Low vitamin D levels may impair thinking and adequate vitamin D levels may help prevent knee osteoarthritis, according to two studies released this last week. Both of these studies, added to the others I’ve discussed in this blog in the past, may lead you to get your doctor to check your vitamin D level at your next physical exam.
More Information:
Reuters Health is reporting that new research suggests that low vitamin D levels in the body are associated with thinking or “cognitive” impairments in older men.
In the study, an investigation of European men, subjects with low levels of vitamin D scored worse on a standard test of cognitive ability than did their peers with normal levels, Dr. David M. Lee, from the University of Manchester, UK, and co-researchers found.
Although, the authors emphasize, the difference in scores was not that great. And, they add, whether vitamin D supplements can help is not yet known
Included in the investigation were 3133 men, 40 to 79 years of age, who were enrolled in the European Male Aging Study (EMAS). The average level of 25-hydroxyvitamin D, an inactive form of vitamin D used to measure levels of the vitamin, was 63 nanomoles per liter. Levels of 90 to 140 nanomoles per liter are typically considered optimal.
The researchers report their findings in the Journal of Neurology, Neurosurgery, and Psychiatry.
As vitamin D levels fell, so did cognitive performance. Further analysis indicated that this relationship was largely confined to men over age 60 and was strongest with vitamin D levels below 35 nanomoles per liter.
While the magnitude of the association was small, Lee and colleagues note, if a simple measure, such as vitamin D supplementation, could improve cognition, then the findings could have important public health implications.
In a second study, low levels of vitamin D were found to be associated with the loss of cartilage in the knee joint of older individuals, researchers in Australia report.
“Cartilage loss is the hallmark of osteoarthritis,” Dr. Changhai Ding told Reuters Health. By the time patients reach the point of needing knee replacement, 60 percent of cartilage has been lost, he said.
However, “achieving vitamin D sufficiency in osteoarthritis patients could significantly delay total knee replacement,” said Ding, at the Menzies Research Institute in Tasmania.
In the study, Ding and colleagues found “osteoarthritis patients with vitamin D sufficiency have approximately 1.5 percent less loss of knee cartilage per year than patients with vitamin D deficiency,” said Ding.
The investigators measured levels of vitamin D in blood samples and knee cartilage volume on X-rays from 880 men and women who were 51 to 79 years old. The team then took similar measurements again almost 3 years later among 353 of the study participants, the researchers report in the journal Arthritis & Rheumatism.
Overall, 58 percent of these subjects showed changes in knee cartilage indicating worsening osteoarthritis between the first and second measurements, and half reported knee pain.
Both at the beginning of the study enrollment and at follow up, men and women with vitamin D deficiency had lower knee cartilage volume and were more likely to experience knee pain.
Ding’s team concludes that vitamin D plays an important role in cartilage changes, and that vitamin D deficiency may predict knee cartilage loss over time.
The researchers call for further research to see if vitamin D supplementation can delay the progression of knee osteoarthritis and the need for total knee replacement in osteoarthritis patients.
In the meantime, I think it’s reasonable for you to consider one of two possibilities:

1. Take 1000 – 2000 IU of 1,25 OH vitamin D daily, OR
2. Ask your physician to check your vitamin D level and if it’s low, consider taking a supplement.

Here are some of my other blogs on vitamin D:

• Specific vitamins and a supplement (B vitamins, vitamin D, and calcium) may lower risk of stroke, blindness, and cancer
• Vitamin D tests soar as deficiency, diseases linked
• Lack of vitamin D raises death risk
• Vitamin D Recommendations for Teens May Be Too Low
• Vitamin D may protect against heart attack
• Low Vitamin D Levels Associated with Artery Disease