Vitamin A for You and Your Embryo

Agnes Ryu Pathways Clinic Vitamin A

In my natural fertility practice, achieving optimal vitamin A status is encouraged for every man and woman during preconception.

The right dosage in the right ratio

As vitamin D gains popularity, I see many taking high dose supplements without balancing intake of other fat-soluble vitamins like A, K2 and minerals like magnesium and zinc. Proper vitamin A to D ratio is essential, as improper dosage and ratio can cause deficiency or toxicity. Increasing one vitamin raises the need for the other.

I am wary of supplementing an individual nutrient as it does not work in isolation in arbitrary concentration in the biological system which is impossible to micromanage. For optimal status of these fat-soluble vitamins, eat traditional foods humans adapted to over evolution, considering the complex ways in which the human body and nutrients interact.


Vitamin A catalyses countless processes, especially mammalian reproduction and embryonic development.

  • During embryonic development, vitamin A enables proper cell growth, organ formation, immunity and vision.
  • It balances the normal cell cycle, preventing excessive proliferation or insufficient programmed cell death. Unchecked growth causes tumors, relevant for women’s health issues like heavy periods, fibroids and endometriosis from abnormal cell cycling and potential vitamin A deficiency.
  • Adequate vitamin A enables healthy sperm, eggs, and reproductive hormones like testosterone and estrogen.
  • Maternal immune tolerance of the fetus requires vitamin A to develop regulatory T cells and prevent autoimmunity. To enable the maternal immune system to accept the foetus, a foreign graft, the aggressiveness of the immune system should be in check and tolerable immunity should be developed. The regulatory T cells (Tregs) modulate the immune system and develop tolerable immunity. Loss of this immune component can result in autoimmunity. Humans require retinol derivatives to develop immunological tolerance and a Vitamin A deficiency is possibly a factor in the development of autoimmunity and resulting negative consequences in reproduction.
  • Vitamin A is essential for embryonic and foetal development. Vitamin A enables cell growth and specialization, the orderly formation of the organs and skeleton. Development of immune function and eye development and vision require vitamin A.

Regarding vitamin A, the nutritional pioneer, Dr Weston Price said,

“While essential throughout the lifespan for growth, immunity, epithelial tissue maintenance, lung and visual function, “[vitamin A’s] influence is particularly critical during periods when cells proliferate rapidly and differentiate, such as during pregnancy and early childhood.”


Sources of Vitamin A, plant? synthetic? animal?

Dr Weston Price observed in indigenous societies, pregnant women consumed special foods rich in vitamin A–such as liver, spring butter and fish eggs–in a conscious effort to produce healthy, well-formed children. Modern research completely validates these traditions. Weston A. Price Foundation is a treasure trove of information on nutrition. Sections on prenatal nutrition, pregnancy, the importance of fat-soluble vitamins are highly recommended to read.


Plants do not contain vitamin A, even Carrots!

Pre-formed vitamin A exists only in animal fats. Provitamin A carotenoids found in plants are not vitamin A and need to be converted into the active form of vitamin A, retinol that the human body requires. The vitamin A content of foods is measured in retinol activity equivalents (RAE).

The most commonly discussed carotenoid, beta carotene, which is found in all yellow, red, orange fruits and vegetables or dark green leaves is up to 28 times less potent than retinol and these are much less reliable sources of Vitamin A than liver and cod liver oil.


The conversion is not given

Many factors determine the efficacy of carotenoid absorption and its conversion to vitamin A and the ability varies about ten-fold between individuals. Children under the age of five and individuals with diabetes, thyroid or liver impairment cannot make this conversion at all. The use of medications, smoking, alcohol consumption, food processing, body composition and genetic variation contribute to poor conversion. Additionally, this conversion cannot take place without the presence of fat in the diet. Therefore, one should never rely solely on plant sources for this incredibly vital nutrient.


Synthetic Supplements: wrong form, potentially dangerous

I would not encourage women to rely on pre-natal vitamins for vitamin A. These tablets contain only precursors to vitamin A or a synthetic form of beta carotene. Many people cannot convert these precursors into usable vitamin A, so they remain vitamin A deficient during pregnancy and lead to the production of vitamin A-deficient breast milk after giving birth. Another danger is synthetic vitamin A’s link with birth defects.


Animal sources

Active vitamin A is stored in the liver and fat, making liver and fats the best sources. Beside these, foods that develop and sustain offspring such as milk and eggs are next best. Butter and cod liver oil are also good sources of Vitamin A.  These natural foods provide the correct ratio of vitamin A and D and minerals.


Controversy regarding the consumption of liver

Unfortunately, official guidelines warn pregnant women to avoid foods like liver and cod liver oil, claiming that too much vitamin A from these foods can cause birth defects. Some of my clients who used to enjoy liver refrain from consuming it while pregnant following the guideline.

The study usually cited in support of these warnings was carried out in 1995 at the Boston University School of Medicine and published in the New England Journal of Medicine. Controversy over this has raged through the years, mostly because in the study, the linkage with birth defects was not between natural vitamin A from real food but between high-dose synthetic A from supplements and processed food like margarine.

As a result of the unfair stigmatization of Vitamin A, most pre-natal vitamin formulations do not contain active vitamin A and only contain carotenoids while pregnant women need extra vitamin A for supporting their increased metabolic needs and foetal growth. High amounts of synthetic vitamin A from supplements can be toxic, especially to those with impaired liver function and to those whose diets are otherwise poor. High levels of natural vitamin A have no toxic effects, regardless of the medical establishment’s dire warnings to the contrary.

The risks for vitamin A deficiency during pregnancy outweigh the risks of high doses of true vitamin A from animal foods. In fact, avoidance of liver is a known risk factor for inadequate vitamin A intake. Liver is incredibly rich in fat-soluble vitamins, including vitamins A, D, E, and K as well as other vitamins and minerals that are required for reproduction but difficult to obtain in other ways.

It is best to obtain vitamin A from natural high-fat sources like grass-fed butter, egg yolks, offal, fish, shellfish and cod liver oil.

My recommendations for ensuring vitamin A status are any of the following:

  • Eat 4 ounces of beef liver once a week or eat a half ounce every day.
  • Eat up to three whole eggs a day.
  • Drink up to three servings of full-fat dairy per day.



Agnes Ryu

Agnes Ryu

Dr. Ryu is a clinician and biochemist specializing in integrative medicine. Her clinical interests include fertility, hormones, metabolism, healthy ageing, menopause, and natural breast cancer care. As an integrative practitioner, Dr. Ryu aims to uncover the root causes of health issues and strives to empower patients with the knowledge and tools to take charge of their own health.

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