All about Vitamin A

Actual vitamin A is only found in the animal kingdom, in the active form called retinol. Retinol is fat-soluble, and a rule of thumb is that the fattier the product, the greater the chance that you will find good amounts of active and "ready to fight" vitamin A in the food.

The plant kingdom does not have vitamin A ready for use. Instead, the body must make this important vitamin by converting other substances, called carotenoids

Beta-carotene, a type of carotenoid that sounds familiar to many, is just a precursor to vitamin A. This substance is found mainly in plant-based foods such as carrots, sweet potatoes, and green leafy vegetables. Although beta-carotene has the potential to be converted into real vitamin A in the body, there are several reasons why it is not as effective a source as retinol, the actual vitamin A.

The conversion of beta-carotene to retinol occurs in the liver, and this process depends on a number of factors, such as the body's perception of a need for vitamin A, some genetics, and the presence of fat in the diet. Without sufficient fat, the body may have difficulty absorbing and converting beta-carotene effectively.

Furthermore, the conversion process from beta-carotene to retinol is very inefficient, even for those who have this trait. The body converts only a very small portion of beta-carotene into active vitamin A, and the efficiency varies between individuals. In the worst case, hardly any beta-carotene is converted to retinol, and a deficiency occurs.

Poor health, for example, can be a contributing factor to lack of conversion, such as liver health, and it can quickly become a rapid downward spiral.

Retinol directly from food is therefore undoubtedly the best solution, and on a carnivore diet we are most likely getting more than enough high-quality retinol every single day. There have been reports of improved vision, and improved night vision, after switching to carnivore.

In developing countries, successful trials have also been conducted with giving children retinol to prevent blindness due to malnutrition.

Vegans may also be at higher risk for vitamin A deficiency, which can affect vision over time, especially if they don't get enough beta-carotene or other sources of provitamin A. This can lead to reduced vision, especially night blindness, which is an early indicator of vitamin A deficiency.

How is vitamin A used in the body?

Retinol, the active form of vitamin A, plays an essential role in several important functions in the body. First and foremost, retinol is essential for vision, especially in maintaining normal retinal function. Retinol is converted into a substance called retinal, which is necessary for the eyes to adapt to different lighting conditions, such as when we see in the dark.

In addition to vision, retinol is important for the immune system, as it supports the production and function of white blood cells that protect the body from infections.

Retinol is also essential for skin health, as it contributes to cell renewal and regeneration of skin tissue, and therefore has a role in wound healing and maintaining a healthy skin barrier.

Furthermore, retinol is important for growth and development, especially during fetal development, as it affects cell differentiation and organ development. Without sufficient retinol, the body may have difficulty maintaining these functions, which can lead to health problems such as night blindness, weakened immune systems, and poor skin health.

Which foods contain a lot of vitamin A retinol?

This list is a good guide for those looking to get more vitamin A from animal sources. Liver, especially beef and pork liver, are arguably the most potent sources. Note that it describes content per 100 grams of product, and that a carnivore typically eats well over a kilogram of food per day.

As we will see below, fattier meats may have a higher retinol content per 100 grams, as the fatty tissue helps to store this fat-soluble vitamin. This is something to keep in mind when considering the nutritional content of different types of meat.

Also note that retinol is fat-soluble and is stored in the body. You do not need to eat retinol every single day, as a normally nourished body will have a small reservoir to draw from when needed. The daily requirement is still described as between 700 and 900 micrograms/mcg, and is intended as an average.

