Is it safe or hazardous? Here’s what you need to know about potential harmful effects before you take that vitamin, mineral, or herbal pill.
When we talk about supplements, there’s so much hype about their potential benefits that it can be hard to separate fact from fiction. While it’s true that vitamins and minerals are essential to health, it’s not true that taking them in pill, capsule, or powder form — especially in megadoses — is necessary, or without risks.
For one thing, dietary supplements can sometimes interact with each other, as well as with over-the-counter (OTC) and prescription medication. In addition, unlike drugs, the U.S. Food & Drug Administration (FDA) is not authorized to review dietary supplements for safety and effectiveness before they are marketed. It’s up to manufacturers to ensure that their products do not contain contaminants or impurities, are properly labeled, and contain what they claim. In other words, the regulation of dietary supplements is much less strict than it is for prescription or OTC drugs.
Yet, according to a study published in October 2016 in the Journal of the American Medical Association, more than one-half of Americans take herbal or dietary supplements daily, making these products a booming industry with sales reaching $128 billion yearly worldwide, according to a report published in 2018 by the Nutrition Business Journal. More than 31 percent of those sales take place in the United States.
When used properly, some supplements may improve your health, but others can be ineffective or even harmful. For example, Tufts University research published April 9, 2019, in the journal Annals of Internal Medicine linked daily doses of more than 1,000 milligrams (mg) of calcium to a higher risk of death from cancer. Furthermore, the data showed that people who took in adequate amounts of magnesium, zinc, and vitamins A and K had a lower risk of death — but only if they got those nutrients from food rather than supplements.
“Buyer beware,” warns JoAnn Manson, MD, chief of the division of preventive medicine at Brigham and Women’s Hospital in Boston, and professor of epidemiology at the Harvard T. H. Chan School of Public Health. “Many supplements on the market have not been rigorously tested. Very few supplements have shown to be of benefit,” says Dr. Manson. And, she says, many carry unsubstantiated health claims.
Confused? National Institutes of Health (NIH) fact sheets can provide detailed information on the benefits and risks of individual vitamins and minerals, as well as herbal supplements. Highlighted here are seven supplements that you should take carefully, if at all.
1. Calcium: The Excess Settles in Your Arteries
Calcium is essential for strong bones and a healthy heart, but too much is not a good thing. In fact, an excess of calcium, which is described by the NIH as more than 2,500 mg per day for adults ages 19 to 50, and more than 2,000 mg per day for individuals 51 and over, can lead to problems.
According to the Cleveland Clinic, “Researchers believe that without adequate vitamin D to help absorb it, the extra calcium settles in the arteries instead of the bones.”
In addition, an analysis of 10 years of medical tests on more than 2,700 people in a federally funded heart disease study, published October 10, 2016, in the Journal of the American Heart Association, suggested that taking calcium supplements may increase plaque buildup in the aorta and other arteries. In contrast, a diet high in calcium-rich foods, such as dairy products and leafy greens, appeared to be protective.
“Get calcium from your diet if you can,” advises Dr. Millstine, noting that research shows that calcium is better absorbed through food than through supplements.
The National Institutes of Health (NIH) recommends 1,000 mg of calcium a day for women ages 19 to 50, and 1,200 mg a day for women 51 and older. The recommendation for men ages 19 to 70 is 1,000 mg a day, and 1,200 mg a day for men 71 and older. According to the U.S. Department of Agriculture (USDA), 6 ounces of plain low-fat yogurt contains about 311 mg of calcium, a little less than one-third of the daily recommendations. Other good calcium sources include tofu, nonfat milk, cheese, fortified cereal, and juices.
Calcium deficiency, or hypocalcemia, may be detected by routine blood tests. If you have low calcium blood levels, your doctor may prescribe a calcium supplement.
2. Fish Oil Supplements: Choose Fish or Flaxseed Instead
Rich in omega-3 fatty acids, fish oil has been touted as a means to reduce heart disease. However, more and more evidence shows that fish oil supplements have questionable heart benefits. A study published January 3, 2019, in The New England Journal of Medicine (NEJM) found that omega-3 fatty acid supplements did nothing to reduce heart attacks, strokes, or deaths from heart disease in middle-aged and older men and women without any known risk factors for cardiovascular disease. An earlier study, published in May 2013 in NEJM, looked at people at high risk for cardiovascular disease and also reported no benefit.
