Dietary supplements are mainly unregulated. Public health experts warn against the cure-all rhetoric boosting sales of an industry where supply chain opacity and poor quality are rampant.

There’s a long history of deceptive, pseudo-scientific remedies for poor health, from snake-oil salesmen traveling across the American frontier to the unproven effects of homeopathic ailments, which have proven time and again a lack of scientific basis: no homeopathic preparation has been proven to differ from any placebo in several studies across the decades.

Even if unregulated and sometimes lacking measurable amounts of the substances they promote in their packaging, dietary supplements can have an effect, positive as advertised or adverse, and medical authorities demand their regulation to protect the public from fraud or unattended health consequences.

During the Age of Discovery, European sailors would fall sick after long periods at sea, surviving on diets lacking fruit and vegetables. The medicine of the time should have accounted for remedies from Antiquity, all but forgotten. A few months after a person’s dietary intake didn’t account for ascorbic acid (vitamin C), sailors would develop bruising, bleeding gums, weakness, and fatigue, eventually developing high fevers and dying.

The supplement that boosted the Age of Discovery

Medicine wouldn’t prove the link between a lack of vitamin C (an essential nutrient involved in the repair of tissue) and the general weakness, poor wound healing, and hemorrhages caused by scurvy, a disease that killed, according to estimates, up to two million sailors between 1500 and 1800.

Portuguese explorer Vasco da Gama lost 116 of 170 sailors while reaching India by circumnavigating Africa in 1499, whereas Magellan’s expedition circumnavigating the globe in 1520 lost 208 out of a crew of 230 in five ships. Magellan faced starvation, mutinies, storms, and hostile encounters, but the main culprit of such mortality was, once again, scurvy. Magellan died in battle in the Phillippines, and when Elcano finally reached Spain on the Victoria, only 18 men were helping him.

Europeans knew about the curative effects of citrus fruit when Columbus, Vasco da Gama, Magellan, Cartier, and others set to travel beyond the limits of the Old World during the Age of Discovery. Portuguese commander Pedro Álvares Cabral, European conquistador of Brazil (and the first known human to set foot on four continents), included “refreshments” aboard to protect his crew from disease.

Already in the 18th-Century, aware of the evidence accumulated over three centuries of long transcontinental voyages decimating crews, British explorer James Cook succeeded in preventing scurvy on his ships by ensuring clean and ventilated quarters, but also including in the diet cress, sauerkraut, and orange extract.

Discovering vitamin C

Scientific evidence establishing an unequivocal relationship between vitamin C and tissue repair in humans didn’t arrive until the 20th century, however: unlike most animals, humans (like other apes, monkeys, bats, or rodents) can’t synthesize their own vitamin C and must acquire it from dietary sources. The threat of scurvy obliged sailors to test conjectures and develop real remedies against lethal disease.

Examples of formerly unknown phenomena leading to the wrong conclusions abound. Unknown diseases like Lyme disease and unhealthy living environments, like poorly ventilated homes that allowed for high concentrations of carbon monoxide, created auditive and visual hallucinations that explain the obsession with haunted houses, people suddenly possessed, or ghosts.

After centuries of exorcisms and disturbing unscientific claims regarding what people perceived when living in poor conditions, only better ventilation, modern heating and cooking systems, and modern medicine were a death sentence to such supernatural occurrences.

Similarly, the defeat of scurvy by trial-and-error (then emulation) before the arrival of modern medicine can be seen as a precursor of the potential of regulated, evidence-based dietary supplements capable of improving well-being and, in some cases, helping prevent disease.

A poorly regulated boom market

Only in the US, the dietary supplement industry was valued at over $140 billion and could reach $200 billion by the end of the decade as demand increases around products offering health or dietary effects and modern medicine takes a more holistic, interdisciplinary approach accounting for epigenetics, lifestyle, environmental factors, and population aging.

Lack of regulation, fraudulent health claims, and product tampering are still rampant and proven, legitimate health supplements to fight deficiencies in children, adults, and prenatal care share the shopping aisle with products that haven’t shown the proven health benefits claimed by niche magazine and social media influencers.

As a consequence of unproven fads and dubious claims often associated with fitness and lifestyle figures, the supplement industry keeps hoarding space in stores, from online retail (Amazon sells supplements from third parties and also provides its own under the brand Amazon Basics) to big retail, supermarkets, and grocery gourmet food stores, from local coops specialized in organic products to chains like Whole Foods (owned by Amazon) and Aldi-owned Trader Joe’s. Costco, Whole Foods, and Trader Joe’s also sell branded and third-party supplements.

