Why (Almost) Everything You Were Taught About Prenatal Nutrition is Wrong

Nearly everything you were taught about prenatal nutrition is wrong. That’s a bold statement, but I stand by it.

As a dietitian who’s all about real food, the majority of what I was taught about prenatal nutrition in my conventional training has turned out to be wrong upon further investigation.

No mother wants to do anything that might risk the health of her future child, but when the information you get from well-meaning doctors and nutritionists isn’t up to date, that’s exactly what can happen.

In this article, I’ll go through 5 prenatal nutrition myths that every paleo mom should know about.

Why (Almost) Everything You Were Taught About Prenatal Nutrition is Wrong

1. You Can’t Eat Fish

Due to the presence of mercury and other contaminants in certain fish, many women have been told not to consume fish while pregnant.

Truth is, many types of fish are perfectly safe to eat while pregnant, even if they contain a small amount of mercury. It sounds counterintuitive, but this little-known fact should put your mind at ease: most fish also contains high amounts of selenium, a mineral that readily binds with mercury, thereby preventing it from exerting toxic effects in the body 1.

Aside from a select few varieties of fish that are very high in mercury, which I do suggest your avoid (this includes tuna, swordfish, tilefish, king mackerel, and shark), eating other varieties of fish is safe and has many benefits.

Fish is an excellent source of protein, iodine (a mineral that’s crucial to normal brain development), zinc, and vitamin D. Fatty fish that thrive in cold water are the best food source of DHA – an omega-3 fat that’s needed for brain and vision development. Some of the best fish to consume are wild-caught salmon, herring, and sardines, due to their high DHA content and low concentrations of mercury and other contaminants.

One caveat: Avoid farm-raised fish, as these tend to contain high amounts of BPA (a chemical that can disrupt estrogen and hormones) and antibiotic residues.

2. You Can Get All of your Omega-3s from Plants

As I stated above, the omega-3 fat, DHA, is crucial to brain development. But there’s confusion on the best food sources.

I remember reading a nutrition pamphlet from a major national nutrition organization suggesting pregnant women need to eat flaxseeds and walnuts to obtain DHA. That’s 100% false. While plant-sourced omega-3s aren’t necessarily “bad” for you, they are not going to boost your baby’s brain development.

That’s because plant-sourced omega-3s (with the exception of certain algae), come in a form called “ALA,” not the type our brain and eyes need, which is “DHA.” As much as people like to argue that our body can make DHA from these plant sources, these claims don’t stand up to science.

It turns out the conversion of ALA to DHA in humans is incredibly poor, topping out at a measly 3.8%. Plus, if your diet is high in omega-6 (which happen to be concentrated in seeds, nuts, and vegetable oils where you obtain ALA), this conversion rate drops to only 1.9% 2.

A diet high in saturated fat improves this conversion rate, but the truth is: no matter what, you cannot provide enough DHA for your growing baby if you do not eat DHA directly.

The best source of DHA, by far, is fish as described above. If you do not eat fish, you can take fish oil, cod liver oil, or algae oil to obtain DHA. You’ll also find smaller amounts of DHA in eggs from pastured chickens and meat from pasture-raised or grass-fed animals (but only if you eat the yolks and fattier cuts of meat).

3. Eating Liver is Dangerous in Pregnancy

Maybe you’ve been in the Paleo/Primal/Real Food world long enough to have been convinced otherwise, but if you read information from conventional sources, they warn against consuming liver during pregnancy.

Why? Because liver is high in vitamin A.

Studies on synthetic vitamin A (from supplements) show that too much can lead to birth defects. So, following that simple logic, liver should be avoided. Ironically, a few decades ago, doctors actually encouraged mothers to consume liver throughout pregnancy. What gives?

It turns out that food-sourced vitamin A does not have the same toxicity as synthetic vitamin A supplements, especially when it’s consumed with adequate vitamin D and vitamin K, both of which happen to be found in liver 3.

Don’t take my word for it, though:

“Liver and supplements are not of equivalent teratogenic potential [risk of causing birth defects]. Advice to pregnant women on the consumption of liver based on the reported teratogenicity of vitamin A supplements should be reconsidered.” 4

Plus, at least one third of pregnant women don’t consume enough vitamin A. So, eating liver would actually be hugely beneficial 5. Liver is also rich in choline, which is necessary for normal brain and eye development and the prevention of neural tube defects. In addition, liver boasts high levels of folate, all the B vitamins, iron, zinc, and more. It’s quite literally like eating a multivitamin!

4. Don’t Eat Too Much Fat

In the field of prenatal nutrition, we have to take a step back and look at which foods traditional cultures prized for fertility and pregnancy and then work backwards to uncover why these foods are so important. When we take this approach, you notice high-fat foods (especially of animal origin) being central to reproductive health – foods like eggs, organ meats, tallow, and fatty fish.

These foods provide an abundance of vitamins A, D, E, and K and the omega-3, DHA, that are needed in higher amounts during pregnancy. Restricting fat limits your access to these nutrients.

