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 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:
- dry skin,
- dry eyes,
- night blindness,
- infertility and trouble conceiving,
- delayed growth,
- throat and chest infections,
- poor wound healing, and
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 around the impact of saturated fat and cholesterol in the diet on heart disease risk).
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.
We 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 actually 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, as noted above, 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.
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).
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, this is rare.
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 largely 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).
While vitamin A in your diet is critical to support healthy immune function, in the current environment you should be careful in the current environment supplementing high levels of preformed vitamin A as it has the potential to overstimulate your immune system and worsen the cytokine storm which causes hyperinflation in the lungs which can lead to breathing difficulties and sometimes death.
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.
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.
Vitamin A works synergistically with vitamins B2, B3, B12, C, D, E, magnesium, selenium, manganese, potassium, phosphorus, iodine, tyrosine and zinc.
Vitamin A rich food sources
Food sources that contain more vitamin A include:
- sweet potato
- almond milk
- lamb liver
- beef liver
- chicken liver
- whole egg
- Parmesan cheese
- cottage cheese
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.
The nutrient fingerprint below shows that we can get 22 times the Adequate Intake for vitamin A from food when we prioritise foods that contain more vitamin A.
If you ensure you’re getting enough Vitamin A (along with ALL the other essential nutrients), we’d love you to check out Nutrient Optimiser. We have designed Nutrient Optimiser to be the quickest and easiest way to optimise your nutrition at the micronutrient level.
You can select from our database of five hundred recipes to plan your meals for the coming week to ensure you will get the nutrients you need to thrive.
Then, if you are able to track your current diet for a few days, Nutrient Optimiser will identify the foods and meals that you need to fill your macro and micronutrient gaps.