Dietary and Health Supplements Scorecard

Dietary supplements are widely used by almost half of the adult population. Unsurprisingly, people are interested in improving their health, and the supplement industry capitalizes on this desire to drive sales.

In contrast to medications regulated by the FDA and requiring evidence of safety and efficacy, dietary supplements fall under different regulations. The Dietary Supplement, Health and Education Act, limits the FDA's ability to regulate these products, which are often marketed for health purposes rather than nutrition. This means that manufacturers can sell supplements without providing evidence of their purity, potency, safety, or effectiveness.

Supplement labels often make claims without providing any proof to back them up.

Moreover, supplement labels often make claims without providing any proof to back them up. The FDA only gets involved after a product is marketed and can only take action against those that are misbranded, adulterated, or likely to cause illness or injury. Since most people use supplements without medical supervision, adverse reactions often go unreported, contributing to the estimated 50,000 cases each year in the United States.

While supplements can provide benefits in certain situations, it's important to recognize these products' limitations and be aware of the potential risks. As always, it's best to consult with a healthcare professional before starting any new supplement regimen.

How Do We Evaluate Supplements?

When it comes to determining the effectiveness and safety of supplements, it can be challenging to separate fact from fiction. Supplement labels and advertisements often make bold claims that may not be supported by scientific evidence.

The most reliable way to assess a supplement's benefits or risks is through careful medical studies. These studies typically begin with observational research, in which scientists compare the health outcomes of people who take a specific supplement with those who don't. While this type of research is essential, the results are not always conclusive.

To gain a more definitive understanding of a supplement's effects, scientists will often conduct randomized clinical trials. In these studies, participants are randomly assigned to either take the supplement or a placebo (a pill that looks identical to the supplement but contains no active ingredients). Throughout the trial, researchers track the participants' health, and neither the participants nor the researchers know who is taking the real supplement until the end of the study.

The most rigorous studies use this double-blind approach to ensure that the results are as unbiased as possible. By comparing the health outcomes of participants who take the supplement with those who take the placebo, researchers can determine whether the supplement is truly effective and safe. While these studies can take time, they provide valuable information that can help guide decisions about supplement use.

What Does the Science Say?

The question of whether supplements can improve health is one that has been asked by many. While we have some answers, it's important to note that our understanding of supplements is constantly evolving as new research emerges. While some supplements have shown promise, others have not lived up to their hype.

Many people take supplements as a preventive measure to maintain good health or prevent illness. Others use supplements to treat specific health conditions. In this section, we'll focus on popular supplements in both of these categories, beginning with preventive supplements that healthy individuals primarily use.

Supplements for Disease Prevention

Vitamin D:

One of the most important preventive supplements is vitamin D. Our bodies produce this vitamin naturally when exposed to sunlight, but many people don't get enough of it due to factors such as spending too much time indoors or using sunscreen. Vitamin D is crucial for healthy bones, as it helps our bodies absorb calcium. While the recommended daily intake for vitamin D is 600 IU for adults under 71 and 800 IU for those over 71, many experts suggest taking 800 to 1,000 IU per day. Supplements are often necessary since it's difficult to get enough vitamin D from diet alone. Vitamin D3 is the most common form of the supplement, but D2 can also be effective.


Another popular category of supplements for prevention is antioxidants, such as vitamin E, vitamin A, beta-carotene, and vitamin C. However, many clinical trials have failed to find any benefit of antioxidants against heart disease, cancer, or other illnesses.

In fact, taking high doses of vitamin A can increase the risk of hip fractures and prostate cancer, while beta-carotene can increase lung cancer risk in smokers. Vitamin E has been linked to an increase in respiratory infections, heart failure, and overall mortality. As a result, it's generally not recommended to take antioxidant supplements. The exception is for people with moderate or advanced age-related macular degeneration (AMD), who can benefit from specific antioxidant supplements that contain zinc. However, these supplements do not prevent AMD in people with healthy eyes


Another category of essential supplements is the B vitamins. Vitamin B12, which is only found in animal-based foods, may be lacking in strict vegetarian diets or in older people who don't produce enough stomach acid to absorb the vitamin from food. However, fortified grain products and synthetic B12 can also provide the necessary daily intake of 2.4 micrograms (mcg). If fortified grain products are not consumed regularly, taking a B12 supplement is reasonable.

Folate, another B vitamin, is critical for the production of red blood cells and plays an essential role in DNA production and genetic code repair. While folate is present in many foods, including leafy green vegetables, fruits, legumes, and meats, many Americans did not meet the recommended daily intake of 400 mcg until the late 1990s. To address this issue, the U.S. and Canadian governments mandated folic acid fortification of all grain products from 1998 onwards, reducing the risk of birth defects. However, obstetricians still recommend folate supplements for women who are pregnant or trying to conceive.

Finally, despite their popularity, multivitamins have not been shown to improve health, prevent illness, or enhance overall well-being. However, some doctors continue to recommend them for their convenience and as a source of vitamin D, although most multivitamins only provide 400 IU, which is less than the currently recommended daily intake of 800 to 1,000 IU.

Other Supplements

Fish Oil:

In addition to the previously mentioned supplements, there are others that people may consider taking. Fish oil, for example, has been shown to provide protection against heart disease and stroke for those who don't regularly consume fish. However, people who eat fish at least twice a week are unlikely to benefit from extra fish oil. It's important to consult with a doctor before taking fish oil, and to avoid fish liver oil due to its high vitamin A content.


Fiber supplements are often thought of as a remedy for constipation, but a high intake of fiber has numerous potential health benefits, including reducing the risk of heart disease, obesity, hernias, varicose veins, and diverticulitis. The recommended daily intake of fiber varies depending on age and gender, but most people do not consume enough fiber from diet alone. Psyllium is a good fiber supplement option, as it also helps lower cholesterol levels.


Selenium is a mineral that has been studied in relation to prostate cancer and heart disease. While early reports suggested that selenium could reduce the risk of prostate cancer, subsequent studies have produced mixed results, and a large-scale study found that selenium had no benefit against prostate cancer. Additionally, selenium has been linked to an increased risk of diabetes. As a result, selenium is not generally recommended as a supplement.

Buyer Beware

When considering taking a supplement, it's important to be cautious and aware of potential risks. Here are a few things to keep in mind:

  • Be skeptical of extravagant claims, as they are often too good to be true.
  • Testimonials and endorsements, especially from celebrities, may not provide reliable information about a product's safety or effectiveness.
  • More is not always better; taking too much of a supplement can be harmful.
  • Beware of meaningless terms like "all-natural" or "clinically proven," as they may not have any real meaning or scientific backing.
  • Supplements can interact with prescription and over-the-counter medications, so discussing all supplements with doctors and pharmacists is important.
  • Beware of adulterated products, which can contain undisclosed pharmaceutical ingredients and pose serious health risks.
  • Supplements may not contain the amount of ingredients that they claim to, so look for products that private organizations like the United States Pharmacopeia or NSF International have approved.

Not Substitutes for Proper Nutrition

Supplements are not a substitute for good health practices and medical care. While some supplements may be helpful, many others can be harmful or ineffective. False hopes and reliance on supplements can be detrimental to your health if they prevent you from taking care of yourself or seeking medical attention when necessary. It's important to maintain a healthy diet, exercise regularly, and work with your doctor to manage your health. Additionally, be open and honest with your doctor about all the supplements you are taking, as they can interact with medications and have adverse effects. Full disclosure is important for your health and well-being.

William H. McDaniel, MD

Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School.

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