Researchers from the University of Warwick performed the first ever systematic review and meta-analysis looking at the association between blood levels of vitamin D and cardiometabolic disorders, such as cardiovascular disease (CVD), type-2 diabetes and metabolic syndrome.
Twenty-eight studies giving data on 99,745 participants across a variety of ethnic groups including men and women were included in the meta-analysis and systematic review, published in the journal Maturitas.
“If the relationship proves to be causal, interventions targeting vitamin D deficiency in adult populations could potentially slow the current epidemics of cardiometabolic disorders,” wrote the researchers, led by Johanna Parker and Dr Oscar Franco.
Potential public health importance
The study adds to a rapidly expanding body of science supporting the benefits of adequate vitamin D levels, which have seen leading scientists around the world call for increases in the daily intakes of the sunshine vitamin.
Such calls have led the US and Canadian governments to sponsor a review, to be conducted by the Institute of Medicine (IOM), of vitamin D and calcium that may lead to the establishment of higher recommended daily intakes.
In adults, it is said vitamin D deficiency may precipitate or exacerbate osteopenia, osteoporosis, muscle weakness, fractures, common cancers, autoimmune diseases, infectious diseases and cardiovascular diseases. There is also some evidence that the vitamin may reduce the incidence of several types of cancer and type-1 diabetes.
Parker and her co-workers reviewed the scientific literature and identified 28 observational studies, with the majority published between 2004 and 2009. No data from clinical trials was included.
According to the analysis, the highest blood levels of the vitamin were associated with a 33 per cent reduced risk of CVD, a 55 per cent reduction in the risk of type 2 diabetes, and a 51 per cent reduction in the risk of metabolic syndrome, compared with the lowest blood levels of vitamin D.
“We found that high levels of vitamin D among middle age and elderly populations are associated with a substantial decrease in cardiovascular disease, type 2 diabetes and metabolic syndrome,” said Dr Franco.
“Targeting vitamin D deficiency in adult populations could potentially slow the current epidemics of cardiometabolic disorders,” he added.
Before such recommendations can be made, however, the researchers noted that additional controlled trials are needed to investigate the association, as well as to test if vitamin D supplementation may reduce the risk of cardiometabolic disease.
Commenting on the potential mechanism, Dr Franco and his co-workers note that the underlying mechanism “is not fully understood”. Previous studies have reported a role for vitamin D in gene expression, with some proposing that the vitamin may enhance the production of a protein that reduced the build up of calcium in the arteries and, therefore, reduces the risk of arterial hardening. Anti-inflammatory roles for the vitamin have also been propsed, while other studies have reported a link between low vitamin D levels and blood pressure via the rennin–angiotensin system.
Data on D
Vitamin D refers to two biologically inactive precursors - D3, also known as cholecalciferol, and D2, also known as ergocalciferol. The former, produced in the skin on exposure to UVB radiation (290 to 320 nm), is said to be more bioactive.
While our bodies do manufacture vitamin D on exposure to sunshine, the levels in some northern countries are so weak during the winter months that our body makes no vitamin D at all, meaning that dietary supplements and fortified foods are seen by many as the best way to boost intakes of vitamin D.
Volume 65, Issue 3, Pages 225-236
“Levels of vitamin D and cardiometabolic disorders: Systematic review and meta-analysis”
Authors: J. Parker, O. Hashmi, D. Dutton, A. Mavrodaris, S. Stranges, N.-B. Kandala, A. Clarke, O.H. Franco