Human Performance & Health › Supplements › Foundational Supplements

This page sets out, nutrient by nutrient, what the NIH Office of Dietary Supplements (ODS) and published research say: what each one does in the body, who is documented as more likely to fall short, what trials of supplementation found, and where too much causes harm. It names no brands and does not say what anyone should take. Whether any of it applies to you is a question for a clinician who knows your history and, for the nutrients that can be measured, a blood test.

Food and supplements

ODS: “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). The Supplements page carries the FDA’s and ODS’s statements on regulation and dose.

Nutrients with documented shortfalls or at-risk groups

Omega-3 fatty acids (EPA and DHA)

ODS: “ALA and linoleic acid are considered essential fatty acids, meaning that they must be obtained from the diet,” and the body’s conversion of ALA to EPA and DHA “is very limited, with reported rates of less than 15%.” “Omega-3s play important roles in the body as components of the phospholipids that form the structures of cell membranes,” and they are precursors of eicosanoids, signaling molecules that affect inflammation. On outcomes, ODS reports that in the VITAL trial “the omega-3 supplement did not significantly reduce the rate of major cardiovascular events combined,” and that “The AHA does not recommend omega-3 supplements for people who do not have a high CVD risk” (ODS, Omega-3 Fatty Acids). The American Heart Association’s 2017 advisory notes that the effects of supplementation for primary prevention “in the general population have not been examined” in randomized trials (Siscovick et al., 2017).

Safety: ODS says fish oil “might prolong clotting times” in people taking warfarin, and that labels of FDA-approved omega-3 products advise that patients on anticoagulants “should be monitored periodically for changes in INR.” Anyone on an anticoagulant should talk to the prescriber before starting or stopping fish oil.

Vitamin D (and the K2 question)

ODS: “Vitamin D promotes calcium absorption in the gut,” and it is involved in “cell growth, neuromuscular and immune function.” The groups ODS names as at risk of inadequacy are breastfed infants, older adults, people with limited sun exposure, people with dark skin, people with conditions that limit fat absorption, and people with obesity or who have had gastric bypass surgery. “Serum concentration of 25(OH)D is the main indicator of vitamin D status.” In the VITAL trial, “Rates of breast, prostate, and colorectal cancer did not differ significantly between the vitamin D and placebo groups,” and “Overall, clinical trials show that vitamin D supplementation does not reduce CVD risk.” The Tolerable Upper Intake Level is 100 mcg (4,000 IU) a day for adults, and “Vitamin D toxicity is almost always a result of excessive intakes of vitamin D through supplements”; ODS also lists interactions with orlistat, statins, steroids and thiazide diuretics (ODS, Vitamin D). Anyone taking one of those medicines should ask the prescriber or a pharmacist before using a vitamin D product.

Vitamin K2 is often sold alongside vitamin D. ODS (fact sheet updated March 29, 2021): “it is unclear whether supplementation with any form of vitamin K reduces the risk of osteoporosis,” and “the role of the different forms of vitamin K on arterial calcification and the risk of coronary heart disease is unclear.” Safety: “People taking warfarin and similar anticoagulants need to maintain a consistent intake of vitamin K,” because sudden changes can raise or lower the drug’s effect (ODS, Vitamin K). Anyone on an anticoagulant should talk to the prescriber before starting, stopping or changing a vitamin K product.

Magnesium

ODS: “Magnesium is a cofactor in more than 300 enzyme systems that regulate diverse biochemical reactions in the body,” including protein synthesis and muscle and nerve function, and “Magnesium is required for energy production, oxidative phosphorylation, and glycolysis.” “Many people in the United States consume less than the recommended amounts of magnesium.” On forms, “the aspartate, citrate, lactate, and chloride forms of magnesium tend to have higher bioavailability than magnesium oxide.” On safety, “high doses of magnesium from dietary supplements or medications often result in diarrhea,” and “The Tolerable Upper Intake Level for supplemental magnesium is 350 mg for adults” (ODS, Magnesium, updated January 6, 2026). The ODS fact sheet does not address magnesium and sleep.

Dietary fiber

A series of meta-analyses in The Lancet reported that “Observational data suggest a 15-30% decrease in all-cause and cardiovascular related mortality” with higher fiber intake, greatest at 25 to 29 grams a day (Reynolds et al., 2019), and “only about 5% of the population meets recommendations” (Quagliani & Felt-Gunderson, 2017). The figures are on Nutrition.

