Lower Plasma Levels of Antioxidant Vitamins in Patients with Metabolic Syndrome: A Case Control Study

Obesity influencing circulating levels of nutrients: Evidence from Mendelian randomization study

Observational studies have established that obesity is associated with nutritional deficiencies, but the exact causality remains uncertain. Thus, this Mendelian randomization (MR) study aimed to identify the causal associations between obesity and circulating levels of nutrients. Single-nucleotide polymorphisms associated with obesity (body mass index and waist-hip ratio), were extracted from a genome-wide association study of 694,649 European ancestry. Summary-level data for minerals (copper, selenium, zinc, calcium, magnesium, and potassium), and vitamins (folate, vitamins A, C, E, B6, and B12), albumin were obtained from the publicly available integrative epidemiology unit OpenGWAS database psychiatric genomics consortium. Inverse-variance weighted method several sensitivity analyses were conducted. Genetically predicted higher body mass index significantly decreased circulating levels of magnesium (β = -0.07, 95% confidence interval [CI]: -0.10 to -0.03, P = 1.47 × 10-4), folate (β = -0.07, 95% CI: -0.10 to -0.04, P = 5.61 × 10-5), vitamin A (β = -0.11, 95% CI: -0.14 to -0.07, P = 3.10 × 10-9), vitamin E (β = -0.10, 95% CI: -0.13 to -0.06, P = 1.84 × 10-8), albumin (β = -0.15, 95% CI: -0.17 to -0.12, P = 9.89 × 10-28); whereas genetically predicted higher waist-hip ratio decreased circulating levels of magnesium (β = -0.07, 95% CI: -0.11 to -0.02, P = 1.87 × 10-3), folate (β = -0.07, 95% CI: -0.11 to -0.03, P = 9.87 × 10-4), vitamin C (β = -0.08, 95% CI: -0.12 to -0.04, P = 2.40 × 10-4), albumin (β = -0.08, 95% CI: -0.11 to -0.04, P = 3.72 × 10-5). The study supports a causal effect of obesity on lower circulating levels of nutrients. Our findings highlight the necessity of adjuvant nutrients in obesity management.

A High Vitamin C Micronutrient Supplement Is Unable to Attenuate Inflammation in People with Metabolic Syndrome but May Improve Metabolic Health Indices: A Randomised Controlled Trial

Chronic low-grade inflammation is a characteristic of people with metabolic syndrome and is thought to contribute to the condition progressing to the more severe type 2 diabetes and cardiovascular disease (CVD). The aim was to carry out a double-blind randomised placebo-controlled trial in people with metabolic syndrome to determine if supplementation with a micronutrient formula containing 1000 mg/d vitamin C could attenuate inflammation in people with metabolic syndrome. We recruited 72 adults aged a median of 52 years with metabolic syndrome, defined as obesity (based on waist circumference or BMI), and at least two of hyperglycaemia, raised triglycerides, lowered HDL cholesterol, hypertension, or taking medications for these conditions. A further inclusion criteria comprised C-reactive protein (CRP) concentrations ≥ 3 mg/L, i.e., high risk of CVD. The participants were randomised to daily micronutrient formula (n = 37) or matched placebo control (n = 35) for 12 weeks. The primary outcome was change in CRP concentrations and secondary outcomes included changes in vitamin C concentrations, pro-inflammatory cytokines (IL-6, TNFα), oxidative stress marker (F2isoprostanes), glycaemic indices (glucose, insulin, HbA1c), lipid markers (triglycerides, LDL and HDL cholesterol), anthropometric parameters (weight, BMI), insulin resistance and insulin sensitivity, and metabolic severity score. The participants had a low median (Q1, Q3) vitamin C status of 29 (15, 41) µmol/L and a high proportion of hypovitaminosis C (38%) and outright deficiency (19%). Following 12 weeks of micronutrient supplementation, at least 70% of the participants reached adequate vitamin C status (≥50 µmol/L), however, there was no change in CRP concentrations relative to the placebo group (Δ-0.3 [95%CI -2.7, 2.1] mg/L, p = 0.8). Similar trends were observed for IL-6, TNFα and F2isoprostanes (p > 0.05). Instead, there were small improvements in BMI, fasting glucose and HbA1c concentrations, insulin sensitivity and metabolic severity score in the micronutrient group relative to placebo (p < 0.05). Overall, 12-week micronutrient supplementation was unable to mitigate systemic inflammation in people with metabolic syndrome but may improve several metabolic health indices.

