It’s natural, so it’s safe … or is it? As a researcher studying the safety and efficacy of natural health products such as herbs and vitamins, I often hear the claim that these products are safe simply because they are natural. Many myths about natural health products continue to circulate despite growing research – more than 5,000 studies on herbal medicine alone have been published in the last five years. Natural health products are not always as natural as many people think, nor are they always safer or better for you than medications designed in a laboratory. Claims of effectiveness are often exaggerated. Only careful study of such claims in clinical trials will help us understand what works and what does not.
In some ways, natural health products are not that much different from any other medicines. Some appear to be beneficial for individuals with specific conditions, and since they work by having some action on the human body, this means natural health products can also have adverse effects or undesirable drug interactions.
What is “natural”?
Canada defines natural health products (known as dietary supplements in the United States) as a group of products used for health-related purposes whose active ingredients “exist in nature.” Most herbal medicines, vitamins, minerals, probiotics and essential fatty acids available for purchase in Canadian pharmacies and health food stores fall into this category. To check a specific product, look for the Natural Product Number on the label, which is a sign that the product is approved for sale under some of the strictest regulations in the world for these types of products. The regulations generally guarantee that what is on the label is in fact what is in the bottle. This is more than can be said for herbs and other supplements purchased in many other countries or over the Internet. However, many assumptions about natural health products (and the regulations) are simply not true.
For example, natural health products are not necessarily made from natural sources – so your “natural” product may in fact be synthesized in an unnatural laboratory. For example, vitamin C, chemically known as ascorbic acid, is much easier and cheaper to synthesize from scratch in a laboratory than it is to isolate from natural sources. As long as the final product (ascorbic acid) is chemically identical to ascorbic acid found in nature (e.g., in an orange), it qualifies as a natural health product. As a scientist, I will argue that your body cannot tell the difference between vitamin C synthesized in a laboratory and vitamin C isolated from natural sources. Some people purport to care a great deal about how their natural products are made. If this matters to you, read the label carefully – if it does not say it is from a natural source, it probably is not.
Do “natural” health products work?
A second assumption is that if a product is legally sold in Canada and the label says it is good for treating headaches, it actually works for treating headaches. What you may not know is that a natural health product can be approved for sale in Canada in one of two ways. One way is to present scientific evidence that the product works for something: It prevents colds or helps you sleep, for example. The other is to provide information that the product has been used in a “traditional system of medicine” (for example, traditional Chinese medicine or Ayurvedic medicine from India) for a specific condition for a minimum of 50 consecutive years.
Some people may want to purchase a medicinal product that has been used for a long time by traditional healers, but this is not the same as scientific evidence of efficacy. For eons, people believed the earth was flat, but that did not make it so. Use by billions of people for thousands of years is not proof that something is effective.
Research, specifically double-blind, placebo-controlled clinical trials, is needed to test the medicinal claims associated with natural health products. Sometimes these studies confirm the traditional use, but more often, the studies show that natural health products do not work as well as originally thought. For example, according to The Cochrane Collaboration, a group dedicated to finding and summarizing all the clinical study evidence on specific products, cranberry juice or tablets really do help to prevent urinary tract infections. In contrast, studies of echinacea for colds have had mixed results. It appears that if it does work, you may not notice a big effect if you take it (e.g., your symptoms may resolve only slightly faster than they would without an intervention).
Yet, people continue to believe that “natural” products (or at least products composed of compounds found in nature) are somehow better for them than are medicines designed and synthesized in a laboratory. There is no evidence that the body somehow “knows what to do with” natural products any more than it “knows what to do with” with other types of medicines. Many things exist in nature that humans are not meant to ingest. Scientists are becoming increasingly sophisticated at figuring out exactly how the body works (and thus what happens when we become sick) and at designing medicines that are specifically targeted to interact with receptors on cells or specific metabolic pathways in order to help mitigate human disease.
Natural does not = safe
Just as natural does not mean “better for you,” it also does not mean it is safe. Imagine a picnic in the country with your family. While playing, your children find some mushrooms. Unless you are a trained botanist, it is unlikely that you are going to suggest adding those mushrooms to your meal. Given they might be poisonous! However, if someone picks those same mushrooms, dries them, puts them in a capsule and labels them as a natural health product, many people suddenly assume that they must be completely safe for everyone.
