Vitamin A is found in many foods and is essential for our well-being. Here’s how much to take and what effects it has on the human body.
Vitamin A is essential for our health , but it is important to get the right amount to avoid problems. This fat-soluble vitamin is found in foods of animal and plant origin in various forms. The most famous are retinaldehyde, essential for vision, and retinoic acid, which plays a primary role in the embryonic stage. Its derivatives, namely retinol and retinoids, are found instead in foods of animal origin, while carotenoids in those of vegetable origin. Just as a deficiency of this vitamin can be worrying, even its surplus can cause various problems for the human body.
What is vitamin A used for?
Vitamin A (present in the form of retinol, retinoic acid, retinaldehyde) is an important nutrient for eyes and eyesight, youthful growth and development and tissue differentiation, cell division, reproduction, and immunity . Furthermore, it is known for its high antioxidant properties against free radicals that attack cells and tissues of the human body every day (oxidative stress). This substance therefore plays essential roles in the human organism.
In summary, vitamin A strengthens the skin and keeps it healthy and young, it also promotes beautiful hair. Vitamin A protects against lung infections and helps bone development, improving the functioning of the testicular and ovarian systems. It is also essential during pregnancy, both for the health of the fetus and that of the mother, as it allows tissue differentiation in the baby. But let’s see in detail what its functions are inside the human body:
- Improve vision in dim light. In fact, vitamin A combines with a protein to form rhodopsin , the pigment that gives the eye sensitivity to light. The first sign deriving from a lack of vitamin A is, in fact, night blindness.
- Preserve the integrity and correct functioning of the skin and mucous membranes , and specifically of the digestive and respiratory tracts. Many organs and tissues in the human body, such as the trachea, lungs, digestive lining, urethra and bladder, depend on adequate amounts of this vitamin to maintain proper function. Vitamin A is famous and is widely used for maintaining skin health and seems to have a protective action against some epithelial tumours. For this reason, retinol derivatives are present in various cosmetic products, used for the well-being of the face.
- Play a role in reproduction, regulation of cell division and control of gene expression. But vitamin A also intervenes in the synthesis of sex hormones, sperm generation, conception and formation of the placenta.
- Support skeletal growth (through bone remodeling), very useful in the stages of adolescence.
- Act as an anti-infective agent. Vitamin A, along with some carotenoids, helps the immune system work properly, helping to control infection and the attack of microbes and other foreign invaders. This point deserves further study, which will be presented in the next paragraph.
Vitamin A and the Immune System:
As far as the immune system and the body’s defenses are concerned, a vitamin A deficiency can compromise the functioning of the first line of defense represented by the anatomical barriers. In a nutshell, vitamin A deficiency can cause structural and functional damage to the skin and mucous membranes in contact with the external environment such as the intestinal epithelium and respiratory mucous membranes, causing pathogenic microbes and viruses to take root more easily. It has been demonstrated that in the absence of vitamin A, the alteration of the body’s mucous membranes causes the loss of cells that produce mucus.
The loss of protective mucus consequently decreases the ability of the mucous membranes to function as barriers that prevent the entry of infection-causing microorganisms. In fact, mucus helps to trap them and transport them outside the body. Furthermore, the regeneration of tissues damaged by infections of various kinds can be hindered or slowed down, thus favoring the penetration of pathogenic bacteria and other dangerous microorganisms.
Vitamin A deficiency can also compromise:
- innate immunity , i.e. the first line of defense offered by eosinophils, basophils, macrophages, neutrophils and dendritic cells ;
- acquired immunity , i.e. the specific one that makes use of B and T lymphocytes.
What foods to eat to supplement vitamin A?
Vitamin A is found in many foods, so it’s not difficult to stock up on it. You can find it in general in all vegetables with a yellow or orange color, but also in cod liver oil, butter, egg yolk and liver. It is also found in vegetables such as spinach, carrots, cabbage, savoy cabbage, broccoli, parsley, squash, spinach, chicory, tomato and lettuce. If you want to fill up on this vitamin, eat melon, peaches, apricots, oranges and watermelon.
Specifically, vitamin A and its derivatives are introduced into the body through food in two forms:
- directly as vitamin A (retinol), through foods of animal origin;
- as provitamin A (carotenoids), precursor of the vitamin, through foods of vegetable origin.
