Common Clinical Topic: Vitamin D

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Experts have suggested that interest in vitamin D supplementation is so strong that it appears to be impervious to evidence. However, research continues into the relationship between various nutrients and health conditions. Recent findings examined links to diabetes, obesity, breast cancer, and COVID. The interest in these studies has led to vitamin D once again becoming the most popular clinical topic of the week. Among the highlights was a new study that replicated an old finding (see chart below).


The new results come from a prospective trial of diabetes prevention with vitamin D (DPVD) in more than 1,200 Japanese participants with impaired glucose tolerance. The data suggest that vitamin D supplementation also failed to improve the rate of regression to blood glucose compared to placebo. In an accompanying editorial, Tatiana Christids, MD, writes that the new trial “was well conducted, with specific, rigorously tested diagnostic criteria, and of sufficient duration, but perhaps too poor to detect a small effect.” She points to a recent meta-analysis of intervention trials, which found a significant 10% reduction in the risk of developing type 2 diabetes with vitamin D supplementation. Christids adds that this was “a difference too small to detect with the new trial…Although the 10% risk reduction is modest, it may be valuable at a population level and warrant further study.”

A separate study, not yet peer-reviewed, found that 25-hydroxyvitamin D (25[OH]D) were inversely associated with glucagon levels and correlated peptide (C-peptide) levels in 4,670 Chinese patients with type 2 diabetes and abdominal obesity. The lowest quartile had 25(OH)D levels ≤ 30.79 ng/mL; The highest quartile had levels ≥ 48.92 ng/mL. Among patients with type 2 diabetes without Abdominal obesity, vitamin D levels were inversely and significantly associated with fasting plasma glucose, A1c, glucagon, and beta cell function, after adjusting for multiple variables. Among patients with type 2 diabetes with Abdominal obesity, vitamin D levels were inversely and significantly associated with A1c, glucagon, fasting insulin, fasting C-peptide, and insulin resistance. In patients with short-term type 2 diabetes in addition to abdominal obesity, those with higher levels of vitamin D had a lower ratio of glucagon to C-peptide; This means that they had a better balance of alpha cells and beta cells than cells with lower levels.

Another study involving vitamin D and weight, which has not yet been peer-reviewed, found that men who were overweight or obese were significantly more likely to have inadequate 25(OH)D levels <20 ng/ml (50). nmol/L) regardless of demographic and lifestyle factors. This was not seen among women. Compared with men of normal weight, men who were overweight were more likely to have vitamin D deficiency (adjusted odds ratio). [OR]1.2; s = .03), as well as obese men (odds rate, 1.4; s = .001), after adjusting for age, gender, place of residence, education, physical activity, alcohol consumption, and smoking.

Vitamin D deficiency has also recently been linked to breast cancer risk in Hispanic and black women. Vitamin D levels were measured from blood samples in 290 black/African American women and 125 non-Hispanic/Latino black women who had had breast cancer as well as 1,084 black/African American women and 461 Hispanic women. Latinas who have not had breast cancer. Over a median follow-up of 9.2 years, women with 25(OH)D (20 ng/mL) had a 21% lower rate of breast cancer than women with concentrations below this cut-off point, although the result was less than Statistics importance (hazard ratio [HR], 0.79; 95% CI, 0.61-1.02). The inverse association was stronger in Hispanic/Hispanic women (HR, 0.52; 95% CI, 0.29–0.93), with a weaker association in African American/Black women (HR, 0.89; 95% CI, 0.68–1.18; s for heterogeneity = .13).

Earlier this year, vitamin D deficiency was also associated with an increased likelihood of severe or dangerous COVID-19 infection. In a study based on data from the first two waves of COVID in Israel, patients with vitamin D deficiency were 14 times more likely to become seriously ill or seriously ill. The mortality rate among those without vitamin D deficiency was 25.6%, compared to 2.3% among those with adequate levels. These differences were consistent even after the researchers controlled for age, sex, and history of chronic disease. Health officials in many countries have recommended vitamin D supplements during the pandemic.

From deficiency to supplementation, vitamin D research is always an incredibly popular area. With a wealth of recent research, it’s no wonder the topic has once again become the most popular medical topic of the week.

Learn more about vitamin D deficiency.

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