Associations of Dietary and Circulating Vitamin E Level With Metabolic Syndrome. A Meta-Analysis of Observational Studies

Objective: The associations of dietary and circulating vitamin E level with metabolic syndrome (MetS) remains conflicting. This meta-analysis of observational study was therefore employed to investigate the issue above.

Methods: The PubMed, Web of Science and Embase database were searched up to April 2021. The observational studies on the associations of dietary and circulating vitamin E level with MetS were specified. The pooled relative risk (RR) of MetS for the highest vs. lowest dietary and circulating vitamin E level, and the standard mean difference (SMD) of dietary and circulating vitamin E level for MetS vs. control subjects, were calculated.

Results: A total of 25 observational studies with 51,276 participants, were included in this meta-analysis. The overall multi-variable adjusted RR demonstrated that the dietary vitamin E level was inversely associated with MetS (RR = 0.92, 95%CI: 0.85–1.00; P = 0.044). In addition, the dietary vitamin E level in MetS was also lower than that in control subjects according to the overall combined SMD (SMD = −0.08, 95%CI: −0.14 to −0.02; P = 0.024). On the other hand, the overall multi-variable adjusted RR showed no significant relationship between the circulating vitamin E level and MetS (RR = 1.46, 95%CI: 0.85–2.48; P = 0.17). However, the circulating vitamin E level in MetS was lower than that in control subjects according to the overall combined SMD (SMD = −0.58, 95%CI: −1.04 to −0.13; P = 0.013).

Conclusions: The results of this meta-analysis suggest that the dietary vitamin E level is inversely associated with MetS. On the other hand, current evidence is still insufficient to conclude a relationship between the circulating vitamin E level and MetS. More well-designed prospective cohort studies are needed to address the issues further.

Vitamin C and Metabolic Syndrome: A Meta-Analysis of Observational Studies

Background: The association between vitamin C and metabolic syndrome (MetS) has been evaluated in several epidemiological studies with conflicting results. This meta-analysis was therefore employed to further investigate the above issue. Methods: The observational studies on the associations of dietary and circulating (serum and plasma) vitamin C levels with MetS were searched in the PubMed, Web of Science, and Embase database up to April 2021. The pooled relative risk (RR) of MetS for the highest vs. lowest dietary and circulating vitamin C levels and the standard mean difference (SMD) of dietary and circulating vitamin C levels for MetS vs. control subjects were calculated, respectively. Results: A total of 28 observational studies were identified in this meta-analysis. Specifically, 23 studies were related to the dietary vitamin C level. The overall multivariable-adjusted RR demonstrated that the dietary vitamin C level was inversely associated with MetS (RR = 0.93, 95% CI: 0.88-0.97; P = 0.003). Moreover, the overall combined SMD showed that the dietary vitamin C level in MetS was lower than that in control subjects (SMD = -0.04, 95% CI: -0.08 to -0.01; P = 0.024). With regard to the circulating vitamin C level, 11 studies were included. The overall multivariable-adjusted RR demonstrated that the circulating vitamin C level was inversely associated with MetS (RR = 0.60, 95% CI: 0.49-0.74; P < 0.001). In addition, the overall combined SMD showed that the circulating vitamin C level in MetS was lower than that in control subjects (SMD=-0.82, 95%CI: -1.24 to -0.40; P < 0.001). Conclusions: Current evidence suggests that both dietary and circulating vitamin C level is inversely associated with MetS. However, due to the limitation of the available evidence, more well-designed prospective studies are still needed.

