The fast spread of the coronavirus disease 2019 (COVID-19) epidemic and its high mortality were quickly noticed by the health community. B vitamins are essential micronutrients for the body with antioxidant, anti-inflammatory and immune-regulating properties. The present study can provide a comprehensive picture of the associations between B vitamins and COVID-19 incidence. This study was undertaken on 9189 adult participants of the Yazd Health Study (YaHS) and Taghzieh Mardom-e-Yazd (TAMIZ) study aged 20 to 69 years. Data on dietary intakes were obtained using a validated FFQ. Multivariable logistic regression analysis was used to evaluate the association between B vitamins and COVID-19. Our findings indicated that participants in the fourth quartile of vitamin B5 intake compared with the first quartile had a protective effect against COVID-19 (OR: 0·53, 95 % CI 0·28, 0·99, P-trend = 0·02) after adjustment for all possible confounds in model 3. In addition, participants in the third quartile of vitamin B12 intake compared with the first quartile (OR: 0·63, 95 % CI 0·40, 0·98, P-trend = 0·11) had fewer odds of COVID-19 after full adjustments for confounders. Our findings indicated no significant relationship between dietary intake of vitamin B1, B2, B3, B9 and B-complex and COVID-19. A higher intake of vitamin B5 could reduce the odds of COVID-19 by 47 %, and a moderate intake of vitamin B12 had a protective effect on COVID-19. Although our study has promising results, stronger clinical studies are needed.

The vitamin status of a child depends on many factors and most of the clinical studies do not take into account the different access to adequate nutrition of children coming from different countries and the consequent major differences in micronutrients or vitamin deficits between low-income and high-income countries. Vitamin supplements are included in the general field of dietary supplements. There is a large amount of not always factual material concerning vitamin supplements, and this may sometimes create confusion in clinicians and patients. Inadequate information may lead to the risk of attributing beneficial properties leading to their over-use or misuse in the paediatric field. Vitamin supplementation is indicated in all those conditions in which a vitamin deficiency is found, either because of a reduced intake due to reduced availability of certain foods, restrictive diets or inadequate absorption. The lack of guidelines in these fields may lead paediatricians to an improper use of vitamins, both in terms of excessive use or inadequate use. This is due to the fact that vitamin supplementation is often intended as a therapy of support rather than an essential therapeutic tool able to modify disease prognosis. In fact, various vitamins and their derivatives have therapeutic potential in the prevention and treatment of many diseases, especially in emerging conditions of paediatric age such as type 2 diabetes and the metabolic syndrome. The aim of the present article is to analyse the state of the art and consider new perspectives on the role of vitamin supplements in children.

Recent studies have shown that micronutrients are involved in the pathology of type 2 diabetes. Antioxidant effects of vitamins C and B2 and homocysteine-lowering effects of vitamins B6, folate and B12 may have protective roles. However, a few reports have investigated the association between dietary water-soluble vitamin intakes and risk of diabetes. In a prospective study encompassing 19 168 healthy Japanese men and women aged 40–79 years, we examined the associations between dietary intakes of water-soluble vitamins, determined by a validated self-administered FFQ, with the risk of 5-year cumulative incidence of type 2 diabetes by using the logistic regression model. Within the 5-year period, there were 494 self-reported new cases of diabetes. Higher dietary intakes of vitamins C, B2 and folate were associated with lower risk of incident diabetes only in women, whereas no associations of dietary intakes of vitamins B1, B3, B5, B6 and B12 were observed in either sex. The multivariable OR in the highest v. the lowest quartile of intakes among women were 0·61 (95 % CI 0·44, 0·94; P-trend = 0·04) for vitamin C, 0·56 (95 % CI 0·34, 0·93; P-trend = 0·03) for vitamin B2 and 0·70 (95 % CI 0·46, 0·98; P-trend = 0·03) for folate. Other than that for sex (P < 0·05), the P-interactions with age, BMI, smoking status or having a family history of diabetes were >0·10. In conclusion, higher dietary intakes of vitamins C, B2 and folate, but not other water-soluble vitamins, were associated with reduced risk of type 2 diabetes in Japanese women.

Experimental studies suggest that B vitamins such as niacin, folate, riboflavin, vitamin B6 and vitamin B12 may protect against DNA damage induced by ionising radiation (IR). However, to date, data from IR-exposed human populations are not available. We examined the intakes of these B vitamins and their food sources in relation to the frequency of chromosome translocations as a biomarker of cumulative DNA damage, in eighty-two male airline pilots. Dietary intakes were estimated by using a self-administered semi-quantitative FFQ. Translocations in peripheral blood lymphocytes were scored by using fluorescence in situ hybridisation whole-chromosome painting. Negative binomial regression was used to estimate rate ratios and 95 % CI, adjusted for age and occupational and lifestyle factors. We observed a significant inverse association between translocation frequency and dietary intake of niacin (P = 0·02): adjusted rate ratio for subjects in the highest tertile compared with the lowest tertile was 0·58 (95 % CI 0·40, 0·83). Translocation frequency was not associated with total niacin intake from food and supplements as well as dietary or total intake of folate, riboflavin or vitamin B6 or B12. However, the adjusted rate ratios were significant for subjects with ≥ median compared with < median intake of whole grains (P = 0·03) and red and processed meat (P = 0·01): 0·69 (95 % CI 0·50, 0·96) and 1·56 (95 % CI 1·13, 2·16), respectively. Our data suggest that a high intake of niacin from food or a diet high in whole grains but low in red and processed meat may protect against cumulative DNA damage in IR-exposed persons.

Numerous case–control and prospective studies have identified elevated plasma homocysteine as a strong independent risk factor for cerebovascular, cardiovascular and peripheral vascular disease. Homocysteine is formed as a result of the breakdown of the dietary amino acid methionine. Once formed, homocysteine is either remethylated to methionine, or undergoes a trans-sulfuration reaction to form cysteine. The re-methylation of homocysteine to methionine is dependent on three B-vitamins, i.e. riboflavin, vitamin B12 and folate. The second pathway of homocysteine metabolism is the trans-sulfuration pathway which requires both vitamin B6 and riboflavin for its activity. Thus, up to four B-vitamins are required for intracellular homocysteine metabolism. Many studies have noted strong inverse relationships between homocysteine levels and the status of both vitamin B12 and folate. However, the relationship between vitamin B6 status and homocysteine is still uncertain. Similarly, numerous intervention studies have demonstrated effective lowering of homocysteine levels as a result of folate and vitamin B12 supplementation, while the homocysteine-lowering ability of vitamin B6 is unclear. Even though riboflavin plays a crucial role in both the trans-sulfuration and remethylation pathways of homocysteine metabolism, the relationship between riboflavin status and homocysteine levels has not been investigated. The exact mechanism that explains the vascular toxicity of elevated homocysteine levels is unknown at present, studies indicate that it is both atherogenic and thrombogenic. To date, no randomized clinical trial has demonstrated that lowering of homocysteine levels is beneficial in terms of reducing the prevalence of vascular disease. It is probable, however, that optimal B-vitamin status is important in the prevention of vascular disease.