Optimal levels of vitamin D – defined as having blood levels of 25-hydroxyvitamin D (25[OH]D) of at least 75 nmol/L – were associated with a 66% reduction in the risk of cardiovascular disease mortality, compared with people with severe vitamin D deficiency.
In addition, so-called all-cause mortality was reduced by 75% in people with optimal vitamin D levels.
The study – published in this month’s edition of Diabetes Care – is said to be the first to show a link between optimal vitamin D and a significant reduction in the risk of all-cause and cardiovascular mortality in subjects with the metabolic syndrome.
“We hope these findings will spur interventional randomized, controlled trials to confirm the effects of vitamin D on mortality and, if positive, help establish recommendations for supplementation in these subjects,” wrote the authors, led by Neil Thomas from the University of Birmingham, England.
Metabolic syndrome (MetS) is a condition characterized by central obesity, hypertension, and disturbed glucose and insulin metabolism. The syndrome has been linked to increased risks of both type-2 diabetes and cardiovascular disease (CVD).
Fifteen per cent of adult Europeans are estimated to be affected by MetS, while the US statistic is estimated to be a whopping 32 percent. Obesity is established to be the main risk factor for MetS.
Vitamin D refers to two biologically inactive precursors - D3, also known as cholecalciferol, and D2, also known as ergocalciferol.
Both D3 and D2 precursors are transformed in the liver and kidneys into 25- hydroxyvitamin D (25(OH)D), the non-active 'storage' form, and 1,25-dihydroxyvitamin D (1,25(OH)2D), the biologically active form that is tightly controlled by the body.
Vitamin D deficiency in adults is reported to 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.
Dr Thomas and his co-workers analyzed data from the Ludwigshafen Risk and Cardiovascular Health (LURIC) cohort of 1,801 people with the metabolic syndrome. Blood samples were taken at the start of the study and the participants were followed for an average of 7.7 years.
Over the course of the study 462 deaths were recorded. Results showed that people with optimal levels of 25(OH)D had substantially reduced risk of all-cause and cardiovascular disease mortality of 75% and 66%, respectively.
“For specific cardiovascular disease mortality, there was a strong reduction for sudden death (85% reduction) and congestive heart failure (76% reduction), but not for myocardial infarction,” they said.
Commenting on the potential mechanism, the researchers said that vitamin D is known to affect blood sugar regulation, and that low vitamin D levels have been linked to increased insulin resistance.
In addition, other studies have indicated that the sunshine vitamin may also protect the walls of blood vessels via anti-inflammatory effects.
The other researchers were affiliated with Heidelberg University (Germany), the Medical University of Graz (Austria), and Ulm University (Germany).
Source: Diabetes Care
May 2012, Volume 35, Pages 1158-1164, doi:10.2337/dc11-1714
“Vitamin D Levels Predict All-Cause and Cardiovascular Disease Mortality in Subjects With the Metabolic Syndrome: The Ludwigshafen Risk and Cardiovascular Health (LURIC) study”
Authors: G.N. Thomas, B. ó Hartaigh, J.A. Bosch, S. Pilz, A. Loerbroks, M.E. Kleber, J.E. Fischer, T.B. Grammer, B.O. Böhm, W. Marz