Dietary supplement

• 1. Introduction

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  A dietary supplement is a manufactured product meant to add to a person's diet, sold as a pill, capsule, tablet, powder, or liquid. In the United States in 2021, the industry behind these products was estimated to be worth $151.9 billion. More than 95,000 such products sit on American shelves. About 60% of American adults take them, and the figure climbs to 74% among those over the age of 60. Yet a striking line runs through the science. There is little evidence of benefit when healthy people with an adequate diet add these products on top of their food. So what counts as a supplement, and what does not? Who decides whether one is safe before it reaches a buyer, and who decides afterward? Why do labels carry the strange admission that a government agency has not evaluated their claim? And what turns up when investigators test what is actually inside the bottle?

• 2. What The Law Calls A Supplement

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  The Dietary Supplement Health and Education Act of 1994, known as DSHEA, set the legal boundaries in the United States. It defines a supplement by the dietary ingredients it carries: a vitamin, a mineral, an herb or other botanical, an amino acid, or a concentrate, metabolite, constituent, extract, or combination of these. The product must be labeled as a dietary supplement and meant to be swallowed. It must not be presented as a conventional food or as the sole item of a meal. Under DSHEA, supplements are deemed to be food, except where the drug definition applies. The act also defines these products largely by what they are not. They are not conventional foods, not meal replacements, not medical foods, not preservatives, and not pharmaceutical drugs. A nasal spray does not qualify, and neither does a lotion applied to the skin. FDA-approved drugs cannot be ingredients. The category stretches across vitamins, essential minerals, amino acids, essential fatty acids, substances pulled from plants, animals, fungi or bacteria, and live microorganisms in the case of probiotics. It even covers synthetic copies of natural substances, such as melatonin. Unlike drugs, supplements need no government approval before they are made or sold. The manufacturer itself confirms their safety, and the FDA steps in only to pull an unsafe product from the market.

• 3. The Claims Game

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  It is against federal regulations in the United States for a supplement maker to claim a product prevents or treats any disease, since only a medication may legally say that. Companies instead use "Structure/Function" wording when scientific evidence supports a potential health effect, such as a product that "helps maintain healthy joints." That phrasing carries a required disclaimer that the FDA "has not evaluated the claim" and that the product is not meant to "diagnose, treat, cure or prevent any disease." A narrow exception exists where the FDA has reviewed the science, found significant scientific agreement, and published exact wording. Calcium earned such a claim for osteoporosis, later amended effective the 1st of January 2010 to cover calcium with or without vitamin D. To qualify, a supplement must contain at least 20% of the Reference Dietary Intake, which for calcium means at least 260 mg per serving. One allowed line reads: "Adequate calcium throughout life, as part of a well-balanced diet, may reduce the risk of osteoporosis." Qualified Health Claims set a lower bar, supported by evidence that falls short of significant scientific agreement, and the FDA dictates their precise wording. The result can be tortured: "One study suggests that selenium intake may reduce the risk of bladder cancer in women. However, one smaller study showed no reduction in risk. Based on these studies, FDA concludes that it is highly uncertain that selenium supplements reduce the risk of bladder cancer in women."

• 4. Vitamins And Minerals

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  Ascorbic acid, known as vitamin C, is a vitamin for anthropoid primates, humans, guinea pigs and bats, but not for other mammals. That detail captures what a vitamin really is: an organic compound an organism cannot make in sufficient quantity and so must get from the diet. Humans require thirteen vitamins, many of them groups of related molecules called vitamers, like the tocopherols and tocotrienols that make up vitamin E. Vitamin D is an exception to the rule, since people with enough ultraviolet light synthesize it in their skin. The U.S. Institute of Medicine sets tolerable upper intake levels for some vitamins, yet these do not stop companies from selling more per serving. The upper level for vitamin D is 100 micrograms, equal to 4,000 IU, but products are sold without prescription at 10,000 IU. Minerals are the chemical elements life cannot do without. Carbon, hydrogen, oxygen, and nitrogen are essential but so common in food that they are not treated as nutrients with recommended intakes. The essential mineral nutrients, ranked by the weight needed, run from potassium, chlorine, sodium, calcium, phosphorus and magnesium down through iron, zinc, manganese, copper, iodine, chromium, molybdenum, selenium and cobalt. There is a curious medical thread here too. People with hypokalemic sensory overstimulation are sometimes diagnosed with attention deficit hyperactivity disorder, and the sensory overload responds to oral potassium gluconate.

