Showing papers on "B vitamins published in 2000"

Plasma Concentration of Asymmetric Dimethylarginine, an Endogenous Inhibitor of Nitric Oxide Synthase, Is Elevated in Monkeys With Hyperhomocyst(e)inemia or Hypercholesterolemia

Abstract: —Hyperhomocyst(e)inemia is associated with endothelial dysfunction. Mechanisms responsible for endothelial dysfunction in hyperhomocyst(e)inemia may involve impaired bioavailability of endothelium-dependent nitric oxide. We tested the hypothesis that hyperhomocyst(e)inemia is associated with an elevated plasma concentration of asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase. One group of adult cynomolgus monkeys was fed either a control or hyperhomocyst(e)inemic diet for 4 weeks in a randomized crossover design. The second group was fed an atherogenic diet that produces both hyperhomocyst(e)inemia and hypercholesterolemia for 17 months, followed by an atherogenic diet supplemented with B vitamins for 6 months to decrease plasma homocyst(e)ine concentration. Human endothelial cells were used to study the effects of methionine and homocysteine in the presence or absence of B vitamins or the methylation inhibitor S -adenosylhomocysteine on the formation of ADMA and its inactive stereoisomer, symmetric dimethylarginine. The hyperhomocyst(e)inemic diet produced 2- to 3-fold increases in plasma levels of homocyst(e)ine and ADMA (both P P S -adenosylhomocysteine but not by B vitamins. We conclude that plasma levels of ADMA are elevated in hyperhomocyst(e)inemia. Because ADMA acts as a competitive inhibitor of endothelial nitric oxide synthase, these findings suggest a novel mechanism for impaired endothelial function in hyperhomocyst(e)inemia.

Nutritional modulation of malaria morbidity and mortality.

Abstract: This review critically examines the relationship between nutritional status and malaria. The data indicate that protein-energy malnutrition is associated with greater malaria morbidity and mortality in humans. In addition, controlled trials of either vitamin A or zinc supplementation show that these nutrients can substantially reduce clinical malaria attacks. Data for iron indicate that supplementation may minimally aggravate certain malariometric indices in some settings and also strongly improve hematologic status. Withholding of iron supplements from deficient population is, therefore, not currently indicated. Available evidence for other nutrients describe varied effects, with some deficiencies being exacerbative (e.g., thiamine), protective (e.g., vitamin E), or both exacerbative and protective in different settings (e.g., riboflavin, vitamin C). The roles of folate, other B vitamins, unsaturated fatty acids, amino acids, and selenium are also examined. Study of the interactions between nutrition and malaria may provide insight to protective mechanisms and result in nutrient-based interventions as low-cost and effective adjuncts to current methods of malaria prevention and treatment.

The human SWI/SNF-B chromatin-remodeling complex is related to yeast Rsc and localizes at kinetochores of mitotic chromosomes

Abstract: The SWI/SNF family of chromatin-remodeling complexes facilitates gene expression by helping transcription factors gain access to their targets in chromatin. SWI/SNF and Rsc are distinctive members of this family from yeast. They have similar protein components and catalytic activities but differ in biological function. Rsc is required for cell cycle progression through mitosis, whereas SWI/SNF is not. Human complexes of this family have also been identified, which have often been considered related to yeast SWI/SNF. However, all human subunits identified to date are equally similar to components of both SWI/SNF and Rsc, leaving open the possibility that some or all of the human complexes are rather related to Rsc. Here, we present evidence that the previously identified human SWI/SNF-B complex is indeed of the Rsc type. It contains six components conserved in both Rsc and SWI/SNF. Importantly, it has a unique subunit, BAF180, that harbors a distinctive set of structural motifs characteristic of three components of Rsc. Of the two mammalian ATPases known to be related to those in the yeast complexes, human SWI/SNF-B contains only the homolog that functions like Rsc during cell growth. Immunofluorescence studies with a BAF180 antibody revealed that SWI/SNF-B localizes at the kinetochores of chromosomes during mitosis. Our data suggest that SWI/SNF-B and Rsc represent a novel subfamily of chromatin-remodeling complexes conserved from yeast to human, and could participate in cell division at kinetochores of mitotic chromosomes.

Biosynthesis of vitamin b2 (riboflavin).

