Vitamin A: All you need to know

06/04/2022

What is Vitamin A?

Vitamin A is a fat-soluble vitamin that is involved in many functions of the human body, is stored mainly in the liver and is obtained through the diet.

It is necessary for the maintenance of normal vision, for the functioning of the immune system and for the health of the skin & mucous membranes, while it contributes to cell differentiation and to the metabolism of iron.

According to studies, the immunoregulatory and anti-inflammatory action of vitamin A is crucial for health, protecting against a number of pathological conditions that affect all organs. It seems, for example, to act protectively on the respiratory system, intestinal health and brain function. [1] [4]

Maintaining the desired levels of vitamin A is considered vital, as deficiency can negatively affect vision, skin and immune system function. [2]

Foods with vitamin A

Animal sources:

  • liver
  • eggs
  • dairy products
  • fish

Plant sources [6]:

  • carrot
  • sweet potato
  • papaya
  • mango
  • peach
  • apricot
  • peppers
  • spinach
  • broccoli
  • asparagus
  • cabbage
  • pumpkin
  • melon

In addition, many foods are often fortified with vitamin A, such as margarine, milk and breakfast cereals. [6]

Daily requirements

The Recommended Daily Allowance (BMI) for healthy adults per day is [6]:

  • 700 μg for women
  • 900 μg per day for men

For children, pregnant and lactating women, the daily BMI is [6]:

  • 300-900 μg
  • 770 μg
  • 1300 μg

Specifically for children, the following PHCs 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)

Vitamin A – Deficiency

Inadequate levels of vitamin A are rarely seen in people living in developed countries. In contrast, vitamin A deficiency is a common occurrence in developing areas, people who follow an unbalanced diet. [2] [6]

For example, rare consumption of meat, dairy products and vegetables rich in carotenoids can lead to vitamin A deficiency. [2]

In people who live in developed areas and show reduced levels of vitamin A, this condition is usually associated with pathological conditions involving the intestine, pancreas & liver and is generally linked to conditions that lead to intestinal malabsorption (e.g. .inflammatory bowel diseases, bariatric surgeries). [2]

The most common symptoms of vitamin A deficiency include dry skin, dry eyes, and night blindness. In fact, vitamin A deficiency is a major cause of blindness in children. [6]

In addition, chronic vitamin A deficiency increases the chance of respiratory and gastrointestinal infections and may be associated with measles, diarrhea, pneumonia, anemia, infertility, and stunted growth. [6]

In cases of insufficiency, it is recommended to take vitamin A supplements. Especially for children, it seems that the restoration of the desired levels through dietary supplement reduces child morbidity. [2]

What causes excessive vitamin A intake?

Unlike water-soluble vitamins (B-complex vitamins), fat-soluble vitamins (A, D, E, K) tend to accumulate in the body. [3]

Large doses of vitamin A can cause hypervitaminosis. Vitamin A overdose can be due to both topical use and oral intake of the vitamin. [3] [6]

Common symptoms that indicate hypervitaminosis A are:

  • blurred vision
  • severe headache
  • bone pain
  • nausea
  • dizziness
  • muscle pain
  • Depression
  • fatigue
  • skin pigmentation (orange)
  • difficulty of coordination
  • liver problems (disorders of the liver markers)

In addition, the most common side effect of topical vitamin A use is skin irritation, erythema and peeling. [3]

Contraindications – Interactions

Vitamin A may interact with certain medications, and high doses are contraindicated in some cases. [6]

In particular, it is recommended to avoid the simultaneous intake of vitamin A and anticoagulant therapy, acne treatment (retinoids), as well as its chronic intake without medical supervision. [6]

Also, it seems that some medications affect the absorption of the vitamin (eg hypolipidemics, antimicrobials and antacids).

It is recommended to be avoided by children, women who are or want to become pregnant, breastfeeding women, and people who consume very large amounts of alcohol (risk of hepatotoxicity).

