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An evidence-based approach to vitamin supplements: Dietitians available for interviews

An eagerness to enhance health and immunity has skyrocketed vitamin sales during the pandemic, yet there is little consensus around the safety and effectiveness of these supplements.

While the product lines might be new, sellers claiming their supplements will address an array of ailments are not. Courtney McGowan, RD, certified specialist in oncology nutrition, Yale New Haven Hospital, who is currently working on a study examining how healthy eating and exercise during chemotherapy impacts outcomes and side effects of the treatment, discusses how to take an evidence-based approach to supplementation.

The rise of vitamin supplements

Vitamins are organic compounds found in food (or in the case of vitamin D, sunlight) that humans need in small amounts to survive.

Vitamin C rose to popularity in the 1970s when Linus Pauling, a scientist who won a Nobel Peace Prize for his research on chemical bonds, published a book promising that vitamin C could cure the common cold. He later added that vitamin C could cure flu and cancer. In response, vitamin sales soared. Long-term rigorous studies did not support Pauling’s ideas about vitamin supplements prolonging life or preventing illness.

Due to its role in immune function, later studies examined vitamin C’s impact on a myriad of conditions including cardiovascular disease and age related eye diseases. Current evidence largely does not support a role for vitamin C supplementation in these conditions with the exception of one study indicating that vitamin C supplementation might slow age related macular degeneration.

With Pauling as a catalyst, by 1999 the National Institutes of Health (NIH) was investing $250 million to $300 million annually to fund dietary supplement research beyond vitamin C with most of those large studies failing to demonstrate health benefits for dietary supplements and in some instances, showing certain supplements were linked to an increase in some cancers.

Supplementation has its place, but it can be a challenge to figure out where exactly that is.

Know what you are getting

“The issue with supplements is that they are in an unregulated space,” said Ms. McGowan, who has anecdotally seen an uptick in people taking supplements. “In 2007 the Good Manufacturing Practices guidelines were put into effect. This assures that the supplement is actually what it says on the bottle. It does not vouch for safety or effectiveness.”

The US Food and Drug Administration (FDA) is not authorized to review dietary supplement products for safety and effectiveness before they are on the shelves. In fact, the FDA relies on reporting of adverse events from physicians and consumers to remove hazardous supplements from the marketplace.

Rarely, but seriously these systems of oversight fail. In September of 2020 researchers tested 10 “brain boosting” supplements and found many of them contained pharmaceutical drugs that had never been approved for use in humans.

“Protect yourself by looking for the Consumer Labs and the United States Pharmacopeia stamp on the side of the bottle to give you validation that the product is following the guidelines,” said Ms. McGowan.

Navigating the supplement aisle

“A lot of nutrition research is being done and previously this type of research would be something that healthcare professionals would read and file away,” said Ms. McGowan. “Now media are publishing studies sometimes without the proper caveats. It is hard to pull out a key takeaway from a study and when you try to force it, the big picture can get lost.”

When reading about a nutrition study, McGowan recommends considering the following:

  • Was the study done on humans? Many things seem promising in mice and never translate to humans.
  • How many participants did the study involve?
  • Was it a randomized, controlled study (as those are considered the most scientifically rigorous)?
  • Who is funding the research and who is conducting it? Was it the supplement creator? Or a less biased institution like the NIH?
  • Has this study been replicated? Conclusions are typically not drawn from one study alone.

No supplement should claim to cure, treat or prevent any disease as clinical trials are not mandated before they are marketed.

Who needs vitamin supplements?

McGowan explains that if someone can’t eat a variety of foods due to things like allergies or a fiber intolerance, a multi-vitamin can be a good insurance policy.

“Multi-vitamins typically stay within the safe limits of daily intake. However, with the single nutrient supplements you want to be careful to not exceed the upper limits of what you should ingest and risk overdosing. More is not always better.”

The Office of Dietary Supplements fact sheets through the NIH can help provide guidance as to the recommended intake for different vitamins.

McGowan adds there is widely accepted research behind some supplement use. For example, calcium and vitamin D can improve bone strength in older women, folic acid in pregnancy can reduce the risk of certain birth abnormalities and vitamin K injections at birth can prevent vitamin K deficiency bleeding. Additionally, people undergoing certain medical procedures such as bariatric surgery are often counseled to take supplements.

“Because some supplements can increase or decrease the absorption of medications due to a competing metabolic pathway, it is a good idea to review your supplements with your doctor.”

The power of food

“Ideally, people should aim to get their nutrients from food as this is the form by which they are best absorbed,” said Ms. McGowan. “Phytonutrients, natural chemicals found in plants, give plants color, so by eating a colorful diet and adding whole grains, you cover most of your vitamin needs.”

To boost energy, McGowan recommends eating 30 grams of fiber a day and limiting added sugar to 30 grams a day. Added sugar is labeled separately from total sugar – discounting the naturally occurring sugars in things like fruit.

Through implementing a nutrient-packed diet – you can fuel your body better than a pill, a gummy or a powder can.