Low Plasma Ascorbate Levels in Type 2 Diabetic Patients With Adequate Dietary Vitamin C

Background  Dietary intake of antioxidative vitamin C plays a protective role in the prevention of oxidative damage in diabetics, demanding increased requirement of vitamin C. Hyperglycemia results in impaired uptake of vitamin C in the cell. The present study was conducted to compare the plasma ascorbate levels in type 2 diabetic patients and controls consuming adequate dietary vitamin C. Methodology  Fifty consented type 2 diabetes mellitus (T2DM) patients who were on treatment with oral hypoglycemic drugs and consuming adequate vitamin C in diet were taken in the study and 50 healthy controls equitably matched for age, gender between 40 and 70 years, and dietary intake of vitamin C were compared. Dietary intake of vitamin C was estimated by a food frequency questionnaire. Subjects consuming more than 35 mg/d of vitamin C were included in the study. Fasting blood sugar was estimated by glucose oxidase and peroxidase method and estimation of ascorbic acid was done by using 2, 4 dinitro phenyl hydrazine method. Result  The mean ± standard deviation levels of plasma ascorbate levels in diabetic subjects were 0.22 ± 0.12 mg/dL, which were significantly lower as compared with controls with plasma ascorbate level of 0.47 ± 0.15 mg/dL. In diabetic subjects, insignificant positive correlation was observed between these parameters with r -value 0.168 and p -value 0.245. Conclusion  This study concludes that even with the recommended dietary intake of vitamin C low plasma ascorbate levels were found among T2DM patients, which necessitates increased demand and dietary advice to diabetic patients on consuming foods rich in vitamin C more than the recommended daily allowance.

Association between serum Vitamin E concentrations and the presence of Metabolic Syndrome: A population-based cohort study

BACKGROUND

Metabolic syndrome (MetS) is a cluster of clinical and metabolic features that include central obesity, dyslipidemia, hypertension and impaired glucose tolerance. These features are accompanied by increased oxidative stress and impaired antioxidant defenses. Vitamin E is a major factor in the non-enzymatic antioxidant defenses. The aim of present study was to investigate the association between serum levels of vitamin E and the presence of MetS and its components in a sample population of Mashhad stroke and heart atherosclerotic disorder (MASHAD) cohort study.

METHODS

This cross-sectional study was carried out in 128 subjects with MetS and 235 subjects without MetS. MetS was defined according to the International-Diabetes-Federation criteria. Serum levels of vitamin E were measured using the HPLC method. Anthropometric and biochemical parameters were measured using standard protocols.  Results. MetS patients had significantly lower serum levels of vitamin E (Vit E), Vit E/Total cholesterol (TC), and Vit E/ (TC+triglyceride(TG)) compared to the control group (P < 0.05).  Vit E/ (TG+TC) was also significantly lower in diabetics or those with elevated levels of high sensitive C-reactive protein (hs-CRP). Additionally, there was a significant association between Vit E/ (TG + Total Cho) and the number of components of the metabolic syndrome (p= 0.02) Conclusions. There is a significant inverse association between indices of Vit E status and the presence of MetS. Moreover, a significantly lower Vit E/ (TC+TG) was observed along with individuals with increasing numbers of components of the MetS.

The Relationship between Serum Vitamin E Level and Risk Factors for Arteriosclerosis in Japanese Postmenopausal Women

Since vitamin E is one of the most potent antioxidant and anti-inflammatory agents, vitamin E can play a role against arteriosclerosis through various actions. Then, we have studied the relationship between serum vitamin E status and risk factors for arteriosclerosis in Japanese postmenopausal women. One hundred and seven subjects (70.0±7.7 y) were evaluated for vitamin E status by measuring serum α- and γ-tocopherol (αT and γT) levels. The number of arteriosclerosis risk factors was defined by the existence of high blood pressure, hyperglycemia, and dyslipidemia. Median serum αT and γT concentrations were 24.32 and 2.79 μmol/L, respectively. In none of the subjects, serum αT level was below the cutoff value (<12 μmol/L) for vitamin E deficiency which causes fragile erythrocyte and hemolysis. While no significant differences were found in serum levels of αT and γT between the groups categorized by the number of arteriosclerosis risks, serum levels of αT adjusted by serum total cholesterol (TC) and triglyceride (TG) decreased with an increasing number of arteriosclerotic risk factors (p=0.074). Serum αT level adjusted by serum TC and TG was also a negative significant predictor for the number of arteriosclerosis risk factors controlled by covariates associated with arteriosclerosis. The present study described that serum vitamin E level was positively associated with a lower number of arteriosclerotic risks, and its role for preventing noncommunicable diseases was suggested.