Abstract: ▪ Abstract The biosynthesis of one riboflavin molecule requires one molecule of GTP and two molecules of ribulose 5-phosphate as substrates. The imidazole ring of GTP is hydrolytically opened, yielding a 4,5-diaminopyrimidine which is converted to 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione by a sequence of deamination, side chain reduction and dephosphorylation. Condensation of 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione with 3,4-dihydroxy-2-butanone 4-phosphate obtained from ribulose 5-phosphate affords 6,7-dimethyl-8-ribityllumazine. Dismutation of the lumazine derivative yields riboflavin and 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione, which is recycled in the biosynthetic pathway. The structure of the biosynthetic enzyme, 6,7-dimethyl-8-ribityllumazine synthase, has been studied in considerable detail.

Improved Vascular Endothelial Function After Oral B Vitamins An Effect Mediated Through Reduced Concentrations of Free Plasma Homocysteine

Abstract: Background—Hyperhomocysteinemia is an independent risk factor for coronary heart disease (CHD). Dietary supplementation with B vitamins lowers plasma homocysteine by up to 30%. However, little is known about the potential beneficial effects of homocysteine lowering on vascular function in patients with CHD. Methods and Results—We investigated 89 men with CHD (aged 56 [range 39 to 67] years). Brachial artery flow‐mediated dilatation (endothelium dependent) and nitroglycerin-induced dilatation (endothelium independent) were measured before and 8 weeks after treatment with either (1) folic acid (5 mg) and vitamin B12 (1 mg) daily (n559) or (2) placebo (n530). Total, protein-bound, and free plasma homocysteine, serum folate, and vitamin B12 were measured at baseline and at 8 weeks. Flow-mediated dilatation improved after treatment with B vitamins (2.563.2% to 4.063.7%, P50.002) but not placebo (2.362.6% to 1.962.6%, P50.5). Vitamin therapy lowered plasma concentrations of total homocysteine (from 13.063.4 to 9.361.9 mmol/L, P,0.001), protein-bound homocysteine (from 8.762.8 to 6.261.4 mmol/L, P,0.001), and free homocysteine (from 4.361.2 to 3.060.6 mmol/L, P,0.001) and raised concentrations of serum folate (from 10.364.3 to 31.2610.8 ng/mL, P,0.001) and vitamin B12 (from 3146102 to 6616297 pg/mL, P,0.001). In regression analysis, improved flow-mediated dilatation correlated closely with the reduction in free plasma homocysteine (r520.26, P50.001), independent of changes in protein-bound homocysteine, folate, and vitamin B12. Nitroglycerin-induced dilatation was unchanged after both B vitamins and placebo. Conclusions—Folic acid and vitamin B 12 supplementation improves vascular endothelial function in patients with CHD, and this effect is likely to be mediated through reduced concentrations of free plasma homocysteine concentrations. Our data support the view that lowering homocysteine, through B vitamin supplementation, may reduce cardiovascular risk. (Circulation. 2000;102:2479-2483.)

Nicotinamide increases biosynthesis of ceramides as well as other stratum corneum lipids to improve the epidermal permeability barrier.

Abstract: Background Stratum corneum lipids, particularly ceramides, are important components of the epidermal permeability barrier that are decreased in atopic dermatitis and aged skin. Objectives We investigated the effects of nicotinamide, one of the B vitamins, on biosynthesis of sphingolipids, including ceramides and other stratum corneum lipids, in cultured normal human keratinocytes, and on the epidermal permeability barrier in vivo. Methods The rate of sphingolipid biosynthesis was measured by the incorporation of [ 14 C]-serine into sphingolipids. Results When the cells were incubated with 1-30 μmol L -1 nicotinamide for 6 days, the rate of ceramide biosynthesis was increased dose-dependently by 4.1-5.5-fold on the sixth day compared with control. Nicotinamide also increased the synthesis of glucosylceramide (7.4-fold) and sphingomyelin (3.1-fold) in the same concentration range effective for ceramide synthesis. Furthermore, the activity of serine palmitoyltransferase (SPT), the rate-limiting enzyme in sphingolipid synthesis, was increased in nicotinamide-treated cells. Nicotinamide increased the levels of human LCB I and LCB2 mRNA, both of which encode subunits of SPT. This suggested that the increase in SPT activity was due to an increase in SPT mRNA. Nicotinamide increased not only ceramide synthesis but also free fatty acid (2.3-fold) and cholesterol synthesis (1.5-fold). Topical application of nicotinamide increased ceramide and free fatty acid levels in the stratum corneum, and decreased transepidermal water loss in dry skin. Conclusions Nicotinamide improved the permeability barrier by stimulating de novo synthesis of ceramides, with upregulation of SPT and other intercellular lipids.