• 5. Protein And Amino Acids

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  Whey protein is the popular ingredient in the powders and ready-to-drink products marketed to athletes, to people recovering from illness or injury, and to those fighting the muscle loss of old age. Other formulas lean on casein, soy, pea, hemp or rice protein. A meta-analysis found a moderate degree of evidence that whey is a safe and effective addition to an athlete's training and recovery, with benefits for endurance, average power, muscle mass, and reduced perceived exercise intensity. The recommended dietary allowance for adults, set for sedentary and lightly active people, is 0.8 grams of protein per kilogram of body weight. The International Olympic Committee recommends roughly 1.2 to 1.8 grams per kilogram per day for both strength and endurance athletes, while one review proposed a ceiling near 2.0 to 2.5 grams per kilogram. Proteins are chains of amino acids, and nine of these are essential because the human body cannot build them from other compounds. Single amino acids are sold on their own claims. The branched-chain trio of leucine, valine and isoleucine is sold to stimulate muscle protein synthesis, though a review of the literature found that claim unwarranted. In elderly people, leucine alone produced a modest 0.99 kilogram gain in lean body mass. Arginine is thought to act as a donor for nitric oxide, a vasodilator, and a review confirmed it lowers blood pressure. Taurine, popular for sports performance, is technically not an amino acid at all, since the body synthesizes it from cysteine.

• 6. Fats, Botanicals And Bacteria

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  Fish oil is the common fatty acid supplement, valued as a source of omega-3 fatty acids. Only two fatty acids count as essential to get from the diet, both polyunsaturated: alpha-linolenic acid, an omega-3, and linoleic acid, an omega-6. The body can elongate alpha-linolenic acid into eicosapentaenoic acid and docosahexaenoic acid, known as EPA and DHA, which otherwise come from oceanic fish, krill oil, or marine algae extracts. The European Food Safety Authority sets 250 mg a day as an adequate intake for combined EPA and DHA. The evidence has disappointed. Supplementing with these does not appear to affect the risk of death, cancer or heart disease, and studies have failed to support claims of preventing heart attacks or strokes. In 2017, the American Heart Association advised that it could not recommend omega-3 fish oil for primary prevention of cardiovascular disease or stroke, while reaffirming it for people with a history of coronary heart disease. Botanical products tell their own story. Supplements drawn from plants, animals, algae, fungi or lichens include ginkgo biloba, curcumin, cranberry, St. John's wort, ginseng, resveratrol, glucosamine and collagen. In 2019, herbal supplement sales in the United States reached $9.6 billion, growing about 8.6% a year, with cannabidiol and mushroom products leading. Probiotic supplements, by contrast, lack sufficient clinical evidence for their claimed benefits, though meta-analyses report a modest reduction of antibiotic-associated diarrhea and acute diarrhea in children, and the products are generally regarded as safe.

• 7. What Is Really In The Bottle

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  Over 2008 to 2011, the Government Accountability Office received 6,307 reports of health problems from supplement use, and its testing found 92% of herbal supplements contained lead and 80% held other chemical contaminants. Undercover staff caught retailers in what the office called "unequivocal deception," pushing baseless health claims, especially at elderly buyers. Consumer Reports found unsafe levels of arsenic, cadmium, lead and mercury in several protein powders, while the Canadian Broadcasting Corporation reported that protein spiking, the addition of amino acids to game the protein count, was common. In 2015, the New York Attorney General named four major retailers selling products with fraudulent and potentially dangerous ingredients and forced the items off store shelves. By that office's testing, only about 20% of the herbal supplements actually contained the plants named on the label, though the DNA-based method was disputed. A study of supplements sold between 2007 and 2016 found 776 that hid pharmaceutical drugs. Some 86% of the adulterated products were marketed for weight loss and sexual performance, many laced with prescription erectile dysfunction medication. Muscle-building products were spiked with anabolic steroids, which can damage the kidney and heart and cause gynecomastia. Despite all of this, fewer than half of the adulterated supplements were recalled.

• 8. Regulators And The Verdict

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  The U.S. Food and Drug Administration treats supplements as a subset of food, holding them to current good manufacturing practices established in 2007 and to science-based labeling. It can inspect facilities, send warning letters, halt production, and demand a recall when a health risk exists, but its Center for Food Safety and Applied Nutrition may review a product for safety and effectiveness only after it is already on the market. The Federal Trade Commission targets deceptive advertising and in 2017 successfully sued nine manufacturers over misleading supplement claims. Across the Atlantic, the European Union's Food Supplements Directive of 2002 requires that products be shown safe in dosage and purity before sale. The directive met fierce resistance. The supplements industry in the United Kingdom opposed it, and over a million UK consumers signed petitions against what they saw as unjustified limits on choice. The Alliance for Natural Health, joined by two British trade associations, brought a legal challenge to the European Court of Justice in 2004. The Advocate General said the plan should be scrapped, but the court overruled him, deciding the measures were necessary to protect public health. Stepping back, the broader verdict is sober. As of 2016, robust clinical data was lacking that any dietary supplementation does more good than harm for healthy people eating a reasonable diet. The strong data points elsewhere, toward dietary pattern and lifestyle, which is why public health guidance urges a plant-based diet of whole foods, less ultra-processed food, salt and sugar, and daily exercise rather than a pill.