taylor B.E.
        • Martindale R.G.
        • Warren M.M.
        • Johnson D.R.
        • Braunschweig C.
        • et al.
        Guidelines for the provision and assessment of nutrition support therapy in the adult critically ill patient: society of Critical Care Medicine (SCCM) and American Society for Parenteral and Enteral Nutrition (ASPEN).
        JPEN - J Parenter Enter Nutr. 2016; 40: 159-221
        • Schorah C.J.
        • Downing C.
        • Pirpitse A.
        • Gallivan L.
        • Al-Hazaa A.H.
        • Sanderson M.J.
        • et al.
        Total vitamin C, ascorbic acid, and dehydroascobric acid concentrations in plasma of critically ill patients.
        Am J Clin Nutr. 1996; 63: 760-765
        • Wesselink E.
        • Koekkoek W.A.C.
        • Grefte S.
        • Witkamp R.F.
        • van Zanten A.R.H.
        Feeding mitochondria: potential role of nutritional components to improve critical illness convalescence.
        Clin Nutr. 2019 Jun; 38: 982-995
        • Hawker F.H.
        • Stewart P.M.
        • Snitch P.J.
        Effects of acute illness on selenium homeostasis.
        Crit Care Med. 1990; 18: 442-446
        • Forceville X.
        • Vitoux D.
        • Gauzit R.
        • Combes A.
        • Lahilaire P.
        • Chappuis P.
        Selenium, systemic immune response syndrome, sepsis and outcome in critically ill patients.
        Crit Care Med. 1998; 26: 1536-1544
        • Bloos F.
        • Trips E.
        • Nierhaus A.
        • Briegel J.
        • Heyland D.K.
        • Jacschinski U.
        • et al.
        Effect of sodium selenite administration and procalcitonin-guided therapy on mortality in patients with severe sepsis or septic shock: a randomized clinical trial.
        JAMA Intern Med. 2016 Sep 1; 176: 1266-1276
        • Heyland D.K.
        • Muscedere J.
        • Wischmeyer P.
        • Cook D.
        • Jones D.
        • Albert M.
        • et al.
        Canadian Critical Care Trials Group. A randomized trial of glutamine and antioxidants in critically ill patients.
        N Engl J Med. 2013; 368: 1489-1497
        • Manzanares W.
        • Lemieux M.
        • Elke G.
        • Langlois P.L.
        • Bloos F.
        • Heyland D.K.
        High-dose intravenous selenium does not improve clinical outcomes in the critically ill: a systematic review and meta-analysis.
        Crit Care. 2016 Oct 28; 20: 356
        • Institute of Medicine (US)
        Panel on dietary antioxidants and related compounds. Dietary reference intakes for vitamin C, vitamin E, selenium, and carotenoids.
        National Academies Press (US), Washington (DC)2000 ([cited 2020 Dec 12]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK225483/)
        • Metnitz P.G.
        • Bartens C.
        • Fischer M.
        • Fridrich P.
        • Steltzer H.
        • Druml W.
        Antioxidant status in patients with acute respiratory distress syndrome.
        Intensive Care Med. 1999; 25: 180-185
        • Mecocci P.
        • Polidori C.
        • Troiano L.
        • Cherubini A.
        • Cecchetti R.
        • Pini G.
        • et al.
        Plasma antioxidants and longevity: a study of healthy centenarians.
        Free Radic Biol Med. 2000; 28: 1243-1248
        • Stephensen C.B.
        • Alvarez J.O.
        • Kohatsu J.
        • Hardmeier R.
        • Kennedy Jr., J.I.
        • Gammon Jr., R.B.
        Vitamin A is excreted in the urine during acute infection.
        Am J Clin Nutr. 1994; 60: 388-392
        • Matos A.C.
        • Souza G.G.
        • Moreira V.
        • Ramalho A.
        Effect of vitamin A supplementation on clinical evolution in patients undergoing coronary artery bypass grafting, according to serum levels of zinc.
