Are Vegan and Vegetarian Diets Safe During Pregnancy?

Drew Ramsey, MD


December 06, 2016

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Are vegan and vegetarian diets safe during pregnancy? I am Dr Drew Ramsey. In this episode of the Brain Food Blog, we are going to focus on this issue, look at some of the literature that is out there, and talk about what to do clinically when you have vegan and vegetarian patients who are thinking about pregnancy.

Vegan and vegetarian diets are plant-based diets. They are gaining popularity as people try to make better choices in terms of their health when it comes to food. Plants, in general, are a great choice, especially colorful plants, because they tend to be more nutrient-dense. Plant-based diets have been linked to a number of health benefits, such as lower body mass index and lower rates of obesity and diabetes, as well as conferring some benefits. Certainly, vegan and vegetarian diets have higher amounts of certain nutrients like magnesium, folate, and fiber, all of which are generally consumed in very low quantities in Western diets.

Focusing on pregnancy, there are two important papers to note. The first, which got me very interested in this issue, was a series of pooled case reports by Drs Dror and Allen in 2008.[1] They looked at 30 cases of severe vitamin B12 deficiency during pregnancy in vegan women as well as in women with pernicious anemia. Among the 30 vegan women who had B12 deficiency during pregnancy, about 60% of their offspring had severe developmental delays and 37% had cerebral atrophy. With repletion, many of the neurologic symptoms in the infants improved right away, but over time, 50% of the infants still had developmental delays even with repletion of B12. Certainly there can be long-standing effects of B12 deficiency. The clinical importance of this is to partner with our patients who are eating plant-based diets and ensure that they have adequate levels of vitamin B12, as well as iron, zinc, and long-chain omega-3 fats during pregnancy.

The second article to take a peek at is from the British Journal of Obstetrics and Gynaecology in 2015.[2] This was a systematic review that looked at all of the literature after screening out the papers. The authors found about 13 papers focusing on maternal and infant outcomes, and about nine of those looked at nutrient deficiency. The main headline of this review is that there are no randomized clinical trials of vegan or vegetarian diets in pregnancy. It is very hard to make a clear clinical recommendation. The epidemiologic data were heterogeneous. As the researchers called it, it was "scant." That is certainly true. Overall, there were no clear associations with bad outcomes. There was some increased risk for hypospadias in one of the larger trials that looked at vegan and vegetarian diets during pregnancy.

The main concern is that vegan and vegetarian diets put patients at risk for a number of nutrient deficiencies—vitamin B12 in vegan diets (and even for vegetarians), iron, zinc, and the long-chain omega-3 fats. Just a quick moment on the long-chain omega-3 fats: Dietarily, these only come from fatty fish and seafood. They are bioconcentrated. They start in algae, but they get bioconcentrated in our food supply via seafood. It is very hard to get those during pregnancy. Certainly, a lot of healthy babies have been born to vegetarian and vegan women. You can supplement, but given the benefits we see with omega-3 fats in patients with things like mood disorders or a history of psychotic disorders, I think it is important to consider the long-chain omega-3 fats. If someone is not going to get those in their diet but has a history, risk, or propensity toward mood disorders, think about supplementation. Some data show that women with higher intakes of fish or higher levels of DHA tend to have a much lower risk for postpartum depression.

Those are some of the issues associated with plant-based diets and how they affect clinical outcomes during pregnancy. I hope this helps to clarify how to partner with your patients. In medicine, we do not get to pick our patients or their diets, but it is our job to help them understand the nutritional consequences of their eating plan and guide them toward full nourishment, either with proper foods or supplementation.

I am Dr Drew Ramsey, reporting for Medscape Psychiatry.


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