Compared to people with optimal vitamin D status, those with low vitamin D levels were three times more likely to die from heart disease and 2.5 times more likely to die from any cause, according to results of a study with 3,400 Americans.
“Current dosage recommendations for vitamin D supplementation appear to be inadequate in most older adults to support these higher [vitamin D] levels that are associated with optimal general health and reduced mortality,” wrote the researchers in the Journal of the American Geriatrics Society.
The dangers of insufficient D
Concerns are growing over the health implications of living with insufficient and deficient vitamin D levels. A recent study from China reported that 94 per cent of people aged between 50 and 70 enrolled in the study were vitamin D deficient or insufficient, which may increase their risk of metabolic syndrome.
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.
Lead author of the study Adit Ginde, MD, MPH, from the University of Colorado Denver School of Medicine said: "It's likely that more than one-third of older adults now have vitamin D levels associated with higher risks of death and few have levels associated with optimum survival.
"Given the aging population and the simplicity of increasing a person's level of vitamin D, a small improvement in death rates could have a substantial impact on public health."
In the US and Canada, where no specific recommendations exist for pregnant women, adequate intakes are inline with the general population and set at 5 micrograms per day (200 International Units).
Study details
Ginde and co-workers analyzed data from 3,488 people aged 65 and old participating in the Third National Health and Nutrition Examination Survey conducted by the National Center for Health Statistics. The subjects were enrolled between 1988 and 1994 and followed until 2000.
After an average of 7 years of follow-up, 1,493 deaths were documented, 767 of which were due to cardiovascular disease. Compared to those with optimal vitamin D status (at least 100 nanomoles of 25(OH)D, the storage form of vitamin D), those with low vitamin D levels (25 nanomoles of 25(OH)D) were 3 times more likely to die from heart disease and 2.5 times more likely to die from any cause.
Dr. Ginde said that the findings suggest that current daily recommendations of vitamin D may not be enough for older adults to maintain optimal health. The team has applied for funding from the National Institutes of Health (NIH) to perform a large, population-based clinical trial of vitamin D supplementation in older adults to see if it can improve survival and reduce the incidence of heart disease.
A role for fish?
Commenting independently on the study June Davison, a senior cardiac nurse at the UK charity the British Heart Foundation told NutraIngredients that while an association is shown between vitamin D levels and heart and circulatory disease and all-cause mortality, more “research is needed in this area before we can assume a casual effect”, she said.
“Oily fish is a good source of vitamin D, so it's another reason to eat at least one portion a week to help keep your heart healthy,” she added.
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.
Source: Journal of the American Geriatrics Society
September 2009, Volume 57, Issue 9, Pages: 1595-1603
“Prospective Study of Serum 25-Hydroxyvitamin D Level, Cardiovascular Disease Mortality, and All-Cause Mortality in Older U.S. Adults”
Authors: A.A. Ginde, R. Scragg, R.S. Schwartz, C.A. Camargo Jr.