The risks of ubiquinone and β-carotene deficiency and metabolic disorders in patients with oral cancer

Background

Cancer development is mediated by oxidative stress and inflammation, which may correlate with metabolic disorders. The aim of this study was to evaluate antioxidant vitamins status and metabolic parameters in patients with oral cancer according to tumor-node-metastasis (TNM) stages.

Methods

A total of 194 patients with oral cancer were enrolled in this study. The patients were stratified for four groups according to cancer stages and that the statistics are comparisons across these groups. The levels of antioxidant vitamins (ubiquinone, β-carotene, vitamin A and E), metabolic parameters, oxidative stress, antioxidant enzymes activity, and inflammatory markers were measured.

Results

More than half of the subjects had high blood pressure, central obesity, hyperglycemia, and hyperlipidemia regardless of TNM stage. With regard to antioxidant vitamins status, 46 and 94% of patients had β-carotene and ubiquinone deficiency, respectively. Patients in T3 and T4 stages had significantly lower antioxidant enzyme (catalase, p = 0.03) activity and higher inflammatory markers levels (high sensitivity C-reactive protein and interleukin-6, p < 0.01) than patients in the other stages. In addition, the level of β-carotene was negatively associated with waist circumference, and ubiquinone was positively associated with the level of high-density lipoprotein cholesterol (p < 0.05). Higher β-carotene and ubiquinone levels were negatively associated with hypertriglyceridemia and the risk of metabolic syndrome (p < 0.05).

Conclusions

A high proportion of patients with oral cancer had ubiquinone or β-carotene deficiency and metabolic disorders. The level of ubiquinone or β-carotene was negatively associated with the risk of central obesity, hypertriglyceridemia, and metabolic syndrome. Since patients with oral cancer suffer from high oxidative stress and inflammation (particularly in the T3 and T4 stages), supplementation with antioxidant vitamins such as ubiquinone or β-carotene could be preferentially applied.

Carotenoids, vitamin A, and their association with the metabolic syndrome: a systematic review and meta-analysis

Context

Modifiable factors that reduce the burden of the metabolic syndrome (MetS), particularly plant-derived biomarkers, have been a recent focus of rising interest.

Objective

This systematic review and meta-analysis, which follows PRISMA guidelines, evaluates evidence from a period of 20 years that links vitamin A and carotenoids with the occurrence of MetS and following the PRISMA guidelines.

Data Sources

PubMed and Cochrane databases (January 1997 through March 2017) were systematically assessed for studies, including case-control, cross-sectional, and cohort studies, that evaluated the associations of MetS with carotenoids and retinyl esters and retinol (vitamin A).

Data Extraction

Key measures of associations were harmonized into odds ratios (ORs) and 95% confidence intervals (95%CI) of MetS per 1 standard deviation (SD) of exposure using forest plots and random effects models that pooled data points from 11 cross-sectional studies. Begg's funnel and harvest plots were constructed.

Results

An inverse association between total carotenoids and MetS was found [ORpooled, 0.66; 95%CI, 0.56-0.78; 1 SD ∼ 0.82 µmol/L; n = 5 studies]. This association was the strongest for β-carotene, followed by α-carotene and β-crypotoxanthin. No association was detected between retinol and MetS (ORpooled, 1.00; 95%CI, 0.88-1.13; 1 SD ∼ 2.14 µmol/L; n = 6 studies). Publication bias was absent, and harvest plots indicated consistency upon replication for β-carotene and total carotenoid exposures.

Conclusions

This review and meta-analysis suggests that, unlike retinol, total and individual carotenoids were inversely related to MetS.