As health, nutrition, and fitness influencers migrated to Instagram and TikTok, the Covid-19 pandemic represented the ultimate boost in the field when dubious or plain false claims regarding certain health benefits. During the first outbreaks, social media experienced increased scams and messages claiming without evidence the effectiveness against Covid-19 of homeopathic remedies, essential oils, tinctures, colloidal silver, supplements, or existing medication to treat other conditions. Some of these claims were sometimes amplified by a minority of doctors, politicians, and other personalities.

Effects of dietary supplements, wanted and unwanted

Most supplements, homeopathic remedies, herbal remedies, or traditional medicine (like the Indian system of alternative remedies known as Ayurveda) may have effects on the human body, though studies differ on how much evidence can be assessed to the known antioxidant attributes, anti-inflammatory, antihistaminic, anti-aging, etc. of traditional substances.

Even if Ayurvedic remedies can help lower blood pressure and cholesterol levels or may help the immune system fight anxiety, insomnia, inflammation, heart disease, arthritis, etc., claims about their potential for curing viruses or, say, any type of cancer have caused painful disappointments to those in a desperate search for a cure of complex diseases.

In his biography on Steve Jobs, Walter Isaacson narrates Jobs’ cancer treatment regrets, caused in part by Jobs’ beliefs in the benefits of acupuncture, dietary supplements (including ayurvedic products), and juices instead of other more aggressive—though evidence-based—treatments offered by modern medicine. The reader can’t help but reflect that Jobs’ magical thinking, a unique factor that helped him in business, may have proven lethal when applied to personal health.

In 30 years, the US supplement industry has grown from offering 4,000 products in 1994 to more than 95,000 nowadays, according to the FDA. Supplements are promoted and sold in capsules, pills, powders, gummies, or tinctures, some of which are labeled with big, vague claims: most supplements won’t “support immune health” or “improve brain performance” better than, say, common products already in the diets of people interested in boosting their health, from antioxidant-rich berries, nuts, and greens to fish and oils rich in healthy fats, vitamins and minerals.

Moreover, according to Dr. JoAnn Manson, a professor at Harvard Medical School, most supplements haven’t been tested for safety (especially when taken with other supplements and/or medication) or effectiveness.

The supplements worth taking

The absence of a clear-cut framework regarding supplements and ingredients used for centuries or millennia in traditional medicines stresses the importance of one question consumers are trying to answer by looking for studies, books, and online resources: which supplements are evidence-based and worth taking?

Even though medicine and public health experts alert that there’s no such thing as a Magic Pill or cure-all supplement strategies, the National Institutes of Health keeps a list of evidence-based reviews proving the effectiveness of several dietary supplements:

“In FY 2001, the NIH Office of Dietary Supplements (ODS) received a Congressional mandate to review the current scientific evidence on the efficacy and safety of dietary supplements and identify research needs. ODS responded by developing an evidence-based review program using the Evidence-based Practice Centers Program established by the Agency for Healthcare Research and Quality (AHRQ) to conduct systematic reviews of the scientific literature and prepare reports of their findings.”

There are completed evidence reports regarding B Vitamins, folates and berries (protecting against neurodegenerative disorders and stroke); ephedra (weight loss and athletic performance); multivitamin and mineral supplements (chronic disease prevention), omega-3 fatty acids (asthma, cancer risk, cardiovascular disease, coronary disease, heart arrhythmia, cognitive function, aging and dementia, eye health, macular degeneration, Crohn’s disease, mental health, organ transplantation); probiotics (disease prevention, antibiotic-associated diarrhea); soy (proactive health); and vitamin D (bone health, healthy calcium levels, prevention of respiratory tract infections).

Maternal iron deficiency has been proven to be linked with maternal anemia and adverse developmental effects on the fetus. Magnesium supplementation has proven effective in reducing cancer mortality and improving glucose parameters in people with diabetes or those at high risk of diabetes.

Vegans and vitamin B12 deficiency

Despite the caution advised regarding claims made online about cure-all or health-boosting strategies based on taking supplements that haven’t shown a proven effect in peer-reviewed studies, there are several instances where several supplements can improve our health or proactively prevent disease: to treat or prevent a nutrient deficiency; when pregnant or looking to become pregnant; and amid the hormonal and body changes of middle or old age.

While commercial genetic tests show whether a person has the variants studied for several diseases, which increases their risk of developing them in the future, especially when carrying a sedentary and unhealthy lifestyle, a simple blood test is enough to reveal if our organism is low in a particular vitamin or mineral, some of them deemed essential: vitamin D, iron, vitamin C, etc.