Vitamin supplements and cardiovascular risk: review of the randomized trials of homocysteine-lowering vitamin supplements.

Abstract: Epidemiological studies have shown that higher blood homocysteine levels appear to be associated with higher risks of coronary, cerebral, and peripheral vascular disease and are inversely related to blood levels of folate and of vitamin B12 and vitamin B6. However, observational studies cannot exclude the possibility that elevated homocysteine levels may be associated with some other factor, rather than being causally related to vascular disease. Large-scale clinical trials of sufficient dose and duration of treatment are required to test this hypothesis, but there was substantial uncertainty about the optimal vitamin regimen to test in such trials. A meta-analysis of 12 randomized trials of vitamin supplements to lower homocysteine levels was carried out to determine the optimal dose of folic acid required to lower homocysteine levels and to assess whether vitamin B12 or vitamin B6 had additive effects. This meta-analysis demonstrated that reductions in blood homocysteine levels were greater at higher pretreatment blood homocysteine levels and at lower pretreatment folate concentrations. After standardization for a pretreatment homocysteine concentration of 12 micromol/L and folate concentration of 12 nmol/L (approximate average concentrations for western populations), dietary folic acid reduced homocysteine levels by 25% (95% confidence interval [CI]: 23 to 28%) with similar effects in a daily dosage range of 0.5 to 5 mg. Vitamin B12 (mean 0.5 mg) produced an additional reduction in blood homocysteine of 7%, whereas vitamin B6 (mean 16.5 mg) did not have any significant effect. Hence, in typical populations, daily supplementation with both 0.5 to 5 mg folic acid and about 0.5 mg vitamin B12 would be expected to reduce homocysteine levels by one quarter to one third (from about 12 micromol/L to about 8 to 9 micromol/L). Large-scale randomized trials of such regimens are now required to determine whether lowering homocysteine levels by folic acid and vitamin B12, with or without added vitamin B6, reduces the risk of vascular disease.

Effect of the inflammatory response on trace element and vitamin status

Abstract: Trace elements and vitamins are required in milligram amounts per day to maintain normal health. If insuf® cient or excessive amounts are present, illness can result. Improvements in atomic absorption spectroscopy for trace metals in the 1970s and high-pressure liquid chromatography methods for vitamins in the 1990s 1 now allow us to detect physiological and pathophysiological variations in blood concentrations of these substances in the absence of clinical evidence of de® ciency or toxicity. Several epidemiological studies have highlighted the association of a reduction in circulating concentrations of antioxidant vitamins and trace elements with an increased risk of

Serum vitamin B12, C and folate concentrations in the New Mexico elder health survey: correlations with cognitive and affective functions.

Abstract: Objectives: 1) To compare serum vitamin B12, C and folate concentrations in a randomly selected sample of elderly (age 65 years or older) male and female Hispanics and nonHispanic whites (NHW) and 2) to examine associations between serum B12, C and folate concentrations compared to measures of cognitive and affective (depression) functions.Methods: Equal numbers of male and female Hispanics and NHW were randomly sampled from the Health Care Financing Administration (Medicare) registrant list for Bernalillo County, New Mexico, and asked to volunteer for a paid home interview followed by a paid comprehensive interview/examination covering health and health-related issues. In addition to serum determinations of B12, C and folate, associations were examined between these vitamins and measures of cognitive and affective functions.Results: Males and Hispanics had lower serum vitamin B12, C and folate concentrations than females and NHW respectively. Participants taking a multivitamin supplement (MVI) had higher...

Do idebenone and vitamin therapy shorten the time to achieve visual recovery in Leber hereditary optic neuropathy

Abstract: Objectives:The authors investigated the effectiveness of idebenone combined with vitamin B2 and vitamin C in the treatment of patients with Leber hereditary optic neuropathy (LHON) in an early stage as compared with untreated patients with LHON. These agents may stimulate the formation of ATP.Materi

Culture of one-cell hamster embryos with water soluble vitamins: pantothenate stimulates blastocyst production

