Vitamins & Supplements Archive

Multivitamins may reduce the risk of cancer in men by 8%. The benefits of multivitamin supplements may mirror those found in vitamin-rich fruits and vegetables, which also have been associated with lower cancer rates in previous studies.

Reliable evidence that supplements actually work is lacking, but exercise and a Mediterranean-style diet support healthy brain aging.

Can taking a pill improve your memory or boost your brain function? Never has one question launched so many health newsletter articles—not to mention so many purchases online and at the drugstore. "My patients and their families ask a lot about supplements, and I try to point them to whatever evidence we have," says Dr. Gad Marshall, an assistant professor of neurology at Harvard Medical School. He also helps to run clinical trials for Alzheimer's disease at Harvard-affiliated Brigham and Women's Hospital.

Dr. Marshall's list of supplements that people ask about include B vitamins (folic acid, B6, and B12), antioxidants (vitamins C and E, coenzyme Q10), herbal supplements (huperzine A, ginkgo biloba), and nutraceuticals (fish oil, curcumin, coconut oil). For now, you can cross most of these products off your shopping list for lack of evidence. "There are a lot of things out there for which we have no data on whether they are safe or do anything to help," Dr. Marshall says.

The right dose for bone health depends on key factors.

If you're wondering how much vitamin D will keep your bones healthy, you're not alone. Supplements of no more than 400 international units (IU) of vitamin D and 1,000 milligrams (mg) of calcium per day don't do much. A recent study in the New England Journal of Medicine said high-dose vitamin D (800–2,000 IU) reduced hip fractures by 30%. "The exact dosage that's required is still very controversial," says Dr. Jill Paulson, an instructor in medicine at Harvard Medical School.

Black cohosh does not appear effective for relieving hot flashes, and there is not enough evidence to confirm its safety or effectiveness for other menopausal symptoms, according to a new review.

Its value in cardiovascular disease prevention has not been confirmed.

Various studies have suggested that higher blood levels of vitamin D may help prevent heart disease, stroke, hypertension, and diabetes. The concept makes sense, because the body converts vitamin D to calcitriol, which inhibits the growth of atherosclerotic plaques and the inflammation inside them. Calcitriol also helps to maintain normal blood pressure, and may play a key role in the production and regulation of insulin, a key component in diabetes.

Do food sources trump supplements?

Calcium is recommended as a way to help prevent osteoporosis, but calcium supplements have come under attack recently due to a possible heart attack risk. A study in the June issue of Heart found a significantly increased risk of heart attack among women taking calcium supplements. Two other studies, in 2010 and 2011, had similar results. Since so many people take the supplements, these studies have received a lot of attention.

But Dr. JoAnn Manson, chief of preventive medicine at Harvard-affiliated Brigham and Women's Hospital, questions the link and notes that such risks haven't been found with calcium-rich foods. "Although I think the jury is still out on the supplement issue, it would be wise to try to get most of your calcium from food sources if possible," she says.

Q. I am 72 years old and in good health, but I am lactose intolerant and can't drink milk to obtain calcium. Should I take calcium supplements?

A. Osteoporosis (low bone density) is less common in men than women, although one in 15 men will have a hip or spinal fracture in his lifetime. Risk factors for osteoporosis include smoking, low body weight, sedentary lifestyle, and low testosterone levels.

Q. My potassium level is high, and my physician stopped the medication that has successfully controlled my blood pressure for years, lisinopril. What is the danger from high potassium, and why is lisinopril a problem?

A. Potassium is important for the electrical activity of the cells in your heart, and levels that are below 3.4 milligrams per deciliter (mg/dL) or above 5.0 mg/dL can lead to heart rhythm problems that may be life-threatening. Some medications used for high blood pressure, heart failure, and other cardiovascular problems can affect potassium levels, so levels must be checked often.

How to follow the changing recommendations without making yourself dizzy.

First we were advised to take calcium and vitamin D supplements to strengthen our bones and protect against fractures. Then in June, the U.S. Preventive Services Task Force recommended against low-dose calcium and vitamin D supplements, citing little evidence that they actually prevent fractures and noting that they can increase the risk of kidney stones.

Research finds DHA may help preserve your vision.

The omega-3 fatty acid known as DHA is touted for its many health benefits, and vision protection may be one of them. A new study published in Investigative Ophthalmology & Visual Science found that DHA, one of three forms of omega-3 fatty acids and the substance that makes up about 30% of brain matter, prevented age-related vision loss in lab mice. DHA is considered the most complex form of omega-3, but is among the most difficult to consume in sufficient amounts because it is contained in so few food sources.

Dr. Ann Bajart, a corneal specialist and clinical instructor in ophthalmology at Harvard Medical School, says the vision study likely applies to humans.