Dietary Supplements - Are They Dangerous?

Kwan H Lo

Dietary supplements refer to any health products that can supplement our diet. They include vitamins, minerals, amino acids, digestive enzymes, Probiotics, herbal supplements, glandular extracts and dietary fibers etc. Dietary supplements are available in many forms such as tablets, capsules, gel caps, liquids and powders.

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. These supplements include: aristolochic acid (human carcinogen, kidney damage), Comfrey (liver damage), androstenedione (cancer risk, reduces HDL cholesterol level), Chaparral (liver damage), Germander (liver damage), Kava (liver damage), bitter orange (increases blood pressure, heart arrythmias, heart attack, stroke), organ / glandular extracts (mad cow disease), Lobelia (breathing problem, low blood pressure), Pennyroyal oil (liver / kidney / nerve damage), Skullcap (liver damage), Yohimbe (increases blood pressure, heart arrythmias, heart attack).

Some of these herbs have been used alone or in compound formulations by herbalists for hundreds of years and are considered as safe. These herbs may contain small amounts of active substances that are harmless and safe if the whole herb is consumed occasionally. However, when these active substances are isolated and extracted in pure or concentrated form and consumed over prolonged period, they can be dangerous to some people.

Many dietary supplements including vitamins and minerals are safe and can supplement what is missing in our diet if consumed properly. 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 long period of time, thinking that the supplement is good for the eyes. Both of her daughters suffered from acute liver failure. One slowly recovered after the supplementation was stopped. The other required a liver transplant to save her life. Vitamin A is not dangerous and in fact, has many health benefits. However, 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. Most blue green algae supplements are made of Aphenizomenon Flos Aquae (AFA), a strain of blue green algae which does not produce microcystins. However, AFA harvested from natural lakes may be contaminated by other strains of blue green algae which produce the toxins.

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. Good manufacturing practice is a set of guidelines that provides a system of processes, procedures and documentation, to ensure that the finished product has the identity, strength, composition, quality and purity that it purports. 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.

Another common misconception about dietary supplements is that natural substances are safe. The most toxic substances can be natural, i.e. they are present in nature in all these years, but they are not safe. Some pharmacologically active botanical compounds are indeed quite safe when consumed in moderation in whole herb forms but may pose harmful effect on healthy individuals or those who already suffer from health problems. Some supplements may also interact with pharmaceutical drugs by either reducing or enhancing their effects. So cautions should be taken even when you are consuming natural supplements.

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? In addition, if you are pregnant, breast feeding, or suffering from pre-existing health conditions, extra precaution should be taken by consulting with your doctors or nutritionists.