Micronutrient intake in relation to all-cause mortality in a prospective Danish cohort

Association between serum folate concentrations and all-cause mortality in U.S. adults: a cohort study based on National Health and Nutrition Examination Survey III

The association between serum folate and all-cause mortality in general population remains unclear. The objective of this study was to investigate the potential association between serum folate concentrations and all-cause mortality in a large, prospective, long-term U.S. cohort. Our study included adults from the National Health and Nutrition Examination Survey (NHANES) III, and mortality data was obtained by linking with the National Death Index (NDI) until December 31, 2019. Cox proportional hazard models were used to calculate hazard ratios (HR) and 95% confidence intervals (CI) to assess the association between serum folate concentrations and all-cause mortality. A total of 12,862 participants were included in this cohort study. After a median follow-up of 26.4 years [interquartile range (IQR), 15.4-28.7 years], a total of 5,299 deaths were recorded. The risk of death was lower by 12% per 1.0 g/L increase in log-transformed serum folate concentrations (HR, 0.88; 95% CI, 0.83-0.94). Compared with the lowest quartiles of serum folate level, the risk of death was lower in the second (HR, 0.84; 95% CI, 0.72-0.97), third (HR, 0.78; 95% CI, 0.68-0.91) and the highest quartiles (HR, 0.78; 95% CI, 0.69-0.88) in multivariable-adjusted model. In subgroup analyses, the inverse association between serum folate and all-cause mortality remained statistically significant for women, men and non-Hispanic White people. Higher serum folate levels were found to be significantly associated with reduced risk of all-cause mortality. However, further studies are needed to verify these findings and explore the underlying mechanism.

Folate Biomarkers, Folate Intake, and Risk of Death From All Causes, Cardiovascular Disease, and Cancer: A Systematic Review and Dose-Response Meta-Analysis of Prospective Cohort Studies

CONTEXT

Existing evidence on the relation between folate intake and biomarkers with mortality risk is controversial.

OBJECTIVE

Previous cohort studies were examined regarding folate intake and biomarkers in relation to risk of all-cause, cardiovascular disease- (CVD), and cancer-related mortality through a systematic review and meta-analysis.

DATA SOURCES

A systematic search was performed of the PubMed, Scopus, and ISI Web of Science databases up to July 2023.

DATA EXTRACTION

Prospective cohort studies examining the association of folate biomarkers (in serum, plasma, red blood cells) and intake with risk of all-cause, CVD-, and cancer-related mortality were considered. A random-effects model was applied to combine study-specific risk estimates. Dose-response relations were assessed by 1-stage weighted mixed-effects meta-analysis.

DATA ANALYSIS

A total of 25 cohorts with 423 304 participants, 36 558 all-cause, 12 662 CVD-, and 2426 cancer-related deaths were included. No significant association was observed between the highest levels of folate biomarkers and all-cause mortality risk (hazard ratio [HR], 0.91; 95% CI, 0.77-1.06; n = 17; I2 = 89.4%; P < .001), CVD-related mortality risk (HR, 0.97; 95% CI, 0.87-1.06; n = 11; I2 = 0.0%; P = .57), and cancer-related mortality risk (HR, 0.85; 95% CI, 0.69-1.05; n = 6; I2 = 57.8%; P = .04) compared with the lowest. Furthermore, each 10 nmol/L increase was marginally related to a 12% reduced all-cause mortality risk but not to CVD- and cancer-related mortality risk. A significant inverse association was found between highest intake of dietary folate and the lowest, and risk of all-cause (HR, 0.87; 95% CI, 0.78-0.96; n = 3; I2 = 63.6%; P = .06) and CVD (HR, 0.77; 95% CI, 0.57-0.93; n = 4; I2 = 80.2%; P = .002) mortality.

CONCLUSIONS

This meta-analysis revealed a significant inverse relation between dietary folate intake and risk of all-cause and CVD mortality. Such an association was not found in the case of folate biomarkers. Further prospective studies are warranted to confirm these findings.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42023401700.