Some of the most potent toxins in the world come from natural sources – arsenic and snake venom for example. Also, natural products can have adverse effects, cause allergic reactions and interact badly with other medications. For example, St. John’s wort is a herbal product that clinical trials tell us is almost as effective as conventional medications for treating depression (see The Cochrane Collaboration review of the evidence at http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD000448.pub3/abstract). However, it causes the body to metabolize a number of conventional medications faster than normal (see a recent warning issued by Health Canada at http://www.hc-sc.gc.ca/dhp-mps/medeff/advisories-avis/prof/_2000/hypericum_perforatum_hpc-cps-eng.php). Therefore, if one takes St. Johns wort with warfarin (a blood thinner) or the birth control pill, the effects of these conventional medicines may be decreased and they may not work as intended. Other herbal products, such as comfrey, have been associated with liver problems (the Food and Drug Administration in the United States issued a warning about comfrey products in 2001: http://www.fda.gov/Food/DietarySupplements/Alerts/default.htm). Under Canada’s regulatory system, known adverse effects, drug interactions and contraindications are listed on the labels of natural health products. Nevertheless, the assumption that these products are completely safe is so strong that some people might not think to check this information.
Too good to be true
Finally, if something seems too good to be true, it probably is. Although there is growing research into the safety and efficacy of natural products, it takes seconds to make a claim about a product and years to test that claim properly. Scientific research is slow in part because natural health products are complicated. Unlike most conventional medicines, which are single chemical entities (which we know a lot about since we constructed them), natural health products often contain many active compounds (sometimes hundreds), thus making it challenging to figure out how the whole product affects the human body. Clinical research is time-consuming and expensive, so we need to make sure the specific product we choose to test contains enough of the “active ingredients” to be a fair test of its effects.
For example, much preliminary work is needed to determine what part of the plant should be used, when it should be harvested, how it should be processed and what dosage should be given. If this preliminary work (sometimes called pre-clinical studies) is not completed properly, scientists risk spending millions of dollars on a clinical trial only to discover that the reason the product seemed not to work in the trial is that they used the leaves instead of the root, or they did not give the trial participants the right dosage. Scientists are making progress, and each trial teaches them something about these products, but it is still a lot easier to make a claim about a natural health product than it is to do the research to test the validity of that claim.
Given the pace of the science, claims of miracle cures from natural health products abound for health conditions that are notoriously difficult to treat (such as cancer). There is simply no reason to believe these claims. Similarly, conspiracy theories that large pharmaceutical companies are trying to keep us from knowing about a herbal product that will cure conditions such as cancer are highly overrated. Rather than being the enemies of natural health products, pharmaceutical companies are big promoters of them since they own some of the most popular natural health product brands. For example, Wyeth Consumer Healthcare, a division of Pfizer, a multi-national pharmaceutical company, owns Centrum®, a well-known multivitamin (and thus a natural health product). Pharmaceutical companies now market “natural” options of familiar products such as Gravol® that are actually natural health products with no relationship to the original products. (Original Gravol® is a chemical called dimenhydrinate; natural-source Gravol® contains the herb ginger.)
Canada has some of the highest quality natural health products in the world, because of our strict regulatory system. Natural health product labels have lots of useful information about the safety of the products; however, not all the claims on the labels are supported by scientific evidence. That they are composed of materials found in nature does not mean natural health products are safe for everyone. Moreover, there is no reason to think that they are somehow better for us than other medicines. The bottom line is that natural health products should be treated like any other medicines. Scientific research clearly shows that some natural health products can be beneficial, but consumers should beware of unrealistic claims of safety or efficacy.
Heather Boon, BScPhm, PhD is a Professor and the Associate Dean – Graduate Education at the Leslie Dan Faculty of Pharmacy, University of Toronto. She originally trained as a pharmacist and currently co-directs IN-CAM (the Canadian Interdisciplinary Network for Complementary and Alternative Medicine Research). She is the President-elect of the International Society of Complementary Medicine Research. She served as the Chair of Health Canada’s Expert Advisory Committee for Natural Health Products from 2006-2009. Her primary research interests are the safety and efficacy of natural health products as well as complementary/alternative medicine regulation and policy issues. She is the author of a textbook on natural health products and over 100 academic publications.
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