Vitamin D may help slow down the ageing process, scientists have found, adding further weight to the importance of adequate intake of the vitamin.
Researchers from King's College, London, measured telomeres - part of a chromosome which shortens with age - in more than 2,000 women and found those who had higher levels of the vitamin in their body had longer telomeres.
Writing in the American Journal of Clinical Nutrition, the scientists looked at 2,160 women aged 18 to 79 years and measured leukocyte telomere length (LTL). LTL is a predictor of ageing-related disease and decreases with each cell cycle and increased inflammation, the scientists said.
Scientists measured concentrations of 25-hydroxyvitamin D (the 'storage' form of vitamin D) and found a link between increased concentrations and telomere length.
They found that after taking into account the age of the volunteer, women with higher levels of vitamin D were more likely to have longer telomeres.
They wrote: "The difference in LTL between the highest and lowest tertiles of vitamin D was 107 base pairs, which is equivalent to five years of telomeric ageing. This difference was further accentuated by increased concentrations of C-reactive protein, which is a measure of systemic inflammation."
The team concluded that higher vitamin D concentrations, which are "easily modifiable through nutritional supplementation", are associated with longer LTL, which underscores the potentially beneficial effects of vitamin D on ageing and age-related diseases.
Lead researcher Dr Brent Richards said: "These results demonstrate for the first time that people who have higher levels of vitamin D may age more slowly than people with lower levels of vitamin D.
"This could help to explain how vitamin D has a protective effect on many ageing related diseases, such as heart disease and cancer. Further studies are required to confirm these findings."
They also found that out of the women tested, 700 already took vitamin D supplements, and had longer telomeres than those who did not.
However, the scientists gave no indication of what levels of supplementation would be needed to achieve these results.
The scientific community has already called for an increase in the recommended level of vitamin D intake.
Currently, the recommended daily intake is set at 400 IU, and the tolerable upper intake level (UL) in Europe and the US is set at 2000 International Units (IU), equivalent to 50 micrograms per day. Research, particularly from clinical trials, suggests that this should be raised.
A recent risk assessment by the US-based trade organisation, the Council for Responsible Nutrition (CRN) concluded that the UL could be raised to 10,000 IU (250 micrograms per day).
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. The latter is derived from plants and only enters the body via the diet.
Both D3 and D2 precursors are hydroxylated in the liver and kidneys to form 25- hydroxyvitamin D, the non-active 'storage' form, and 1,25-dihydroxyvitamin D, the biologically active form that is tightly controlled by the body.
Source: The American Journal of Clinical Nutrition, November 2007
Higher serum vitamin D concentrations are associated with longer leukocyte telomere length in women
Authors: Brent Richards, Ana Valdes, Jeffrey Gardner, Dimitri Paximadas, Masayuki Kimura, Ayrun Nessa, Xiaobin Lu, Gabriela Surdulescu, Rami Swaminathan, Tim Spector and Abraham Aviv.