Should you take a personalized multivitamin? A nutrition expert explains one big problem with these regimens

Personalized beauty and wellness products are all the rage these days. For example, you can easily get personalized shampoo, skincare, and vitamins. The basis of this “personalization” is often an online questionnaire on the company’s website. Is your hair thick and curly? Are you hoping for more hydrated hair or more volume? Is your skin dry or oily? Do you break out frequently or infrequently?

When it comes to personalized vitamins, these questions can get more nebulous. It's harder, often impossible, to know if you are deficient in a vitamin by looking in the mirror. And yet, many of us are deficient in specific vitamins and minerals and may benefit from a multivitamin that meets those needs. So are “personalized vitamins” useful?

Are personalized vitamins necessary?

Inverse checked out several companies selling personalized vitamins. Each one used some kind of online quiz for at least part of that personalization. Most of them ask for a health self-assessment and health goals; typically, these revolve around sleep, energy, mood, stress, hair, skin, and nails. And while low energy can undoubtedly mean that you may be iron deficient, it doesn’t confirm that you are. That’s where things can get tricky.

David Jenkins, a professor in the departments of Nutritional Sciences and Medicine at the University of Toronto, tells Inverse that he has “hesitations” about some multivitamins, including personalized multivitamins, because some “micronutrients may not be good in excess.”

Jenkins thinks about this as a U-shaped curve, with the incidence of disease on the Y-axis and the micronutrient in question on the X-axis. In this U-shaped curve, the lowest incidences of the disease are toward the base of the U.

Ultimately, this means too much of a micronutrient can be harmful, but too little also can. And what those levels are can be different for different people.

While some personalized vitamin companies say they offer consultations with healthcare professionals, none of them appear to involve collecting lab work like blood panels that can clearly show what micronutrients someone may need more of.

“I don't think the supplement companies are criminals; they're just trying to fill a need,” Jenkins says. “But the need has to be supplemented by trained physicians as well as dieticians.”

We need better data about micronutrients

Further confounding this problem is the fact that researchers don’t have clear data about where the bottom of the U is, Jenkins says. Folate is one example. The B-vitamin is crucial for healthy pregnancies as it aids fetal development and can help prevent premature births. A synthetic form of folate, called folic acid, is often added to foods and supplements, a practice known as “fortification.”

It’s well established that folate is vital for pregnant people. But data about the effect of high amounts of folic acid in people who aren’t pregnant is much murkier. In the 1960s and 1970s, the United States and Canada started mandating the fortification of some vitamins, including folic acid, in foods. A 2007 study published in the journal Cancer Epidemiology Biomarkers and Prevention found that between 1986 and 2002, levels of folic acid in the blood doubled. It was also associated with an uptick in men developing colorectal cancer. A 2008 study in the same journal found that people who took high levels of folic acid were more than twice as likely to have colon polyps (which can turn into cancer) than those who didn’t.

Still, as Harvard Medical School’s blog says of the study, it “doesn't tell us whether folic acid supplements prevent or promote the development of polyps in the first place. But it raises concerns about the effects of excessive folic acid from both supplements and fortification, especially on people ages 50 and over, who are more likely to already have polyps.”

So what does this have to do with personalized multivitamins, or any multivitamins, for that matter?

Two things, according to Jenkins. First, if you’re not positive that you’re deficient in a micronutrient, it may not be a good idea to take that micronutrient as a supplement or even in fortified food. In some cases, it may not matter; in others, it may help, and in others still, it may hurt. We just don’t know.

Second, Jenkins says, we should know.

“We have to know more about the micronutrients that should be in the diet, and how that should be reflected in blood levels, or 24-hour urine levels or whatever,” he says. “We really do need much more research in this area. It’s important.”

He does say, however, that B12 monitoring and as-necessary supplementation are crucial for those starting on a vegan diet. Such diets can be very healthy but need checking B12 status at intervals with their physician and ideally advice from an experienced dietitian.

If you’re concerned about your micronutrient levels or suspect you might be deficient in something, talk to your doctor about getting labwork done, rather than take an online quiz. If your physician determines that you’re deficient in any vitamins, they’ll be able to advise you about any changes you should be making in your diet, or suggest appropriate vitamin supplements. That’s far more personalized than any online questionnaire can give you.