The consumption of dietary supplements has been rising every year. Whereas many people believe that dietary supplements can improve their health or prevent certain diseases, some consumer groups or medical professionals have warned that dietary supplements can be dangerous. So, the question is: are dietary supplements really dangerous? Unfortunately, the question does not have a simple answer.



Dietary supplements, by its broad definition, include thousands of different products. In 2004, Consumer Reports listed 12 potentially dangerous dietary supplements. Many of them are herbal products. Some of these herbs have been used by herbalists for hundreds of years and are considered as safe. However, when the active substances in these herbs are extracted in pure or concentrated form and consumed over prolonged period, they can be dangerous to some people.

Many dietary supplements such as vitamins and minerals are safe and can supplement what is missing in our diet. However, even the benign supplement can become dangerous in overdose. In local news, a woman was reported to give her two teenage daughters mega dose of vitamin A for prolonged period, thinking that the supplement is good for the eyes. Both suffered from acute liver failure and one required a liver transplant to save her life. Vitamin A is not dangerous but mega dose of vitamin A is hepatotoxic. In this case, ignorance itself is dangerous!

The quality of dietary supplement is also an important factor. The presence of contaminations, such as heavy metal, drugs, and toxic substances can make a benign supplement dangerous. One example is the presence of microcystin toxin in blue green algae dietary supplements. Microcystins are natural toxins from certain strains of blue green algae that can cause liver damage and liver tumors. According to the research conducted by Health Canada, only one strain of blue green algae, Spirulina, is free from microcystins as Spirulina is harvested from controlled ponds. Most of the non-Spirulina blue green algae supplements are contaminated by microcystins, especially those harvested from natural lakes. Daily consumption of these dietary supplements would exceed the acceptable level of microcystin intake established by Health Canada and WHO.

Good manufacturing practice (GMP) is another key factor to safeguard the quality and safety of dietary supplements. Dietary supplement manufacturers in compliance of GMP standards have to test the identity of raw materials, implement a quality control unit, provide expiration date for the finished products, maintain good records of batch production and written procedures, and hire personnel who are trained to understand and follow GMP. This practice can reduce the chance of having batch to batch variation in strength, composition, purity and quality of finished products.

To sum up, although most dietary supplements are safe when consumed according to the label, consumers are advised to educate themselves before taking these supplements. What are the functions of these supplements? How long should I be taking them? Are they manufactured by reputable companies in compliance of good manufacturing practices? Never consume more than the recommended dose unless supervised by health care professionals. If you are pregnant, breast feeding, or suffering from pre-existing health conditions, you should also take extra precaution and consult with your doctors or nutritionists.