High red blood cell folate is associated with an increased risk of diabetes death among a hypertensive cohort

The relationship between folate and diabetes remains inconclusive, possibly because of folate measured differentially between studies. Interference from mandatory folic acid fortification (FAF) has also been blamed. With both folate intake and circulating concentration measured, we assessed the relationship between folate and the risk of diabetes death in a hypertensive cohort established before FAF. We hypothesized that the association between folate and diabetes death is measurement dependent. We analyzed the data of 3133 hypertensive adults aged ≥19 years who participated in the Third National Health and Nutrition Examination Survey (1991-1994) and were followed up through December 31, 2010. Hazard ratios of diabetes death were estimated for participants with high (4th quarter) folate compared with those with moderate (2nd and 3rd quarters) or low (1st quarter) concentrations of folate. Dietary folate intake, total folate intake (including folate from supplements), serum, and red blood cell (RBC) folate were measured. After 42,025 person-years of follow-up, 165 diabetes deaths were recorded, and a dose-response positive association was observed between diabetes death and RBC folate. The adjusted hazard ratios of diabetes death were 1.00 (reference), 1.42 (95% CI. 1.20-1.68), and 2.21 (1.73-2.82), respectively, for hypertensive adults with low, moderate, and high RBC folate. No association was detected between diabetes death and serum folate concentration, folate intake, or either dietary intake or total intake. With minimized interference from FAF, neither dietary nor serum folate was associated with diabetes death, but elevated RBC folate was associated with a high risk of diabetes deaths among hypertensive patients.

Intakes of Folate, Vitamin B6, and Vitamin B12 in Relation to All-Cause and Cause-Specific Mortality: A National Population-Based Cohort

The evidence regarding the intake of dietary folate, vitamin B6, and vitamin B12 in relation to mortality in the general population is limited. This study aimed to examine the relationship between dietary intakes of folate, vitamin B6, and vitamin B12 in relation to all-cause and cause-specific mortality in a large U.S. cohort. This study included a total of 55,569 adults from the Third National Health and Nutrition Examination Survey (NHANES III) and NHANES 1999–2014. Vital data were determined by linking with the National Death Index records through 31 December 2015. Cox proportional hazards models were used to investigate the relationships of all-cause and cause-specific mortality with dietary folate, vitamin B6, and vitamin B12 intake. Dietary intakes of folate and vitamin B6 were inversely associated with mortality from all-cause, cardiovascular disease, and cancer for men and with mortality from all-cause and cardiovascular disease for women. In men, the multivariable hazard ratios (95% confidence intervals) for the highest versus lowest quintiles of folate and vitamin B6 were 0.77 (0.71–0.85) and 0.79 (0.71–0.86) for all-cause mortality, 0.59 (0.48–0.72) and 0.69 (0.56–0.85) for CVD mortality, and 0.68 (0.56–0.84) and 0.73 (0.60–0.90) for cancer mortality, respectively. Among women, the multivariable hazard ratios (95% confidence intervals) for the highest versus lowest quintiles of folate and vitamin B6 were 0.86 (0.78–0.95) and 0.88 (0.80–0.97) for all-cause mortality and 0.53 (0.41–0.69) and 0.56 (0.44–0.73) for CVD mortality, respectively. No significant associations between dietary vitamin B12 and all-cause and cause-specific mortality were observed. In conclusion, higher dietary intakes of folate and vitamin B6 were significantly associated with lower all-cause and cardiovascular mortality. Our findings suggest that increasing the intake of folate and vitamin B6 may lower the mortality risk among U.S. adults.

Association of folate intake with cardiovascular-disease mortality and all-cause mortality among people at high risk of cardiovascular-disease

BACKGROUND & AIMS

Due to the beneficial effect of folate on cardiovascular disease (CVD), folic acid supplementation is a more common practice among people at high-risk of CVD. However, long-term prospective investigations regarding the association of folate-intake with CVD-mortality and all-cause mortality among this specific population are still lacking. Therefore, this study aims to assess the association of folate-intake with CVD-mortality and all-cause mortality.

METHODS

A total of 14,234 participants at high-risk of CVD were enrolled. Total folate equivalent (TFE), dietary folate equivalent (DFE), food folate, folic acid in fortified food, folic acid supplements, serum folate and red blood cell (RBC) folate were measured. The main outcome measures were CVD-mortality and all-cause mortality from baseline until 31 December 2015.