        Nutr Hosp. 2012; 27: 1981-1986
        • Berger M.M.
        Vitamin C requirements in parenteral nutrition.
        Gastroenterology. 2009; 137 (suppl): S70-S78
        • Carr A.C.
        • Rosengrave P.C.
        • Bayer S.
        • Chambers S.
        • Mehrtens J.
        • Shaw G.M.
        Hypovitaminosis C and vitamin C deficiency in critically ill patients despite recommended enteral and parenteral intakes.
        Crit Care. 2017 Dec 11; 21: 300
        • Fowler 3rd, A.A.
        • Truwit J.D.
        • Hite R.D.
        • Morris P.E.
        • DeWilde C.
        • Priday A.
        • et al.
        Effect of vitamin C infusion on organ failure and biomarkers of inflammation and vascular injury in patients with sepsis and severe acute respiratory failure: the CITRIS-ALI randomized clinical trial.
        J Am Med Assoc. 2019 Oct 1; 322: 1261-1270
        • Zanten van A.R.
        • Sztark F.
        • Kaisers U.X.
        • Zielmann S.
        • Felbinger T.W.
        • Sablotzki A.R.
        • et al.
        High-protein enteral nutrition enriched with immune-modulating nutrients vs standard high-protein enteral nutrition and nosocomial infections in the ICU: a randomised clinical trial.
        J Am Med Assoc. 2014; 312: 514-524
        • Fowler 3rd, A.A.
        • Syed A.A.
        • Knowlson S.
        • Sculthorpe R.
        • Farthing D.
        • DeWilde C.
        • et al.
        Phase I safety trial of intravenous ascorbic acid in patients with severe sepsis.
        J Transl Med. 2014 Jan 31; 12: 32
      2. Critical care nutrition: systematic reviews. Intravenous vitamin C supplementation. 2019 Oct ([cited 2020 October 23rd] Available from: https://www.criticalcarenutrition.com/docs/systematic_reviews_2018/11.3%20Intravenous%20Vitamin%20C%20Supplementation%20%202019.pdf)
        • Richard C.
        • Lemonnier F.
        • Thibault M.
        • Couturier M.
        • Auzepy P.
        Vitamin E deficiency and lipid peroxidation during adult respiratory distress syndrome.
        Crit Care Med. 1990; 18: 4-9
        • Vasilaki A.T.
        • Leivaditi D.
        • Talwar D.
        • Kinsella J.
        • Duncan A.
        • O'Reilly D.
        • et al.
        Assessment of vitamin E status in patients with systemic inflammatory response syndrome: plasma, plasma corrected for lipids or red blood cell measurements?.
        Clin Chim Acta. 2009; 409: 41-45
        • Donnino M.W.
        • Carney E.
        • Cocchi M.N.
        • Barbash I.
        • Chase M.
        • Joyce N.
        • et al.
        Thiamine deficiency in critically ill patients with sepsis.
        J Crit Care. 2010 Dec; 25: 576-581
        • Cruickshank A.M.
        • Telfer A.B.
        • Shenkin A.
        Thiamine deficiency in the critically ill.
        Intensive Care Med. 1988; 14: 384-387
        • Manzanares W.
        • Hardy G.
        Thiamine supplementation in the critically ill.
        Curr Opin Clin Nutr Metab Care. 2011; 14: 610-617
        • Huang Y.C.
        • Lan P.H.
        • Cheng C.H.
        • Lee B.J.
        • Kan M.N.
        Vitamin B6 intakes and status of mechanically ventilated critically ill patients in Taiwan.
        Eur J Clin Nutr. 2002 May; 56: 387-392
        • Ghashut R.A.
        • McMillan D.C.
        • Kinsella J.
        • Vasilaki A.T.
        • Talwar D.
        • Duncan A.
        The effect of the systemic inflammatory response on plasma zinc and selenium adjusted for albumin.
        Clin Nutr. 2016 Apr; 35: 381-387