Nutrient intake for women of reproductive age shifted greatly since 1999

Key takeaways:

• Vitamin A, vitamin C and iron intake decreased among women of reproductive age in the U.S. since 1999.
• During the same period, intake of calcium, magnesium and vitamin K increased.

In the past 2 decades, vitamin A, vitamin C and iron intake decreased among women of reproductive age in the U.S., which may substantially impact maternal and fetal health, according to study findings published in JAMA Network Open.

“Dietary patterns in the U.S. have changed over recent decades, with overall dietary quality decreasing among adults older than 20 years of age, which is associated with the prevalence of inadequate nutrient intake and the inability to meet nutritional needs through diet alone,” Derek Miketinas, PhD, RN, assistant professor in the department of nutrition and food sciences at Texas Woman’s University, and colleagues wrote. “According to a previous analysis of National Health and Nutrition Examination Survey (NHANES) data, adequate nutrient intake appears to be a concern in pregnant U.S. women, with more than 40% of pregnant women not meeting the estimated average requirement for vitamin D, vitamin E and magnesium, and most pregnant women also struggling to consume above the adequate intake for choline, vitamin K and potassium, despite reporting greater supplementation frequency compared with nonpregnant counterparts.”

Miketinas and colleagues conducted a secondary series of cross-sectional analyses of 1,392 pregnant (mean age, 28.5 years) and 9,737 nonpregnant (mean age, 32.2 years) women who completed the NHANES survey between 1999 and 2018. All women provided at least one reliable dietary recall, and researchers assessed trends in nutrient intake from foods, beverages and supplements.

Primary outcomes were mean usual intake of macronutrients, micronutrients and prevalence of inadequate micronutrient intake.

Among pregnant women, 27% were in the first trimester and 33.8% were in the second trimester.

Mean carbohydrate intake decreased for pregnant women from 306.9 g per day in 1999 to 274.9 g per day in 2018 (P < .001). Nonpregnant women also had a decrease in mean carbohydrate intake during the same time period (mean, 251.9 g to 216.9 g per day; P = .002).

The proportion of pregnant women who consumed below the estimated average requirement of vitamin A and vitamin C increased by 10.9 and 8.9 percentage points, respectively, from 1999 to 2018. In addition, during the same time period, the proportion of nonpregnant women with an inadequate intake of vitamin A, vitamin C and iron increased by 19.9, 11.1 and 4.9 percentage points, respectively.

From 1999 to 2018, researchers observed increases in mean calcium intake for pregnant women (1,120.6 mg to 1,308.7 mg per day; P = .03) and nonpregnant women (849.5 mg to 981.2 mg per day; P = .03). For pregnant women, the prevalence of inadequate magnesium and vitamin K intake decreased by 16.1 and 33.2 percentage points, respectively, from 1999 to 2018 (P < .001 for both). For nonpregnant women, from 1999 to 2018, the proportion of women with inadequate calcium, magnesium and vitamin K intake decreased by 16.1, 15.5 and 33.3 percentage points, respectively (P < .001 for all).

“It is necessary to understand how women’s dietary patterns change over time among those who are pregnant and who may become pregnant, to better improve the nutritional status for these populations,” the researchers wrote. “By identifying these nutrient gaps and trends in inadequate intake in this at-risk population, scientific, health care and regulatory communities may be better poised to adopt recommendations to improve nutrient intake.”