The “D” in vitamin D doesn’t stand for dementia. Or does it?
We know that many older adults don’t get enough vitamin D, and that’s a problem. It can leave your bones brittle and more easily broken if you slip and fall.
What we didn’t know, until now, is that a lack of vitamin D may be every bit as bad for your brain as it is for your body.
According to a spate of recent studies, people age 60 and older who have low levels of vitamin D are significantly more apt to suffer cognitive decline.
More research is needed, but the findings so far are too compelling to ignore. If you’re serious about staying mentally sharp and protecting yourself against the threat of Alzheimer’s, you need to make sure you’re getting enough vitamin D.
“It’s growing as a concern,” says Joshua Miller, professor of nutritional science at Rutgers University. “We have a lot of circumstantial evidence that older adults have a high prevalence of low vitamin D, and low vitamin D status is associated with faster rates of cognitive decline, independent of race or ethnicity. And independent of sex as well.”
Miller was the lead author in one of the more important studies so far linking vitamin D deficiency to cognitive loss. He and colleagues at the University of California-Davis looked at 382 adults ranging in age from their 60s to their 90s, and tested them once a year for vitamin D and cognition for an average of five years.
Miller says people with low levels of vitamin D experienced cognitive decline at a rate two to three times as fast as those with adequate levels of vitamin D.
Other studies have reported similar results, but this one was more diverse in the population it looked at. It included a broad cross-section of whites, African-Americans and Hispanics, as well as both men and women.
“About 60 percent of the group, regardless of their age or ethnicity, was low in vitamin D,” Miller says. “Those who had dementia had lower vitamin D status than those who had mild cognitive impairment or normal cognitive function.”
Those with a lack of vitamin D also declined more in both short-term memory and in performing complex cognitive tasks over the course of the study.
Two other studies have shown similar results. One looked at nearly 1,200 women between 60 and 70 years of age and found those with low vitamin D had significantly greater cognitive decline nine years later. Most recently, a study published in July found that among a group of more than 1,100 elderly people in China, those with vitamin D deficiency were twice as likely to suffer cognitive decline over a two-year period.
What’s not clear yet is how vitamin D may act to protect the brain, or whether increasing the levels of vitamin D in older adults can effectively prevent them from developing dementia.
“The missing piece is a randomized control trial that proves that raising vitamin D levels will actually reduce your risk of dementia or Alzheimer’s disease, or will slow cognitive decline,” Miller says. “Those studies just haven’t been done yet.”
And it may be a good while before that research gets done.
“It’s really difficult to get those human studies funded,” Miller says. “They’re expensive, they take a while to do and to be really frank about it, there’s a little bit of a bias in the funding agencies against nutrients, vitamins, minerals, that sort of thing, being used in this manner versus drugs.”
Part of that bias, Miller says, is drug companies can’t make money on something as inexpensive and readily available as vitamin D supplements. “But if they develop a new drug that cures Alzheimer’s, they can make a lot of money,” he says. “That comes into play.”
So you can sit around and hope for a more definitive answer someday.
Or you can act now to determine if you have a “D-ficiency,” and take steps to address it.
Getting the right amount of vitamin D is easy to do, whether through natural sources, or by taking a supplement. And it’s more important than ever for your health, giving you potential protection against dementia — not to mention reducing your risk of falls and broken bones. One analysis of more than 40,000 senior citizens found taking vitamin D daily reduced hip and other bone fractures by 20 percent.
Want to know more? Here are answers to some basic questions about vitamin D.
Q. What are the best sources of vitamin D?
A. The primary way our body gets vitamin D naturally is through exposure to sunlight. That’s why it’s called the “sunshine vitamin.” Other sources include certain foods (including fortified milk, cheese, salmon and tuna) and supplements.
Q. How common is it to not be getting enough vitamin D?
A. Good estimates are hard to come by, but we can safely say somewhere between 25 and 50 percent of Americans are deficient in vitamin D. For older people, the percentage probably is much higher.
Q. Why are so many of us not getting enough vitamin D?
A. There are a variety of reasons. Older people are particularly susceptible because they have trouble absorbing enough vitamin D from sunlight as their skin thins and their metabolism slows down.
Among other common reasons:
- Concerns about skin cancer is causing more people to use sunscreen, which can reduce our ability to absorb UV rays from the sun.
- People who have darker skin are at greater risk because they absorb less UV rays. In Miller’s study, 70 percent of African-Americans and Hispanics had low levels of vitamin D, compared to 54 percent of whites. “Everything else being equal, darker skin color will reduce the amount of vitamin D that can be produced by exposure to sunlight, because darker skin blocks UV radiation,” Miller says.
- Some people get less exposure to the sun because of the geographic region they live in, or because they spend little time outdoors.
- The food sources for vitamin D are somewhat limited, and not particularly popular in the Western diet. “There are large proportions of our population that don’t eat those foods,” Miller says. “For instance, people who are lactose intolerant don’t drink milk.”
Q. Should I consider a vitamin D supplement?
A. “As long as you are taking the right amount of vitamin D, in other words, not too much, I see no harm in taking a supplement,” Miller says. “It’s relatively inexpensive. Go to your doctor and say, ‘Hey, what about measuring my vitamin D status?’ Most doctors these days will likely do it. If it’s low, and with your doctor’s advice on what levels to take, start taking supplements.”
Q. But I’ve heard that getting tested for vitamin D isn’t recommended. What’s up with that?
A. It’s a matter of debate these days. Some health experts say testing for vitamin D is overdone. The American Geriatrics Society issued a consensus statement in 2013 that strongly advised doctors to recommend a vitamin D supplement of at least 1,000 international units (IU) for most adults over the age of 65, but said testing for vitamin D levels was not necessary for most people.
“I usually tell people (to take) 1,000 IU/day, since it’s a nice round number recommended by AGS. I call this the ‘healthy aging’ dose of daily vitamin D. The idea is that if people take a daily vitamin D supplement as recommended above, they’ll be highly unlikely to have a level that is too low or too high. I agree with those who say that vitamin D testing is often overused.”
The best advice is to seek your own opinion on testing and take your doctor’s advice.
Q. So is 1,000 IU the right dose? Is that how much I should take?
A. There is no one recommendation that’s right for everyone. It depends on your age, your ethnicity and a variety of other factors. Consult your physician, and take the amount that’s most appropriate for you. For many people over the age of 65, that may be in the range of 1,000 to 2,000 IU. “The issue, though, is that you can take too much,” cautions Miller. “The upper level is 4,000 IU per day. You have to remember you get some Vitamin D in your diet, so you don’t want to be taking pills that are 4,000 or more.”