Vitamins, minerals, herbs, and supplements Archive

On call

Q. I have read that vitamin K supplements can help prevent heart disease. Should I take them?

A. Vitamin K — which is found in high levels in green leafy vegetables like spinach, kale, and romaine lettuce — plays a role in helping the body make blood clotting proteins. Although some observational studies have suggested a heart benefit from diets high in vitamin K, studies of supplements have not shown a protective effect.

On call

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Q. How can I get my daily requirement for calcium if I am lactose intolerant?

A. We usually associate high-calcium foods with dairy products, like milk, cheese, and yogurt. If you cannot tolerate these foods from a digestive standpoint, you can still meet your calcium requirement by increasing your consumption of certain green leafy vegetables and calcium-fortified foods.

The net benefit of these popular supplements is very limited.

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Millions of Americans swallow an amber-colored capsule of fish oil each day, lured by its alleged health benefits. In the supplement aisle of most pharmacies, supermarkets, and big-box stores, the shelves are crowded with different brands of fish oil supplements (see "Fish oil: A brief history"). Many tout benefits for the heart. In fact, the label of one popular brand includes the phrase "May reduce coronary heart disease risk."

But those bold marketing claims haven't caught up with the latest science. Earlier this year, the American Heart Association (AHA) issued an updated advisory about fish oil supplements and their cardiovascular benefits. Their verdict: Fish oil supplements may slightly lower the risk of dying of heart failure or after a recent heart attack. But they do not prevent heart disease. (A separate AHA advisory about fish consumption is slated for release in 2018.)

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.)

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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.

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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.