According to the NIH, omega-3 deficiency is “very rare in the United States.” Still, many people fail to consume enough omega-3s daily for optimal health. The best way to get adequate amounts is by eating a variety of foods that are rich in them, including:
- Fish and other seafood, especially cold-water fatty fish, such as salmon, mackerel, tuna, herring, and sardines
- Nuts and seeds, such as flaxseed, chia seeds, and walnuts
- Plant oils, such as flaxseed oil, soybean oil, and canola oil
- Fortified foods, such as certain brands of eggs, yogurt, juices, milk, and soy beverages
3. Soy Isolate: Careful With the Estrogen
Tofu, tempeh, and soy milk are all good sources of protein, fiber, and a number of minerals. Some women also take soy in supplement form because the plant contains estrogen-like compounds called isoflavones that may help relieve symptoms of menopause. However, concerns have been raised that the isoflavones in soy supplements may contribute to an increased risk of breast cancer.
The good news is that large-scale studies have not shown any increased breast cancer risk from eating whole soy foods, such as tofu and edamame, according to the Dana Farber Cancer Institute in Boston.
In fact, at least one study, published March 6, 2017, in the journal Cancer, which looked at 6,235 breast cancer survivors, linked eating the equivalent of one serving of soybeans a week to a 21 percent lower risk of death from all causes during the nearly 10-year follow-up period.
But not enough research has been done on soy protein isolate (SPI) — the powder formed by removing the protein from the rest of the plant — to know its effect on breast cancer risk, Millstine says. (In addition to supplements, SPI is often found in power bars, veggie burgers, and some soups, sauces, smoothies, and breakfast cereals.)
The bottom line: “If you’re concerned about breast cancer, stay away from soy supplements and soy-based protein,” Millstine advises. “Soy intake from foods has not been shown to be of concern though.”
4. Multivitamins and Multiminerals: No Substitute for a Healthy Diet
Think that a healthy lifestyle requires not just eating good-for-you foods, exercising, and getting enough sleep, but also taking a daily multivitamin-multimineral supplement? You may be surprised to learn that the jury’s still out on whether those supplements are truly helpful.
One surprising study published in the journal JAMA Internal Medicine, which used data from nearly 40,000 women over 19 years, found that, on average, women who took supplements had an increased risk of dying compared with women who didn’t take supplements. Multivitamins also did little or nothing to protect against common cancers, cardiovascular disease, or death.
However, more recent research has found benefits to taking multivitamins. For example, a study published August 9, 2017, in the journal Nutrients concluded that frequent use of multivitamin and mineral supplements helped prevent micronutrient shortfalls that might otherwise cause health problems.
For women of childbearing age, taking prenatal vitamins with folic acid is recommended by the American College of Obstetricians and Gynecologists to help prevent birth defects. Multivitamins might also be prescribed by your doctor if you have malabsorption syndrome, a condition in which the body does not properly absorb vitamins and minerals.
But for healthy people, Manson says, “a supplement can never be a substitute for a healthy diet.”
5. Vitamin D: Too Much Can Harm Your Kidneys
Vitamin D favours calcium absorption in the body, and getting enough is paramount to health and well-being, offering the promise of protecting bones and preventing bone diseases like osteoporosis. Supplemental vitamin D is popular because it’s difficult (if not impossible) to get enough from food. Also, as the Centers for Disease Control and Prevention (CDC) notes, our bodies produces vitamin D when bare skin is exposed to sunlight, but increased time spent indoors and widespread use of sunblock has minimized the amount of vitamin D many of sync get from sun exposure.
But enthusiasm for vitamin D supplements is outpacing the evidence. As it turns out, when healthy women take low doses of vitamin D (up to 400 international units, or IU) it does not necessarily prevent them from breaking bones, according to a U.S. Preventive Services Task Force report published in May 2013 in the journal Annals of Internal Medicine.
And taking over doses is not a better option either. In healthy people, vitamin D blood levels higher than 100 nanograms per milliliter (ng/mL) can trigger extra calcium absorption — and lead to muscle pain, mood disorders, abdominal pain, and kidney stones, notes the Cleveland Clinic. It may also raise the risk of heart attack and stroke.
“More is not necessarily better when it comes to micronutrient supplements,” says Manson.
The result is different for women who are over age 71, deficient in vitamin D, live in institutions, or have dark skin pigmentation. For them, the National Academy of Medicine reports, vitamin D supplements prescribed by a doctor are beneficial. To achieve vitamin D recommendations — 600 IU per day for people 1 to 70 years old and 800 IU per day for individuals 71 or older — include whole foods, such as salmon, tuna, milk, mushrooms, and fortified cereals in your daily diet. You can also spend a brief time in the sun without sunblock — about 10 to 15 minutes a day, according to the NIH.