The latter is modified and converted into vitamin A within the portion of the small intestine responsible for its absorption and passage within the bloodstream. Once vitamin A has been absorbed, it is deposited in the liver which, according to the needs of the organism, will store it or release it little by little, linked to a plasma protein which carries it in the blood. The two sources of vitamin A are not equivalent, and in fact the human body absorbs retinol derived from animal sources better and faster . There are also other types of carotenoids present in foods of plant origin, which are not converted into vitamin A but which have healthy antioxidant and preventive properties of numerous pathologies of the body, such as for example lycopene, lutein and zeaxanthin .
List of foods rich in vitamin A:
Below is a table with the main foods rich in vitamin A, expressed in retinol equivalents:
| Food | Vitamin A retinol eq. (mcg/100g pe) |
| Raw carrots | 1148 |
| Dandelion or dandelion | 992 |
| Parsley | 943 |
| Hot peppers | 824 |
| Rughetta or rocket | 742 |
| Basil | 658 |
| San Marzano tomatoes | 610 |
| Ripe tomatoes | 610 |
| Yellow pumpkin | 599 |
| Green radish | 542 |
| Spinach, frozen | 500 |
| Mixed vegetables, frozen: peas, corn, carrots, beans | 500 |
| Raw spinach | 485 |
| Peppers, red and yellow | 424 |
| Tomatoes, canned peels [fruit plus natural juice] | 400 |
| Agretti | 392 |
| Brussels sprouts, cooked [boiled in distilled water without adding salt] | 300 |
| Field chicory, cooked [boiled in distilled water without adding salt] | 300 |
| Turnip leaves | 299 |
| Cut chicory, cultivated | 267 |
| Raw chard | 263 |
| Courgette flowers | 252 |
Vitamin A deficiency symptoms:
The daily requirement of vitamin A is equal to 0.6-0.7 mg , which can reach 0.95 mg per day during breastfeeding . Its presence is quite ubiquitous in foods of both animal and vegetable origin and despite this a lack of vitamin A is very frequent, especially in those suffering from intestinal problems and malabsorption of nutrients (celiac disease and inflammatory bowel diseases). The symptoms of the problem are particularly noticeable. Usually there is a decrease in vision, especially in the dark, the mucous membranes of the mouth and nose dry out, while the skin appears dull, wrinkled and chapped. Below is a detailed list of the symptoms deriving from a lack of vitamin A in one’s diet:
- night blindness (i.e. difficulty seeing in the evening and at night).
- alterations of the conjunctiva and cornea, from simple dryness to thickening, but also pigmentation and the formation of small whitish-gray spots, up to keratomalacia . It is a serious disorder in which the cornea becomes very opaque and ulcerations appear which can worsen until it is destroyed with the lens leaking and consequent loss of vision.
- thickening of the mucous membranes of the respiratory system, with an increase in airway infections.
- thickening of the renal epithelium, with the onset of renal infections.
- infertility and pregnancy problems .
- dysfunctions of the immune response in all its components.
- tooth enamel defects and accentuated chromatic variations.
- bone deformation
Excess vitamin A in the diet:
As repeated, the daily requirement is 0.6-0.7 mg, so it can be very easy to overload the body with vitamin A (especially through supplements and health products). If a lack of vitamin A can be dangerous, an excess of this substance in the body can also cause serious damage. Vitamin A is a fat-soluble molecule (meaning that it dissolves in fat), which means that any amount not immediately needed by the body’s cells is absorbed and stored by the body in adipose tissue or the liver. But if it is stored in excess it can become toxic to the cells and organs of the human body. Amounts of vitamin A greater than 300 milligramsthey cause acute intoxication and can generate disturbances such as:
- Nausea
- Vomit
- Dizziness and headache
- Blurry vision (especially at night)
Even higher doses (6 milligrams and up) taken over a long period can cause:
- hair loss or change in texture
- inappetence and weight loss
- anemia
- joint and bone pain, but also muscle pain and cramps
- bone thinning
- liver damage
- neurological disorders
During pregnancy, the excessive use of vitamin A, as well as its serious lack, can lead to malformations of the fetus ( teratogenesis ). All medicines (even for acne), supplements and health products based on vitamin A should always be monitored by the doctor during their intake. Additionally, retinoids in skin-applied creams can cause the skin to become highly sensitive to bright light ( photosensitivity ), so you may want to avoid sun exposure after using vitamin A-containing creams and apply them the night before. to go to sleep.
Follow the advice of a nutrition expert , to have the right vitamin A intake starting from the foods that arrive on our tables every day and avoiding the intake of specific supplements and health products.