Contraindications of Nutritional Supplements


Published: 12 May 2015

Nutritional supplements comprise a great deal of the products available over the counter in most pharmacies. Although most vitamin supplements are relatively harmless—except for the fat soluble ones A, D, E, and K—they are not the only supplements available to patients. Some of these other, non-vitamin supplements can actually be harmful to patients and often they have been proven to be ineffective. This doesn’t mean that patients will stop taking them though, which in turn leaves the potential for contraindications of nutritional supplements with prescription-based drugs wide open.

Fish Oil

Omega three symbol in fish oil tablets.

If your patient is not on omega-3, perhaps you should suggest that they start.

Of all of the non-vitamin nutritional supplements, the one that is most commonly consumed is fish oil or omega-3 fatty acids. One reason for this is that the American Heart Association recommends two servings per week of the nutrient to help prevent arrhythmias. In response to this recommendation, older adults usually end up taking a supplement every day rather than trying to get the nutrients by diet. The NIH agrees that the effect of fish oil on all cardiovascular incidents makes the supplement worthwhile. It also allows that it can be obtained through the diet or through a supplement. Side effects are minor, and the benefits are relatively assured. If your patient is not taking this supplement, perhaps you should suggest that they start.

Coenzyme Q10

Coenzyme Q10, also known as CoQ10, is another popular supplement taken for a wide variety of reasons. It is an antioxidant that can decrease as you age, prompting many older adults to take the medication. CoQ10 has shown promise in helping patients overcome the effects of heart failure and can shown to improve outcomes after heart bypass surgery. However, it has not been as effective in treating high blood pressure. The rhabdomyolysis that can sometimes come with statins has also shown response to CoQ10, but the research into this benefit is still ongoing. This nutrient is mostly harmless, causing the usual side effects of insomnia, diarrhoea, and so on. However, you and the patient should be aware that this nutrient will decrease the effectiveness of warfarin, and so is contraindicated in those patients.

Glucosamine and Chondroitin

Glucosamine and chondroitin are often taken by patients suffering from osteoarthritis, particularly of the knee. It is supposed to help repair the cartilage in the joint and make the pain decrease. In fact, this combination has also been used in veterinary practices but does it really work? For glucosamine, the jury is still out. Two large, double-blind studies have been conducted with conflicting results and more information is necessary to determine which is accurate. For chondroitin, no statistical benefit has been found for its usage. Although these supplements do not have side effects of any note, they can impact the usage of warfarin, and should be contraindicated in these patients.


Nearly all herbal cold medicines now include the herb Echinacea, but the science behind this supplement is not definitive. It is supposed to help with upper respiratory infections, such as head cold, chest colds, the common cold, and so on. Some research has shown that it is effective in treating upper respiratory infections, but two large, double-blind studies have shown the exact opposite. Since these studies were larger and governmentally backed, it stands to reason that taking Echinacea is unlikely to help a cold. The only side effects from this medication are allergic reactions that can become serious and GI side effects.


Asian ginseng has few side effects, mostly gastrointestinal and possibly allergic.

Asian ginseng has few side effects, mostly gastrointestinal and possibly allergic.

Ginseng comes in a variety of types from around the world. Most of the ginseng on the market is Asian ginseng, as opposed to its American counterpart. This nutrient has been used for centuries in Asian medicine for a wide variety of ailments, but scientific research into it has been scarce. It shows some promise in helping to lower glucose, but the claims made by vendors of the herb have not been verified. In fact, some of them have even been disproven, including claims of helping insulin resistance, cancer, and Alzheimer’s disease. Asian ginseng has few side effects, mostly gastrointestinal and possibly allergic. Although some patients taking it have experienced menstrual abnormalities and cardiovascular related effects, it isn’t clear if this was from the ginseng or from another herb contaminating the preparation.


It is important that nurses understand these optional supplements, what they do in the patient’s body, and whether they work. You should also know what possible side effects these medications can have that adversely affect the patient’s health and, investigate medication errors if they happen to occur. The National Institute of Medicine lists at least 30 possible supplements that are currently on the market. It isn’t necessary to know all of them, but some of the more popular are well worth knowing about for the patient’s sake.

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  • American Heart Association; Fish and Omega-3 Fatty Acids; May 14, 2014
  • National Institutes of Health; Omega-3 Fatty Acids and Health; October 28, 2005