In an article published today in Australian Prescriber, University of Queensland Adjunct Associate Professor of Pharmacology Geraldine Moses has warned of major potential harms associated with the use of dietary supplements.

“One reason for the persistent popularity of vitamins and minerals is the perception that they are harmless,” says Moses. But that perception masks a troublesome reality.

“When it comes to complementary medicines, most consumers are only given information about the possible benefits of these products, and little if anything about risk – and there’s always potential risk.”

The advice comes as supplement use is soaring. In July, a US survey claimed that nearly 30% of Americans are now taking more supplements than they were before the COVID-19 pandemic. Commissioned by the US health non-profit Samueli Foundation, the Harris Poll concluded that 76% of US citizens were taking supplements.

The article in Australian Prescriber discusses six potential harms of using dietary supplements:

• They can have adverse effects, particularly at high doses.
• They can interact with other medicines.
• They cost money, which may be better spent on other things.
• Time spent taking dietary supplements may delay more effective treatments.
• They may bring false hope and disappointment.
• By taking dietary supplements, people add to the number of medicines they are taking, increasing the risk of medication error, interactions and adverse effects.

The US survey was small and not based on a probability sample, so more research is required to build an accurate picture. But the trend it highlights is supported by evidence globally of an upturn in supplement use.

Accurate figures for Australia are hard to obtain, but market researchers report that sales of vitamins and supplements soared during the pandemic. 

The trend suggests that pandemic-related fear may be driving the use of these products, which some experts say are not regulated or evidenced as rigorously as registered medicines. And while the pandemic may have bolstered supplement sales, the scale of their use has always been profound: in 2018, around a third of Australians – 8.3 million people – reported buying supplements, according to Roy Morgan.

Supplementary harms?

Supplements can be benign and are critical for people with particular conditions or deficiencies, but there are notable cases in which they’ve been shown to cause long-term damage.

Just last week, doctors at a Sydney liver transplant centre went public with concerns that drug-induced liver injuries linked to dietary and herbal supplements were on the rise. 

Their study, which spanned 2009 to 2020, found that the proportion of drug-induced liver injuries that were caused by supplements (as opposed to things such as paracetamol and other medications) rose from 15% in 2009–11 to 47% in 2018–20. 

“We observed a link to bodybuilding and weight-loss supplements as has been seen in reports internationally, but also a link to traditional Chinese medicines,” says co-author Simone Strasser, president of the Gastroenterological Society. “Both groups of supplements are rising in popularity in Australia.”

Strasser says that in many cases supplement-related drug-induced liver injuries (DILIs) were potentially severe: while 90-day transplant-free survival was 74% for liver injuries caused by paracetamol, it was 59% for those caused by supplements. 

“There’s an old saying that the difference between a drug and a poison is the dose,” says Moses. “What many people don’t realise is that high doses of some supplements can be dangerous.”

Moses says that because consumers aren’t aware of the potential toxicity of supplements, they may be skirting perilously close to the line without even knowing.

“Vitamin B6 is the classic one,” Moses says. “In Australia, the toxic dose is considered to be 200mg a day or more, and lots of people that I see now in hospital will be on four products with 50mg in each one, so they’re at the toxic dose, but they’re completely unaware of that.”

The authors of the liver-damage study have expressed concern that so many supplements are escaping regulatory oversight by the Therapeutic Goods Administration (TGA), not least, Strasser says, because “not infrequently these compounds were purchased online, bypassing the Australian regulatory system”.

Strasser adds that because reporting adverse events associated with supplements to the TGA is voluntary, many severe adverse reactions go unreported.

Health anxiety drives demand

As the pandemic progresses, reports of health anxiety naturally rise. A July 2020 study among 5,070 adult Australians of varying ages and from various locations found that 25% were very or extremely worried about contracting COVID-19, and around half (52%) were worried about family and friends contracting the disease.

“When people are fearful, especially now with COVID, they will reach out and do whatever they can to assuage their anxiety, including taking natural health products,” Moses says. 

