Custom supplements formulated on the basis of DNA or blood tests are trending — but do they deliver results?

If you’ve ever walked down the vitamin and supplement aisle at the drugstore and been confused — which supplements do I really need? What dose is appropriate? Can I just take this multivitamin and be done with it? — know you’re not alone. Several companies have identified this consumer issue and set out to solve it and change the vitamin industry along the way.

These new companies, including Care/of, Ritual, among others, started popping up in ads online (and likely in your Instagram feed, too) starting in 2015. Most of them work in similar ways: They try to get to know you and then recommend vitamins and supplements specific to your needs.

Multivitamins are extremely popular — about half of Americans older than 50 take one, according to data from the Centers for Disease Control and Prevention (CDC). But the question of whether they’re needed or even helpful is up for debate.

In one large analysis of more than 4,900 people, those who regularly took multivitamins reported approximately 30 percent better health compared with nonusers, but researchers found no hard evidence that this was true. The study results, which were published in BMJ Open in 2020, showed no corresponding reduction in multivitamin users' risk of chronic illnesses or improvements in health markers. And a review published in June 2018 in the Journal of the American College of Cardiology analyzed 179 studies and found that multivitamins (plus single-nutrient supplements like vitamin C, calcium, and vitamin D) didn't benefit heart health or help people live longer.

Multivitamins have shown some benefits for certain groups of people, such as pregnant women, who have greater nutritional needs, and people dealing with specific vitamin deficiencies, according to the National Institutes of Health Office of Dietary Supplements.

“Generally, we are better off getting the essentials through whole foods, but most people don’t eat this way,” says Ian Smith, MD, the Chicago-based author of several diet books. “It turns out that, especially with some of these restrictive and trendy diets that people are following, most of us are severely lacking in terms of adequate nutrient consumption.” He says taking high-quality vitamins and supplements can help fill in these gaps.

One of the criticisms of multivitamins is that not everyone needs the same nutrients in the same amounts, and even one person’s needs tend to change over the course of their lifetime. People who follow a vegetarian diet, for instance, may be more likely to skimp on vitamin B12, calcium, and vitamin D, according to the Mayo Clinic. Smokers, on the other hand, might need extra calcium and vitamins C and D, according to Beth Israel Lahey Health Winchester Hospital.

Custom vitamin companies propose to offer a solution to the one-size-fits-all approach. Many of these companies, including Care/of, Vous Vitamin, and Persona, start with a short quiz (which can usually be completed in five minutes or less) that covers your gender, age, health goals, lifestyle, diet, exercise routine, concerns, and allergies. Then, you’ll receive a recommendation for a supplement or supplements, which will be delivered to you monthly (or at some other interval) if you purchase a subscription. It may be a supply of one multivitamin or a packet of a few capsules.

Some custom vitamin companies, including Mytamin and the Switzerland-based Baze, use a more scientific — but also more invasive — approach, basing the formulations of their custom supplements on blood tests. Still other companies, including Rootine and VitaminLab use DNA tests — the latter will even use results of tests from 23andMe and Ancestry that you may have taken previously.

There are two major benefits of personalized vitamins: convenience and personalization. Instead of having to remember to go to the drugstore to stock up, the vitamins and supplements are delivered to your door every month. “The subscription and direct-to-consumer model is a smart one for consumers who increasingly seek convenience and ‘at your door’ service,” Dr. Smith says. “Many people may stop taking vitamins because they don’t have a chance to replenish their supply.”

The second major benefit is that the vitamins you receive are specific to your needs. These companies try to get enough information about you to determine which nutrients you might be missing and which you need to stay healthy and meet your goals. That personalization factor helps set them apart. “While a grocery store multivitamin uses data from thousands of people, these personalized vitamin services try to use data from people closer to your demographic for a more individualized [approach],” says Caitlin Self, a licensed nutritionist based in Baltimore.

At first glance, these companies have lots of bells and whistles: sleek websites with fancy quizzes, a curated social media presence, and cute packaging. But your quiz responses are self-reported rather than objective, and Self worries they may not be sufficient.

As for blood tests, they are reliable — when done correctly. “The issue may be human error, considering that those doing the test are not trained in drawing, handling, and storing blood,” says Trista Best, RD, MPH, an environmental health specialist and consultant with Balance One Supplements (a company that sells supplements) in Dalton, Georgia. Blood drawn in a lab is more likely to be stored correctly, while blood samples sent through the mail run the risk of being degraded by temperature changes or other conditions.

Both Smith and Self say shopping these companies is likely better than simply buying off the shelf. “I do believe that these personalized approaches are better than the average grocery store multivitamin, but not nearly as good as a clinical signs and symptoms assessment by a nutritionist,” Self says. A registered dietitian nutritionist can identify nutritional gaps in your diet and offer ways to fix them through whole foods, which is generally preferable to supplements of any kind.

Also, even though many of these brands have a team of doctors or nutritionists on staff who develop recommendations and research specific nutrients, there’s no Food and Drug Administration (FDA) oversight of these products. “That means most of these companies have not been properly vetted by third-party groups,” Self says.

If you’re interested in giving personalized vitamins a try, Smith suggests doing your own research so you can make a smart decision. Make sure you agree with the recommendations, that the dosages are correct, and note any potential side effects of the ingredients (MedlinePlus is a good resource for this information). It’s also a good idea to consult with your doctor before you take any new supplements and make sure the supplements are legitimate.

“The primary way to know whether you should trust a supplement manufacturer to provide a safe and quality product is to check for third-party testing,” says Best. According to the National Institutes of Health, seals from NSF, ConsumerLab.com, and U.S. Pharmacopeia (USP) certify the supplement was properly manufactured, contains the ingredients the label says it does, and does not contain harmful contaminants. Not all these supplement companies put their products through third-party testing, but Best points out that Ritual is one that does.

Overall, Smith thinks these companies can make it easier for you to prioritize your health. “An investment in your health is always a good one, in my estimation,” he says.

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