Studies over the past few years have linked vitamin D deficiency to a range of ills in older age, from heart disease to brittle bones. Now, a team of scientists has confirmed a link between low D levels and dementia, along with Alzheimer’s.

It’s estimated that one in four seniors is vitamin D deficient based on current recommended levels.

The international team followed 1,658 men and women aged 65 and over for six years and were surprised by their own findings. They expected to see a correlation between vitamin D deficiency and cognitive impairment; they didn’t expect a 53 percent increase in the risk for dementia among people who were moderately D deficient and a staggering 125 percent increase among those who were severely deficient. For increased Alzheimer’s risk, those figures were 69 and 122 percent.

The study authors aren’t yet sure that low levels actually cause Alzheimer’s and dementia; and they say clinical trials are needed to establish whether increasing vitamin D levels can prevent their onset. But they’re hopeful. “Our findings are very encouraging, and even if a small number of people could benefit, this would have enormous public health implications given the devastating and costly nature of dementia.”

The study also suggested an optimal level of vitamin D circulating in the bloodstream below which the risk of developing dementia and Alzheimer’s increases – good brain health, the researchers say, depends on blood levels above 50 nmol/L. On average, 1000 IU per day increases vitamin D blood levels 25 nmol/L (see a helpful chart here).

Besides brain health, vitamin D is also associated with heart health, bone health, lower diabetes risk and better mood regulation. Some laboratory studies also suggest a link between D deficiency and colorectal cancer. See our article 5 Reasons Why You May Need More Vitamin D.

What You Should Know

Vitamin D3 comes from three main sources: foods such as oily fish (salmon contains the most, at about 1000IU per 4 ounce serving) and to a lesser degree eggs, along with fortified milk and orange juice; vitamin supplements; and sunlight on exposed, unscreened skin. But each of these has limitations, especially as we get older:

• It’s hard to get enough vitamin D from food, and our bodies becomes less efficient at producing and processing dietary vitamin D as we age.
• Older skin doesn’t do as good a job of converting sun into vitamin D, and we might spend less time outdoors. In some northern regions, the skin ceases to produce D vitamins during the winter months; in Boston and areas to the north, “winter” means between October and April. According to the Harvard School of Public Health, if you live north of the line connecting San Francisco to Philadelphia, chances are you’re not getting enough vitamin D. And if you apply sunscreen, you’re reducing your exposure to the D producing rays by 90 percent.
• Not all supplements are created equal. As we reported last year, researchers studied bottles of randomly purchased D supplements and found that potency ranged widely – from 9 percent to 140 percent. Your safest best is to pick supplements that have the USP seal (U.S. Pharmacopeia).
• Some medications – including Steroid medications such as prednisone, certain weight loss and cholesterol lowering dugs – can interfere with vitamin D metabolism. (See more about drug interactions with D here.)
• People who are overweight or obese tend to have lower D levels.

How Much Vitamin D Should Older Adults Take?

The recommended dietary allowance for vitamin D in food or supplements is at least 600 IUs for adults 51 to 70 and 800 after age 70, but many endocrinologists say these allowances are too low. The upper recommended limit is 4000 IUs.

• Read more about the study here.
• 5 Reasons Why You May Need More Vitamin D

How often does your doctor check vitamin D levels in your blood? Let us know in the comments section below.