What is vitamin A?
Vitamin A is a fat-soluble vitamin that participates in many functions of the human body, is stored mainly in the liver, and is obtained through the diet.
It is necessary, among other things, for the maintenance of normal vision, for the functioning of the immune system, for the health of the skin and mucous membranes, for cell differentiation (cells have different functions), and for the metabolism of iron.
According to studies, the anti-inflammatory and immunoregulatory effect of vitamin A is of crucial importance for health, protecting against a multitude of pathological conditions affecting all organs. It appears, for example, to have a protective effect on the respiratory system, intestinal health, and brain function.
Maintaining the desired levels of vitamin A is considered vital, as deficiency can lead to ophthalmological, dermatological, and immune decline.
Foods with vitamin A
Animal sources :
- Liver
- Eggs
- Dairy products
- Fish
Plant sources :
- Carrot
- Sweet potato
- Papaya
- Mango
- Peach
- Apricot
- Peppers
- Spinach
- Broccoli
- Asparagus
- Kale
- Pumpkin
- Melon.
In addition, many foods are often fortified with vitamin A, such as margarine, milk, and breakfast cereals.
Daily requirements
The Recommended Daily Intake (RDI) for healthy adults per day is :
- 700 µg for women
- 900 µg per day for men
As regards children, pregnant and lactating women, the SIP per day ranges from:
- 300-900 µg
- 770 µg
- 1300 µg
Specifically for children, the following SIP apply by age:
- 0-6 months: 400 µg
- 7-12 months: 500 µg
- 1-3 years: 300 µg
- 4-8 years: 400 µg
- 9-13 years: 600 µg
- 14-18 years: 900 µg (boys), 700 µg (girls)
Beneficial properties of vitamin A
.As mentioned above, vitamin A is involved in many body functions and has a protective effect on many health conditions
1. Skin health
Vitamin A has been studied for years for its beneficial effects in maintaining skin health and is successfully used in conditions such as acne and psoriasis.
The use of retinoids is very beneficial in skin conditions stimulated by the immune system. In fact, people with psoriasis have been shown to have lower levels of carotenoids than people without psoriasis.
Low levels of the vitamin can cause skin manifestations such as inflammation, dryness, and hyperkeratosis.
Additionally, vitamin A is known for its ability to stimulate collagen synthesis, and vitamin A supplementation appears to increase collagen deposition in the skin.
In fact, specific forms of vitamin A are used in many cosmetic products, not only to control acne and psoriasis but also to reduce fine lines and wrinkles.
For example, various facial cosmetics contain retinol in their composition, to enhance radiance and treat the signs of skin aging.
Additionally, many women seem to take vitamin A supplements to support maintaining healthy skin. These supplements can either be in capsule/tablet form, or in liquid form.
2. Wound healing
Vitamin A regulates activity at the cellular level and has numerous effects on the body through its interaction with various hormones (insulin, thyroid hormones, etc.). Among other things, it seems to play a critical role in all stages of wound healing.
3. Gut health
Serum retinol levels in adults and children with inflammatory bowel diseases – Crohn's disease and ulcerative colitis – are usually lower than in other people.
In general, it is considered that vitamin A provides an important anti-inflammatory effect on the body, contributing to the control of inflammation concerning the intestinal mucosa.
In fact, according to research published in 2021, it appears that taking a vitamin A dietary supplement by mouth could benefit people with ulcerative colitis, a chronic inflammatory bowel disease with periods of flare-ups and remissions.
4. Vision
In fact, many studies have shown that vitamin A contributes to protection against various eye diseases, and diets rich in vitamin A seem to be associated with reduced cataracts and age-related macular degeneration. Vitamin A plays a very crucial role in vision. On the one hand, it contributes to the protection of the health of the cornea, and on the other hand, it is the ability of the body to see under low conditions.
In addition, both vitamin A deficiency and vitamin A hypervitaminosis present manifestations related to vision and eyes (eg nyctalopia, dry eye).
5. Metabolic Syndrome – Diabetes
According to recent research data, vitamin A participates in the regulation of glucose and lipid metabolism.
More and more studies are investigating its relationship with Metabolic Syndrome (MetS) and the individual pathological conditions that characterize it (e.g. diabetes).
