5C. Oral Communication

Iodine is an essential micronutrient and an integral part of the thyroid hormones. In women of childbearing age, the estimated average iodine requirement is 95 µg/day and the recommended daily intake is 150 µg/day. While severe iodine deficiency poses reproductive risks, including infertility and abortions, the potential impact of mild-to-moderate iodine deficiency on subfecundity is unknown. 

We examined whether iodine intake was associated with risk of subfecundity (i.e. >12 months trying to get pregnant) in a large cohort of mild-to-moderately iodine deficient women. 

Women enrolled in the Norwegian Mother and Child Cohort Study in gestational week 15 were asked to report whether the pregnancy was planned and how many months the couple had sexual relations without any contraception before getting pregnant. Information about time to pregnancy, maternal characteristics and iodine intake was available for 56,416 planned pregnancies. The median (interquartile range) time to pregnancy was 1.5 (0.5-6.0) months and the prevalence of subfecundity was 10.8%). We used iodine intake assessed by a validated food frequency questionnaire administered in pregnancy as a proxy for long-term (pre-pregnancy) iodine intake. We used logistic regression to estimate the association between iodine intake and subfecundity, using flexible modelling with restricted cubic splines, and adjusted for maternal age, BMI, parity, education, smoking status, energy intake and fiber intake. The median calculated iodine intake was 121 µg/day and the median urinary iodine concentration in a subsample of n=2795 women was 69 µg/L.

The prevalence of subfecundity was lowest for iodine intakes ~100 µg/day and increased at lower intakes (p overall=0.005). Compared to an intake of 100 µg/day (reference), intakes ~75 µg/day was associated with 5% (95%CI: 1%, 9%) higher prevalence and intakes ~50 µg/day with 14% (95%CI: 4%, 26%) higher prevalence. Use of dietary supplements was recorded only for the last 6 months prior to conception and women were included in the analysis regardless of their reported supplement use. In a sensitivity analysis, we excluding women who reported iodine-containing supplement use in the period 26-9 weeks before conception and the result remained unchanged. We also modelled time to pregnancy by Cox regression, and the result was consistent with the result for subfecundity.   

The only good dietary sources of iodine in Norway are milk and white fish, and many women of fertile age have low intakes of these food items. This study shows that low habitual iodine intake may be a risk factor for subfecundity.

Marianne H. Abel is employed by a Norwegian dairy company (TINE SA), and she participates in this project as an industrial Ph.D.-student financed partly by the dairy company and partly by The Research Council of Norway. This project is designed, owned and administered by The Norwegian Institute of Public Health and analysis of the data follow from protocol. All results of analysis in the project are to be published regardless of the results. The other authors have no conflicts of interest.

Background 

Low 25-hydroxyvitamin D (25(OH)D) has been linked with adverse health outcomes, including cancer, cardiovascular disease and mortality. The Irish Longitudinal Study on Ageing (TILDA) has previously shown that 13.1% of the Irish population over 50 are deficient in 25(OH)D, after adjusting for seasonality. The aim of this study is to assess whether low 25(OH)D concentrations are associated with all-cause mortality in the over 50s in Ireland.

Methods 

Data from Wave 1 (2009-2011) of TILDA, a prospective population representative study of community dwelling adults aged over 50, were used. Blood was obtained during the health assessment, and analysis of 25(OH)D was performed. Mortality was confirmed through official death records, and all participant deaths between baseline and March 2017 were included. Logistic regression assessed whether baseline levels of 25(OH) D, both continuous and categorised into deficient (25(OH)D < 30 nmol/l), insufficient (30<= 25(OH)D < 50 nmol/l) or sufficient (25(OH)D >= 50 nmol/l), are associated with mortality.

Results 

Of the 8,175 over 50s recruited, 25(OH)D data was available for 5,388 participants. Of these, 366 individuals had died prior to March 2017. Higher concentrations of 25(OH)D were associated with lower odds of mortality (OR 0.70; 95% CI 0.60, 0.81, p-value), controlling for confounders. On categorising 25(OH)D, those with insufficient 25(OH)D concentrations had higher odds of mortality than those with sufficient levels (OR 2.04; 95% CI 1.48, 2.8; p-value <0.001). Stratifying between men and women, there was no gender difference in this association.

Conclusion 

Insufficient baseline 25(OH)D concentrations are associated with an increased odds of all-cause mortality in community dwelling adults over 50 in Ireland. Further research evaluating whether treatment of vitamin D deficiency improves mortality is warranted.

There is no conflict of interest

Given the increasing number of individuals afflicted by mental health problems, nutritional interventions may represent a realistic method to reduce the incidence of mental illness and provide psychological benefits. The B vitamin family has been studied extensively in clinical settings to redress frank clinical deficiencies, typically as adjunct therapy. Less well understood is the potential benefits of B vitamin treatment for mood in ‘at-risk’ populations, i.e. those with suboptimal, but non-clinical, nutrient and/or psychological status.  We therefore undertook a systematic review and meta-analysis to examine and quantify the effects of B vitamin supplementation on mood outcomes in cohorts drawn from both healthy and ‘at-risk’ populations. A systematic search of all available RCTs was conducted up to January 2019 in the following databases; Medline, Scopus and PsycINFO. Studies involving a daily supplement containing ≥3 B group vitamins with an intervention period of at least 4 weeks were included in the review. Random effects models for standardised mean difference was used to test for overall effect. Heterogeneity was tested using I² statistic on all models.

Eighteen articles (16 trials, 2015 participants) were included in the present review, of which 12 were deemed eligible for meta-analysis. Eleven of the 18 articles reported a positive effect for active treatment over placebo for overall mood or a facet of mood. Of the eight studies using ‘at-risk’ participants, five found a significant benefit to mood. Two extreme outliers compromised the meta-analysis by causing unacceptably high heterogeneity (I² = 95%), these were removed. When examining the facets of mood, meta-analysis revealed that providing a supplement containing B vitamins resulted in decreased stress (n=958, SMD= 0.23, 95% CI= 0.02, 0.45, p= .03). The positive effect on depressive symptoms did not reach statistical significance (n=568, SMD= 0.15, 95% CI= -0.01, 0.32, p= .07). There was no evidence of benefits to anxiety (n=562, SMD= 0.03, 95% CI= -0.13, 0.20, p= .71).

The present review provides evidence for the benefit of B vitamin supplementation in healthy and at-risk populations for stress, but not for depressive symptoms nor anxiety. Given B vitamins are water soluble and well-tolerated, the potential for B vitamins to redress nutritional deficiencies not met through diet is promising and offers a preventative approach to maintain mood. B vitamin supplementation may particularly benefit populations who are at risk due to 1) poor nutrient status or 2) poor mood outcomes.

This work was partly funded by Bayer Healthcare.