Vitamin A: What Is, Roles, Deficiency, and Excess

One of the fundamental roles of vitamin A is to maintain healthy skin. It also plays a vital role in vision, the development of epithelial cells, and supporting the immune system. As an antioxidant, it helps protect cells from the damaging effects of free radicals.

Vitamin A, due to its solubility in fats, is classified as a lipophilic vitamin. It belongs to the vitamins with antioxidant effects, which defend cells from the hurting effects of free oxygen radicals.

The vitamin of youth is the best-known and most frequently used anti-wrinkle ingredient, which allows you to prolong the youthfulness of your skin. Its useful effect on the skin results from the presence of receptors in it, which selectively bind vitamin A molecules.

Retinol

Retinol is an alcoholic form of vitamin A, which (as the only one) exhibits full biological activity. Retinoids include:

• Retinal, or retinaldehyde – is a relatively poorly understood form of vitamin A.
• Retinoic acid, or tretinoin – is the most powerful form of vitamin A, which should be handled with caution. It can cause irritation, flaking, and skin burns.
• Vitamin A esters, including retinyl palmitate (proretinol) and retinyl acetate – the most gentle forms of vitamin A, moisturize and prevent skin flaking and have antioxidant effects. They are safe even for sensitive skin, which is why they are a prevalent component in ointments and cosmetics. β-carotene – provitamin A – found in plant products. It is an intense antioxidant, so it has anti-aging effects.

Norms

The need for vitamin A varies based on age, gender, and individual health. Pregnant women, people on low-fat diets (such as athletes following a high-carb, low-fat regimen), and patients with liver damage should pay special attention to their vitamin A intake.

Data from 2020 collected and developed by the National Institute of Public Health – National Institute of Hygiene indicate the following recommended daily RDAs (Recommended Dietary Allowances):

• Children up to 3 years old – 300 micrograms of retinol equivalent
• Children up to 8 years old – 400 micrograms of retinol equivalent
• Boys and girls from 10 to 13 years old – 600 micrograms of retinol equivalent
• Boys from 14 to 18 years old, as well as adult men – 900 micrograms of retinol equivalent
• Girls aged 14 to 18 and adult women – 700 micrograms of retinol equivalent
• Pregnant women – 750 micrograms of retinol equivalent (for those under 19) and 770 micrograms of retinol equivalent (for older pregnant women)
• Breastfeeding women – between 1200 and 1300 micrograms of retinol equivalent, depending on age

It is assumed that the daily intake of vitamin A from retinol (UL, Upper Intake Level) should not exceed 15 thousand micrograms.

Different Forms

It is worth noting that individual forms of vitamin A differ in their chemical structure and their impact strength. Therefore, to determine the content of the compound, the so-called retinol equivalent was used, developed in the 1990s by the SCF (Scientific Committee for Food). It is assumed that 1 mg of retinol corresponds to 6 mg of beta-carotene and 12 mg of other carotenoids. Of course, this does not mean vitamin A should be taken exclusively from animal products. Fruits and vegetables contain much more valuable nutrients than just beta-carotene.

Roles

Vitamin A is one of the vitamins that patients often supplement. It is in fact a group of fat-soluble compounds, which includes retinol (vitamin A1), retinal, retinoic acid, and carotenoids. The main carotenoid compounds are: β-carotene, α-carotene, β-cryptoxanthin, lutein, and lycopene.

The most active carotenoid is β-carotene, which is provitamin A. To gain biological activity, it must be transformed, only then does it gain full functionality. α-carotene and β-cryptoxanthin also demonstrate vitamin A activity. Lycopene is a carotenoid that provides vegetables and fruits their red color. It is an antioxidant, which – according to research – prevents DNA damage, thanks to which it can limit the development of prostate cancer, and also plays a role in circulatory system disease prevention. Lutein, on the other hand, prevents macular degeneration.

Vitamin A plays an essential role in the proper vision process, being a component of visual purple or rhodopsin. In addition, it participates in the proper differentiation of epithelial and bone tissue cells and takes part in the production and release of adrenal and thyroid hormones. It is an important factor supporting the maintenance of the accurate shape of mucous membranes and skin and is involved in the sense of taste. In addition, vitamin A has antioxidant potential, thanks to which, together with vitamins C and E, it prevents excessive oxidation of fatty acids, protects against the harmful effects of free radicals, and affects the proper structure of erythrocytes.

