Most pregnant people lack nutrients, while supplements fall short and contain toxic metals

New research claims that over 90% of pregnant individuals may lack key nutrients in their diets, while another study finds many prenatal vitamins on the market lack essential nutrients like choline and iodine. Some of the supplements exceed safety limits for toxic metals, raising accuracy and safety concerns.

Despite the general estimate of 10% of pregnant people struggling to meet nutritional needs, research from the Stevens Institute of Technology, US, claims a majority of them are failing to get enough iron, vitamin D or vitamin E from their diets.

The study in the Journal of Nutrition says one-third may lack sufficient calcium, vitamin C and vitamin A, while two-thirds are not getting enough dietary folate. The nutrient is underlined for its critical role in preventing birth defects in the brain and spine.

“It’s important to remember that many pregnant people take prenatal vitamin supplements, which might help prevent nutritional deficiencies,” says study lead author, Dr. Samantha Kleinberg, professor at the Charles V. Schaefer, Jr. School of Engineering and Science at Stevens. 

“Nonetheless, this is a startling finding that suggests we need to be looking much more closely at whether pregnant individuals are getting the nutrients they need.”

Advancing research methods

Most previous studies relied on food diaries, which depend on participants’ memory. This approach often leads to inaccuracies in estimating portions or recalling meals.

In contrast, the Stevens study used a new method: participants took before-and-after photos of meals over two 14-day periods. Researchers then analyzed these images to calculate nutrient intake more precisely. Kleinberg says this approach is more accurate. 

“Most surveys only track diet over a day or two — but if you feel off one day and don’t eat much, or have a big celebratory meal over the weekend, that can skew the data,” says Kleinberg.

“We often had to reach out to participants to ask what kind of meat they’d put in their sandwich or whether their coffee had sugar in it. If we can streamline that process, then we’ll be able to capture data more easily and help shed new light on how pregnant people actually eat.”

The research team plans to streamline this process with AI tools that can automate follow-up questions, making it easier to capture accurate dietary data.

Nutritional gap in pregnancy

Co-author Dr. Andrea Deierlein, director of public health nutrition at New York University, also saw that diets were not only different between participants but also between what each one ate day after day.

One-third may lack sufficient calcium, vitamin C, and vitamin A, while two-thirds are not getting enough dietary folate.Based on the diet variations, she suggests shorter and population-based studies are overlooking nutritional deficits.

“Some people eat really well, and others don’t — so if you just take an average, it looks like everything’s fine,” says Kleinberg. “[Our] study suggests that in reality, an alarming number of pregnant people may not be getting the nutrients they need from their food.”

The team also noticed that pregnant people eating later in the day are likely to consume “significantly more total calories.” This finding is underlined as it may help researchers looking at health problems such as gestational diabetes.

Inefficient and harmful supplements 

The Stevens study encourages pregnant people to take supplements, however, other recent research finds several prenatal vitamins don’t contain enough of the nutrients needed for healthy pregnancy, with some even containing high levels of toxic metals.

The study in the American Journal of Clinical Nutrition checked choline and iodine levels in nonprescription and prescription prenatal vitamins.

“During pregnancy, many women rely on prenatal vitamins and minerals to support their health and their baby’s development. Among the most crucial nutrients for fetal development are choline and iodine,” says first author Dr. Laura Borgelt, MBA, professor at the University of Colorado Skaggs School of Pharmacy and Pharmaceutical Sciences at CU Anschutz. 

“However, some prenatal vitamins may not contain the exact amounts listed on the label and some may not contain any choline or iodine,” she notes.

“Our study aims to help women better understand the nutrient content in prenatal supplements, empowering them to make more informed choices and select the best options for their health and their baby’s well-being.”

Unchecked claims 

Researchers examined a sample of 47 different prenatal vitamins (32 nonprescription and 15 prescription products) bought online and in local shops. They then compared the nutrition levels, checking their labels and comparing them to official safety standards within 20% of the claimed amount.

Women who are 19 years of age and older should consume 150 mcg of iodine per day, which rises to 220 mcg during pregnancy.“We’re one of the first studies to measure the actual amounts of choline and iodine in a large sample of prenatal supplements. The presence of contaminants, especially cadmium, was also concerning. Our findings highlight a significant gap between what’s listed on the labels and what’s actually in the products, underscoring the urgent need for stronger regulatory oversight in this area,” Borgelt adds.

Results reveal most prenatal vitamins do not list choline, those 12 that did, did not contain the right amount. Only five had the right amount as promised on the label.

Similarly, prenatal vitamins contained less iodine than seen on labels. Only four had the claimed amount of iodine on the label.

Alarmingly, heavy metals in some products were higher than expected: seven contained arsenic, two lead and 13 cadmium, all above the purity limits set by the US Pharmacopeia. Heavy metal exposure in pregnancy is known to cause negative impacts on birth.

Recommendations for pregnancy

The Institute of Medicine’s Food and Nutrition Board suggests dietary reference intakes of choline at 450 mg per day during pregnancy and 550 mg per day during lactation, with a tolerable daily maximum of 3,500 mg.

Women who are 19 years of age and older should consume 150 mcg of iodine per day, which rises to 220 mcg during pregnancy and 290 mcg during lactation. The tolerable upper limit for iodine is 1,100 mcg/day.

According to the authors, prenatal supplements are still beneficial to take while pregnant, but they advise confirming the ingredients or consulting a physician or other healthcare provider before making a decision.