U-shaped association between dietary thiamine intake and new-onset diabetes: a nationwide cohort study

Joint B Vitamin Intake and Type 2 Diabetes Risk: The Mediating Role of Inflammation in a Prospective Shanghai Cohort

BACKGROUND AND AIMS

Type 2 diabetes (T2D) is a global and complex public health challenge, and dietary management is acknowledged as critical in its prevention. Recent studies have highlighted the involvement of micronutrients in T2D pathophysiology; our study aims to assess the association between B vitamin intake and T2D risks and the mediating role of inflammation.

METHODS

In a prospective cohort design, data on B vitamins intake, including thiamine (B1), riboflavin (B2), niacin (B3), pyridoxine (B6), folate (B9), and cobalamin (B12), was obtained using a validated food frequency questionnaire (FFQ), and blood inflammatory biomarkers were analyzed according to standard protocol in the local hospitals at baseline from 44,960 adults in the Shanghai Suburban Adult Cohort and Biobank (SSACB). Incident T2D cases were identified according to a physician's diagnosis or medication records from the electronic medical information system. We employed logistic and weighted quantile sum regression models to explore the associations of single and combined levels of B vitamins with T2D and mediation analyses to investigate the effects of inflammation.

RESULTS

Negative correlations between B vitamins and T2D were observed in the single-exposure models, except for B3. The analyses of joint exposure (B1, B2, B6, B9, and B12) also showed an inverse association (OR 0.80, 95% CI 0.71 to 0.88), with vitamin B6 accounting for 45.58% of the effects. Further mediation analysis indicated a mediating inflammatory impact, accounting for 6.72% of the relationship.

CONCLUSIONS

Dietary intake of B vitamins (B1, B2, B6, B9, B12) was associated with a reduced T2D risk partially mediated by inflammation in Shanghai residents.

J-shaped association between dietary thiamine intake and the risk of cognitive decline in cognitively healthy, older Chinese individuals

Background

The prospective association of dietary thiamine intake with the risk of cognitive decline among the general older adults remains uncertain.

Aims

To investigate the association between dietary thiamine intake and cognitive decline in cognitively healthy, older Chinese individuals.

Methods

The study included a total of 3106 participants capable of completing repeated cognitive function tests. Dietary nutrient intake information was collected through 3-day dietary recalls and using a 3-day food-weighed method to assess cooking oil and condiment consumption. Cognitive decline was defined as the 5-year decline rate in global or composite cognitive scores based on a subset of items from the Telephone Interview for Cognitive Status-modified.

Results

The median follow-up duration was 5.9 years. There was a J-shaped relationship between dietary thiamine intake and the 5-year decline rate in global and composite cognitive scores, with an inflection point of 0.68 mg/day (95% confidence interval (CI): 0.56 to 0.80) and a minimal risk at 0.60-1.00 mg/day of dietary thiamine intake. Before the inflection point, thiamine intake was not significantly associated with cognitive decline. Beyond the inflection point, each unit increase in thiamine intake (mg/day) was associated with a significant decrease of 4.24 (95% CI: 2.22 to 6.27) points in the global score and 0.49 (95% CI: 0.23 to 0.76) standard units in the composite score within 5 years. A stronger positive association between thiamine intake and cognitive decline was observed in those with hypertension, obesity and those who were non-smokers (all p<0.05).

Conclusions

This study revealed a J-shaped association between dietary thiamine intake and cognitive decline in cognitively healthy, older Chinese individuals, with an inflection point at 0.68 mg/day and a minimal risk at 0.60-1.00 mg/day of dietary thiamine intake.

L-shaped association between dietary zinc intake and cognitive decline in Chinese older people

BACKGROUND AND OBJECTIVE

The prospective association between dietary zinc (Zn) intake and cognitive decline remains uncertain. We aimed to assess the relationship of dietary Zn intake with the risk of cognitive decline in the Chinese older people, and examine the possible effect modifiers on this association.

METHODS

A total of 3,106 older Chinese adults aged 55 years or older from China Health and Nutrition Survey were included. Dietary nutrients intake information was collected by combined 24-h dietary recalls with weighing food inventory. The cognitive decline was defined as the 5-year decline rate in global and composite cognitive scores, based on a subset of items from the Telephone Interview for Cognitive Status-modified.

RESULTS

The median follow-up duration was 5.9 years. There was an L-shaped association between dietary Zn intake and the 5-year decline rates in global and composite cognitive scores, with an inflection point at 8.8 mg/day of dietary Zn. For the composite cognitive scores, compared with the first quantile (<7.9 mg/day) of dietary Zn intake, quantiles 2-6 (≥7.9 mg/day) had a significantly slower cognitive decline rate (β: -0.24; 95% confidence interval: -0.40 to -0.07). Similar results were found for the global cognitive scores. Moreover, the inverse association between dietary Zn intake and cognitive decline in composite cognitive scores was significantly stronger in those with lower levels of physical activity (P-interactions = 0.041).

CONCLUSION

Dietary Zn intake was negatively associated with cognitive decline in the older people. Maintaining appropriate dietary Zn levels may prevent cognitive decline.

