Vitamin A has many important physiological functions. It participates in the synthesis of steroid hormones and the maturation of immune system cells, ensures the proper structure of bones and tooth enamel, and as a component of the retinal pigment, it affects the reception of visual stimuli. This important substance also causes the growth of epithelial tissue and is involved in sperm production and embryo development.
Vitamin A and its properties
Vitamin A is responsible for the condition of the skin, hair and nails. Its deficiency causes weakened hair, lackluster nails, brittle and brittle nails, and rough and calloused skin. Retinol in its pure form and some derivatives of this substance (m.in. retinaldehyde), present in many cosmetic preparations, have a particular effect on the skin. These compounds accelerate the exfoliation of dead skin cells, leading to its renewal. In the deeper layers of the skin, they stimulate the synthesis of collagen fibers, responsible for elasticity. Systematic use of preparations containing these substances makes wrinkles less visible and the skin smoother and more elastic.
In addition, by influencing the process of melanin formation (skin pigment) and regulating the process of exfoliation of the epidermis, vitamin A lightens discolorations of various origins and significantly improves color. However, it should be remembered that skin exposed to retinol in contact with UV radiation may react with irritation and the appearance of discoloration on the surface. For this reason, creams containing this compound are best used at night, during periods of low sun exposure, and during the day use products containing sunscreens.
Sources of vitamin A
Vitamin A is provided by very different food sources. In animal products such as liver, fish oil, egg yolks, milk and dairy products, it is found in the form of an ester – retinol palmitate. On the other hand, in foods of plant origin, such as spinach, lettuce, broccoli, carrots, red peppers, pumpkins, tomatoes, peaches, apricots, watermelons, plums, oranges, melons and cherries, it is present in the form of carotenoids. It is worth remembering that products rich in it should be taken during or after a meal containing fats. The absorption of vitamin A by the body is increased by other vitamins (B, C, D and E), as well as some elements (calcium, phosphorus and zinc). Caffeine, nicotine and alcohol significantly reduce its absorption.
Vitamin A and its dosage
The daily requirement for vitamin A in men is 900 mcg, and in women 700 mcg. It is worth knowing that in excess it is very harmful to the body. Symptoms of vitamin A toxicity in adults are observed with a daily intake of 15,000 mcg of retinol.
Symptoms of vitamin A overdose Symptoms of vitamin A overdose are:
- irritability
- Weakness
- nausea
- vomiting
- Headaches
- yellow-orange skin coloration,
- alopecia
- liver damage,
- decreased bone calcification,
- in women, menstrual disorders are also affected.
Vitamin A is essential for everyone, but in the right amounts. Pregnant women must be extremely careful with its excess, as it can cause miscarriage or perinatal complications, and even congenital defects in the baby. For this reason, future mothers should avoid oral preparations and cosmetics containing retinol or its derivatives.
Vitamin A as an antioxidant
The most active carotenoid is beta-carotene – a precursor of vitamin A, which is converted to retinol in the liver. This compound is a powerful antioxidant. It inhibits cholesterol oxidation, reducing the risk of developing atherosclerosis. By protecting the thymus gland (gland of the immune system) from the harmful effects of free radicals, it supports the body in the fight against infections. Thanks to its antioxidant properties, it also reduces the risk of developing certain cancers. However, it should be noted that in people who smoke cigarettes, excess beta-carotene increases the risk of developing lung cancer.
Provitamin A also reduces the skin’s sensitivity to UV radiation. It protects against photoaging, and at the same time strengthens and prolongs the tan. To prepare the skin for intense contact with the sun, it is worth reaching for products containing this valuable carotenoid.