Results of a review published in 2019 suggest that, unlike retinol, various carotenoids are inversely associated with MetS. It appeared, therefore, that the high levels of carotenoids provide a protective effect against cardiometabolic diseases.
In addition, retinoic acid - the active metabolite of vitamin A - has been extensively studied to prevent diabetes.
6. Bone health
Vitamin A has been studied extensively because of its important role in bone health. According to a review published in 2021, it appears that both vitamin A and its provitamin are likely to be protective and contribute to the maintenance of healthy bones.
Vitamin A deficiency
Vitamin A deficiency is rarely seen in people living in countries of the developed world. Conversely, vitamin A deficiency is a common phenomenon in developing regions, especially in people who follow an unbalanced daily diet. For example, infrequent consumption of meat, dairy products, and vegetables rich in carotenoids can lead to vitamin A deficiency.
As for people living in developed areas who show reduced levels of vitamin A, this condition is usually associated with pathological conditions involving the intestine, pancreas & liver and, in general, is inextricably linked to conditions that lead to intestinal malabsorption (e. .eg inflammatory bowel diseases, bariatric surgery).
The most common symptoms that indicate vitamin A deficiency include dry skin, dry eyes, and nyctalopia (night blindness). In fact, vitamin A deficiency is the leading cause of blindness in children.
In addition, chronic vitamin A deficiency increases the likelihood of respiratory and gastrointestinal infections and may be associated with measles, diarrhea, pneumonia, anemia, and delayed growth. In cases of deficiency, it is recommended to take nutritional supplements of vitamin A. Especially regarding children, it seems that restoring the desired levels through nutritional supplementation reduces childhood morbidity.
What does taking too much vitamin A cause?
Unlike water-soluble vitamins (vitamin B), fat-soluble vitamins (A, D, E, K) have a tendency to accumulate in the body. Massive doses of vitamin A could cause hypervitaminosis. Vitamin A overdose can result from both topical use and oral intake of the vitamin.
Common symptoms that indicate hypervitaminosis A are:
- blurred vision
- severe headache
- bone pain
- nausea
- dizziness
- muscle pain
- depression
- fatigue
- coloring of the skin ( orange color )
- coordination difficulty
- liver problems (disturbances of liver markers)
Additionally, the most common side effect from topical vitamin A use is skin irritation, erythema, and peeling.
Contraindications – Interactions
Vitamin A can interact with certain medications while taking large doses is contraindicated in some cases.
In particular, it is recommended to avoid the simultaneous intake of vitamin A and anticoagulant treatment, anti-acne treatment (retinoids), as well as chronic intake without medical supervision.
Also, certain medications affect the absorption of the vitamin (eg hypolipidemic, antimicrobials, and antacids).
Its additional intake, if there is no need, is recommended to be avoided by children, women who are or wish to become pregnant, breastfeeding women, as well as by heavy drinkers of alcohol (risk of hepatotoxicity).
It is also worth noting that taking nutritional supplements with beta-carotene (a precursor form of vitamin A) is recommended to be avoided by chronic smokers.
Vitamin A and children
In some cases, children do not receive the necessary daily amount of vitamin A required for the proper functioning of the body and for their healthy development.
The administration of dietary vitamin A supplements to children at increased risk of vitamin A deficiency appears to reduce the risk of developing nyctalopia (night blindness) and Bitot's spots (tiny protein flakes in the eye), while also improving the levels of the vitamin in their blood.
More generally, it has been shown that administering vitamin A to children who need it significantly reduces childhood morbidity. Oral vitamin A supplementation is therefore recommended in these cases, as it is safe and provides significant benefits. The only adverse effect appears to be the possibility of vomiting within 48 hours of ingestion when large amounts of the vitamin are taken.
Vitamin A and pregnancy
During pregnancy, there are significant differences in the daily requirements of certain nutrients, to maintain the health of the mother and fetus.
Regarding vitamin A, there is an increased daily need during pregnancy and, in particular, during the 3rd trimester, due to the rapid development of the fetus in that phase.
It is important, therefore, to cover the daily needs and to maintain adequate levels of vitamin A in pregnancy, but without taking significantly higher amounts than recommended.