Risk assessment of nutrients: There must be a threshold for their effects

Nutrients serve physiological functions in a dose-dependent manner and that needs to be recognized in risk assessment. An example of the consequences of not properly considering this can be seen in a recent assessment by the European Food Safety Authority (EFSA). EFSA concluded in 2022 that the intake of added and free sugars should be "as low as possible in the context of a nutritionally adequate diet". That conclusion of EFSA is based on the effects on two surrogate endpoints for an adverse effect found in randomized controlled trials with high sugars intake levels: fasting glucose and fasting triglycerides. The lowest intake levels in these trials were around 10 energy% and at this intake level there were no adverse effects on the two outcomes. This indicates that the adverse effects of sugars have an observable threshold value for these two endpoints. The most appropriate interpretation from the vast amount of data is that currently no definitive conclusion can be drawn on the tolerable upper intake level for dietary sugars. Therefore, EFSA's own guidance would lead to the conclusion that the available data do not allow the setting of an upper limit for added sugars and hence, that more robust data are required to identify the threshold value for intake of sugars.

Association Between Dietary Copper Intake and Cognitive Decline: A Perspective Cohort Study in Chinese Elderly

OBJECTIVE

The association between dietary copper (Cu) intake and cognitive decline remains uncertain. We aim to investigate the longitudinal association of dietary Cu with cognitive decline in Chinese elderly.

METHODS

A total of 3,106 Chinese adults aged older than or equal to 55 years from China Health and Nutrition Survey (CHNS) were included. Dietary nutrients information was collected by 24-hours dietary recalls in combination with a food-weighted method. The 5-year change rates in global or composite cognitive scores based on a subset of items from the Telephone Interview for Cognitive Status-modified (TICS-m) was calculated as the last-survey score minus the baseline score, then divided by the follow-up time (unit, years) and multiplied by five.

RESULTS

The median follow-up duration was 5.9 years. There was a nonlinear association of dietary Cu intake with the 5-year change rates in global or composite cognitive scores, with the inflection point at approximately 1.3 mg/day of dietary Cu intake. Accordingly, for the composite cognitive score, compared to the first quantile (<1.28 mg/day), those with dietary Cu in quantiles 2-8 (≥1.28 mg/day) had a significantly slower cognitive decline rate (B, 0.30; 95% CI, 0.13, 0.47). Similar results were found for the global cognitive score. Moreover, the inverse association between dietary Cu and cognitive decline was stronger in those with lower dietary fat intake and lower levels of physical activity (All p-interactions <0.05).

CONCLUSION

There was a nonlinear inverse association of dietary Cu intake with cognitive decline in the elderly, with an inflection point at approximately 1.3 mg/day of dietary Cu intake.

Dietary low- and high-quality carbohydrate intake and cognitive decline: A prospective cohort study in older adults

BACKGROUND & AIMS

The association of dietary intake of carbohydrate (CHO), especially high- and low-quality CHO, with the decline of cognitive function remains uncertain. We aimed to investigate the prospective association of dietary total, low- and high-quality CHO intake with cognitive decline, and further examine the effect of isocaloric substitution with protein or fat, in the elderly population.

METHODS

A total of 3106 Chinese participants aged ≥55 years from China Health and Nutrition Survey (CHNS) were included in this study. Dietary nutrient intake information was collected by 24-h dietary recalls on 3 consecutive days. The cognitive decline was defined as the 5-year decline rates in global or composite cognitive scores based on a subset of items from the Telephone Interview for Cognitive Status-modified (TICS-m).

RESULTS

The median follow-up duration was 5.9 years. There was a significantly positive association of dietary low-quality CHO (per 10 percentage energy [%E] increment, β, 0.06; 95%CI, 0.01-0.11) and a no significant association of dietary high-quality CHO (per 10%E increment, β, 0.04; 95%CI, -0.07-0.14) with the 5-year decline rate in the composite cognitive scores. Similar results were found for the global cognitive scores. In model simulations, substituting dietary low-quality CHO with isocaloric animal protein or fat, instead of isocaloric plant protein or fat, was significantly and inversely associated with cognitive decline (All P values < 0.05).

CONCLUSIONS

The dietary intake of low-quality CHO, rather than high-quality CHO, was significantly associated with a faster cognitive decline in the elderly. In model simulations, isocaloric substitution of dietary low-quality CHO with animal protein or fat, rather than plant protein or fat, was inversely associated with cognitive decline.

The Association between Maternal B Vitamins in Early Pregnancy and Gestational Diabetes Mellitus: A Prospective Cohort Study

Background: This study evaluated the association between maternal B vitamins in early pregnancy and gestational diabetes mellitus (GDM) risk. Methods: A cohort of 1265 pregnant women was recruited at 8−15 weeks of gestation in 2021−2022 (Shanghai, China). Pregnancies with both serum B vitamin measurements at recruitment and glucose measurements at 24−28 weeks of gestation were included in the final analysis. Results: Of the 1065 pregnancies, in the final analysis, GDM occurred in 121 women (11.36%). In multivariate logistic models, an increased risk trend across serum vitamin B1 quartiles with GDM was observed (p-Trend = 0.001). Compared with women in the lowest quartile of serum vitamin B6, those in the upper two quartiles had approximately twofold higher odds of GDM. Moreover, compared with women with vitamin B12 levels < 150 pmol/L, those with vitamin B12 levels > 150 pmol/L had lower odds of GDM (p = 0.005). The restricted cubic spline regression models also revealed that serum vitamin B6 and vitamin B12 were associated with an increased risk of GDM in a nonlinear fashion. Conclusions: Our study shows that higher maternal serum vitamin B1 and B6 levels in early pregnancy are associated with increased GDM risk, while sufficient vitamin B12 status is associated with lower GDM risk.