Plant-based pregnancy: Experts spotlight supplementation to offset vegan diet deficiencies

24 Jan 2024 --- Researchers are raising concerns about the risks tied to vegan diets during pregnancy in a new study. However, some experts say the small number of actual vegans included in the sample size may not be representative of the quality of mothers’ plant-based diets overall and the shortfalls may be addressed through supplementation.

According to the study, which explores the dietary habits of 65,872 women, the results reveal a higher incidence of preeclampsia among vegan mothers, alongside a noticeable reduction in their newborns’ average birth weight — about 240 grams less than the children of omnivorous mothers.

Despite the health benefits often attributed to veganism, the results suggest a need for caution and further examination, particularly as existing public health guidelines for plant-based diets during pregnancy are somewhat inconclusive.

Moreover, the researchers acknowledge that their findings are inconclusive, writing that “further research is needed regarding possible causality between plant-based diets and pregnancy and birth outcomes to strengthen the basis for dietary recommendations.” 

“The 66,738 pregnancies in this population-based study were recruited over 20 years ago, when few women followed a plant-based or vegan diet,” comments Dr. Keith Godfrey, professor of epidemiology and human development at the University of Southampton, UK. 

“As acknowledged by the authors, their main findings of higher risks of low birth weight and preeclampsia among vegans are subject to some uncertainty, being based on only 18 vegans.”

Plant-based shortcomings
A recent review of the EAT-Lancet Diet for Planetary Health found significant micronutrient shortcomings for perinatal women, including deficiencies in folate and iron.

The study, published in Acta Obstetricia et Gynecologica Scandinavica, examines pregnant women’s protein and micronutrient intake, revealing that those on vegan diets reported significantly lower levels than their omnivorous peers.

Leveraging data from the extensive Danish National Birth Cohort, the study includes interviews and a detailed Food Frequency Questionnaire to assess dietary practices and their impacts on pregnancy outcomes. 

The findings reveal a predominance of omnivorous participants, with only a minimal fraction identifying as vegan, and show that vegan mothers not only faced a heightened risk of preeclampsia but also were more likely to have newborns with lower birth weights. 

While the study’s authors note lower dietary intakes of specific nutrients among vegans, incorporating nutritional supplements appeared to compensate for some of these deficiencies.

In support of supplementation
The study underscores the critical need for detailed dietary assessments and guidance for pregnant women following vegan diets and stresses the importance of ensuring sufficient protein intake and micronutrient supplementation to safeguard the health and well-being of both mothers and infants.

Moreover, the authors highlight the need for more research and for refined public health guidelines to support the nutritional needs of this demographic.

“A lower intake and status of a number of micronutrients by non-supplemented vegans, and to a lesser degree vegetarians, has been reported in a number of studies,” Dr. Ian Givens, professor of food chain nutrition at the University of Reading, UK, underscores. “These tend to be nutrients that plants cannot supply or supply very little and include iodine, vitamin B12, vitamin D and calcium.”

While Givens notes that the present study indicates that supplements can compensate for the deficiency of essential micronutrients in vegan and vegetarian diets, he advises that caution and often professional guidance are advisable to ensure appropriate supplementation.

Experts react
Dr. Tom Sanders, professor emeritus of nutrition and dietetics at King’s College London, UK, spotlights a study focusing on a specific population of Seventh-Day Adventists in the US that indicates no variation in birth weight or outcomes among individuals adhering to plant-based diets.

Several scientists state that supplementation can make up for micronutrient deficiencies in plant-based diets.“A weakness of the study is that it does not report the ethnic origin of the mothers and dietary intakes were assessed by questionnaire, which is not very reliable for assessing micronutrient intake and the bioavailability of minerals such as iron and zinc,” Sanders explains.

“Although protein intakes were lower on the plant-based diets as would be expected, it is an unlikely explanation as protein supplementation has adverse effects on birth weight and outcomes. Low bioavailability of iron from plant-based diets is a more plausible explanation for the lower birth weights.”

At the same time, Dr. Duane Mellor, a registered dietitian and senior lecturer at Aston Medical School, Aston University, UK, stresses that following a vegan diet requires careful planning to make it nutritionally adequate due to potential deficiencies in iron, iodine, vitamin B12 and vitamin D, which can impact the health of the mother and the baby’s development.

Additionally, he points out that within the limited participation of vegans in the study, only two vegan women experienced preeclampsia, which suggests that the reported higher incidence among vegans may be attributable to statistical variance.

“When planning a pregnancy and during pregnancy, whatever your dietary patterns and preferences, it is key to eat a varied and balanced diet, including supplements as advised by government and health guidelines,” Mellor concludes. “If a diet is balanced and includes the necessary nutrients including protein, vitamins and minerals, the type of diet is not as important.”

By William Bradford Nichols