RESULTS

During the 98,890 person-year follow-up, 2036 deaths including 682 deaths due to CVD were documented. After multivariate adjustment, a J shaped association was found: modest intake of TFE and DFE was associated with lower risk of CVD-mortality and all-cause mortality, whereas higher intake did not persistently reduce these risks. Compared to the participants without folic acid supplementation matched 28-covariates using propensity score, folic acid supplementation was associated with higher risk of CVD-mortality (HR:1.44, 95%CI:1.06-1.97, P = 0.022) and all-cause mortality (HR:1.28,95%CI:1.09-1.51, P = 0.003). The levels of serum-folate and RBC-folate in participants with folic acid supplementation were significantly greater than participants without folic acid supplementation (41.8 nmol/l vs. 64.2 nmol/l, P < 0.001 for serum-folate; 1201 nmol/l vs. 1608 nmol/l, P < 0.001 for RBC-folate). Compared with the lowest-quintile of serum-folate, the second-quintile was consistently associated with CVD-mortality (HR:0.72, 95%CI:0.53-0.99, P = 0.048) and all-cause mortality (HR:0.78, 95%CI:0.64-0.94, P = 0.013). Compared to the lowest-quintile of RBC-folate, the second-quintile was associated with lower all-cause mortality (HR:0.71,95%CI:0.56-0.90, P = 0.005), whereas the highest-quintile was associated with higher CVD-mortality (HR:1.40,95%CI:1.02-1.93, P = 0.030). The J shaped association of serum-folate and RBC-folate with CVD-mortality and all-cause mortality was also demonstrated, further supporting the results of TFE and propensity score analysis.

CONCLUSIONS

This study suggested the beneficial effects of modest folate-intake on the improvement of long-term survival, and emphasized the potentially deleterious effects of excess folic acid supplementation among US adults at high-risk of CVD.

Nutrient Adequacy Is Associated with Reduced Mortality in US Adults

BACKGROUND

Americans are underconsuming essential nutrients while overconsuming several nutrients, including sodium, saturated fat, and added sugars. Suboptimal nutrition may be linked with mortality risk; however, few studies have evaluated the associations of underconsumed and overconsumed nutrients in a comprehensive manner among the US population.

OBJECTIVES

This study investigated the association between nutrient intake through diet and mortality focusing on adequacy, moderation, and macronutrient quality in US adults.

METHODS

Based on the 1999-2010 NHANES, 20,602 adults aged ≥30 y were followed up until December 2015. Nutrient intake was assessed using a 1-d 24-h dietary recall. Adequacy of major underconsumed nutrients in the United States was evaluated using the RDA (percent of RDA) or Adequate Intake (percent of AI). Overconsumed nutrients for which moderation is needed were assessed based on various dietary recommendations. Macronutrient quality was evaluated using the ratio of carbohydrates to dietary fiber, essential amino acids, and EPA + DHA. The association between nutrient intake and mortality was evaluated using Cox proportional hazards regression analysis.

RESULTS

Higher intakes of vitamin E, magnesium, iron, dietary fiber, and potassium relative to the RDA/AI were associated with lower all-cause mortality. High intake of vitamin A (tertile 3: ≥80.1% of RDA) was associated with lower mortality from cardiovascular disease (CVD; HR: 0.75; 95% CI: 0.57, 0.99) and cancer (HR: 0.76; 95% CI: 0.62, 0.94), and high intake of calcium (tertile 3: ≥87.8% of RDA) was inversely associated with cancer mortality (HR: 0.72; 95% CI: 0.56, 0.93). Higher intakes of essential amino acids and EPA + DHA evaluated as quartiles were inversely associated with all-cause and CVD mortality.

CONCLUSIONS

These findings suggest that higher intakes of underconsumed nutrients and improving macronutrient quality are associated with lower risk of CVD and cancer deaths in US adults.

Association of Antioxidants Use with All-Cause and Cause-Specific Mortality: A Prospective Study of the UK Biobank

Prospective studies and randomized controlled trials elucidating the impact of antioxidants supplementation on mortality risk are inconclusive. The present analysis determined association between regular antioxidants use and all-cause (primary objective), as well as cause-specific, mortality in 345,626 participants of the UK Biobank cohort using Cox proportional hazard models. All models were adjusted for confounders and multiple testing. Antioxidants users were defined as participants who indicated to regularly use at least one of the following: multivitamins, vitamin C, vitamin E, selenium, and zinc. Median age of antioxidants users (n = 101,159) and non-users (n = 244,467) at baseline was 57 years. During 3.9 million person-years and a median follow-up of 11.5 years, 19,491 deaths occurred. Antioxidants use was not significantly associated with all-cause, cancer, and non-cancer mortality including several cancer and non-cancer subtypes. Interestingly, mortality risk from respiratory disease was significantly 21% lower among antioxidants users as compared to non-users (hazard ratio: 0.79; 95% confidence interval: 0.67, 0.92). In conclusion, the present study findings do not support recommendations for antioxidants supplementation to prevent all-cause, cancer, or non-cancer mortality on a population level. The significant inverse association between antioxidants use and respiratory disease mortality needs further study.

