Globally, there has been a dramatic increase in the use of dietary supplements over recent decades and the market may become even larger due to the COVID-19 pandemic, according to a new editorial published in Nutrients.
But the two authors of the editorial, from the College of Health Sciences at Qatar University and the Center for Advancing Population Science at the Medical College of Wisconsin, voice their concerns over increasing usage, citing the lack of audience specific research, regulatory consensus, the potential side effects, and the ultimate importance of whole food diets.
They do state that dietary supplements are necessary for specific groups of people. For example, they point out that vegetarians are required to have vitamin B12 supplementation and people with iron deficiency need to have iron supplementation. They also note that nutrient supplements have contributed substantially to human health.
However, they point out that some consumers take supplements unnecessarily as they don't know what they need and many consumer take them to increase longevity, despite the 1999–2010 National Health and Nutrition Examination Survey (NHANES) suggesting supplement use does not reduce the risk of mortality in the general population.
Their paper states: "...it is wise to take caution towards the use of dietary supplements, especially for people with chronic conditions. There is no evidence suggesting that people with a healthy dietary pattern can receive extra benefits from the use of dietary supplements. Dietary supplements should not and cannot be used as a method to treat the problems caused by an unhealthy diet."
The authors outline changes that they feel are necessary in the supplements industry.
The gold standard to test the efficacy of a dietary supplement is through a randomised clinical trials (RCTs) but the current paper argues these are often conducted in a selected population, do not have sufficient duration of follow-up and have a limited number of hard outcome events. They therefore argue more research is needed before solid conclusions can be made for most dietary supplements.
They state: "Even for omega-3s, the most-studied supplements, their health effects remain uncertain. The effect of dietary supplement use in the general population is not the same as we expected. The latest systematic reviews and meta-analyses of the most common dietary supplements yielded disappointing findings.
"For example, the latest meta-analysis of clinical trials and prospective cohort studies showed that multivitamin/mineral (MVM) supplementation does not improve cardiovascular outcomes in the general population."
The authors say that country specific research is needed, as even if some supplements are proven to be beneficial in one country and one specific dietary pattern, this does not mean that it is appropriate in other countries and contexts.
They add: "But it is not possible for many countries to afford the costs associated with such research. The ultimate solution to promote health should be through healthy eating. Our decisions on eating should not be based purely on our understanding of the bioactive components. There are far more chemicals in food than what we know and treat as nutrients or bioactive components."
The paper notes that taking more dietary supplements than needed costs more and might elevate the risks of side effects, adding that herbal products can interact with medication, notably in patients with cardiovascular diseases.
The authors says they worry that physicians are not often aware of their patients’ use of herbal products, but more worrying still is when patients use herbal products instead of following formal medical treatment.
"This is particularly the case in Asia, where the use of traditional herbal medicine is common. For example, in China, functional foods are accredited and allowed to advertise their functions. This puts some people at risk because it is difficult for some consumers to distinguish the difference between a functional food and a drug.
"Unlike drugs, the adverse effects of dietary supplements, including herbal products, are not systematically reported and monitored. In fact, RCTs on herbal products with long follow-up durations are rare.
"Herbal supplements and multivitamin and multimineral use are common in children but studies on the longer-term effects are limited.
"...The need for iron supplementation in the general population does not exist. In contrast, high iron intake has been shown to increase the risk of diabetes, hyperuricemia and cognitive impairment among adults in China."
"Due to the high use of dietary supplements and the potential health benefits as well as adverse effects, there is an urgent need for better regulation," the paper states.
In their review article, Dwyer J.T. et al. examined the challenges in the use, regulation, and research of dietary supplements.Based on their review, one of the challenges is that there is no consensus on the definition of dietary supplements internationally. It varies between nutritional supplements, herbal medicines and traditional medicines.
Regulations are different from country to country. However, it is clear that the regulations on dietary supplements in different countries are much less stringent than those of prescribed or over-the-counter medicines.
"If scientists, governments and industries do not have a clear consensus on the regulations of dietary supplements, how can consumers make the right choices?
"Taking melatonin as an example, as pointed out by Dwyer J.T. et al., it is treated as a dietary supplement in the USA but regulated as a prescription medicine in Australia. In China, melatonin is approved as a functional food. The main ingredient of one of the most popular health supplements, named “Nao Bai Jing,” is melatonin. It is widely advertised as a panacea for brain health in China and many consumers purchase it as a gift.
"Consumers need valid, scientifically-based information on dietary supplements to guide their consumption rather than advertisements from dietary supplement companies. In many countries, the health-food market is largely driven by advertisements. Although these food advertisements are regulated, violation of the regulations is not uncommon."
The authors argue there should be dietary supplement guidelines for the public specific to each country's population.
Shi. Z., and Yan. A.
"Dietary Supplements: Are Current Policies Adequate for Promoting Health?"