Abstract: The effects of water-soluble vitamins, singly or in combinations, on development of hamster 1-cell embryos were examined in a protein-free, chemically defined culture medium, HECM-6. Pantothenate significantly stimulated blastocyst development compared to the vitamin-free control and to every other single vitamin, except thiamine. Ascorbic acid, biotin, choline, folic acid, inositol, niacinamide, pyridoxal, riboflavin and thiamine had no detectable stimulation or inhibition on cleavage stage development or morula/blastocyst formation. When combinations of vitamins were tested, embryo development was either unchanged or significantly greater than in the control, but never significantly greater than development with pantothenate alone. A dose response to pantothenate indicated that 3 micromol/l was the optimum concentration. After embryo transfer, the percentage of live fetuses recovered per 100 1-cell embryos cultured in HECM-6 plus pantothenate (now designated HECM-9) was 24%, significantly higher than the 11% recovered from 100 1-cell embryos cultured in HECM-6 alone. This is the first report to show a stimulatory effect of a single vitamin on in-vitro development of preimplantation embryos in any mammalian species.

Vascular complications of severe hyperhomocysteinemia in patients with homocystinuria due to cystathionine beta-synthase deficiency: effects of homocysteine-lowering therapy.

Abstract: Homocystinuria (HCU) due to cystathionine beta-synthase (CBS) deficiency leads to severe hyperhomocysteinemia (HHcy). Vascular events (VE) remain the major cause of morbidity and mortality in the untreated patients with HCU. The study on the natural history of untreated HCU disclosed that, at the time of maximal risk, in other words beyond 10 years old, there was one event per 25 years. Recent studies from Australia (n = 32), The Netherlands (n = 28), and Ireland (n = 24) have documented the effects of long-term treatment on the vascular outcome of a total of 84 patients with 1314 patient-years of treatment for HCU. The mean (range) age was 27.8 (2.5 to 70) years. Five VE were recorded during treatment; one pulmonary embolism, two myocardial infarctions, and two abdominal aneurysms. All five VE occurred in B6-responsive patients at a mean (range) age of 48.8 (30 to 60) years. In 1314 patient-years of treatment, 53 VE would have been expected if they remained untreated; instead only 5 were documented, relative risk = 0.091 (95% confidence interval [CI] 0.043 to 0.190; p < 0.001). Appropriate homocysteine-lowering therapy for severe HHcy significantly reduced the vascular risk in patients with HCU. VE were rare with treatment despite the fact that the post-treatment homocysteine levels were several times higher than the cutoff point for homocysteine in the normal population. The present findings may have relevance to the current concept of "mild HHcy" as a risk factor for vascular disease, with elevated plasma homocysteine levels considerably lower than that of the post-treatment levels in this group of reported patients.

The Potential for Dietary Supplements to Reduce Premenstrual Syndrome (PMS) Symptoms

Abstract: Many types of dietary supplements have been advocated for the reduction of certain symptoms of premenstrual syndrome (PMS). However, only one supplement-calcium-has been demonstrated to be of significant benefit in a large, rigorous, double-blind, placebo-controlled trial. Limited evidence suggests that magnesium, vitamin E and carbohydrate supplements might also be useful, but additional research is needed to confirm these findings. Trials of vitamin B6 supplementation have had conflicting results, and high doses of this vitamin taken for prolonged periods of time can cause neurological symptoms. Trials of evening primrose oil have also had conflicting results; the two most rigorous studies showed no evidence of benefit. A variety of herbal products are suggested to reduce symptoms of PMS. The efficacy of these products is uncertain because of a lack of consistent data from scientific studies. Health professionals should be aware of the possible use of these supplements and ask those with PMS about their use of such products and counsel them based upon the totality of evidence.

Case-control study of plasma folate, homocysteine, vitamin B12, and cysteine as markers of cervical dysplasia.