Red blood cell folate and cardiovascular deaths among hypertensive adults, an 18-year follow-up of a national cohort

A shift towards high folate concentration has emerged following folate fortification. However, the association between folate and health outcomes beyond neural tube defects remains inconclusive. To assess the relationship between red blood cell (RBC) folate and the risk of cardiovascular death among hypertensive patients, we analyzed the data of 2,986 adults aged 19 or older with hypertension who participated in the National Health and Nutrition Examination Survey (1991-1994) as the baseline examination and were followed up through December 31, 2010. After 32,743 person-years of follow-up with an average of 11.7 (standard error = 0.03) years, 1192 deaths were recorded with 579 cardiovascular deaths. The median survival time was significantly shorter in adults in the high folate quartile than in patients in the low folate quartile: 11.97 vs. 13.85 years for heart diseases and 13.37 vs. 14.82 years for myocardial infarction deaths. The cardiovascular mortality was 13.04, 16.95, and 26.61/1,000 person-years for the groups with low, intermediate and high folate quartiles, respectively. After adjustment for age, sex and other factors, a J-shaped association emerged. The hazard ratios (HRs) of all cardiovascular deaths in patients with low, intermediate, and high folate quartiles were 1.09 (0.94, 1.27), 1.00 (reference), and 1.44 (1.31, 1.58), respectively. The corresponding HRs of acute myocardial infarction were 1.13 (0.86, 1.50), 1.00, and 2.13 (1.77, 2.57), respectively. The estimates remained significant after adjustment for BMI and medication use. Compared to moderate RBC folate levels, high folate levels were significantly associated with an increased risk of cardiovascular deaths, especially acute myocardial infarction.

Association between serum folate and cardiovascular deaths among adults with hypertension

BACKGROUND

A significant shift toward high folate concentrations has been taking place following the mandatory folate fortification. Yet the relationship between folate and health outcomes beyond neural tube defects remains understudied. We longitudinally examined relationships between serum folate and risk of cardiovascular death.

METHODS

We analyzed data of 3116 adults aged ≥19 who participated in the Third National Health and Nutrition Examination Survey, 1991-1994 and were diagnosed with hypertension. Vital status was followed through December 31, 2010. Cox regression was used to estimate hazard ratios (HRs) of cardiovascular deaths for individuals with serum folate in the first quartile and fourth quartile compared with the patients with interquartile folate.

RESULTS

After 33627 person years (p*ys) of follow-up, 1298 deaths were recorded with 638 cardiovascular disease (CVD) deaths (109 strokes and 529 heart diseases). A U-shaped association appeared after multivariable adjustment for heart disease, acute myocardial infarction, and overall CVD deaths. The mortality rate for heart disease in patients with low, moderate, and high folate were 12.18/1000 p*ys, 14.12/1000 p*ys, and 23.80/1000 p*ys, respectively, and the corresponding adjusted HRs were 1.79 (95% confidence interval, CI = 1.63-1.98), 1.00 (reference), and 1.31 (1.17-1.46). The HRs of acute myocardial infarction were 2.28 (1.80-2.88), 1.00 (reference), and 1.77 (1.42-2.20) for hypertensive patients with serum folate in low quartile, interquartile, and high quartile, respectively.

CONCLUSIONS

Among hypertensive adults, both low and high folate were associated with an elevated risk of dying from cardiovascular diseases compared with adults with moderate serum folate concentration.

Dietary intake and blood concentrations of antioxidants and the risk of cardiovascular disease, total cancer, and all-cause mortality: a systematic review and dose-response meta-analysis of prospective studies

Background

High dietary intake or blood concentrations (as biomarkers of dietary intake) of vitamin C, carotenoids, and vitamin E have been associated with reduced risk of cardiovascular disease, cancer, and mortality, but these associations have not been systematically assessed.

Objective

We conducted a systematic review and meta-analysis of prospective studies of dietary intake and blood concentrations of vitamin C, carotenoids, and vitamin E in relation to these outcomes.

Design

We searched PubMed and Embase up to 14 February 2018. Summary RRs and 95% CIs were calculated with the use of random-effects models.

