Eating Liver in Pregnancy - Is it Safe?

I received a wonderful comment on another blog post of mine, "Top 10 Foods to Prepare for Labor and Delivery." In that post I list Liver as one of my Labor and Delivery prep superfoods. The commenter brought up the concern that liver is an extremely rich source of Vitamin A, and excess Vitamin A in pregnancy is associated with birth defects. Her concern was that I may be giving out dangerous information in regards to suggesting liver consumption for labor preparation. I truly welcome these comments and concerns, as they offer an avenue for discussion, and this is a great topic of discussion.

Written by Sarah Thompson Functional Medicine Acupuncturist & Doula

I love liver. Yes, I literally do, and so do my children. My family is a subsistence meat eating family, meaning we hunt for our meat. Every fall we fill our freezer with some of the highest quality meat to be found, this includes the organs. My children will fight each other over the last sliver of heart fajitas (a fall delicacy at our home). You've also never seen two little girls more excited over the giblets in a bird. There is nothing more enjoyable than watching them "patiently" waiting for the fried liver and heart of little game birds and chickens. 

Not everyone loves liver as much as I do, for various reasons. But no one hates liver more than the modern medical system. There have been several myths over the decades, in regards to liver, that have been debunked. Like the "it filters toxins and therefore is toxic." Which we know is not the case. The liver is not a storage organ for toxins, it is a storage organ for vitamins...which is why it is one of my superfoods. 

In 1995 an article written in the New York Times stirred the prenatal nutrition pot. This article Study Links Excess Vitamin A to Birth Defects create a swirl of thought and discussion over the dietary intake of foods like in Vitamin A, like liver. The article stated;

Women who consume excessive amounts of vitamin A during the early months of pregnancy can cause serious birth defects in their unborn children, a large new study has shown...The study showed that 1 baby in 57 born to women taking doses of vitamin A above 10,000 international units daily was damaged as a result...The higher the doses consumed, the greater the risk, the researchers found. Babies born to women who consumed more than 10,000 international units of the vitamin daily were 2.4 times as likely to be born with such defects as babies exposed to 5,000 international units or less. But babies exposed to 20,000 international units during the first three months of gestation were about four times as likely to be born with defects that included cleft lip, cleft palate, hydrocephalus and major heart malformations.

Let's come back to this. First, before I continue, I think it is pertinent to explain what Vitamin A is, exactly.

Understanding Vitamin A

Vitamin A comes in 2 dietary forms; Provitamin A Carotenoids (Beta-Carotene, Alpha-Carotene, Beta-Crypoxanthin) and Preformed Vitamin A Retinoids (Retinol, Retinal, and Retinoic Acid).

There are also synthetic versions of Vitamin A. These are created in the laboratory, and are often used in supplementation, and in research. The tend to be more water-soluble, and easier to regulate in trials, but also more toxic. 

Carotenoids in the diet are converted to Retinol (the more usable form of Vitamin A). The Liver stores Vitamin A in an alcohol based form called Retinyl Esters. (which is why it is such an nutritional powerhouse for dietary retinol - esters are converted to retinol in the small intestines). There is a negative feedback mechanism in place that "measures" the levels of retinol in the liver. When there are adequate levels of Vitamin A in the body, there is actually an inhibition of both absorption of of Carotenoids from the diet and a decrease in conversion to Retinol in the Liver.  The ratio varies from 4:1 to 55:1. Conversion is also limited in the presence of other nutritional deficiencies, such as zinc. 

Carotenoids are potent antioxidants. There are over 750 of them found in plants with only Beta-Carotene, Alpha-Carotene and Beta-Cryptoxanthin being able to convert to Vitamin A Retinol. Beta-Carotene is the one most commonly referenced. On their own, Carotenoids are potent antioxidants that help neutralize toxins in the body. In order to actually function, they must be converted to retinol. There main dietary function is the serve as a source of Retinol, as Retinol is the true Vitamin A.

When you hear "Vitamin A" what you should really be hearing is "Retinol." This is the usable form of Vitamin A in the body. It is ESSENTIAL for human health and development. It is converted into Retinal and Retinoic Acid dependant on the body's needs.  Retinol functions on a cellular level, controlling cellular development and growth. Retinol plays a very important part in the development of embryos. Retinal is used in eye health and development. Retinoic Acid is necessary for hormone function and genetic expression, as well as tooth and bone growth...all important functions for pregnancy, childbirth and fetal development.

