Study: Prenatal Supplements Fail to Meet Nutrient Needs

Robert Fulton

April 10, 2023

Although drugstore shelves might suggest otherwise, affordable dietary supplements that provide critical nutrients in appropriate doses for pregnant women are virtually nonexistent, researchers have found.

In a new study published this month in the American Journal of Clinical Nutrition, investigators observed what many physicians have long suspected: most prenatal vitamins and other supplements do not adequately make up the difference of what food-based intake of nutrients leave lacking. Despite patients believing they are getting everything they need with their product purchase, they fall short of guideline-recommended requirements.

"There is no magic pill," said Katherine A. Sauder, PhD, an associate professor of pediatrics at the University of Colorado Anschutz Medical Campus in Aurora and lead author of the study. "There is no easy answer here."

The researchers analyzed 24-hour dietary intake data from 2450 study participants across five states from 2007 to 2019. Sauder and colleagues focused on six of the more than 20 key nutrients recommended for pregnant people, and determined the target dose for vitamin A, vitamin D, folate, calcium, iron, and omega-3 fatty acids.

The researchers tested more than 20,500 dietary supplements, of which 421 were prenatal products. Only 69 products — three prenatal — included all six nutrients. Just seven products — two prenatal — contained target doses for five nutrients. Only one product, which was not marketed as prenatal, contained target doses for all six nutrients but required seven tablets a serving and cost patients approximately $200 a month.  

For many years, Sauder and her colleagues have struggled to identify the gold standard of vitamins for pregnant patients.

More than half of pregnant people in the United States are at risk of inadequate intake of vitamin D, folate, and iron from their diet alone, and one third are at risk for insufficient intake of vitamin A and calcium.

Although more than 70% of pregnant women take dietary supplements, the products do not eliminate the risks for deficiencies.

The effects of inadequate nutrition during pregnancy may include neural tube defects, alterations in cardiovascular structure, and impaired neurocognitive development.

The researchers also looked at the challenges within the dietary supplement industry. The US Food and Drug Administration regulates dietary supplements as foods rather than drugs, and therefore does not require third-party verification that would ensure product ingredients match labels.

The researchers acknowledged the challenges in creating a one-size-fits-all nutritional supplement.

"The supplement industry is difficult because you're trying to create a product that works for a large, diverse group of people, but nutrition is very personal," Sauder said.

Kendra Segura, MD, an ob/gyn at the To Help Everyone Health and Wellness Center in Los Angeles, said she was unsurprised by the results.

"There's no good prenatal vitamin out there," Segura said. "There's no 'best.' "

Segura said she advises her patients to focus on increased nutritional intake with foods, but added that that the lack of nutrients in diets and the need for supplements reflects the lack of availability of healthy food in some communities (known as 'food deserts'), as well as poor dietary choices.

Diana Racusin, MD, an assistant professor of obstetrics, gynecology, and reproductive services at the University of Texas Health Science Center's McGovern Medical School in Houston, also "wasn't terribly surprised" by the findings. She stresses the importance of what patients eat more than the availability of supplements.

"What this is really showing us is we have work to do with our nutrition," Racusin said.

Sauder's biggest takeaway from her study is the need for more patient guidance for their nutrition beyond advising a supplement.

"We need better support for women to help them improve their diet during pregnancy so that they're getting the nutrients they need from food," she said, "and not having to rely on supplements as much."

The study was supported by the Environmental Influences on Child Health Outcomes Program of the National Institutes of Health and by the nonprofit organization Autism Speaks. Sauder reports no relevant financial relationships. Co-author Regan L. Bailey has served as a consultant in the past to the NIH Office of Dietary Supplements, Nestlé, the General Mills Bell Institute, RTI International, and Nutrition Impact; is a trustee of the International Food Information Council; is a former board member of International Life Sciences Institute–North America; is a member of Schiff Scientific Advisory Board; and in the past has received travel support to present her research on dietary supplements. Co-author Karen M. Switkowski is a paid consultant of prenatal nutrition to Modern Fertility.

Am J Clin Nutr. Published in the April 2023 edition. Full text

Robert Fulton is a journalist living in Los Angeles.


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