Results

Sixty-nine prospective studies (99 publications) were included. The summary RR per 100-mg/d increment of dietary vitamin C intake was 0.88 (95% CI: 0.79, 0.98, I2 = 65%, n = 11) for coronary heart disease, 0.92 (95% CI: 0.87, 0.98, I2 = 68%, n = 12) for stroke, 0.89 (95% CI: 0.85, 0.94, I2 = 27%, n = 10) for cardiovascular disease, 0.93 (95% CI: 0.87, 0.99, I2 = 46%, n = 8) for total cancer, and 0.89 (95% CI: 0.85, 0.94, I2 = 80%, n = 14) for all-cause mortality. Corresponding RRs per 50-μmol/L increase in blood concentrations of vitamin C were 0.74 (95% CI: 0.65, 0.83, I2 = 0%, n = 4), 0.70 (95% CI: 0.61, 0.81, I2 = 0%, n = 4), 0.76 (95% CI: 0.65, 0.87, I2 = 56%, n = 6), 0.74 (95% CI: 0.66, 0.82, I2 = 0%, n = 5), and 0.72 (95% CI: 0.66, 0.79, I2 = 0%, n = 8). Dietary intake and/or blood concentrations of carotenoids (total, β-carotene, α-carotene, β-cryptoxanthin, lycopene) and α-tocopherol, but not dietary vitamin E, were similarly inversely associated with coronary heart disease, stroke, cardiovascular disease, cancer, and/or all-cause mortality.

Conclusions

Higher dietary intake and/or blood concentrations of vitamin C, carotenoids, and α-tocopherol (as markers of fruit and vegetable intake) were associated with reduced risk of cardiovascular disease, total cancer, and all-cause mortality. These results support recommendations to increase fruit and vegetable intake, but not antioxidant supplement use, for chronic disease prevention.

Dietary Antioxidants, Circulating Antioxidant Concentrations, Total Antioxidant Capacity, and Risk of All-Cause Mortality: A Systematic Review and Dose-Response Meta-Analysis of Prospective Observational Studies

The associations of various dietary or circulating antioxidants with the risk of all-cause mortality in the general population have not been established yet. A systematic search was performed in PubMed and Scopus, from their inception up to October 2017. Prospective observational studies reporting risk estimates of all-cause mortality in relation to dietary intake and/or circulating concentrations of antioxidants were included. Random-effects meta-analyses were conducted. Forty-one prospective observational studies (total n = 507,251) involving 73,965 cases of all-cause mortality were included. The RRs of all-cause mortality for the highest compared with the lowest category of circulating antioxidant concentrations were as follows: total carotenes, 0.60 (95% CI: 0.46, 0.74); vitamin C, 0.61 (95% CI: 0.53, 0.69); selenium, 0.62 (95% CI: 0.45, 0.79); β-carotene, 0.63 (95% CI: 0.57, 0.70); α-carotene, 0.68 (95% CI: 0.58, 0.78); total carotenoids, 0.68 (95% CI: 0.56, 0.80); lycopene, 0.75 (95% CI: 0.54, 0.97); and α-tocopherol, 0.84 (95% CI: 0.77, 0.91). The RRs for dietary intakes were: total carotenoids, 0.76 (95% CI: 0.66, 0.85); total antioxidant capacity, 0.77 (95% CI: 0.73, 0.81); selenium, 0.79 (95% CI: 0.73, 0.85); α-carotene, 0.79 (95% CI: 0.63, 0.94); β-carotene, 0.82 (95% CI: 0.77, 0.86); vitamin C, 0.88 (95% CI: 0.83, 0.94); and total carotenes, 0.89 (95% CI: 0.81, 0.97). A nonsignificant inverse association was found for dietary zinc, zeaxanthin, lutein, and vitamin E. The nonlinear dose-response meta-analyses demonstrated a linear inverse association in the analyses of dietary β-carotene and total antioxidant capacity, as well as in the analyses of circulating α-carotene, β-carotene, selenium, vitamin C, and total carotenoids. The association appeared to be U-shaped in the analyses of serum lycopene and dietary vitamin C. The present study indicates that adherence to a diet with high antioxidant properties may reduce the risk of all-cause mortality. Our results confirm current recommendations that promote higher intake of antioxidant-rich foods such as fruit and vegetables.

Dietary Antioxidant Micronutrients and All-Cause Mortality: The Japan Collaborative Cohort Study for Evaluation of Cancer Risk

Background

Oxidative stress, the imbalance between pro- and antioxidants, has been implicated in the etiology and pathophysiology of the incidence and mortality of many diseases. We aim to investigate the relations of dietary intakes of vitamin C and E and main carotenoids with all-cause mortality in Japanese men and women.

Methods

The Japan Collaborative Cohort Study for Evaluation of Cancer Risk had 22,795 men and 35,539 women, aged 40–79 years at baseline (1988–1990), who completed a valid food frequency questionnaire and were followed up to the end of 2009.