People following a vegan diet cannot replenish their vitamin B12 reservoirs and are at a greater risk of pernicious anemia caused by vitamin B12 deficiency (vegan diets have to ensure proper intake of, other than B12, B6, D, and DHA/DPA). Medical conditions that prevent the organism from efficiently absorbing nutrients from food, like celiac disease, Crohn’s disease, or ulcerative colitis, can improve nutrient absorption and prevent low levels of vitamins and minerals by taking supplements.

Those of us who have children know about the importance of ensuring a healthy pregnancy proactively by taking 400 to 800 micrograms of folic acid per day, which helps prevent major birth defects. Critical nutrients like iron, calcium, and vitamin D are also recommended to keep the mother and fetus healthy.

Healthy, active adults get enough nutrition from their food, especially when their eating habits are inspired or similar to the Mediterranean diet or other diets rich in vegetables, fruits, herbs, whole grains, healthy fatty acids (fish and some vegetal oils), and probiotics to boost and maintain gut health.

Slowing down cognitive decline

However, age may increase our requirements for some nutrients during processes like menopause. Older adults may have trouble absorbing vitamin B12, calcium, or vitamin D (especially when poor sun exposure due to latitude, lifestyle, or skin color may counter vitamin D absorption through outdoor exposure).

Several studies on adults 50 or older show that a few supplements can help maintain good health. In one such study, participants who didn’t eat fatty fish but took omega-3 fatty acid supplements better preserved their cardiovascular health than those who took a placebo. Those taking vitamin D were less likely to develop autoimmune diseases, from rheumatoid arthritis to psoriasis.

According to JoAnn Manson, there’s a strong correlation between multivitamin intake and slower memory and cognitive decline in older adults; future studies could corroborate such positive effects.

Another supplement with effects backed by studies is AREDS (or AREDS 2), which combines vitamin C, vitamin E, zinc, copper, lutein, and zeaxanthin and can slow vision loss for people prone to age-related macular degeneration, a disease that can blur your central vision once age damages the macula (a light-sensitive tissue at the back of the eye).

Using unproven supplements or natural compounds with components deemed safe for human consumption can have unintended consequences, especially if the daily intake is greater than the amount one would find in a healthy diet. A 2017 academic review found a rising incidence of liver injury associated with the use of supplements.

Manufacturers of dietary supplements have to demonstrate that their products are safe before they are approved; however, there are reported adverse effects: joint pain, liver disease, allergic reactions, muscle cramps, or hair loss, with one in three individuals affected in need of hospitalization.

When taking medication or combining several supplements

According to the incidents reported to the US Federal and Drug Administration, there’s a higher risk of adverse effects when the daily amount of vitamins and minerals greatly exceeds the necessary daily amount to maintain body processes and functions. Another common cause of reported adverse effects comes from using several combination products with multiple ingredients each, which could cause excess supplementation. According to the American Medical Association (AMA):

“Many products that have medical benefits are commonly overused among the general population in an attempt to improve or maintain health and use in these ways provides little benefit.”

Council on Science and Public Health. Dietary supplements: update on regulation, industry, and product trends. American Medical Association; 2020

Even legitimate supplements such as vitamin C can cause secondary effects if a person’s intake greatly exceeds the recommended allowance of 75 to 90 mg for adults: diarrhea, nausea, abdominal pain, and other gastrointestinal disturbances.

Who should take dietary supplements?

Who should take dietary supplements? The answer isn’t as straightforward as it should be. They are regulated as foods and not drugs, and their claimed “health benefits” must be taken with a grain of salt, especially statements promising to cure, treat, or prevent disease.

More than half of all Americans take one or more dietary supplements (daily or on occasion), though the number may be higher since supplements don’t require any medical prescription. According to Carol Haggans, dietitian and consultant to NIH,

“It’s possible to get all of the nutrients you need by eating a variety of healthy foods, so you don’t have to take one. But supplements can be useful for filling in gaps in your diet.”

Though promoted as “natural,” herbal supplements aren’t necessarily safe. Comfrey and kava, for example, can seriously damage the liver. After several reports regarding liver damage, ashwagandha supplements (present in traditional ayurvedic remedies) are banned in Denmark, and the rest of EU is also looking at removing ashwagandha-based herbal formulations from shelves.

There are also reports of aloe vera intake and liver injury, though such causes remain rare. Herbal teas (like Anamu tea) and plant-based food supplements (like Tara flour) can also cause damage.

When wondering about vitamins and minerals, experts recommend checking the daily value for each nutrient to be sure one isn’t getting too much.