Vitamin A takes part in sperm formation, the development of the placenta, and the proper growth of the fetus. Its significant role also involves participation in keeping proper immunity, helping to protect against infections and fight them.

Vitamin A Deficiency

Primary vitamin A deficiency results from an improper diet, and poor in vitamin A and carotenoids. Secondary vitamin A deficiency is caused by diseases that impair the proper absorption, metabolism, and storage of vitamin A. Sick people, despite keeping a healthy and balanced diet, are at risk of hypovitaminosis or total avitaminosis. Conditions that predispose to secondary vitamin A deficiency include:

• Cystic fibrosis
• Celiac disease
• Inflammatory bowel diseases, such as Crohn’s disease or ulcerative colitis
• Structural defects in the gastrointestinal tract, including partial resection of the small intestine and bariatric surgery
• Pancreatic diseases, including chronic inflammation and cancer of this organ
• Liver cirrhosis
• Infections of the digestive system, especially parasitic infections

Symptoms of Vitamin A Deficiency

Vitamin A deficiency is diagnosed when the concentration of retinol in the blood serum drops below 0.7 μmol/L. A drop below 0.35 μmol/L is considered a severe deficiency, which may pose a risk of permanent damage to health.

Symptoms of vitamin A deficiency mainly affect the eyes. One of the earliest symptoms is nyctalopia, or night blindness, in which vision is worsen in low-light conditions. Eye diseases caused by vitamin A deficiency also include:

• Xerosis (dryness) of the conjunctiva and cornea
• Bitot’s spots on the surface of the conjunctiva
• Corneal ulceration
• Corneal scarring

Vitamin A is involved in keeping the proper functioning of the skin and its products – hair and nails. Characteristic symptoms of vitamin A deficiency include hyperkeratosis or excessive keratinization of the epidermis. The skin all over the body becomes rough and unpleasantly dry, and this is accompanied by excessive hair loss and brittle nails.

The immune system’s functioning also depends on the correct level of vitamin A in the body. Multiple scientific studies have shown that vitamin deficiency increases the risk of contracting numerous infectious diseases. Additionally, in children, lack of vitamin A can cause growth and development disorders, especially when it is accompanied by lacks of other vitamins and minerals.

Diet for Vitamin A Deficiency

Along with supplementation, a properly balanced diet rich in products with vitamin A should be introduced. The best sources are animal products, in which it occurs in the form of retinol.

Beta-carotene is in vegetables and fruits with vibrant yellow, orange, or red. Carrots, pumpkins, sweet potatoes, red peppers, and apricots are particularly high in beta-carotene. Additionally, dark green leafy vegetables like spinach, kale, and broccoli are excellent sources. The body converts this element into the active form of vitamin A.

Diagnosing

The functions of vitamin A in the body are very important, so it is important to take care of its proper level in the blood. Vitamin A supplementation may be advised in various situations, especially when there is a risk of lack or there are specific medical indications.

When laboratory test results confirm a vitamin A deficiency, supplementation may be necessary to increase the levels of this vitamin in the blood and improve health.

Indications for Vitamin A Supplementation

Women during pregnancy and breastfeeding have an increased need for vitamin A because it is important for the proper development of the fetus and the production of breast milk. In the case of a lack or low intake of vitamin A in the diet, supplementation may be advised. However, it is important not to overdo it, which can be toxic to the fetus.

Some chronic diseases, such as digestive diseases of the digestive system, can lead to impaired absorption of vitamin A. In such cases, supplementation may be necessary to compensate for the lack of it.

In some cases, especially when you have trouble seeing in low-light conditions, your doctor may recommend a vitamin A supplement to improve your vision.

As you age, your body may become less able to absorb and utilize vitamin A. Older adults may have increased vitamin A requirements and supplements may be advised.

Vitamin A plays an essential role in maintaining the health of your skin, mucous membranes, and immune system. Therefore, supplementation may be advised to prevent certain conditions, such as acne.

It is important to remember that you should always consult your doctor before starting a vitamin A supplement, who can perform an appropriate assessment and recommend the appropriate dosage to avoid the risk of toxicity and adverse effects.