Results

There were 6,179 deaths in men and 5,355 deaths in women during the median follow-up of 18.9 years for men and 19.4 years for women. Multivariate hazard ratios for the highest versus lowest quintile intakes in women were 0.83 (95% confidence interval [CI], 0.76–0.90; P for trend < 0.0001) for vitamin C, 0.85 (95% CI, 0.78–0.93; P for trend < 0.0001) for vitamin E, 0.88 (95% CI, 0.81–0.96; P for trend = 0.0006) for β-carotene, and 0.90 (95% CI, 0.82–0.98; P for trend = 0.0002) for β-cryptoxanthin. The joint effect of any two of these highly correlated micronutrients showed significant 12–17% reductions in risk in the high-intake group compared with the low-intake group in women. These significant associations were also observed in the highest quintile intakes of vitamin C, vitamin E, and β-carotene in female non-smokers but were not observed in female smokers, male smokers, and non-smokers.

Conclusions

Higher dietary intakes of antioxidant vitamins may reduce the risk of all-cause mortality in middle-aged Japanese women, especially female non-smokers.

Dietary antioxidant vitamins intake and mortality: A report from two cohort studies of Chinese adults in Shanghai

Background

Few studies have evaluated dietary antioxidant vitamins intake in relation to risk of mortality in Asia.

Methods

We examined the associations between total carotene, vitamin C, and vitamin E from diet and risk of mortality from all causes, cancer, and cardiovascular disease in 134,358 participants (59,739 men and 74,619 women) from the Shanghai Men's Health Study and Shanghai Women's Health Study, two prospective cohort studies of middle-aged and elderly Chinese adults in urban Shanghai. Participants were followed up for a median period of 8.3 and 14.2 years for men and women, respectively. Hazard ratios (HRs) and 95% confidence interval (CIs) were estimated using Cox proportional hazards regression models.

Results

During the 495,332 and 1,029,198 person-years of follow-up for men and women, respectively, there were 10,079 deaths (4170 men and 5909 women). For men, compared with the lowest quintiles, the multivariable-adjusted risk reductions in the highest categories were 17% (HR 0.83; 95% CI, 0.76–0.92) for dietary total carotene and 17% (HR 0.83; 95% CI, 0.75–0.91) for dietary vitamin C. Associations were weaker in women than in men, though they were still statistically significant (highest versus lowest quintiles of dietary total carotene, HR 0.87; 95% CI, 0.80–0.95; dietary vitamin C: HR 0.83; 95% CI, 0.77–0.91). Significant inverse associations were observed between dietary total carotene, vitamin C, and risk of cardiovascular disease mortality but not cancer mortality.

Conclusion

This study suggests that total carotene and vitamin C intake from diet were inversely associated with deaths from all causes and cardiovascular disease in middle-aged or elderly people in China.

•

Dietary vitamin C and carotene were inversely associated with total deaths in China.

•

These associations were more pronounced for cardiovascular disease mortality.

•

Dietary antioxidant vitamins might not be associated with cancer mortality risk.

Dietary, circulating beta-carotene and risk of all-cause mortality: a meta-analysis from prospective studies

Observational studies evaluating the relation between dietary or circulating level of beta-carotene and risk of total mortality yielded inconsistent results. We conducted a comprehensive search on publications of PubMed and EMBASE up to 31 March 2016. Random effect models were used to combine the results. Potential publication bias was assessed using Egger’s and Begg’s test. Seven studies that evaluated dietary beta-carotene intake in relation to overall mortality, indicated that a higher intake of beta-carotene was related to a significant lower risk of all-cause mortality (RR for highest vs. lowest group = 0.83, 95%CI: 0.78–0.88) with no evidence of heterogeneity between studies (I² = 1.0%, P = 0.416). A random-effect analysis comprising seven studies showed high beta-carotene level in serum or plasma was associated with a significant lower risk of all-cause mortality (RR for highest vs. lowest group = 0.69, 95%CI: 0.59–0.80) with low heterogeneity (I² = 37.1%, P = 0.145). No evidence of publication bias was detected by Begg’s and Egger’s regression tests. In conclusion, dietary or circulating beta-carotene was inversely associated with risk of all-cause mortality. More studies should be conducted to clarify the dose-response relationship between beta-carotene and all-cause mortality.

Antioxidant vitamin intake and mortality in three Central and Eastern European urban populations: the HAPIEE study

PURPOSE

The aim of the study was to assess the relationships between individual-level dietary intakes of antioxidant vitamins C, E and beta-carotene with all-cause and cause-specific mortality in three Central and Eastern European (CEE) populations.

METHODS

Data from the Health, Alcohol and Psychosocial factors in Eastern Europe cohort study were used. At the baseline survey, between 2002 and 2005, 28,945 men and women aged 45-69 years were examined in Novosibirsk (Russia), Krakow (Poland) and seven Czech towns. Deaths in the cohorts were identified through mortality registers. Cox regression was used to estimate the association between vitamin consumption and all-cause, cardiovascular (CVD) disease and cancer mortality.

