The keto diet is soaring in popularity. It’s the most commonly searched diet online and, chances are, you know somebody on it. Many doctors recommend the keto diet for certain medical conditions, such as polycystic ovary syndrome (PCOS), epilepsy and diabetes. But is it safe during pregnancy? Here’s what you need to know, whether you are currently on the diet and recently pregnant or you’re currently pregnant and wondering if the keto diet is a good idea.
The ketogenic diet takes low-carb to another level. If you consume the average diet, you probably get about 250 grams of carbohydrates a day. Popular low-carb diets, such as paleo and Atkins, will slash that to about 150 grams a day. That’s just shy of the minimum 175 grams per day recommended during pregnancy.
Enter the ketogenic diet: On the keto diet, you eat about 20 grams of carbs a day. For context, one small apple has 24 grams of carbs. As you can see, this diet is extremely carb-restricted.
Instead of carbs, those on a keto diet get 75 percent of their calories from fat, meaning that they eat lots of cheese, oil, avocado, meat, nuts and seeds. These are healthy foods, but they may not provide all the nutrients you need during pregnancy.
“Nobody is exactly sure if the keto diet is safe, but research suggests that it’s not the best way to eat,” says Elizabeth Ward, a dietitian and pregnancy expert and author of Expect the Best: Your Guide to Healthy Eating Before, During and After Pregnancy.
There are many concerns about the ketogenic diet in pregnancy. For one, the goal of the keto diet is to reach a state of ketosis, which is when the body does not have enough glucose (a type of carb) for energy, so it burns fat instead. But in the first trimester, your body is trying to store fat for energy that’s used later in pregnancy.
The keto diet can also result in a build-up of ketones (by-products of fat breakdown that are used as energy when there is no glucose around), which can freely cross through to the placenta. It’s normal for the body to make some ketones during pregnancy, but it’s unclear what effect an abundance of ketones will have on a developing fetus.
“There have been no randomized, controlled trials of ketogenic diets in pregnancy, so there is no safety data,” says Howard Berger, the head of maternal fetal medicine and deputy chief of obstetrics at St. Michael’s Hospital in Toronto. “But the fetal brain requires glucose for function and development, and forcing the developing brain to convert to a ketone energy supply has potential adverse effects.”
While there haven’t been studies on the keto diet in pregnant women for obvious ethical reasons, there have been some in mice, and the results weren’t good. “Studies in pregnant mice have found that eating a keto diet affects embryo function and organ development, notably the heart and brain, which may have negative consequences in adulthood,” says Ward. “Organs that do not form properly can result in cardiovascular disease later in life, among other health problems.”
While most people go on the keto diet to lose weight, Berger says that weight loss is generally not recommended in pregnancy. Instead, you should focus on nourishing your body and your growing baby. By restricting carb-rich whole grains, beans, fruits and certain vegetables, you can easily fall short of fibre, vitamins and antioxidants.
There’s also a very practical side to why keto is not the right choice: Pregnancy often causes constipation, and you need fibre to combat that. Also, if you are feeling nauseated and want to munch on a handful of plain crackers, you can’t on the keto diet because crackers contain lots of carbs.
Doctors and dietitians may recommend the keto diet to treat epilepsy, diabetes and PCOS in non-pregnant women. If you’re on a medical keto diet, you may wonder if you can continue on the diet during pregnancy.
Ward still advises against keto in this situation but recommends working with a dietitian to come up with an eating plan that makes sense in these cases. In the end, the safety of the baby is paramount. “You only have one shot at giving your baby the best start in life,” says Ward.
Berger concurs: “With pregnancy, caution is always prudent, so until the safety of maternal ketosis is proven, I would not recommend this diet.”