(HealthDay News) – Serum 25-hydroxyvitamin D (25[OH]D) seems to be a marker of ill health and not a causal factor, according to a review published online Dec. 6 in The Lancet Diabetes & Endocrinology.
Philippe Autier, MD, from the International Prevention Research Institute in Lyon, France, and colleagues conducted a systematic review of prospective and intervention studies that assessed the effect of 25(OH)D concentrations on non-skeletal health outcomes. Two hundred ninety prospective studies and 172 randomized trials of major health outcomes were included.
The researchers found that in most prospective studies, moderate to strong inverse associations were seen between 25(OH)D concentrations and health outcomes, including cardiovascular diseases, serum lipid concentrations, inflammation, glucose metabolism disorders, infectious diseases, multiple sclerosis, declining cognitive function, impaired physical functioning, and all-cause mortality. With the exception of colorectal cancer, high 25(OH)D concentrations were not associated with a lower risk of cancer. In intervention studies, vitamin D supplementation had no effect on disease occurrence. Results were no better in 34 intervention studies involving supplementation for 2,805 individuals with baseline serum 25(OH)D concentration <50nmol/L. All-cause mortality was slightly reduced in elderly people with 20µg vitamin D per day supplementation.
“Associations between 25(OH)D and health disorders reported by investigators of observational studies are not causal,” the authors write. “Low 25(OH)D could be the result of inflammatory processes involved in the occurrence and progression of disease.”