Vitamin A Excess

Excess vitamin A in the body is called hypervitaminosis. It occurs when the amount of the compound provided to the body exceeds its capacity to use it and this condition persists for a long time. As a rule, exceeding the advised standards by supplying vitamin A only from food is impossible, although it can happen in the case of unjustified use of vitamin supplementation. Scientific studies confirm the toxic effects of excess vitamin A, including teratogenic effects (harmful to the fetus and may result in the development of congenital defects), which is why pregnant women should pay special attention to their diet.

Typical symptoms of hypervitaminosis include:

• Hyperactivity and irritability
• Joint, muscle, and headache pain
• Loss of appetite
• Hemorrhages
• Hair loss
• Yellow-orange skin discoloration

Hypervitaminosis can even lead to spontaneous bone fractures as a result of a decrease in their thickness.

Retinol Cosmetics

Retinol is a fat-soluble vitamin with hydrophobic properties. It is a lipophilic liquid that is highly sensitive to oxidation. Due to its action, it is one of the active substances often used in cosmetics. Natural retinoids can be found in the cosmetics composition, which include the weakest retinyl esters and substances with similar biological activity: retinol and retinaldehyde.

When the first wrinkles appear on the skin, it is a sign that it is worth asking a cosmetologist for advice and reaching for the first cosmetic with retinol, preferably for use at night.

Usage

To obtain optimal, side-effect-free action, it is worth checking whether the cosmetic contains, in addition to retinol, the following ingredients:

• Vitamin E, which, in combination with retinol, has an enhanced antioxidant effect
• Vegetable oils, e.g. grape seed oil or blackcurrant oil, which replenish the lack of lipids in the epidermis and thus protect it from burning and drying
• Ceramides, which fill the intercellular spaces and rebuild the skin’s hydrolipid barrier
• Plant extracts, e.g. from Asian pennywort or witch hazel, which have a regenerating effect
• Hyaluronic acid, which binds water, therefore preventing dryness and irritation of the skin

Concentration

The concentration of retinol in cosmetics is also crucial. Retinol creams usually contain 0.05-1% retinol. Cosmetics with a low concentration of retinol are advised for people starting the treatment until the skin tolerance to retinol is built up. It is also worth using them in more delicate areas, i.e., around the eyes and on the contours of the lips. Cosmetics containing higher retinol concentrations should be used for facial and décolleté skin care.

Do Not Combine With

Retinol is a substance with a strong effect on numerous processes in the skin. For this reason, the use of retinol preparations must be well thought out. They should not be combined with substances such as:

• AHA and BHA acids with irritating potential, especially glycolic, mandelic and salicylic acid
• Vitamin C works in a different pH range than retinol, so the combination of these ingredients reduces the effectiveness of cosmetics

During retinol treatment, you should not use a solarium. You should also avoid sunlight and use creams with high SPF 50+ protection. You should also not perform mechanical peeling, microdermabrasion, or laser therapy.

Alternatives

In recent years, a natural plant substance called bakuchiol, which is called vegan retinol, has become increasingly popular. In reality, it is a completely different chemical substance. However, it has similar desirable properties to retinol without the undesirable irritating effects.

Bakuchiol is a phenol that is a derivative of terpenes. It occurs, among others, in the Psoralea corylifolia plant, growing in China and India, where it has long been used in Ayurvedic medicine. Bakuchiol can also be safely used in the summer. It has, among others, the following effects:

• Anti-acne
• Antioxidant
• Anti-inflammatory
• Anti-aging
• Brightening discolorations
• Stimulating collagen production

Sources

• Retinol: The Ideal Retinoid for Cosmetic Solutions. NIH.
  https://pubmed.ncbi.nlm.nih.gov/35816071/
• Vitamin A and Carotenoids. NIH.
  https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/
• Vitamin A and Carotenoids. NIH.
  https://ods.od.nih.gov/factsheets/VitaminA-Consumer/
• Vitamin A Deficiency. NIH.
  https://www.ncbi.nlm.nih.gov/books/NBK567744/
• Vitamin A. NIH.
  https://www.ncbi.nlm.nih.gov/books/NBK482362/
• Vitamin A Toxicity. NIH.
  https://www.ncbi.nlm.nih.gov/books/NBK532916/
• Bakuchiol, a natural constituent and its pharmacological benefits. NIH.
  https://pmc.ncbi.nlm.nih.gov/articles/PMC10683784/