B vitamins are important mediators of immune function and deficiency can increase susceptibility to infections. Covid-19 severity is dependent on the robustness of individual immune systems and therefore it was hypothesised that adequate B vitamin intake could reduce virus risk.
This theory is supported by a previous study that found B6 deficiency in 42.5% of Covid-19 patients and another that observed remedial effects of cobalamin (B12).
“Nutrition and dietary components as modifiable factors can play a bilateral role in strengthening or weakening the immune system. Diet is also proposed as a potentially responsible factor for differences in COVID-19 death rates between and within countries,” say the authors of the current study, published in 'The British Journal of Nutrition'.
“B vitamins are not synthesised in the human body. So, they must be consumed regularly in the diet. Many body functions, including energy production, methylation, synthesis, DNA repair, and enzyme functions, depend on B vitamins’ functions.”
To analyse the association between B vitamins and Covid-19, researchers recruited 9,189 adults aged 20-69 years, of which 48.5% were men. Dietary information was extracted from the TAMIZ study on changing consumer dietary habits and incidence of chronic disease and associated risk factors from the YAHS study.
Covid-19 incidence was determined through PCR tests and serologic assays were used to estimate immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies in symptomatic or asymptomatic Covid subjects.
Dietary intake was assessed with a food frequency questionnaire (FFQ) covering one year and included all food groups. A questionnaire was also used to assess level of daily physical activity.
Subjects were divided into four quartiles based on B vitamin intake, with the first comprising those with the lowest intake and used as a reference. Subjects in the second quartile reported low intake, the third moderate intake, and the fourth high intake.
B vitamin activity
The authors note that dietary intake of vitamin B5 demonstrated the highest protective association with Covid-19 and corresponded to a significant reduction in odds.
“The protective effect of vitamin B5 may partially be explained by its involvement in immune response as well as its anti-inflammatory properties. Vitamin B5 boosts macrophage maturation, increases macrophage phagocytosis, and promotes Th1 and Th17 cell differentiation,” they say.
Moderate vitamin B12 also reduced the odds of Covid-19, compared to the lowest quartile, but there was no significant relationship between vitamins B1, B2, B3, B9, B-complex and Covid-19.
In subgroup gender analysis, the researchers note high intake of vitamin B6 in women and moderate intake by men lowered the odds of infection after adjusting for confounders and compared to the lowest quartile. High intake of B5 and B7 also reduced the odds for men.
Only subjects with a BMI less than 25 and consuming high B7 and B12 displayed lower Covid-19 odds, in subgroup BMI analyses, although high B6 was effective for those with a BMI greater than 25.
The authors maintain that modifying effects of BMI, gender, and chronic disease status on virus incidence offer further proof that men with a high BMI are at greater disease and mortality risk and reinforce the benefit of vitamin B9 for vulnerable individuals with at least one chronic disease.
Tests revealed low virus odds with high vitamin B9 and B-complex where subjects presented with at least one chronic disease, compared to the lowest quartile, and moderate consumption of B7 and B12 reduced the odds in subjects with no chronic disease.
The inverse association with moderate consumption on subjects with no chronic disease “indicate that each micronutrient in its optimal amount can have protective effects, and not necessarily the higher the intake the lower the disease”, they comment.
It may also be explained by the influence of B vitamins on a variety of biological functions, and particularly proper activation of innate and adaptive immune responses.
“Considering the beneficial effects of B vitamins in reducing COVID-19 risk and the possibility of disruption in intestinal production of B vitamins, dietary intake of these vitamins needs more attention,” they authors conclude.
Source: The British Journal of Nutrition
Published online: http://doi.org/10.1017/S0007114522003075
‘The association between B vitamins and the risk of Covid-19’
Authors: Mina Darand, Shirin Hassanizadeh, Fahime Martami, Shamim Shams-rad, Masoud Mirzaei, Mahdieh Hosseinzadeh