Vitamin supplements are often advertised as bolstering your immune system or strengthening your bones, and sometimes even as protecting against Covid-19 or healing cancer. Market studies show their sales have boomed during the pandemic. Experts warn, however, that using them is generally not only a waste of money, but also potentially dangerous.
How prevalent is their use? A third of the German population, for example, takes vitamins as dietary supplements at least once a week, according to a representative survey by Germany's Federal Institute for Risk Assessment (BfR). One in six takes vitamin tablets or powders daily.
And recent data from the US National Health and Nutrition Examination Survey show that among US adults aged 20 and over, 57.6% used a dietary supplement in the past 30 days, and that use increased with age. The most common dietary supplements used by all age groups were multivitamin-mineral supplements.
BfR President Andreas Hensel throws cold water on vitamin lovers' high hopes though: "A balanced and varied diet provides your body with sufficient amounts of almost all vitamins," he says. "Most people don't need vitamin supplements. If you take high-dose vitamins unnecessarily, you risk an overdose with undesirable health effects."
An overdose will result at best in your body producing "expensive urine," quips Wiebke Franz, a nutritionist for the consumer advice centre in the German state of Hesse. At worst you'll harm your health.
Dietary supplements, including vitamins, aren't subject to the quality and safety testing that medicines are, she notes. Consequently, it's not uncommon for vitamin tablets and powders to have impurities.
And she says it's important to be aware of possible drug interactions. Beta carotene, a precursor to vitamin A, can increase smokers' lung cancer risk, warns Franz, and a vitamin A overdose "isn't harmless" either. Too much vitamin D can cause headaches, nausea and kidney calcification, and taking excessively high doses of vitamin C for too long can lead to bladder and kidney stones.
Vitamin overdoses sometimes go unnoticed, she says, because people who take the tablets and powders ingest vitamins naturally in their food too, some of which is also enriched with vitamins. There are no specified safe limits for vitamin intake, something that consumer advocates have been criticizing for years.
"Vitamin deficiencies aren't a problem in Germany. The vast majority of people in this country are sufficiently supplied with vitamins," asserts the German Nutrition Society (DGE). Dietary supplements are recommended only for a few segments of the population, for example pregnant women, chemotherapy patients, the extreme elderly and strict vegans.
Sales of vitamin supplements are booming anyway. German pharmacies alone sold nearly 2.3 billion euros (2.5 billion US dollars) in dietary supplements in 2020, more than half of which were vitamins and minerals, according to the Germany branch of IQVIA, a US-based market research and pharmaceutical consulting company.
The vitamin and mineral sales represented an increase of 11% over 2019. Immunostimulants saw the greatest growth, 12%, and combinations of vitamins A and D, as well as those including vitamin C, also posted double-digit growth.
"The 2020 boom in sales of dietary supplements such as vitamin A and D combinations, and vitamin C too, is likely due to the Covid-19 pandemic," says Thomas Heil, vice president of IQVIA Germany's consumer health division. "Consumers expected that taking them would provide a certain amount of protection against infection."
Experts say they were mistaken. "No studies are known that show taking vitamin D supplements protects either against infection with the novel coronavirus or the onset of disease symptoms," the BfR reports.
And the Robert Koch Institute (RKI), responsible for disease control and prevention in Germany, writes: "There's no evidence to date that people with an adequate vitamin D status are benefited in this regard by taking vitamin D supplements."
Consumer adviser Franz warns against giving credence to health claims made by manufacturers and distributors of vitamin supplements. The products are touted as wonder drugs of sorts, she says, particularly on the internet and via direct marketing.
"The providers are deceiving consumers by promising health benefits or even cures," she remarks.
Marketing on social media channels is an especially big problem, says Christiane Seidel, a food adviser for the Federation of German Consumer Organizations (VZBV). Although suppliers are forbidden from making false assertions about their products, they often make inadmissible health claims on social media, sometimes even going as far as to say the products "help against cancer."
"Vitamins can help the body function normally," Seidel says. "Dietary supplements don't help to treat diseases."
Vitamin supplements are a "super lucrative business," she notes, adding that direct internet marketing is difficult to control. The illegal advertising is often propagated by influencers who receive a commission for plugging or reselling the products. Many of the companies are located in other countries, and their websites often give no company details and pop up only briefly, all of which presents "a huge problem for enforcing the law."
The vitamin supplement business has grown enormously since the start of the Covid-19 pandemic, according to the VZBV. Whether it shrinks when the pandemic recedes remains to be seen. The latest IQVIA data show that while pharmacy sales of vitamin A+D supplements in Germany continued to rise in 2021 - by nearly 17% - sales of purely vitamin C supplements fell.