RESULTS

In multivariable-adjusted analyses, there were no clear inverse associations between antioxidant vitamin intakes and mortality, although in some groups, several hazard ratios (HRs) were significant. For example, in men, compared with the lowest quintile of vitamin C intake, all-cause mortality in the third and fourth quintiles was lower by 28 % (HR 0.72; 95 % CI 0.61-0.85) and by 20 % (HR 0.80; 95 % CI 0.68-0.95), respectively. CVD mortality was lower by 35 % (HR 0.65; 95 % CI 0.50-0.84) and by 23 % (HR 0.77; 95 % CI 0.59-0.99) in third and fourth quintile of vitamin C intake, respectively. In women, the third and fourth quintiles of dietary intake of vitamin E were associated with reduced risk of all-cause death by 33 % (HR 0.67; 95 % CI 0.53-0.84) and by 23 % (HR 0.77; 95 % CI 0.61-0.97), respectively. Consumption of vitamin C, vitamin E and beta-carotene was not related to CVD mortality in women and to cancer mortality in either gender.

CONCLUSION

This large prospective cohort study in CEE populations with low prevalence of vitamin supplementation did not find a strong, dose-response evidence for protective effects of antioxidant vitamin intake.

Antioxidant vitamin intake and mortality: the Leisure World Cohort Study

To assess the relationship between antioxidant vitamin intake and all-cause mortality in older adults, we examined these associations using data from the Leisure World Cohort Study, a prospective study of residents of the Leisure World retirement community in Laguna Hills, California. In the early 1980s, participants (who were aged 44-101 years) completed a postal survey, which included details on use of vitamin supplements and dietary intake of foods containing vitamins A and C. Age-adjusted and multivariate-adjusted (for factors related to mortality in this cohort—smoking, alcohol intake, caffeine consumption, exercise, body mass index, and histories of hypertension, angina, heart attack, stroke, diabetes, rheumatoid arthritis, and cancer) hazard ratios for death were calculated using Cox regression for 8,640 women and 4,983 men (median age at entry, 74 years). During follow-up (1981-2013), 13,104 participants died (median age at death, 88 years). Neither dietary nor supplemental intake of vitamin A or vitamin C nor supplemental intake of vitamin E was significantly associated with mortality after multivariate adjustment. A compendium that summarizes previous findings of cohort studies evaluating vitamin intake and mortality is provided. Attenuation in the observed associations between mortality and antioxidant vitamin use after adjustment for confounders in our study and in previous studies suggests that such consumption identifies persons with other mortality-associated lifestyle and health risk factors.

Associations between antioxidants and all-cause mortality among US adults with obstructive lung function

Chronic obstructive pulmonary disease is characterised by oxidative stress, but little is known about the associations between antioxidant status and all-cause mortality in adults with this disease. The objective of the present study was to examine the prospective associations between concentrations of α- and β-carotene, β-cryptoxanthin, lutein/zeaxanthin, lycopene, Se, vitamin C and α-tocopherol and all-cause mortality among US adults with obstructive lung function. Data collected from 1492 adults aged 20-79 years with obstructive lung function in the National Health and Nutrition Examination Survey III (1988-94) were used. Through 2006, 629 deaths were identified during a median follow-up period of 14 years. After adjustment for demographic variables, the concentrations of the following antioxidants modelled as continuous variables were found to be inversely associated with all-cause mortality among adults with obstructive lung function: α-carotene (P= 0·037); β-carotene (P= 0·022); cryptoxanthin (P= 0·022); lutein/zeaxanthin (P= 0·004); total carotenoids (P= 0·001); vitamin C (P< 0·001). In maximally adjusted models, only the concentrations of lycopene (P= 0·013) and vitamin C (P= 0·046) were found to be significantly and inversely associated with all-cause mortality. No effect modification by sex was detected, but the association between lutein/zeaxanthin concentrations and all-cause mortality varied by smoking status (P interaction= 0·048). The concentrations of lycopene and vitamin C were inversely associated with all-cause mortality in this cohort of adults with obstructive lung function.

Folic acid handling by the human gut: implications for food fortification and supplementation

BACKGROUND

Current thinking, which is based mainly on rodent studies, is that physiologic doses of folic acid (pterylmonoglutamic acid), such as dietary vitamin folates, are biotransformed in the intestinal mucosa and transferred to the portal vein as the natural circulating plasma folate, 5-methyltetrahydrofolic acid (5-MTHF) before entering the liver and the wider systemic blood supply.

