Vitamins & Supplements Archive

Your body depends on the mineral potassium for many bodily functions, including keeping control of the electrical balance of your heart, metabolizing carbohydrates, and building muscle.

Low potassium levels can cause muscle weakness and heartbeat irregularities. On the other hand, too much potassium can cause your heart to stop.

In the journals

Smoking causes lung cancer — no surprise there. But a new study found that high dosages of vitamin B6 or B12 supplements were associated with three to four times the lung cancer risk in male smokers compared with smokers who did not take the supplements. The results were published in the Aug. 22, 2017, Journal of Clinical Oncology.

Researchers examined information from more than 44,000 men ages 50 to 76. At enrollment, the men reported on their smoking history and their B vitamin supplement use over the previous 10 years. In the study, high intake of B vitamin was classified as 20 milligrams (mg) of B6 per day or 55 micrograms (mcg) of B12. (The recommended daily intakes for men ages 51 and older are 1.7 mg for B6 and 2.4 mcg for B12.)

Ask the doctor

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Q. I'm confused about vitamin D. How much should I take?

A. There's considerable controversy as to whether most people should take a vitamin D supplement at all. Most of the vitamin D in our bodies is made by our skin, when it is exposed to sunlight. In contrast to most other vitamins, we don't get much vitamin D in our diet. Authorities recommend, however, that children from age 1, and adults through age 70, take 600 international units (IU) daily, and that adults 71 years and older take 800 IU daily. People with, or at risk for, certain bone diseases need to take more than this amount. There's general agreement that doses above 4,000 IU daily can be toxic to adults, with lower doses toxic to kids.

Research we're watching

Have you considered taking a red yeast rice supplement to "naturally" lower your cholesterol, either instead of or in addition to a prescription statin? Think again. These popular over-the-counter supplements contain an ingredient identical to the one found in the prescription drug lovastatin (Mevacor) — but in completely unpredictable amounts, a new study finds.

Researchers tested 28 different brands of red yeast rice from four mainstream retailers (GNC, Walgreens, Walmart, and Whole Foods). Two brands contained no detectable levels of the active ingredient, called monacolin K. In the other 26, monacolin K levels ranged from a trace to nearly 5.5 milligrams (mg) per 1,200 mg of red yeast rice. For some brands, the recommended daily serving overlapped with the dosage of prescription lovastatin.

Ask the doctors

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Q. I suffer from vertigo and have heard that taking a magnesium supplement might help. Is that true? If so, how much should I take?

A. Vertigo can be caused by almost anything that interferes with the normal function of the inner ear, which is instrumental in preserving balance. The most common form of vertigo — benign paroxysmal positional vertigo (BPPV) — results when tiny calcium carbonate crystals migrate from one part of the inner ear to the semicircular canal in another part of the ear, triggering a false message to the brain about the direction in which the head is moving and the speed of its motion. Dizziness is a result of the brain's attempt to resolve the conflicting messages from the ear and the other senses.

In the journals

Adequate levels of vitamin D can help strengthen bones and lower the risk for diabetes and some cancers. But research published online April 5, 2017, by JAMA Cardiology found that high monthly doses of supplemental vitamin D did little to ward off cardiovascular disease.

The recommended daily amount of vitamin D is 600 international units (IU) for men ages 51 to 70 and 800 IU for men ages 71 and older. It is not yet clear how vitamin D may improve heart health, but studies have found a higher rate of cardiovascular disease among people with low levels of vitamin D.

Dietary supplements may be natural but not risk-free.

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A quick stroll through your pharmacy or supermarket wellness aisle will show you that dietary supplements and herbal remedies are big business. Americans spend over $32 billion annually on thousands of herbal products, many of which claim to improve heart health.

Popular misconceptions

People look to herbs and supplements as a natural, safe alternative to the conventional medications they're taking, says Dr. Pieter Cohen, an assistant professor of medicine at Harvard Medical School. Providers, on the other hand, may think of supplements as fancy placebos — expensive but benign. "These are all misconceptions," says Dr. Cohen.

Research we're watching

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Do you swallow a daily multivitamin, hoping to make up for a less-than-ideal diet? Sorry, but this strategy won't stave off heart disease, according to a study published online April 5, 2017, by JAMA Cardiology.

Previous research has also failed to find convincing evidence that a daily multivitamin lowers the risk of heart disease or cancer. But these studies didn't always account for the participant's dietary habits, which could potentially skew the results. In theory, people with poor diets might reap greater benefits from vitamins than those who eat healthier diets.

In the journals

Much research has shown that oxidative stress plays a key role in the development of neurodegenerative disorders, such as Alzheimer's and Parkinson's disease. As a result, antioxidant supplements like vitamin E and selenium have been proposed to prevent dementia. Yet a new study on older men published online March 20, 2017, by JAMA Neurology found no evidence they can help.

The Prevention of Alzheimer's Disease by Vitamin E and Selenium clinical trial included 7,540 men, average age of 67. Over a five-year period, the men were randomly assigned to receive 400 international units of vitamin E each day, 200 micrograms of selenium, both supplements, or a placebo. The supplements were stopped and 3,786 of these men agreed to be followed for an additional six years. They were routinely screened for cognitive problems and encouraged to see their doctor if the results suggested any kind of cognitive impairment.

It's easy enough to look up how much vitamin C or calcium you should get each day. It is also easy to read the back of a vitamin bottle to see just how much of a given vitamin or mineral the product provides. But how can you tell if what you eat — which should be your primary source of important nutrients — is giving you what you need?

One way is to focus on the big picture: eat a balanced diet that contains a variety of colorful fruits and vegetables, whole grains, beans, nuts, dairy products, seafood, lean meats, and poultry. Focus on nutrient-dense foods like these, which are packed with vitamins and minerals relative to the number of calories they deliver, and you should be fine.