Retinol (or vitamin A) gets its name from its role in the retina in your eye.
Vitamin A is a fat-soluble vitamin that is critical to your vision, fertility and reproduction. vitamin A helps your heart, lungs, kidneys, and other organs work properly.
Vitamin A plays an essential role in maintaining your immune system, preventing infection and avoiding acne.
Vitamin A is also essential for reproduction and the maintenance of epithelial tissue found in the skin, both inside and outside your body, including your face, lungs and gastrointestinal tract.
Vitamin A is one nutrient that many people are not getting enough of, particularly in developing countries. However, it is also possible (though not common) to get too much of it from food.
Deficiency symptoms of vitamin A
Deficiency symptoms of vitamin A include:
poor wound healing, and
acne.
Availability of vitamin A in the food system
The chart below shows that the availability of vitamin A in our diet has decreased since the introduction of the US Dietary Guidelines in 1977, as people were encouraged to consume more grains and fewer animal products due to concerns at that time about excessive saturated fat and cholesterol in the diet.
As shown in the chart below (data from USDA Economic Research Service), the amount of vitamin A typically available in the food system is now well below the Estimated Average Requirement (EAR) and the Daily Recommended Intake (DRI), hence most people need to prioritise foods that contain more vitamin A.
Bioavailability of Vitamin A
It’s important to understand that there are two types of vitamin A, provitamin A and preformed vitamin A.
You get provitamin A carotenoids (e.g. alpha-carotene, beta-carotene and beta-cryptoxanthin) from plant-based foods (e.g. carrots), while preformed vitamin A is found in animal-based products. Most people can convert adequate amounts of provitamin vitamin A to preformed vitamin A if they are getting enough in their diet.
While people talk about the fact that plant-based vitamin A is not as bioavailable, this rate-limiting step may be beneficial because it is possible to exceed the recommended upper limit for vitamin A with a nutrient-dense diet that contains too much Preformed Vitamin A from animal-based food (such as liver).
However, the reduced bioavailability of vitamin A from plant-based foods may be an issue if you are relying on a highly processed grain-based diet with minimal animal products or leafy veggies.
Vitamin A excess and toxicity
While rare, you can get excessive levels of preformed vitamin A from animal products such as liver. Vitamin A is fat-soluble, so it is harder to excrete than water-soluble vitamins.
Some animals (e.g. seals, polar bears, halibut and huskies) have very high levels of vitamin A in their livers. There have been reports of hypervitaminosis A when hungry and dehydrated explorers consume livers from these animals. But otherwise, significant cases of hypervitaminosis A are rare.
Vitamin A overdose symptoms and side effects
Taking excessive supplemental amounts of vitamin A for a long time can cause fatigue, hair loss, nausea, peeling of the skin, cracked lips and headache.
Your vitamin A intake may be excessive if it comes exclusively from animal-based foods (e.g. if you regularly consume a lot of raw liver). However, high levels of vitamin A from a nutrient-dense diet are unlikely to be a concern because the body will not convert more preformed vitamin A to provitamin A than it needs. You will lose your taste for more liver once your Vitamin A stores are replete, hence you are unlikely to consume excessive Vitamin A from food.
Although harmless, higher doses of vitamin A can give your skin a yellow or orange tint. This is known as carotenosis (you look like a carrot if you get too many carotenoids from too many carrots).
Satiety response and weight loss
Our satiety analysis shows that foods with more vitamin A tend to be more satiating. People consuming more vitamin A tend to eat about 10% fewer calories than those consuming less vitamin A.
The average intake of Optimisers is 16,000 IU per 2000 calories, which is significantly greater than the EAR of 2,000 IU per day and the DRI of 3000 IU per day.
Note: The DRI is based on the amount of vitamin A required to prevent deficiency in generally well-nourished subjects.
Upper Limit Intake of Vitamin A
The Upper Limit set for vitamin A (10,000 IU) is based on abnormal liver pathology in adults and developmental issues in babies of women taking excess supplementary Preformed Vitamin A.
It is fairly easy to consume vitamin A intake above the Upper Limit. However, this is unlikely to be a concern unless you are eating minimal plant foods and a LOT of raw liver (i.e. all your vitamin A intake is preformed).
Does vitamin A help your skin and acne?
Vitamin A is essential for healthy skin and the management of acne. One popular treatment for severe acne is Accutane which is a megadose version of a derivative of vitamin A.
Females commencing Accutane therapy have to ensure that there is no chance of them becoming pregnant while taking Accutane due to the risk of congenital disabilities with excessive amounts of supplemental vitamin A.
Synergistic nutrients
Vitamin A works synergistically with vitamins B2, B3, B12, C, D, E, magnesium, selenium, manganese, potassium, phosphorus, iodine, tyrosine and zinc. So it is important to get your phosphorus from whole food sources that typically come packaged with these other nutrients rather than relying on supplements.
Vitamin A rich food sources
Note: The vegetable sources of vitamin A will be pre-vitamin A which your body will need to convert for use, while the animal and seafood will be preformed vitamin A.
Food sources that contain more vitamin A per calorie include:
Vegetables
Animal
Seafood
Nutrient profile
The nutrient fingerprint below shows that we can get up improve the Adequate Intake for vitamin A from food when we prioritise foods that contain more vitamin A.
