Source: Clifford Rosen, MD Viamin D. Myths and Realities. How does it work? VuMedi Jan 18, 2021 VuMedi Talk 1 Talk 2 Talk 3
Individuals with darker skin produce less D.
Measuring vitamin-D might be unreliable in African American patients. According to a 2013 new England Journal of Medicine article, levels of both total 25-hydroxyvitamin D and vitamin D–binding protein were lower in blacks than in whites (total 25-hydroxyvitamin D, 15.6±0.2 ng per milliliter vs. 25.8±0.4 ng per milliliter, P<0.001; vitamin D–binding protein, 168±3 μg per milliliter vs. 337±5 μg per milliliter, P<0.001). Genetic polymorphisms independently appeared to explain 79.4% and 9.9% of the variation in levels of vitamin D–binding protein and total 25-hydroxyvitamin D, respectively. BMD was higher in blacks than in whites (1.05±0.01 g per square centimeter vs. 0.94±0.01 g per square centimeter, P<0.001). Levels of parathyroid hormone increased with decreasing levels of total or bioavailable 25-hydroxyvitamin D (P<0.001 for both relationships), yet within each quintile of parathyroid hormone concentration, blacks had significantly lower levels of total 25-hydroxyvitamin D than whites. Among homozygous participants, blacks and whites had similar levels of bioavailable 25-hydroxyvitamin D overall (2.9±0.1 ng per milliliter and 3.1±0.1 ng per milliliter, respectively; P=0.71) and within quintiles of parathyroid hormone concentration. Community-dwelling black Americans, as compared with whites, had low levels of total 25-hydroxyvitamin D and vitamin D–binding protein, resulting in similar concentrations of estimated bioavailable 25-hydroxyvitamin D. Racial differences in the prevalence of common genetic polymorphisms provide a likely explanation for this observation. [6]
Observational studies suggested lower risk with D supplementation. Randomized trial showed Taking 2000 units D for 5 years did not lower cancer risk. 12,944 people took D vs placebo. [1]
Taking D for 5 years did not lower risk of MI or stroke. [1]
VIt D is lower in higher BMI [2]
Vit D deficient individuals (10-15 ng/mL) might have slightly higher risk of blood clot in a vein i.e. venous thromboembolism (VTE). Data biased by patients with lower D being less mobile.
No randomized trials. Some data predict Covid incidence with Vit D levels. Level <20 had more Covid. Most were Afr American and more obese as they have lower Vit D.
Those with less than 30 mg/mL had 12x risk of dying. 30% risk of low O2. [3]
Prevention
800 units a day is adequate. Increasing the dose doesn't help much.
Psoriaisis
In a trial of 122 participants with psoriasis and low vitamin D, 60 got vitamin D supplements and 62 got placebo. Psoriasis did not improve significantly in either group though it was of relatively low severity to begin with so might be hard to show difference. [4]
Dentition and D
In a 6-year follow-up of a double-blind randomized clinical trial that included 623 pregnant women, high-dose vitamin D supplementation during third trimester was associated with reduced odds of enamel defects in the offspring by approximately 50%. No associations with caries were observed. Prenatal high-dose vitamin D supplementation may be a clinically relevant preventive intervention for enamel defects. [5]
