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Supplements

Human Performance & Health › Supplements

This page explains what dietary supplements can and cannot do, according to the public health bodies that study them, when a lab test adds information, and how the supplement pages on this site are organized. It does not tell you what to take. That decision belongs with you and, where it matters, a clinician who knows your history.

What Supplements Are (and Are Not)

The NIH Office of Dietary Supplements: “Some dietary supplements can help you get adequate amounts of essential nutrients” if you do not eat a nutritious variety of foods, but “supplements can’t take the place of the variety of foods that are important to a healthy eating routine” (ODS, What You Need to Know).

On the broader claim that a daily multivitamin improves health in people who already eat well, the ODS review of the research says: “Most studies have found that taking MVMs has little or no effect on these health outcomes,” and “People should get most of their nutrients from food and beverages” (ODS, Multivitamin/mineral Supplements).

When Supplementation Is Studied as Useful

ODS names the groups for whom a multivitamin may make sense: “People who don’t get enough vitamins and minerals from food alone,” including people on low-calorie diets, with poor appetite, or who avoid certain foods, such as strict vegetarians and vegans; pregnant people; adults over 50 for vitamin B12; and patients whose “health care providers might also recommend MVMs” for a medical reason (ODS, MVMS).

Individual nutrients are covered one at a time, each with its NIH fact sheet, on Foundational Supplements.

Regulation and Risk

Supplements are regulated differently from medicines. ODS: “Medicines must be approved by FDA before they can be sold or marketed. Supplements do not require this approval.” The FDA states that manufacturers, not the FDA, are responsible for the safety and labeling of their products before they reach the market (FDA, Dietary Supplements).

On dose, ODS: “You are most likely to have side effects from dietary supplements if you take them at high doses,” and, as one example, “too much vitamin A can cause headaches and liver damage.” ODS also asks that you “tell your health care providers … about any dietary supplements you’re taking,” because supplements can interact with medicines and with each other (ODS, What You Need to Know).

Lab Testing

A blood test measures nutrient status directly, and for some nutrients both too little and too much cause harm; ODS uses serum 25-hydroxyvitamin D as the example (ODS, Vitamin D).

Ordering and reading the test is a clinician’s job.

How the Supplement Pages Are Organized

By purpose, not by marketing claim:

  1. Foundations: nutrients for which the NIH fact sheets document common shortfalls or specific uses. Live: Foundational Supplements.
  2. Performance and energy: compounds studied for physical output and focus. Not yet published.
  3. Recovery and sleep: compounds studied for rest and repair, read alongside Sleep & Recovery. Not yet published.
  4. Longevity: long-term and still-contested research. Not yet published.

Each published page carries the NIH or peer-reviewed source beside every claim, states dose ranges only as the source states them, and says plainly where the evidence is thin.

How This Fits the System

Supplements sit inside the larger Human Performance & Health system. Nutrition covers what the research says about food. The Biological Foundation covers the cellular side. If fatigue is the reason for looking, Energy, Fatigue & Capacity covers the medical causes MedlinePlus lists and when to see a clinician.

Disclosure

Educational, Nutritional & Affiliate Disclosure

This content is provided for educational and informational purposes only. It is not intended as medical, nutritional, dietary, or professional advice, and should not be relied upon as a substitute for guidance from a qualified healthcare or nutrition professional.

These statements have not been evaluated by the Food and Drug Administration. Nothing described here, and no supplement or product referenced, is intended to diagnose, treat, cure, or prevent any disease.

Nutritional needs vary based on individual health conditions, activity levels, and circumstances. Always use appropriate judgment and consult a qualified healthcare professional before starting, stopping, or combining any supplement, especially if you are pregnant or nursing, managing a medical condition, or taking medications.

This page has no affiliate links. Pages that do have them say so next to the links (see our Affiliate Disclosure).

Additional terms, limitations, and disclosures apply as outlined in our site-wide Disclaimer and Terms & Conditions.

Sources and Further Reading

The load-bearing claims on this page, that supplements support rather than replace a good diet, that blood testing identifies real nutrient deficiencies, that both too little and too much of a nutrient can cause harm, and that supplements are regulated differently from medicines, are drawn from the following public health sources. Structure and function context only; none of these sources is an endorsement of any product.

  • Supplements support a diet, they do not replace it; most people should get most nutrients from food. NIH Office of Dietary Supplements, “Multivitamin/mineral Supplements” (Consumer fact sheet). ods.od.nih.gov/factsheets/MVMS-Consumer
  • Supplements are regulated differently from drugs, are not intended to diagnose, treat, cure, or prevent disease, and you should tell your healthcare providers what you take. NIH Office of Dietary Supplements, “Dietary Supplements: What You Need to Know” (Consumer fact sheet). ods.od.nih.gov/factsheets/WYNTK-Consumer
  • A blood test measures nutrient status, and both deficiency and excess can be harmful. NIH Office of Dietary Supplements, “Vitamin D” (Consumer fact sheet), which uses serum 25-hydroxyvitamin D as the example. ods.od.nih.gov/factsheets/VitaminD-Consumer
  • Manufacturers and distributors are responsible for evaluating the safety and labeling of their products before marketing; FDA acts after a product reaches the market. U.S. Food and Drug Administration, “Dietary Supplements,” content current as of October 1, 2024 (read 2026-10-18). fda.gov/food/dietary-supplements

For a deeper, supplement-by-supplement look at the individual nutrients above, the citations on the Foundational Supplements page point to the matching NIH Office of Dietary Supplements Health Professional fact sheets.