Meat

• Liver (beef): Approx. 9,000 mcg retinol per 100 grams
• Liver (turkey): Approximately 5,000 mcg retinol per 100 grams
• Liver (pork): Approx. 6,000 mcg retinol per 100 grams
• Chicken breast: Approximately 80 mcg retinol per 100 grams
• Beef (lean meat): Approximately 50 mcg retinol per 100 grams
• Lamb (lean): Approximately 40 mcg retinol per 100 grams
• Pork chop (lean): Approximately 35 mcg retinol per 100 grams

Meat (fattier cuts)

• Entrecôte (beef, with fat): Approximately 150–200 mcg retinol per 100 grams
• Highback (cattle, with fat): Approx. 150-250 mcg retinol per 100 grams
• Lamb (fatty parts): Approximately 70–100 mcg retinol per 100 grams
• Beef (with fat): Approximately 100–150 mcg retinol per 100 grams
• Pork chop (with fat): Approximately 70–120 mcg retinol per 100 grams

Seafood

• Liver slices from fish (such as cod liver): Approximately 20,000 mcg retinol per 100 grams
• Salmon (wild): Approximately 800 mcg retinol per 100 grams
• Mackerel: Approximately 600 mcg retinol per 100 grams
• Cod: Approximately 50 mcg retinol per 100 grams
• Seafood (mollusks, such as oysters and clams): Approximately 300 mcg of retinol per 100 grams
• Crab: Approx. 200 mcg retinol per 100 grams
• Shrimp: Approx. 100 mcg retinol per 100 grams
• Sardines (whole): Approx. 300 mcg retinol per 100 grams

Egg

• Egg yolk: Approximately 500 mcg retinol per 100 grams
• Whole eggs (with yolk and whites): Approximately 140 mcg of retinol per 100 grams
• Egg white (without yolk): 0 mcg retinol (no vitamin A)

Dairy products

• Milk (full fat): Approx. 50 mcg retinol per 100 grams
• Butter: Approx. 700 mcg retinol per 100 grams
• Parmesan (hard cheese): Approx. 500 mcg retinol per 100 grams
• Cheddar (mature cheese): Approx. 300 mcg retinol per 100 grams
• Jarlsberg (hard cheese): Approximately 250 mcg retinol per 100 grams
• Brie (soft cheese): Approximately 160 mcg retinol per 100 grams
• Gouda: Approx. 150 mcg retinol per 100 grams
• Mozzarella: Approx. 90 mcg retinol per 100 grams
• Sour cream: Approximately 170 mcg retinol per 100 grams
• Cottage cheese (natural): Approximately 80 mcg retinol per 100 grams
• Yoghurt (full fat): Approx. 60 mcg retinol per 100 grams
• Cream cheese: Approximately 100 mcg of retinol per 100 grams

Can you get vitamin poisoning from vitamin A?

Vitamin A poisoning, also known as hypervitaminosis A, can occur when the body gets too much vitamin A, either through diet or supplementation. This usually occurs when consuming too much preformed vitamin A, or retinol, found in animal products such as liver, or in high doses of vitamin A supplements.

Poisoning occurs because vitamin A is a fat-soluble vitamin. As mentioned, this means that retinol is stored in the body's fatty tissue and liver rather than being excreted through the urine like water-soluble vitamins.

When too much vitamin A accumulates, the body cannot eliminate it quickly enough, and blood levels rise to dangerous levels. This can lead to both acute and chronic symptoms of poisoning.

The symptoms of acute Vitamin A poisoning can occur after consuming large amounts in a short period of time and includes:

• Nausea and vomiting
• Headache
• Dizziness
• Tiredness
• Dry and itchy skin
• Loss of appetite

The symptoms of chronic Vitamin A poisoning develops gradually with prolonged intake of high doses over time, and they can include:

• Increased intracranial pressure, which can lead to headaches and visual disturbances
• Liver damage (which can lead to jaundice, a condition in which the skin turns yellow)
• Damage to bones and joints, which can lead to pain and an increased risk of fractures
• Dry, flaky skin
• Dry eyes and visual disturbances
• Symptoms that may resemble depression or irritability

Chronic poisoning can also affect fetal/foetal development during pregnancy, especially if the pregnant woman ingests excessively high doses of vitamin A. Therefore, pregnant women are advised to be extra careful with the intake of liver and high doses of vitamin A supplements.