OBJECTIVE

We tested the assumption that, in humans, folic acid is biotransformed (reduced and methylated) to 5-MTHF in the intestinal mucosa.

DESIGN

We conducted a crossover study in which we sampled portal and peripheral veins for labeled folate concentrations after oral ingestion with physiologic doses of stable-isotope-labeled folic acid or the reduced folate 5-formyltetrahydrofolic acid (5-FormylTHF) in 6 subjects with a transjugular intrahepatic porto systemic shunt (TIPSS) in situ. The TIPSS allowed blood samples to be taken from the portal vein.

RESULTS

Fifteen minutes after a dose of folic acid, 80 ± 12% of labeled folate in the hepatic portal vein was unmodified folic acid. In contrast, after a dose of labeled 5-FormylTHF, only 4 ± 18% of labeled folate in the portal vein was unmodified 5-FormylTHF, and the rest had been converted to 5-MTHF after 15 min (postdose).

CONCLUSIONS

The human gut appears to have a very efficient capacity to convert reduced dietary folates to 5-MTHF but limited ability to reduce folic acid. Therefore, large amounts of unmodified folic acid in the portal vein are probably attributable to an extremely limited mucosal cell dihydrofolate reductase (DHFR) capacity that is necessary to produce tetrahydrofolic acid before sequential methylation to 5-MTHF. This process would suggest that humans are reliant on the liver for folic acid reduction even though it has a low and highly variable DHFR activity. Therefore, chronic liver exposure to folic acid in humans may induce saturation, which would possibly explain reports of systemic circulation of unmetabolized folic acid.

Dietary folate and related micronutrients, folate-metabolising genes, and ovarian cancer survival

OBJECTIVE

Folate is essential for DNA synthesis and methylation and is implicated in tumour progression. Few studies have examined its role in ovarian cancer survival. Our objective was to determine relationships between intake of folate, related one-carbon nutrients, single nucleotide polymorphisms (SNPs) in folate-metabolising genes and survival following ovarian cancer diagnosis.

METHODS

This analysis included 1270 women with invasive epithelial ovarian cancer diagnosed in 2002-2006. Pre-diagnostic and some post-diagnostic lifestyle, dietary, and sociodemographic information was collected via self-administered questionnaires. DNA samples were genotyped for SNPs in methylenetetrahydrofolate reductase (MTHFR), methionine synthase (MTR) and methionine synthase reductase (MTRR) genes. Adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated using Cox regression.

RESULTS

Multivariate analyses did not identify associations between higher pre-diagnostic intake of folate, folic acid, vitamins B2, B6, and B12, methionine, betaine or choline and survival overall. In stratified analyses, higher folic acid and folate intake was associated with significantly worse survival among women with mucinous tumours (HRs per 100 μg 1.30 and 1.43, respectively) and smokers (HRs per 100 μg 1.23 and 1.16 respectively). There was also a suggestion that higher supplemental folic acid use post-diagnosis was associated with worse survival (HR per 100 μg 1.03, 95%CI 1.00-1.05). MTHFR SNP rs2066470 was significantly associated with survival (per allele HR 0.81, 95%CI 0.67-0.98).

CONCLUSIONS

Our data provide little evidence that folate intake affects ovarian cancer survival. However, combined effects with smoking, and findings within the mucinous subtype and for post-diagnosis folic acid, warrant further investigation.

Early infant exposure to excess multivitamin: a risk factor for autism?

Autism, a neurodevelopmental disorder that affects boys more than girls, is often associated with altered levels of monoamines (serotonin and catecholamines), especially elevated serotonin levels. The monoamines act as both neurotransmitters and signaling molecules in the gastrointestinal and immune systems. The evidence related to monoamine metabolism may be summarized as follows: (i) monoamine neurotransmitters are enzymatically degraded/inactivated by three mechanisms: oxidative deamination, methylation, and sulfation. The latter two are limited by the supply of methyl groups and sulfate, respectively. (ii) A decrease in methylation- and sulfation-mediated monoamine inactivation can be compensated by an increase in the oxidative deamination catalyzed by monoamine oxidase, an X-linked enzyme exhibiting higher activity in females than in males. (iii) Vitamins can, on one hand, facilitate the synthesis of monoamine neurotransmitters and, on the other hand, inhibit their inactivation by competing for methylation and sulfation. Therefore, we postulate that excess multivitamin feeding in early infancy, which has become very popular over the past few decades, may be a potential risk factor for disturbed monoamine metabolism. In this paper, we will focus on the relationship between excess multivitamin exposure and the inactivation/degradation of monoamine neurotransmitters and its possible role in the development of autism.