Plus, fat usually accompanies other essential nutrients, especially protein. For example, the classic advice to “eat lean meat” ends up limiting the quantity of glycine in the diet, an amino acid that becomes essential to obtain from the diet during pregnancy.

Glycine is critical for normal cardiovascular and tissue development in a growing baby 6. The primary sources of glycine in the diet are the skin, bones, and connective tissue of meat, poultry, and fish. So, enjoy the crisp skin on your chicken, relish some yummy pulled pork, and don’t trim the fat off your steak.

Clearly, the whole idea of eating a low-fat diet, pregnant or not, is not founded on solid scientific evidence.

5. Pregnant Women Need to Eat More Carbohydrates

Since I specialize in gestational diabetes, I get asked about carbohydrates a lot. Conventional advice suggests pregnant women eat a higher carbohydrate diet, warning that “inadequate” intake could impair brain development of a growing baby.

However, after putting this advice into practice with my prenatal clients (many of whom had gestational diabetes), I found their blood sugar readings often got worse (along with skyrocketing blood pressure and weight gain). I had to wonder if these clients weren’t “failing the diet,” but wondered if the diet was “failing them.”

Once I really dug into the research, I was shocked at what I found. Not only is there no evidence to prove that pregnant women need more carbohydrates or that the fetal brain requires extra, there’s actually quite a bit of data to suggest that some women may benefit from fewer carbohydrates in pregnancy (particularly those with blood sugar problems).

The primary reason clinicians are afraid to endorse a lower-carbohydrate diet for pregnancy is that they’ve been given outdated information regarding ketosis, in other words, the state that the body goes into when it’s burning fat for fuel.

However ketosis is a loaded term that can have several manifestations during pregnancy. This topic is so complex that I devote an entire chapter to in my book, Real Food for Gestational Diabetes, and spoke on this topic in my presentation, The Carbohydrate and Pregnancy Controversy, at Paleo f(x)™ 2016.

But, the short answer is that low-level nutritional ketosis is common during pregnancy, does not carry the same risks as starvation ketosis or diabetic ketoacidosis, and does not negatively impact the brain development of a baby.

Summary

Hopefully these examples helped explain why (almost) everything you were taught about prenatal nutrition is wrong. This is, by all means, not an exhaustive list.

The take home message here is to trust that real food is optimal in pregnancy. Any “expert” who tries to convince you that you need fortified cereal or must avoid some of nature’s most nutrient-dense foods hasn’t dug deep enough into the research.

So, if you feel good basing your diet on pasture-raised meats (including organ meat), eggs, wild-caught fish, a variety of vegetables, nuts, seeds, some fruit (and maybe some grass-fed dairy if that works with your body), rest assured, you are providing your baby with optimal nutrition!

Real Food for Gestational Diabetes


To learn more about my real food approach to managing gestational diabetes, check out my book, Real Food for Gestational Diabetes, or take a listen to my interview with Robb Wolf.

And if you’d like my personal support managing your gestational diabetes and access to a private support community of other real food mamas, check out my online course of the same name.

References

  1. Ralston, Nicholas VC, and Laura J Raymond. “Dietary selenium’s protective effects against methylmercury toxicity.” Toxicology 278.1 (2010): 112-123.
  2. Gerster, H. “Can adults adequately convert alpha-linolenic acid (18: 3n-3) to eicosapentaenoic acid (20: 5n-3) and docosahexaenoic acid (22: 6n-3)?.” International journal for vitamin and nutrition research. Internationale Zeitschrift fur Vitamin-und Ernahrungsforschung. Journal international de vitaminologie et de nutrition 68.3 (1997): 159-173.
  3. Masterjohn, Christopher. “Vitamin D toxicity redefined: vitamin K and the molecular mechanism.” Medical hypotheses 68.5 (2007): 1026-1034.
  4. Buss, NE et al. “The teratogenic metabolites of vitamin A in women following supplements and liver.” Human & experimental toxicology 13.1 (1994): 33-43.
  5. Strobel, Manuela, Jana Tinz, and Hans-Konrad Biesalski. “The importance of β-carotene as a source of vitamin A with special regard to pregnant and breastfeeding women.” European journal of nutrition 46.9 (2007): 1-20.
  6. Persaud, Chandarika et al. “The excretion of 5‐oxoproline in urine, as an index of glycine status, during normal pregnancy.” BJOG: An International Journal of Obstetrics & Gynaecology 96.4 (1989): 440-444.
Salmon photo licensed under the Creative Commons.

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Lily Nichols

Lily Nichols is a researcher, speaker, and author with a passion for evidence-based prenatal nutrition and a unique specialty in gestational diabetes. A Registered Dietitian/Nutritionist, Certified Diabetes Educator, and Certified Pilates Instructor, Lily is the first dietitian to publicly advocate for a nutrient-dense, lower carb diet for managing gestational diabetes. Her book, Real Food for […]

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