Should I take a vitamin D supplement to protect my memory? Will a vitamin D supplement protect me against becoming demented? The short answer to both questions is no.
Referred to by some as the “sunshine vitamin” (Tom Spector, of King’s College in London, in a review in The Conversation, January), many in the medical community (including him) have toted vitamin D supplementation as the “magic cure” for things ranging from cancer to dementia.
It has been used for decades to treat osteoporosis and other bone problems and to prevent fractures and improve muscle strength.
There have also been claims that vitamin D boosts the immune system and reduces aging. It has been thought of as necessary to survive sun-starved winters.
However, careful review of the evidence on supplementation with vitamin D (even with calcium supplements) shows it is not effective in preventing fracture, cancer or heart disease.
The sentiment based on more recent reviews (such as a review in The British Medical Journal in 2014) has become that the benefits of supplementation with vitamin D, except vitamin deficiency and macular degeneration, are spurious. This conclusion holds for most supplements.
Then why are supplements so widely used? Basically the vitamin and mineral industry have become a multibillion-dollar business with effective marketing.
Furthermore, we as human beings do not make decisions based on evidence but rather operate with a number of cognitive biases that must be actively confronted to make informed decisions.
In addition, there is the belief (I have often used this argument) “If it does no harm” then it must be OK.
This assumption of “no harm, no foul” is not justified based on the evidence.
For example, calcium supplements not only don’t prevent fracture, they increase the risk of cancer in some. A 2015 randomized clinical trial of vitamin D showed no benefit from vitamin D compared with a placebo or exercise in preventing hip fracture.
Indeed, the data indicated a slightly higher risk in those taking the supplement. Other evidence has shown that doses of 24,000 to 36,000 IUs of vitamin (the medically recommended dose) may be safe, but doses of 40,000 to 60,000 IUs per month increase the risk of fracture by 20 to 30 percent. The Select trial of vitamin E and selenium increased the risk for prostate cancer in some men.
You might argue that low or high blood levels of vitamin D allow informed use of the supplement. But there is no standard blood level, as genetics determines your concentrations so what is normal for you may be high or low for your friend.
So what do you do? First, be aware that there is no convincing evidence based on a large body of evidence that dietary supplements can prevent worsening of cognitive symptoms or diseases. Don’t supplement unless advised by your physician.
Second, some supplements can cause harm, and overdosing is risky.
Third, rely on diet (and in the case of vitamin D, sun exposure) to provide needed nutrients. Supplements are not natural and may seriously imbalance the push and pull of natural biological symptoms.
Don’t waste your money on supplements, as there is evidence that some supplements increase the risk for cancer, heart disease and dementia and may hasten death.