Vitamin B12

ODS names older adults, people with pernicious anemia or gastrointestinal disorders, and people who follow vegetarian diets among the groups at risk of deficiency. It states that for vegetarians and vegans “vitamin B12 supplements can substantially reduce the risk of deficiency,” and that regular users of metformin or acid-reducing drugs “should discuss their vitamin B12 status with their health care providers” (ODS, Vitamin B12). The deficiency signs and blood tests are on Energy, Fatigue & Capacity.

Electrolytes

ODS describes the sodium-potassium gradient across cell membranes as “required for proper nerve transmission, muscle contraction, and kidney function,” and states that “people in the United States consume less potassium than recommended” (ODS, Potassium, updated June 2, 2022). For heavy sweating, NIOSH’s guidance for work in heat is that “for prolonged sweating lasting several hours, sports drinks with balanced electrolytes are another option to replace salt lost in sweat” (NIOSH 2017-126), and the American College of Sports Medicine’s goal after exercise is “to replace any fluid electrolyte deficit” (Sawka et al., 2007). A clinician can say what applies to a person with a medical condition or on medication.

Studied for training

Protein

The International Society of Sports Nutrition puts daily protein for most exercising people at about 1.4 to 2.0 grams per kilogram (Jäger et al., 2017), and a meta-analysis found that “Protein supplementation beyond total protein intakes of 1.62 g/kg/day resulted in no further RET-induced gains in FFM” (Morton et al., 2018). The figures, with the general-population range from the Dietary Guidelines, are on Nutrition.

Creatine monohydrate

The International Society of Sports Nutrition position stand calls creatine “one of the most popular nutritional ergogenic aids for athletes” and states that supplementation raises muscle creatine, which may explain improvements in high-intensity exercise; that short- and long-term supplementation is “safe and well-tolerated in healthy individuals” and in a range of patient populations; that “Creatine monohydrate is the most effective ergogenic nutritional supplement currently available to athletes with the intent of increasing high-intensity exercise capacity and lean body mass during training”; that “There is no compelling scientific evidence that the short- or long-term use of creatine monohydrate (up to 30 g/day for 5 years) has any detrimental effects on otherwise healthy individuals or among clinical populations who may benefit from creatine supplementation”; and that “creatine monohydrate is the most extensively studied and clinically effective form of creatine.” Its final point: “Further research is warranted to examine the potential medical benefits of creatine monohydrate” (Kreider et al., 2017; numbered points read on Texas A&M’s Exercise and Sport Nutrition Lab posting). Creatine is studied for performance, not for filling a dietary gap.

Narrow or absent evidence

CoQ10. The National Cancer Institute’s summary states that statins “cause a decrease in serum levels of coenzyme Q10 and reduce the effects of coenzyme Q10 supplementation” (NCI PDQ, Coenzyme Q10, October 31, 2024). A 2020 review of seven placebo-controlled trials (321 participants), reported by Harvard Health Publishing, “showed no benefit for people with statin-associated muscle pain who took CoQ10” (Harvard Health, June 1, 2020).

Branched-chain amino acids (BCAAs). A 2017 review concluded “that the claim that consumption of dietary BCAAs stimulates muscle protein synthesis or produces an anabolic response in human subjects is unwarranted” (Wolfe, 2017).

Where excess causes harm

ODS sets Tolerable Upper Intake Levels (ULs) for adults and describes the harm from excess:

• Iron: UL 45 mg. “Adults with normal intestinal function have very little risk of iron overload from dietary sources of iron”; hemochromatosis, caused by a mutation in the HFE gene, “is associated with an excessive buildup” of iron; “Often, health care providers will use multiple measurements to diagnose iron deficiency” (ODS, Iron, updated September 4, 2025).
• Zinc: UL 40 mg. Doses of 50 mg or more taken for weeks “can interfere with copper absorption (which can cause low copper status)” (ODS, Zinc, updated January 6, 2026).
• Iodine: UL 1,100 mcg. Iodine is “an essential component of the thyroid hormones thyroxine (T4) and triiodothyronine (T3)”; deficiency causes “inadequate thyroid hormone production,” and “Iodine-induced hyperthyroidism can also result from high iodine intakes” (ODS, Iodine, November 5, 2024).
• Vitamin D: UL 100 mcg (4,000 IU), above.
• Magnesium (supplemental): UL 350 mg, above.