Back to the Studies: Vitamin A Toxicity Fear

So, this specific study that is mentioned in the New York Times was a survey study done at Boston University School of Medicine. Meaning the Dr. conducting the study interviewed 22,748. He did in depth interviewing into the supplements they were taking and the foods they were eating. 98.6% of the women interviewed were well under the toxic amount of Vitamin A. Those that were consuming higher amounts, received the majority of this Vitamin A in synthetic form from prenatal vitamins and fortified foods. When you read the actual article published in the New England Journal of Medicine, very little of the Vitamin A supplied was via natural foods. The majority was via supplementation.

This isn't the only study that has been done. In fact there have been several, dating back to 1967 in fact.  The finding were slightly varied, based on methods, but there are some key features in these articles that need to be addressed.

• The first thing to note is that the research done between 1967 - 1986 that are most frequently referenced were done using a synthetic and isolated form of Vitamin A that was water soluble. This meant that it did not accumulate in the tissues as readily as dietary Vitamin A and was easier to regulate for testing. But, because it did not accumulate, it did not activate the negative feedback mechanisms in the Liver that regulate Vitamin A metabolism. (interesting) The synthetic forms have a long history of being linked with birth defects, in lab animals and humans.
• In one study, dosages of 35,000iu of were given daily during the first 10 days of a rats gestation cycle (gestation is 16 weeks longs) in one study to induce birth defects. That's a HUGE amount per weight.
• Isotretinoin is a synthetic Vitamin A that was been linked to birth defects, and is commonly found in Accutane.
• These defects are only seen when high doses of Vitamin A are consumed in the first trimester. 
• In order to elicit birth defects, dosage needed to be maintained at high levels daily over the course of weeks - months.

The link between dietary Vitamin A and birth defects is literally non-existent. In fact, you would need to consume in excess of 20,000iu per day of retinol (not beta-carotene) over the course of weeks/months in order to induce an overdose dietarily. (if you are eating that much liver, you like liver way more than I am giving the population credit for.) Not a single study links Beta-Carotene consumption to birth defects.

Because Liver is a rich source of Retinol (via esters), it has been the dietary black sheep for the prenatal diet since the first study linked high levels of Vitamin A (via synthetic). The amount of Vitamin A reserves found in Liver is not static and can range from 3,000iu per 3oz to 12,000iu per 3o, with some sources (depending on region and diet) can be upward of 25,000iu per ounce serving. This includes your Cod Liver Oil Fish Oil supplements. 

Liver in Pregnancy Take Home

So, to reiterate:

• Check your prenatal, other supplements (life fish oils) and your consumption of synthetic, fortified vitamins in the diet. You are more likely to be exposed to overdoses that are linked to birth defects from those sources. Need a good prenatal, let me know. 
• Birth defects were seen after DAILY CONSUMPTION OVER WEEKS - MONTHS at high levels (exceeding 10,000 iu) of preformed Vitamin A, not ProVitamin A Carotenoids.
• Play it safe and limit Liver to 1x per month in the first trimester...if you just love Liver and need to eat it.

Comment Revisited - Vitamin A Benefits Labor

To answer the question and concern left on my previous post about the fear of Liver consumption, excess Vitamin A and the possibility that I was giving out dangerous information. The answer is that consuming Liver in the last couple of weeks of pregnancy WILL NOT cause birth defects in your baby. The research supports these concerns IF, and only IF, there is an excess consumption of preformed (either dietary Retinol esters, or synthetic) during preconception and the first trimester. 

Liver is fair game in the preparation for Childbirth.

In fact, the Retinoic Acid + Increasing levels of Estrogen at term are responsible for the stimulation and increase of Oxytocin receptors on the uterus.

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1. Informed Health Online [Internet]. Cologne, Germany: Institute for Quality and Efficiency in Health Care (IQWiG); 2006-. How does the liver work? 2009 Sep 17 [Updated 2016 Aug 22]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK279393/
2. ​https://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/carotenoids
3. https://lpi.oregonstate.edu/mic/vitamins/vitamin-A
4. Accutane and birth Defects
5. Effects of Retinoic Acid and Estrogens on Oxytocin Gene Expression
6. USDA Food Composition Database