Dietary Supplements

What are dietary supplements? The short and obvious answer is that they are products that are intended to enhance one’s regular diet and perhaps supply nutrients that otherwise would be absent. Examples include vitamins, other tablets or capsules, gummies, drinks, and energy bars. All are sold with an enclosed information sheet that lists all the ingredients, but it is likely that many consumers are more likely to read the package than the enclosure. Americans spend more each year on dietary supplements than on all over-the-counter medicines combined; in 2019, the best estimate was almost 49 billion dollars in sales.

Always talk with your doctor about supplements that you are considering.

People buy and use these supplements for many reasons. Some hope to fill known gaps in their diets while others hope to maintain health or prevent illness. Although I have not seen estimates of the numbers of cancer patients/survivors who use them, we do know that more than half of people on active cancer treatment use one or another type of complementary and alternative medicine (CAM), and supplements are among the most popular.

It is important to note that dietary supplements are treated differently by the FDA than over-the-counter or prescription medicines. The latter all are regulated and approved; dietary supplements are classified as food and don’t need the same kind of official attention. This can be especially tricky for cancer patients. For example, many supplements are touted as bolstering or improving the immune system. They may or may not work. Manufacturers don’t have to prove to the FDA that their products are effective. Indeed, the converse is truer as the FDA can only prohibit them if they are proven to be dangerous.

Generally speaking, supplements can be vitamins or botanicals/herbals. Vitamins are more straightforward as we know what any one vitamin is intended to do for us. (Note: We don’t know that any particular supplement fulfills that intent.) There are no standards or recommendations of how much of a botanical one ought to take. The kind of label that we are accustomed to seeing on packages, the one that says that this product provides X% of the normal daily recommendation, does not exist. Safety depends on many things, including how a supplement is prepared and the amount you take. For example, peppermint tea is fine, but peppermint extract, if taken in too large (and no one knows exactly that that means) a quantity can be toxic.

The best plan is to always talk with your doctor about supplements that you are considering. Since so little is known about them, the most common advice for cancer patients is to avoid them during active treatment. We know, for example, that large doses of certain vitamins may interfere with the efficacy of radiation therapy. Once active treatment is done, many providers will be at least neutral about their use. You can also consider speaking with a dietitian about your particular concerns.

My own recommendations are these:

• Always talk with your doctor about anything you consider taking
• Be skeptical of marketing claims. Anything that sounds too good to be true is likely not true. There are no known vitamin or supplement cancer preventions or cures.
• Beware of miracle cures, anything that purports to do everything, quick fixes, and advertising that includes personal testimonials. Email and text scams are the modern-day equivalent of the proverbial snake oil salesman.