Vitamin C: A Review on its Role in the Management of Metabolic Syndrome

Oxidative stress and inflammation are two interlinked events that exist simultaneously in metabolic syndrome (MetS) and its related complications. These pathophysiological processes can be easily triggered by each other. This review summarizes the current evidence from animal and human studies on the effects of vitamin C in managing MetS. In vivo studies showed promising effects of vitamin C, but most of the interventions used were in combination with other compounds. The direct effects of vitamin C remain to be elucidated. In humans, the current state of evidence revealed that lower vitamin C intake and circulating concentration were found in MetS subjects. A negative relationship was observed between vitamin C intake / concentration and the risk of MetS. Oral supplementation of vitamin C also improved MetS conditions. It has been postulated that the positive outcomes of vitamin C may be in part mediated through its anti-oxidative and anti-inflammatory properties. These observations suggest the importance of MetS patients to have an adequate intake of vitamin C through food, beverages or supplements in order to maintain its concentration in the systemic circulation and potentially reverse MetS.

Effect of Omega-3 and vitamin E co-supplementation on serum lipids concentrations in overweight patients with metabolic disorders: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Results of the studies assessed the effect of omega-3 and vitamin E co-supplementation on lipid profile in patients with metabolic syndrome (MS) are contradictory. Therefore, we carried out a systematic review and meta-analysis of randomized controlled trials (RCTs), to assess the effect of omega-3 and vitamin E co-supplementation on total cholesterol (TC), triglycerides (TG), low-density lipoprotein (LDL) and high-density lipoprotein (HDL) in patients with MS.

METHODS

A systematic search was performed to find the related articles, up to April, 2019. There was no language and time limitation. Meta-analyses were carried out using both the random and fixed effects model where appropriate, and I2 index was used to evaluate the heterogeneity.

RESULTS

Search yielded 1236 publications. Five RCTs with 254 patients were eligible. Results of the meta-analysis indicated that omega-3 and vitamin E co-supplementation significantly reduced the serum concentrations of TG and LDL, whereas, it had no significant effect on the serum levels of TC and HDL in overweight patients with MS.

CONCLUSION

Present systematic review and meta-analysis revealed that omega-3 and vitamin E co-supplementation have beneficial effects on lipid profile of overweight patients with MS. It significantly reduced the serum levels of TG and LDL in such patients.

Reversion of down-regulation of intestinal multidrug resistance-associated protein 2 in fructose-fed rats by geraniol and vitamin C: Potential role of inflammatory response and oxidative stress

Intestinal multidrug resistance-associated protein 2 is an ABC transporter that limits the absorption of xenobiotics ingested orally, thus acting as essential component of the intestinal biochemical barrier. Metabolic Syndrome (MetS) is a pathological condition characterized by dyslipidemia, hyperinsulinemia, insulin resistance, chronic inflammation, and oxidative stress (OS). In a previous study we demonstrated that MetS-like conditions induced by fructose in drinking water (10% v/v, during 21 days), significantly reduced the expression and activity of intestinal Mrp2 in rats. We here evaluated the potential beneficial effect of geraniol or vitamin C supplementation, natural compounds with anti-inflammatory and anti-oxidant properties, in reverse fructose-induced Mrp2 alterations. After MetS-like conditions were induced (21 days), animals were cotreated with geraniol or vitamin C or vehicle for another 14 days. Decreased expression of Mrp2 protein and mRNA due to fructose administration was reversed by geraniol and by vitamin C, consistent with restoration of Mrp2 activity evaluated in everted intestinal sacs. Concomitantly, increased intestinal IL-1β and IL-6 levels induced by fructose were totally and partially counterbalanced, respectively, by geraniol administration. The intestinal redox unbalance generated by fructose was improved by geraniol and vitamin C, as evidenced by decreasing lipid peroxidation products and activity of Superoxide Dismutase and by normalizing glutathione reduced/oxidized glutathione ratio. The restoration effects exhibited by geraniol and vitamin C suggest that local inflammatory response and OS generated under MetS-like conditions represent important mediators of the intestinal Mrp2 down-regulation. Additionally, both agents could be considered of potential therapeutic value to preserve Mrp2 function under MetS conditions.

