Low levels of the vitamin and higher blood levels of the parathyroid hormone (PTH) were associated with higher rates of depression among 1,282 community residents aged between 65 and 95, according to results published in the Archives of General Psychiatry.
"This large population-based study shows, for the first time, an association of depression status and depression severity with decreased serum 25(OH)D levels and increased serum PTH levels in older subjects," wrote lead author Witte Hoogendijk from the Vrije Universiteit Amsterdam.
If the study can be repeated in further study, it may see brain health added to the long list of health benefits reported for the vitamin, ranging from bone and cardiovascular health, to protection against certain cancers, and improved muscle strength.
Recently, a review by Bruce Ames and Joyce McCann from the Children's Hospital and Research Center Oakland highlighted the role of the vitamin in maintaining brain health, noting the wide distribution of vitamin D receptors throughout the brain.
According to the review (FASEB Journal, Vol.22, pp. 982-1001), the vitamin has been reported to affect proteins in the brain known to be directly involved in learning and memory, motor control, and possibly even maternal and social behaviour.
Hoogendijk and co-workers measured vitamin D (25-hydroxyvitamin D - 25(OH)D) and PTH blood levels in the volunteers taking part in the Longitudinal Aging Study Amsterdam. In the whole cohort, 26 had major depressive disorder, 169 had minor depression, and 1,087 were not depressed. The researchers note that the average blood 25(OH)D level was 21 nanograms per milliliter (ng/ml) and the average PTH level was 3.6 picograms per millilitre (pg/ml).
Amongst the people with major and minor depression, blood 25(OH)D levels were 14 per cent lower, while PTH levels were, on average, five and 33 per cent higher in people with minor and major depression, respectively, compared to non-depressed individuals.
"From the patient's perspective, our findings may be of clinical relevance because the prevalence of minor depression in older persons is high (13 per cent) and both decreased serum 25(OH)D levels and increased serum PTH levels can, in theory, be treated with higher dietary intake of vitamin D3 or calcium and increased exposure to daylight," said Hoogendijk.
"Underlying causes of vitamin D deficiency such as less sun exposure as a result of decreased outdoor activity, different housing or clothing habits and decreased vitamin intake may be secondary to depression, but depression may also be the consequence of poor vitamin D status," wrote the authors.
"Long-term longitudinal studies with repeated assessments should be performed to explore the question of whether decreased 25(OH)D levels and increased PTH levels precede depression or follow it. In other words, are these biological changes a cause or a consequence of depression?" they concluded.
Experts call for higher levels
Calls to increase the current recommendations of 200 IU per day for children and adults up to 50 years of age for vitamin D up to 800 - 1000 IU vitamin D3, have become more frequent in both scientific and public circles.
Vitamin D refers to two biologically inactive precursors - D3, also known as cholecalciferol, and D2, also known as ergocalciferol. The vitamin can be manufactured in the body on exposure to sunlight and also consumed in relatively low quantities from the diet.
However because of the low dietary amounts, and lack of sunshine in northern climates, with some estimates claiming that as much as 60 per cent of northern populations may be vitamin D deficient.
In adults, vitamin D deficiency may precipitate or exacerbate osteopenia, osteoporosis, muscle weakness, fractures, common cancers, autoimmune diseases, infectious diseases and cardiovascular diseases.
Source: Archives of General Psychiatry
May 2008, Volume 65, Number 5, Pages
"Depression Is Associated With Decreased 25-Hydroxyvitamin D and Increased Parathyroid Hormone Levels in Older Adults"
Authors: W.J.G. Hoogendijk, P. Lips, M.G. Dik, D.J.H. Deeg, A.T.F. Beekman, B.W.J.H. Penninx