Dietary Supplements Basics

You already know that eating a balanced, nutritious diet supports good health. But have you ever wondered whether your own diet provides everything your body needs? Maybe you’ve thought about taking a vitamin or mineral supplement—or one of the many products that promise to help you lose weight, build muscle, ease joint pain, or boost your gut health.

You’re not alone! In a large national survey published in the Journal of the American Medical Association,  more than half of U.S. adults (52%) reported using dietary supplements between 2011 and 2012.^[1]

With so many people taking supplements, it’s worth asking:

• Are they safe?

• Do they really work?

• Who actually needs them?

Let’s explore these questions together.

What Counts as a Dietary Supplement?

A dietary supplement is a product that:

• Adds nutrients or other substances to the diet.

• Contains one or more ingredients such as vitamins, minerals, herbs, botanicals, amino acids, or enzymes.

• Is taken by mouth (pill, capsule, tablet, or liquid).

• Is clearly labeled as a “dietary supplement.”

How Are Supplements Regulated?

Dietary supplements are regulated by the Food and Drug Administration (FDA)—but not in the same way as foods or drugs.

In 1994, the Dietary Supplement Health and Education Act (DSHEA) set the rules that are still in place today. Under DSHEA, the FDA does not review supplements for safety or effectiveness before they reach the market. Instead, manufacturers themselves are responsible for ensuring their products are safe. ^[2]

The FDA can only remove a product after proving it is unsafe—a major difference from prescription drugs, which must demonstrate safety and effectiveness before approval.

To improve quality control, the FDA issued Good Manufacturing Practices (GMPs) in 2007. GMPs outline standards for how supplements must be made, stored, and tested to ensure identity, purity, and strength. ^[3]

If consumers or companies report side effects, the FDA can investigate and take action, such as issuing warnings or removing unsafe products from the market. However, the FDA notes that it’s impossible to test every supplement sold, so consumers still need to use caution.

Are Dietary Supplements Safe?

Because safety oversight occurs after products reach the market, supplement safety is largely in manufacturers’ hands. Unfortunately, not all companies follow best practices—especially when profits are at stake.

According to the FDA, supplements have been recalled for contamination (with bacteria, pesticides, or heavy metals) and for containing incorrect or misleading ingredient amounts. ^[4]

Here are some key takeaways from the National Center for Complementary and Integrative Health (NCCIH):^[5]

• Labels aren’t always accurate. Some “supplements” have been found to contain prescription drugs such as warfarin or phenytoin.

• Illegal claims are common. In one government study, 20% of weight-loss or immune-support supplements made false or illegal claims.

• Interactions can be dangerous. For instance, St. John’s wort can reduce the effectiveness of some medications.

• “Natural” doesn’t always mean safe. Ephedra, once used in energy and weight-loss supplements, caused heart attacks and deaths before being banned in 2004.

• Supplements can cause real harm. A 2015 study estimated 23,000 emergency room visits each year in the U.S. are linked to dietary supplements—often due to heart problems from energy or weight-loss products or swallowing issues in older adults.

• “Certified” or “standardized” isn’t a guarantee. These terms are marketing tools, not legal standards.

If you ever experience a reaction to a supplement, you can report it through the U.S. Health and Human Services Safety Reporting Portal.

With current regulations, the safety of dietary supplements is the manufacturer’s responsibility. Unfortunately, manufacturers don’t always have the public’s best interest in mind, especially when there is a profit to be gained.

Do Supplements Really Work?

Scientific evidence for dietary supplements varies dramatically. Some have solid research behind them—others have almost none.

According to the National Center for Complementary and Integrative Health:

• Supplements can’t legally claim to diagnose, treat, cure, or prevent diseases. Instead, they use vague structure/function claims like “boosts immunity” or “supports heart health,” which require no proof.

• A few supplements may be beneficial in specific situations—melatonin, for example, is helpful for jet lag.

• Others show little or no benefit, such as ginkgo for memory or echinacea for colds.

• Most studies on multivitamin/mineral (MVM) supplements show no clear benefit in preventing chronic disease or extending life.^[6]

The takeaway? Research is mixed, and many products simply don’t live up to their claims.

