Low blood levels of vitamin D have again been linked to lower survival in the elderly – a study which strengthens calls to confirm if vitamin D supplements could offer protection.

Writing in the journal Clinical Endocrinology, scientists from the Netherlands, Austria, and the US report that low blood levels of the sunshine vitamin are associated with increased risk of all-cause mortality, and mortality from heart disease.

“Our results provide a rationale for future studies to test whether vitamin D supplementation reduces mortality and/or cardiovascular diseases in persons with vitamin D deficiency,” wrote the researchers, led by Stefan Pilz from the Medical University of Graz in Austria

“These studies are urgently needed to answer the question whether vitamin D deficiency is a cause or a consequence of a poor health status,” they added.

Snowballing science

The research follows hot on the heels of similar findings published in Nutrition Research by scientists led by Richard Semba from the Johns Hopkins University. The researchers looked at vitamin D levels in the form of 25- hydroxyvitamin D (25(OH)D), , in 714 community-dwelling women, aged between 70 and 79 years, participating in the Women's Health and Aging Studies I and II.

Semba and his co-workers noted that several biologic mechanisms could explain a causal relationship between vitamin D deficiency and mortality, with the vitamin’s active form (1,25-dihydroxyvitamin D) linked to a range of effects including control of inflammatory compounds, regulating immune health and blood pressure, or reducing arterial hardening.

Prior to this, a study published in the Archives of Internal Medicine grabbed headlines around the world when it reported that . This earlier study used data from 13,331 men and women participating in the Third National Health and Nutritional Examination Survey (NHANES III).

New data

The new study used data from 614 people participating in the Hoorn Study, a prospective population-based study with men and women with an average age of 69.8. Blood levels of 25(OH)D were measured at the start of the study.

After an average of six years of follow-up, 51 deaths had been documented, 20 of which were due to cardiovascular health.

People with the lowest average vitamin D levels (30.6 nanomoles per litre) were found to be at a 124 and 378 per cent increased risk of all-cause mortality and cardiovascular mortality, respectively.

Commenting on the potential mechanism, the researchers note: “Apart from the maintenance of muscular and skeletal health, vitamin D may also protect against cancer, infections, autoimmune and vascular diseases, suggesting that vitamin D deficiency might contribute to a reduced life expectancy.”

D details

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.

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.

Source: Clinical Endocrinology

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November 4, 2009