Association of serum copper, zinc and selenium levels with risk of metabolic syndrome: A nested case-control study of middle-aged and older Chinese adults

Trace elements, such as copper, zinc and selenium, have been linked to the development of metabolic syndrome. However, previous studies concerning these trace elements in association with metabolic syndrome have presented conflicting results in different countries. The aim of this study was to analyse the association between serum copper, zinc and selenium concentrations and the risk of metabolic syndrome among middle-aged and older Chinese adults. We performed a nested case-control study that included 349 individuals who developed metabolic syndrome (125 males and 224 females) during a 3-year follow-up and 349 controls matched by baseline age (±1 years), sex and area. Serum trace element concentrations were measured using atomic absorption spectrometry. The median serum selenium levels in males and females in the metabolic syndrome group were 82.2 (13.4) μg/L and 82.6 (11.1) μg/L, respectively, which were significantly higher than the serum selenium levels in the control group (p = 0.001 and p < 0.001). After adjusting for potential confounders, the odds ratios of risk for metabolic syndrome in the highest tertile of serum selenium levels were 2.72 [95% confidence interval (CI) 1.43-5.20; p for trend 0.002] for males and 5.30 (95% CI 3.31-8.74; p for trend <0.001) for females, respectively, compared with the lowest tertile. In addition, serum selenium levels were positively correlated with postprandial plasma glucose in both genders (for males: odds ratio 2.42; 95% CI 1.27-4.61; for females: odds ratio 2.11; 95% CI 1.32-3.37) and negatively associated with high-density lipoprotein in only females (odds ratio 3.21; 95% CI 1.75-5.91). These results suggest that higher levels of serum selenium might be an independent risk factor for metabolic syndrome, especially in relation to elevated postprandial plasma glucose and reduced high-density lipoprotein levels. However, we failed to demonstrate an association between copper or zinc status and metabolic syndrome or its components.

Vitamin E Metabolic Effects and Genetic Variants: A Challenge for Precision Nutrition in Obesity and Associated Disturbances

Vitamin E (VE) has a recognized leading role as a contributor to the protection of cell constituents from oxidative damage. However, evidence suggests that the health benefits of VE go far beyond that of an antioxidant acting in lipophilic environments. In humans, VE is channeled toward pathways dealing with lipoproteins and cholesterol, underlining its relevance in lipid handling and metabolism. In this context, both VE intake and status may be relevant in physiopathological conditions associated with disturbances in lipid metabolism or concomitant with oxidative stress, such as obesity. However, dietary reference values for VE in obese populations have not yet been defined, and VE supplementation trials show contradictory results. Therefore, a better understanding of the role of genetic variants in genes involved in VE metabolism may be crucial to exert dietary recommendations with a higher degree of precision. In particular, genetic variability should be taken into account in targets concerning VE bioavailability per se or concomitant with impaired lipoprotein transport. Genetic variants associated with impaired VE liver balance, and the handling/resolution of oxidative stress might also be relevant, but the core information that exists at present is insufficient to deliver precise recommendations.

Correlates of toenail selenium and its cross-sectional association with metabolic syndrome

BACKGROUND

The present study aimed to identify independent correlates of toenail selenium levels and to examine the association between toenail selenium levels and metabolic syndrome in Korean adults.

METHODS

Cross-sectional analysis was conducted using baseline data from the Trace Element Study of Korean Adults in the Yeungnam area, an ongoing cohort study of Korean adults over the age of 35 years. The baseline survey consisted of questionnaires on demographics, lifestyle characteristics and medical information. Dietary information was obtained through a validated semi-quantitative food frequency questionnaire. Toenail selenium levels were quantified using neutron activation analysis. Biomarkers associated with metabolic syndrome were obtained from biennial medical check-ups.

RESULTS

In the multivariable-adjusted analyses, independent lifestyle and dietary correlates of higher selenium levels were alcohol drinking (4.62% higher than nondrinking) and egg intake (0.43% higher per weekly serving), whereas current smoking (5.42% lower than nonsmoking) and vegetable consumption (0.05% lower per weekly serving) were associated with lower toenail selenium levels. In the multivariable adjusted logistic regression, no significant association was observed between toenail selenium levels and metabolic syndrome (odds ratio = 1.33, 95% confidence interval = 0.58-3.05).

CONCLUSIONS

Multiple lifestyle and dietary factors influenced toenail selenium levels, although no meaningful association was observed between toenail selenium levels and metabolic syndrome in Korean adults. Future prospective large-scale cohort studies are required to determine whether there is a causal relationship between selenium levels and metabolic syndrome in Korean adults.