Getting Nutrients: Food First

Nutrition expert Marion Nestle sums it up perfectly:

“Unless you have been diagnosed with a deficiency and need to replenish that nutrient quickly, it’s always better to get nutrients from foods—the way nature intended.”^[7]

She explains three main advantages of getting nutrients from food instead of supplements:

1. Variety: Foods naturally provide a wide range of nutrients—vitamins, minerals, antioxidants, and more—not just one isolated nutrient.

2. Balance: Nutrients in foods occur in proportions that support each other’s effectiveness without interfering with digestion or absorption.

3. Safety: Nutrients from foods are unlikely to reach toxic levels (with rare exceptions, such as polar bear liver, which is extremely high in vitamin A).

High doses of single nutrients don’t necessarily improve health—and in some studies, they’ve made things worse. For example, excess beta-carotene, vitamin E, or folic acid has sometimes been linked with higher risks of heart disease or cancer. And, of course, food tastes much better!

 Who Might Benefit from Supplements?

While most people can meet their needs through food, certain groups may benefit from taking a multivitamin/mineral (MVM) or specific nutrient supplements:

• Older adults may have trouble absorbing vitamin B₁₂ or getting enough vitamin D.

• Vegans or strict vegetarians, who may need vitamin B₁₂, iron, or zinc.

• People on calorie-restricted diets or with food insecurity.

• Pregnant individuals need folate, iron, and sometimes omega-3 fatty acids.

If you fall into one of these categories, a supplement may help fill nutrient gaps—but moderation and careful selection are key.

Smart Tips for Choosing Supplements

Use these seven evidence-based tips to make safer, more effective choices:

1. Don’t substitute for whole foods.

According to the Dietary Guidelines for Americans, 2025–2030, nutrient needs should be met primarily through nutrient-dense foods and beverages. Whole foods provide not only essential vitamins and minerals, but also fiber, phytochemicals, and other bioactive compounds that work together to support health in ways supplements cannot fully replicate. Supplements can be useful in specific situations, but they are intended to fill gaps—not replace a healthy eating pattern.  ^[8]

2. Check the dose carefully.

Because supplements aren’t pre-approved by the FDA, some products contain nutrient levels far above the safe Upper Intake Level (UL). Choose products that stay close to 100% of the Daily Value (DV) unless a healthcare provider recommends otherwise.

3. Add up your total intake.

Supplements can come in pill, powder, or drink form, such as vitamin water or protein shakes. Always consider the combined total of all sources to avoid accidental overdosing.

4. Be skeptical of big claims.

Manufacturers can make structure/function claims such as “boosts immunity” or “supports joint health” without proving that their product works. If something sounds too good to be true, it probably is.

5. Look for third-party testing.

Independent organizations such as ConsumerLab.com, NSF International, U.S. Pharmacopeia (USP), and UL conduct third-party testing to verify product quality. ^[9]
Supplements with these verification seals have been tested to confirm they:

• Contain the listed ingredients in the right amounts.

• Are free from harmful levels of contaminants (like heavy metals).

• Break down properly in the body for absorption.

6. Choose the right formula for you.

Different life stages have different nutrient needs:

• Seniors: More calcium and vitamin D.

• Women: More iron.

• Prenatal supplements: Contain folate and iron but avoid preformed vitamin A (retinol).

• Children: Age-appropriate nutrient levels.

Always check the label for your age, sex, and health status.

7. Talk with your healthcare provider.

Supplements can interact with both prescription and over-the-counter medications—sometimes with serious or even life-threatening effects. Always discuss any new supplement with your healthcare provider or pharmacist.

🎥 Watch & Learn

Video: “Supplements and Safety” – PBS Frontline (54:11)

An in-depth look into the hidden dangers of vitamins and supplements—a multibillion-dollar industry with limited FDA oversight. Produced by FRONTLINE, The New York Times, and the Canadian Broadcasting Corporation, the documentary investigates marketing, regulation, and cases of contamination and serious health risks.