The ULs are ODS’s figures for healthy adults; whether a lower or higher amount applies to a given person, and whether a measured level is low or high, is a question for a clinician who can order the blood tests.

How this page is grouped

The headings above group nutrients by what the sources document: a common shortfall or at-risk group, use in training studies, narrow or absent evidence for the claim usually made, and an upper limit above which harm is described. The grouping is not a ranking or a list to take.

Where this fits in the system

The Supplements overview covers regulation and dose. Nutrition covers what the research says about food. The Biological Foundation covers the cellular side, including the trial in which high-dose vitamins C and E blocked a benefit of exercise. Energy, Fatigue & Capacity covers the medical causes of fatigue. All of it lives under the Human Performance & Health hub.

GoldBlock Workshop is educational. We explain how nutrients work and what the research says. We do not diagnose, treat, or give personal medical advice, and dietary supplements are not intended to diagnose, treat, cure, or prevent any disease. Talk to a qualified healthcare professional before starting, stopping, or changing any supplement, especially if you are pregnant or nursing, take medication, or have a health condition.

Sources and further reading

We credit the work below by pointing to it rather than reproducing it. ODS fact sheets were read 2026-10-19 unless noted; the date shown is the fact sheet’s own “updated” date where the page gives one.

General. NIH ODS, “Dietary Supplements: What You Need to Know” (verified 2026-10-18). NIH ODS

Omega-3s. NIH ODS, “Omega-3 Fatty Acids” (Health Professional). NIH ODS · Siscovick et al., “Omega-3 Polyunsaturated Fatty Acid (Fish Oil) Supplementation and the Prevention of Clinical Cardiovascular Disease,” AHA Science Advisory, Circulation 135(15):e867-e884 (2017); abstract read 2026-10-19 (USUHS listing). PubMed

Vitamin D. NIH ODS, “Vitamin D” (Health Professional), including the VITAL results. NIH ODS

Vitamin K. NIH ODS, “Vitamin K” (Health Professional), updated March 29, 2021. NIH ODS

Magnesium. NIH ODS, “Magnesium” (Health Professional), updated January 6, 2026. NIH ODS

Fiber. Reynolds et al., The Lancet (2019). Dundee manuscript · Quagliani & Felt-Gunderson, American Journal of Lifestyle Medicine (2017). Journal

Vitamin B12. NIH ODS, “Vitamin B12” (Health Professional; verified 2026-10-18). NIH ODS

Electrolytes and hydration. NIH ODS, “Potassium” (Health Professional), updated June 2, 2022. NIH ODS · NIOSH, “Heat Stress: Hydration,” Publication No. 2017-126 (verified 2026-10-18). stacks.cdc.gov · Sawka et al., ACSM Position Stand, “Exercise and Fluid Replacement,” Medicine & Science in Sports & Exercise (2007; verified 2026-10-18). PubMed

Protein. Jäger et al., ISSN position stand (2017). PubMed · Morton et al., British Journal of Sports Medicine (2018). AUT repository

Creatine. Kreider et al., “International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation in exercise, sport, and medicine,” Journal of the ISSN 14 (2017); abstract read 2026-10-19 (DOAJ), numbered points read on the Texas A&M Exercise and Sport Nutrition Lab posting of June 13, 2017. DOAJ · Texas A&M ESNL

CoQ10. National Cancer Institute, “Coenzyme Q10 (PDQ), Health Professional Version,” October 31, 2024 (read 2026-10-19). NCBI Bookshelf · Harvard Health Publishing, “CoQ10 supplements unlikely to benefit statin users,” June 1, 2020 (read 2026-10-19). Harvard Health

BCAAs. Wolfe RR, “Branched-chain amino acids and muscle protein synthesis in humans: myth or reality?” Journal of the ISSN 14:30 (2017; read 2026-10-19). JISSN

Iron, zinc, and iodine. NIH ODS Health Professional fact sheets: Iron (updated September 4, 2025) · Zinc (updated January 6, 2026) · Iodine (November 5, 2024)