Abstract: BACKGROUND An association between B-complex vitamins and related compounds with the development of cervical neoplasia is biologically plausible, yet to the authors' knowledge epidemiologic investigations of these potential biomarkers are limited. METHODS A case-control study was designed to examine the relation between plasma folate, homocysteine, vitamin B12, and cysteine and early, premalignant changes in cervical epithelial cells among women identified from several clinics on Oahu, Hawaii, between 1992 and 1996. Fasting blood samples for plasma nutrient analysis, cervical smears for cytologic diagnosis, exfoliated cervical cells for human papillomavirus DNA testing by polymerase chain reaction, and a personal interview were obtained from 185 women with atypical squamous cells of undetermined significance (ASCUS) of the cervix, 147 women with squamous intraepithelial lesions (SIL), and 191 women with cytologically normal (Papanicolaou) smears. RESULTS Age-adjusted and ethnicity-adjusted mean plasma concentrations of cysteine, but not other nutrients, were significantly lower among ASCUS cases (P = 0.006) and SIL cases (P = 0.01) than controls. A positive trend in the odds ratio for SIL but not ASCUS was found for increased plasma homocysteine concentrations, but this finding was not statistically significant. High plasma levels of cysteine were associated with a reduced risk of ASCUS (P value for trend = 0.006), with an odds ratio of 0.3 (95% confidence interval, 0.2–0.7) for the highest compared with the lowest quartile of cysteine concentration. A weak, negative relation between cysteine and the development of low grade SIL (LSIL) but not high grade SIL (HSIL) also was found. CONCLUSIONS The results of the current study do not support the hypothesis that folate, homocysteine, or B12 are markers of cervical dysplasia risk. A possible inverse association between plasma cysteine concentrations and the risk of cervical dysplasia needs further study. Cancer 2000;89:376–82. © 2000 American Cancer Society.

The major and a minor class II beta-chain (B-LB ) gene flank the Tapasin gene in the B-F /B-L region of the chicken major histocompatibility complex.

Abstract: We have identified the major histocompatibility complex class II β-chain (B-LB) genes present in the B-F/B-L region of the B complex of nine well-characterized lines of chickens and have cleared up much of the confusion concerning numbers and location of B-LB genes in this region. By amplifying DNA sequences between adjacent genes, we found two B-LB genes that lie on either side of Tapasin. The dominantly expressed 'major' B-LB gene in all haplotypes lies between Tapasin and RING-3, and belongs to the B-LBII family of class II β-chain genes. The poorly expressed 'minor' B-LB gene in all haplotypes lies between B-lec1 and Tapasin, and belongs either to the B-LBII family or to the previously unmapped B-LBVI family of class II β-chain genes. The data suggest that the B-LBII and B-LBVI genes are two lineages of B-LB genes and we propose that they all be termed B-LB genes. The location of a third B-LB gene in the B12 haplotype (and possibly other haplotypes as well) has yet to be determined. The structural organization and expression of the class II β-chain genes in the B-F/B-L region is similar to that of chicken class I (B-F) genes, one functional result of which is differential resistance to disease and response to vaccines.

Relationship between plasma homocysteine and vitamin status in the Framingham study population. Impact of folic acid fortification.

Abstract: Recent studies have demonstrated associations between occlusive vascular disease and hyperhomocysteinemia of both genetic and nutritional origin. In the present study we analyzed plasma samples from the 20th biannual examination of the Framingham Heart Study cohort to determine distribution of plasma homocysteine concentrations with emphasis on relationships to vitamins that serve as coenzymes in homocysteine metabolism and to prevalence of carotid artery stenosis. Results showed that homocysteine exhibited strong inverse association with plasma folate and weaker associations with plasma vitamin B12 and pyridoxal-5'-phosphate. We saw similar inverse associations between homocysteine and intakes of folate and vitamin B6, but not vitamin B12. Prevalence of high homocysteine (> 14 mumol/L) was 29.3% in this cohort, and was greatest among subjects with low folate status. Inadequate plasma concentrations of one or more B vitamins appear to contribute to 67% of the cases of high homocysteine. Prevalence of stenosis > or = 25% was 43% in men and 34% in women, with an odds ratio of 2.0 for individuals in the highest homocysteine quartile (> or = 14.4 mumol/L) compared with those in the lowest quartile ( 13 mumol/L) decreased from 18.7 to 9.8% (P < 0.001) between study visits. There were no statistically significant changes in the control group for folate or homocysteine between examinations. These data indicate a high prevalence of hyperhomocysteinemia in the Framingham Study population, the majority of which can be attributed to vitamin status and that this hyperhomocysteinemia is clinically relevant because of its association with increased risk of occlusive extracranial carotid stenosis. Insufficient levels of folate, and to a lesser extent vitamin B6, appear to predict part of this elevated risk through their role in homocysteine metabolism. These studies also indicate that the recently-implemented fortification of grain and cereal products with folic acid resulted in a substantial decline in plasma homocysteine. The impact of fortification on the US population is likely to be similar; however it awaits the next survey for further confirmation.

Production of B-group vitamins by two Azotobacter strains with phenolic compounds as sole carbon source under diazotrophic and adiazotrophic conditions.