In general, vitamin A poisoning is rare with a normal diet, but can be a problem when taking high doses of supplements over a long period of time, especially if these are preformed vitamin A (retinol).

To avoid poisoning, it is important to follow recommended doses and be aware of sources such as liver or high-dose supplements.

Does vitamin A have more exciting functions in the body?

Retinol has several functions in the body, beyond the vitamin's commonly known role in vision and the immune system. Retinol and other forms of vitamin A (such as retinoic acid) also have a number of other biological effects, some of them less well known, and there are hypotheses about several potential effects that are still under research.

Skin health and cell renewal:
Retinol plays an important role in cell growth and differentiation, which is essential for skin health. Retinoic acid, an active form of vitamin A, is often used in the treatment of acne and signs of aging, as it promotes cell turnover and reduces inflammation in the skin. Retinol helps maintain skin integrity and promotes wound healing.

Reproduction and embryonic development:
Vitamin A is necessary for reproduction and is particularly important in early embryonic development. It plays an essential role in the formation of organs, especially in the early stages of pregnancy. Retinol is necessary for the formation of important genetic signals that control the development of the nervous and immune systems in the embryo.

DNA synthesis and cell growth:
Vitamin A plays a critical role in DNA synthesis and cell growth. Retinoic acid influences gene expression and stimulates specific genes involved in cell proliferation and differentiation, which are essential for maintaining the body's cellular structure and function.

Reduction of oxidative stress:
Retinol acts as an antioxidant in the body and may help protect cells from oxidative stress. This may have a protective effect on tissues and organs, and it is also hypothesized that adequate levels of vitamin A may help reduce the risk of certain chronic diseases that may be linked to oxidative stress.

Hypotheses and ongoing research on other effects of vitamin A

Cancer prevention:
There is research suggesting that vitamin A may have a protective effect against certain types of cancer, particularly those related to epithelial function (such as skin cancer and lung cancer). Retinoic acid is known to affect the growth and differentiation of cancer cells, and some studies have investigated the use of retinoids (synthetic forms of vitamin A) in cancer treatment. However, the results are mixed, and there is still uncertainty about the exact role of vitamin A in cancer prevention and treatment.

Neurological effects and cognitive health:
Research has also investigated the possible effects of vitamin A on the brain and cognitive health. Retinoic acid is involved in brain development, and there are ongoing studies investigating whether vitamin A may have protective effects against neurodegenerative diseases such as Alzheimer's and Parkinson's disease. Some experimental studies have suggested that vitamin A deficiency may lead to cognitive problems, and it is hypothesized that vitamin A may be important in maintaining brain function throughout the lifespan.

Effects on metabolic processes:
There are hypotheses that vitamin A may play a role in metabolism, particularly in relation to fat storage and glucose metabolism. Some studies have suggested that vitamin A may affect insulin resistance and the body's ability to handle sugar, which may be important for diseases such as diabetes. Vitamin A is known to affect adipose tissue, and research is ongoing into whether it has a role in the development of metabolic syndrome.

Immunomodulation:
Vitamin A is known to be important for the immune system, but there is also research suggesting that it may affect the immune system's response to infections in more subtle ways. It is particularly important in regulating the response to bacterial and viral infections, and research is ongoing into how vitamin A can be used to improve vaccine effectiveness, especially in developing countries where vitamin A deficiency is more prevalent.

Fatty acids and heart disease:
There are some hypotheses that suggest that vitamin A may affect fat metabolism in a way that could protect against cardiovascular disease. This is a relatively new area of ​​research, and while some studies have suggested a protective effect, it is still unclear whether vitamin A alone has a direct effect on reducing the risk of heart disease.

Retinol is thus an essential component for several physiological processes, and while its traditional functions in vision and the immune system are well documented, there is increasing research on vitamin A and its potential role in other areas of health.

The hypotheses about vitamin A as a protective factor against cancer, neurological diseases, metabolic disorders, and heart health are interesting, but require more research before they can be considered established medical facts.

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