Fat-soluble micronutrients and metabolic syndrome

PURPOSE OF REVIEW

Metabolic syndrome (MetS) is associated with increased risk of obesity, type 2 diabetes mellitus and cardiovascular diseases. MetS prevalence has been associated with diet inadequacy. Conversely, the cumulative incidence of MetS has been inversely associated with a Mediterranean-style diet that includes many different health-beneficial nutrients. Adherence to a Mediterranean-style diet could reduce or at least stabilize metabolic risk factors.

RECENT FINDINGS

Low serum level of fat-soluble micronutrients, such as carotenoids, vitamin (vit) A, D and E, has been linked to MetS. Fat-soluble micronutrients could contribute to prevent MetS thanks to their antioxidant and anti-inflammatory properties (vit E, carotenoids) or to their central role as hormone regulators (vit D) and/or lipid metabolism and glucose homeostasis sensors (vit D and E).

SUMMARY

This review summarizes recent epidemiological studies linking fat-soluble micronutrients to MetS and highlights new evidence on their mechanisms of actions.

Association of Vitamin E Levels with Metabolic Syndrome, and MRI-Derived Body Fat Volumes and Liver Fat Content

We aimed to relate circulating α- and γ-tocopherol levels to a broad spectrum of adiposity-related traits in a cross-sectional Northern German study. Anthropometric measures were obtained, and adipose tissue volumes and liver fat were quantified by magnetic resonance imaging in 641 individuals (mean age 61 years; 40.6% women). Concentrations of α- and γ-tocopherol were measured using high performance liquid chromatography. Multivariable-adjusted linear and logistic regression were used to assess associations of circulating α- and γ-tocopherol/cholesterol ratio levels with visceral (VAT) and subcutaneous adipose tissue (SAT), liver signal intensity (LSI), fatty liver disease (FLD), metabolic syndrome (MetS), and its individual components. The α-tocopherol/cholesterol ratio was positively associated with VAT (β scaled by interquartile range (IQR): 0.036; 95%Confidence Interval (CI): 0.0003; 0.071) and MetS (Odds Ratio (OR): 1.83; 95% CI: 1.21–2.76 for 3rd vs. 1st tertile), and the γ-tocopherol/cholesterol ratio was positively associated with VAT (β scaled by IQR: 0.066; 95% CI: 0.027; 0.104), SAT (β scaled by IQR: 0.048; 95% CI: 0.010; 0.087) and MetS (OR: 1.87; 95% CI: 1.23–2.84 for 3rd vs. 1st tertile). α- and γ-tocopherol levels were positively associated with high triglycerides and low high density lipoprotein cholesterol levels (all P_trend < 0.05). No association of α- and γ-tocopherol/cholesterol ratio with LSI/FLD was observed. Circulating vitamin E levels displayed strong associations with VAT and MetS. These observations lay the ground for further investigation in longitudinal studies.

Total Antioxidant Capacity from Dietary Supplement Decreases the Likelihood of Having Metabolic Syndrome in Korean Adults

This study was conducted to estimate antioxidant vitamin intake and total antioxidant capacity (TAC) from diet and dietary supplements and to examine their association with metabolic syndrome (MetS) in Korean adults. Out of 6308 adults 19~64 years old from the 2010~2011 Korea National Health and Nutrition Examination Survey, 1847 adults were classified as dietary supplement users and the other 4461 adults were classified as non-users. Antioxidant intake and TAC from diet and dietary supplements were estimated using dietary intake data and linked with the antioxidant and TAC database for common Korean foods. The prevalence of MetS was lower in dietary supplement users (odds ratio (OR) = 0.82; 95% confidence interval (CI), 0.68–0.98) than that in non-users. Among dietary supplement users, a lower prevalence of MetS was observed in the highest tertile for vitamin A (OR = 0.72; 95% CI, 0.53–0.99) and vitamin E (OR = 0.74; 95% CI, 0.55–0.99) intake than that in the lowest tertile among non-users. Subjects in the highest tertile of TAC among dietary supplement users showed a lower prevalence of MetS (OR = 0.72; 95% CI, 0.52–0.99) than non-users. The results imply that intake of vitamin A, vitamin E, and TAC from dietary supplements might have a protective effect on MetS among Korean adults.