Abstract: Azotobacter vinelandii strain ATCC 12837 and A chroococcum strain H23 (CECT 4435) were able to grow on N-free or NH4Cl-amended chemically-defined (Burk's) media, with protocatechuic acid (1-2 mmol 1(-1)) or sodium p-hydroxybenzoate (1-10 mmol 1(-1)) as sole carbon (C) sources At a concentration of 2 mmol 1(-1), both substrates supported nitrogen fixation (acetylene reduction assay) at similar or higher rates than bacteria grown in control media amended with 2 mmol 1(-1) sodium succinate as C source The two strains produced the B-group vitamins niacin, pantothenic acid, thiamine, riboflavin and biotin after 72 h of growth in chemically-defined media with 2 mmol 1(-1) protocatechuic acid, sodium phydroxybenzoate or sodium succinate as sole C source, either in N-free media or in media amended with 01% NH4Cl Quantitative production of all vitamins was affected by the use of the different C and N substrates

Anemia and deficiencies of folate and vitamin B-6 are common and vary with season in Chinese women of childbearing age.

Abstract: Little is known about the micronutrient status of Chinese women of childbearing age. We assessed nonfasting plasma concentrations of folic acid vitamin B-12 vitamin B-6 (as pyridoxal-5’-phosphate) hemoglobin (Hb) ferritin and transferrin receptor (TfR) in 563 nonpregnant textile workers aged 21–34 y from Anqing China. All women had obtained permission to become pregnant and were participating in a prospective study of pregnancy outcomes. Mean (SD) plasma concentrations were 9.7 (4.1) nmol/L folic acid 367 (128) pmol/L vitamin B-12 40.2 (15.8) nmol/L vitamin B-6 108 (12.9) g/L Hb 42.6 (34.2) µg/L ferritin and 5.2 (2.7) mg/L TfR. Twenty-three percent of women had biochemical evidence of folic acid deficiency 26% were deficient in vitamin B-6 and 10% had low vitamin B-12. Overall 44% of women were deficient in at least one B vitamin. Although anemia (Hb < 120 g/L) was detected in 80% of women only 17% had depleted iron stores (ferritin < 12 µg/L); 11% had elevated TfR concentrations. Distinct seasonal trends were observed in the prevalence of moderate anemia (Hb < 100 g/L) and deficiencies of folic acid and vitamin B-6 with significantly lower concentrations of folate and Hb occurring in summer and lower concentrations of vitamin B-6 occurring in winter and spring than in other seasons. We conclude that deficiencies of folic acid vitamin B-6 and iron were relatively common in this sample of Chinese women of childbearing age and were contributing to the high prevalence of anemia. Without appropriate supplementation these deficiencies could jeopardize the women’s health and increase their risk of adverse pregnancy outcomes. (authors)

Elite athlete immunology: importance of nutrition.

Abstract: Immunosuppression in athletes involved in heavy training is undoubtedly multifactorial in origin. Training and competitive surroundings may increase the athlete's exposure to pathogens and provide optimal conditions for pathogen transmission. Heavy prolonged exertion is associated with numerous hormonal and biochemical changes, many of which potentially have detrimental effects on immune function. Furthermore, improper nutrition can compound the negative influence of heavy exertion on immunocompetence. An athlete exercising in a carbohydrate-depleted state experiences larger increases in circulating stress hormones and a greater perturbation of several immune function indices. The poor nutritional status of some athletes may predispose them to immunosuppression. For example, dietary deficiencies of protein and specific micronutrients have long been associated with immune dysfunction. An adequate intake of iron, zinc and B vitamins is particularly important but the dangers of over-supplementation should also be emphasized; many micronutrients given in quantities beyond a certain threshold will in fact reduce immune responses and may have other toxic effects that are detrimental to health. Although it is impossible to counter the effects of all of the factors that contribute to exercise-induced immunosuppression, it has been shown to be possible to minimize the effects of many factors. Athletes can help themselves by eating a well-balanced diet that includes adequate protein and carbohydrate, sufficient to meet their energy requirements. This will ensure a more than adequate intake of trace elements without the need for special supplements. Consuming carbohydrate (but not glutamine) during exercise attenuates rises in stress hormones such as cortisol and appears to limit the degree of exercise-induced immunosuppression. By adopting sound nutritional practice, reducing other life stresses, maintaining good hygiene, obtaining adequate rest and spacing prolonged training sessions and competition as far apart as possible, athletes can reduce their risk of infection.