In my work as a registered dietitian and postpartum doula, working with pregnant and postpartum women, I choose to intentionally focus on FOOD rather than specific nutrients.
In modern nutrition research, the focus on individual nutrients, whether they are a certain vitamin, mineral or macronutrient like protein or fat. The result of this is often focusing on prenatal vitamins as the holy grail or stopping there instead of extrapolating that data into how it looks on your plate.
The truth is that food will ALWAYS be better than nutrition supplements.
My focus professionally is to start with food and if needed, fill in the gaps with some intentional supplementation.
Sometimes though - it is helpful to look at why certain foods are important and look at the building blocks they contain that help build a healthy baby.
An easy way to think about what a healthy diet looks like in pregnancy, when healing from birth and when breastfeeding - is to think about how your grandmother and great grandmother likely ate.
Chances are good that your grandparents or great grandparents ate "nose to tail" of the animal. They would have cooked and ate all cuts of meats, even the tough ones, instead of selecting only the favoured parts of the animal (like boneless, skinless chicken breast). And they would have boiled the leftover parts of the animal like the bones, skin and connective tissue to make nutrient rich broths for soups and stews.
This way of eating is very wise. In cultures around the world, these foods were and still are favoured for women who are pregnant and postpartum as they help grow healthy babies and ensure the health of mothers.
On a scientific level this makes a lot of sense. The reason? Those foods are rich in glycine.
Why you should know about glycine and ensure you're getting enough glycine containing foods onto your plate.
Here's a quick lesson in protein metabolism. All proteins are made up of building blocks called amino acids. There are some amino acids that are "non-essential" and can be synthesized or made in the body. Other amino acids are "essential" which means they cannot be created in the body and need to be consumed from food.
Glycine is often overlooked in pregnancy because generally we can make plenty of it from other amino acids.
But this is not the case in pregnancy. Glycine becomes "conditionally essential" because "the demand for glycine during pregnancy may already exceed the capacity for its synthesis, making it conditionally indispensable." - Real Food for Pregnancy by Lily Nichols
Glycine is needed for many important processes in the body.
In pregnancy, glycine is needed for the synthesis of DNA and collagen in your baby...the building blocks of their body. Glycine is also needed for development of bones, connective tissues, blood vessels, organs, skin...you name it.
For the mother, glycine is needed to support your growing uterus, breasts, ligaments and stretching skin.
The protein collagen is 1/3 glycine by weight. The uterus alone contains up to 800% more collagen at the end of pregnancy compared to pre-pregnancy!
Glycine helps with skin integrity. This is important as our skin is stretched to beyond what we thought possible and allows the stretching of the perineum to allow an entire baby to pass through!
Glycine can even help to prevent stretch marks by supporting the integrity of the skin...though this is not guaranteed! Anecdotally, I have hear this reportedly helps from other women as well as noticed this as a difference between my two pregnancies. With my second pregnancy, I focused on foods containing glycine and did not experience stretch marks.
Detoxification is another important function of glycine. It's needed for an essential enzyme in the liver (glutathione) to naturally detoxify chemicals we encounter on a daily basis.
Glycine also helped to lower blood pressure and blood sugar levels. Low glycine status has been associated with preterm infants.
Not enough glycine can interfere in the development of the cardiovascular system of the baby. This is because it's required for the production of elastin, a protein that allows the blood vessels to expand and contract.
And your circulatory system needs more glycine to maintain normal blood pressure and to accommodate all the extra fluids of pregnancy. This could be why some research suggests it may help prevent preeclampsia.
What foods are a good source of glycine?
First let's talk about what foods are NOT good sources of glycine.
This next point is really important and surprises a lot of people...glycine is NOT abundant all protein containing foods.
Glycine is NOT abundant in lean meats, skinless poultry, dairy products or vegetarian sources of protein.
If someone is eating foods exclusively from low-glycine protein sources, this can cause another issue of excessive methionine intake. Excessive methionine is an issue because it reduces glycine stores and has been linked to increased markers of inflammation in the body (homocysteine) and pregnancy complications such as neural tube defect, preeclampsia, spontaneous abortion and premature delivery.
Glycine IS abundant in bone broth, slow-cooked tough cuts of meat (such as pulled pork, stewing beef, pot roast), skin-on and bone-in poultry (like chicken wings, thighs, whole roasted chicken), pork rinds, bacon, sausages and ground meats (as these often are made from tougher cuts).
Glycine can also be obtained from adding pure gelatin powder or collagen powder to other foods as they are naturally very rich in glycine. You can add a spoonful to your morning coffee or tea, to soup, smoothies or stir into yogurt.
What about plant based diets?
Plant based diets are rising in popularity, but the problem is that all except a handful of foods which are a source of glycine, are animal foods.
There is no official recommended dietary allowance (RDA) for glycine, but the estimated minimum amount of glycine needed in the diet for non-pregnant adults is 10,000 mg per day. This need is likely higher during pregnancy.
Insufficient intake of glycine is of significant concern for both vegetarians and vegans since concentrations of this amino acid are generally low in plant foods. Of the plant food sources, spirulina algae is one of the best.
However, keep in mind that the quantity required to meet glycine demands is probably unfeasible.
For example - 2 oz of pork rinds contain 6,760 mg of glycine compared to only 1,760 mg in 2 oz of dried spirulina powder (which is about 1/2 a cup).
If you are consuming a vegetarian or vegan diet, consult with a registered dietitian with expertise in prenatal and postpartum nutrition to discuss how to optimize your diet and nutrient intake. Specific supplementation is likely necessary.
Summary
Glycine is an amino acid that is essential in pregnancy. The function of glycine is to support the growth and development of almost all structures of the baby and support the growth and stretching of tissues in the mother.
You can find glycine primarily in animal foods such as bone broth, tougher cuts of meat, skin-on and bone-in poultry, pork rinds, bacon, sausages and ground meats.
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