New findings of oxidative stress biomarkers in nutritional research

PURPOSE OF REVIEW

The aim of this article is to present a brief overview of recently published articles assessing oxidative stress markers in nutritional studies.

RECENT FINDINGS

Intervention and observational studies were carried out in both, healthy subjects and patients and describe the association of foodstuffs as well as isolated nutrients with biomarkers of oxidative stress. The results from human intervention studies on healthy participants and patients are controversial. Long-term interventions (>8 weeks) seem to be more effective than short-term or single-dose interventions. Results are difficult to compare because not only the methods used, also the assessed biomarkers and outcomes were very diverse. In addition, studies vary in the compounds and doses used, duration, participants and so on. Different biomarkers (damaged molecules together with antioxidants from different compartments) should be assessed to evaluate the true 'redox-status' of an individual and the impact of a nutritional intervention.

SUMMARY

Both observational and interventional studies performed in healthy participants and patients show possible beneficial effects of nutrients and foodstuffs by improving oxidative stress markers and antioxidant enzyme activities. Biomarkers should be standardized to allow better comparison of results of antioxidant intervention studies.

Vitamin C Status Correlates with Markers of Metabolic and Cognitive Health in 50-Year-Olds: Findings of the CHALICE Cohort Study

A cohort of 50-year-olds from Canterbury, New Zealand (N = 404), representative of midlife adults, undertook comprehensive health and dietary assessments. Fasting plasma vitamin C concentrations (N = 369) and dietary vitamin C intake (N = 250) were determined. The mean plasma vitamin C concentration was 44.2 µmol/L (95% CI 42.4, 46.0); 62% of the cohort had inadequate plasma vitamin C concentrations (i.e., <50 µmol/L), 13% of the cohort had hypovitaminosis C (i.e., <23 µmol/L), and 2.4% had plasma vitamin C concentrations indicating deficiency (i.e., <11 µmol/L). Men had a lower mean plasma vitamin C concentration than women, and a higher percentage of vitamin C inadequacy and deficiency. A higher prevalence of hypovitaminosis C and deficiency was observed in those of lower socio-economic status and in current smokers. Adults with higher vitamin C levels exhibited lower weight, BMI and waist circumference, and better measures of metabolic health, including HbA1c, insulin and triglycerides, all risk factors for type 2 diabetes. Lower levels of mild cognitive impairment were observed in those with the highest plasma vitamin C concentrations. Plasma vitamin C showed a stronger correlation with markers of metabolic health and cognitive impairment than dietary vitamin C.

Should antioxidant vitamin supplementation be applied in patients with metabolic syndrome? A case-control study

INTRODUCTION

All cells in the human body are exposed to reactive oxygen species (ROS), which disturb the metabolic reactions in the organism. The antioxidant system in the human body consists of enzymatic and non-enzymatic mechanisms, among which vitamins A, C, and E play a major role.

THE AIM OF THE STUDY

The aim of the study was to evaluate the supply of vitamins A, C, and E from daily food rations (DFR) in postmenopausal women with metabolic syndrome (MS) in relation to current nutrition standards.

MATERIAL AND METHODS

The study involved 184 women with MS, aged 45-68 years (mean 57.38 ±8.17 years). The control group comprised 90 women, aged 41-65 years (mean 57.48 ±5.79 years) without MS. The food intake was assessed using 24-hour dietary recalls.

RESULTS

The evaluation of intake of vitamins measured with daily food rations (DFR) demonstrated that the optimal level of 90-110% according to standards was achieved only in 3.62% of women with metabolic syndrome for vitamin A, in 8.88% for vitamin C, and in 11.41% for vitamin E, which was significantly less often found than in the control group (p < 0.001).

CONCLUSIONS

Women with MS are characterised by diversified intake of vitamins A, C and E, and a subgroup of this patients present low level of antioxidant vitamins intake. Supplementation with antioxidant vitamins should be prescribed individually to postmenopausal women with MS.