Ken Harvey, a professor at Bond University’s school of Health Sciences and Medicine and an outspoken critic of pharmaceutical marketing, says that supplements can be helpful in specific cases. For example, pregnant women are encouraged to take folic acid to reduce the risk of foetal defects, and older people may need certain nutritional supplements to make up for deficiencies caused by poor diet, lack of activity and a lack of sunlight. 

But Harvey says most Australians can get enough of what they need from a reasonably healthy diet, so any vitamin they take will simply be filtered out by the kidneys and excreted in urine, because the body already has enough. 

Meanwhile, social media and wellness ‘influencers’ are patently contributing to the problem. A 2020 study in BMC Allergy, Ashthma and Clinical Immunology found that use of the popular Instagram hashtag #immunebooster increased by over 46% between 15 April and 15 May 2020.

The myth of “immune-boosting” products

One of the most touted phrases by both wellness influencers and supplement brands is ‘immune-boosting’, a term that had become synonymous with “wellness” even before the global pandemic. But how accurate is the term ‘immune-boosting’?

Well, not very. According to Harvey, the immune-boosting myth is based on the fact that a lack of vitamins and minerals is known to weaken immunity, for example among malnourished populations. But Harvey says that in Australia, “there is no good evidence of widespread vitamin deficiencies in the population”.

In fact, the idea of immune-boosting is based on a misconception about how the immune system works. The immune system is better off balanced than boosted – if it could be boosted by supplements (which it can’t), users would experience symptoms of an immune response, such as fever and a runny nose, and in extreme cases would end up very sick.

“To ‘boost’ your immune system against specific diseases, you’ve got to either catch one, or you’ve got to be vaccinated,” Harvey says, adding that consumers often buy supplements under the mistaken belief – promoted by some brands – that they will offer immunological benefits.

Even more alarming, there is evidence that some people may use ‘immune-boosting’ natural remedies as an alternative to vaccinations against viral conditions such as the flu, meaning the immune-boosting myth could hamper the fight against disease.

Harvey says the TGA has regulated against advertising that promotes immune-boosting products by reference to the pandemic – but there’s a major loophole, because products can still be marketed as ‘immune-boosting’, provided they don’t mention COVID-19. 

So, how are supplements regulated?

Under the TGA’s classification process, there are two major categories of medicines. Registered medicines include all prescription medications and most over-the-counter (OTC) medicines. Prescription medications are considered higher risk, and OTC medicines a lower but still palpable risk, so all registered medicines are assessed by the TGA for quality, safety and efficacy.

Efficacy, in pharmacological terms, refers to the ability of a drug to provide the benefits to which it claims, including establishing the dosage required to provide that benefit. Efficacy is established during clinical trials.

Complementary medicines such as supplements fall into the category of listed medicines, which generally contain well-known, low-risk ingredients with long histories of use, such as vitamin and mineral products and sunscreens. These medicines are those that the TGA considers to be generally benign or low risk, so, “listed medicines do not undergo a full pre-market assessment of safety, quality and efficacy,” according to the TGA.

The TGA does do yearly post-marketing surveillance on around 150 of the thousands of listed medicines on the Australian market, the results of which can be found in its annual performance statistics reports. 

A review of the performance statistics over the five years from 2015 to 2020 reveals that around 75% to 80% of the listed medicines tested are found to breach compliance in some way, which would appear to point to what Harvey refers to as a “light-touch regulatory process” for listed medicines.

Where to now?

Approached for comment, the TGA informed Cosmos that enhancements to the listed medicines post-market compliance scheme are coming. 

But the supplement sector has always been resilient, offering an alluring alternative to Western medicine, whether because the supplements are perceived as low risk, or because of an inherent distrust of public-health messaging.

“They [the TGA] have a pretty tough job to do, trying to cover every possible pharmaceutical product throughout Australia,” Moses says. “But I certainly think that with complementary medicines we could do a better job if we required manufacturers to provide consumers with information about potential risks.”

Strasser says that a lack of public education is hampering both the TGA and the medical profession’s ability to clamp down on unsafe supplement use.

“There is still a perception that supplements are natural and therefore healthy,” she says. “Time after time, patients who experience severe DILI are incredibly surprised that something they purchase over the counter or online with the aim of improving their health could have harmed them.”