The Dietary Supplement Experiment Begins

We are about to start a large informal medical experiment in Australia. Following the recall of products made by Pan Pharmaceuticals there is likely to be a shortage of dietary supplements, as Pan was the largest manufacturer of these in the country and produced many of the best-known brands. If these chemicals are as essential as we have been told then the effect of a shortage should be noticeable.

What are dietary supplements?
As the name suggests, they add to the value of food. Many of the things needed for life are made inside the body by processing the food intake, but some chemicals must be included in the food for the process to operate correctly. Some of these are catalysts, some are essential ingredients for the digestion process, and some are broken down in the body because their component elements are necessary. In a balanced diet, all are obtained from food in suitable quantities. Dietary supplements are packages of these chemicals consumed as medication rather than as food.

Are supplements necessary?
Humans have evolved to survive on a broad omnivorous diet, which has allowed us to live almost anywhere on Earth. The fact that we are here shows that for a very long time we must have been able to get all we need from our food, so it must be possible to live and reproduce without pills.

It is also a fact that we didn't evolve with the processed foods that many eat today, but experience suggests that problems of poor diet are more evident in places where people live closer to nature than in countries where the majority think that "pizza" is a food group. Not everyone eats properly, so there may be times when extra vitamins or a mineral supplement could be beneficial, and there is also evidence that certain vitamins can protect against some diseases when taken in quantities greater than the minimum.

These comments only apply to vitamins and essential minerals, where deficiencies can lead to specific diseases. It is much harder to make a case for many of the other products sold as supplements.

Are supplements safe?
Vitamins and essential minerals are probably relatively harmless when taken in amounts close to the recommended doses because these recommendations are deliberately conservative. Some fat-soluble vitamins, like Vitamin A, can be dangerous if taken in large quantities because the body stores them for later use and excessive consumption can be toxic. Generally the result of taking more vitamins than your body needs is to produce brightly coloured, expensive urine. The danger comes from products sold as supplements that are, in fact, chemicals with a pharmacological action.

The average person assumes that anything with official approval will be safe, of good quality, and will work as described. The Therapeutic Goods Administration (TGA) has two classifications for medical products – "listing" (AUST L) and "registration" (AUST R). Both require evidence of manufacturing quality, safety when used as recommended, and truth in describing the contents on package labels. Registration is the higher standard and is required for products that are more dangerous. Leaving aside the manufacturing problems at Pan, the public generally assumes that anything with an "AUST L" number is safe to take. This assumption leads to two dangerous possibilities.

The first is adverse interactions with other drugs taken either as supplements, over-the-counter medications or by prescription. The "alternative medicine" industry has done such a good job of equating "natural" with "completely safe" that people tend to think that no harm can come from such products no matter what they are mixed with. When your doctor asks if you are taking any other medication, answering "No" because the other things being taken are "natural" herbal supplements can lead to disaster.

Another danger is the risk inherent in all alternative medicine. People may avoid effective medication because they prefer to self-medicate with products that they believe are effective without the dangers and side-effects of pharmaceutical drugs.

Do supplements work?
It might surprise many to find out that TGA listing carries no obligation to prove efficacy. (Registration does have this requirement, as products with higher risk are expected to have some balancing benefit.) Listed products are assumed to be safe because they have no bad effects, but this just means that they may have no good effects either. Provided that no specific claims are made about cures, supplements with an "AUST L" number can exist for no other reason than to transfer money from your wallet to a herb seller's bank account.

Like any true skeptic or scientist, I look for evidence that things are so. In alternative medicine, the claim is often made that the onus is on skeptics to prove that things are not so. I don't think that the big experiment will satisfy either side, but I also don't expect epidemics of the illnesses that these supplements are supposed to prevent.

This article was published as the Naked Skeptic column in the June 2003 edition of Australasian Science