It is also worth noting that taking dietary supplements with β-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 growth.

Vitamin A supplementation in children at increased risk for vitamin D deficiency appears to reduce the risk of developing night blindness (Bit blindness) and Bitot spots (tiny protein flakes in the eye), while improving blood levels.

In general, it has been shown that the administration of vitamin A to children in need significantly reduces childhood morbidity. [4] [10] Oral vitamin A supplementation is therefore recommended in these cases, as it is safe and provides a significant benefit. The only side effect seems to be the possibility of vomiting within 48 hours of taking large amounts of the vitamin. [10]

Vitamin A and pregnancy

During pregnancy there are significant differences in the daily requirements of certain nutrients, in order to maintain the health of mother and fetus.

As for vitamin A, there is an increased daily need during pregnancy and, especially, in the 3rd trimester, due to the rapid development of the fetus in that phase. [6] [11]

It is important, therefore, to meet daily needs and maintain adequate levels of vitamin A in pregnancy, but without consuming significantly larger amounts than recommended. [11]

Vitamin A and health

As mentioned above, vitamin A is involved in many functions of the body and acts protectively in many health conditions.

  • Skin Health

Vitamin A has been studied for years regarding its beneficial effect in maintaining healthy skin, while it is used successfully in conditions such as acne and psoriasis.

The use of retinoids has been shown to be very beneficial in skin diseases that are stimulated by the immune system. In fact, it has been shown that people with psoriasis have lower levels of carotenoids than people without psoriasis. [4] [13]

Low levels of the vitamin are likely to lead to skin manifestations such as roughness, dryness and hyperkeratosis.

In addition, vitamin A is known for its ability to stimulate collagen synthesis, while taking vitamin A supplements appears to increase collagen deposition in the skin. [12]

Certain forms of vitamin A are used in many cosmetic products, not only to manage acne and psoriasis, but also to reduce fine lines and wrinkles.

For example, various cosmetics for the face area contain retinol in their composition, in order to enhance skin radiance and treat the signs of skin aging.

In addition, many women seem to be taking vitamin A supplements to support the maintenance of healthy skin. These supplements can either be in the form of a capsule / tablet or in liquid form.

  • Wound Healing

Vitamin A regulates activities at the cellular level and – through its interaction with various hormones (insulin, thyroid hormones, etc.) – affects the body in various ways. Among other things, it seems to play an important role in all stages of wound healing. [12]

  • Intestinal Health

Serum retinol levels in adults and children with inflammatory bowel disease – Crohn’s disease and ulcerative colitis – are usually lower than in other people. [4]

In general, vitamin A is considered to provide significant anti-inflammatory action in the body, helping to control inflammation of the intestinal mucosa. [4]

In fact, according to research published in 2021, it seems that taking a dietary supplement of vitamin A orally could benefit people with ulcerative colitis, a chronic inflammatory bowel disease with periods of exacerbation and remission. [5]

  • Vision

Vitamin A plays a crucial role in the function of vision. On the one hand it contributes to maintaining the health of the cornea and on the other hand it contributes to the body’s ability to see in low light conditions. [6]

In fact, a number of studies have shown that vitamin A helps protect against various eye diseases, while diets rich in vitamin A appear to be associated with a reduced risk of cataracts and age-related macular degeneration. [1] [6]

In addition, both vitamin A deficiency and hypervitaminosis have manifestations that affect the eyes and vision (e.g. night blindness, dry eyes).

  • Metabolic Syndrome (MetS) – Diabetes

According to recent research data, vitamin A is involved in regulating glucose and lipid metabolism. [9]

More and more studies are investigating its connection to Metabolic Syndrome (MetS) and the individual pathological conditions that characterize it (e.g. diabetes).

The results of a review published in 2019 suggest that, unlike retinol, the various carotenoids are inversely related to MetS. In particular, high levels of carotenoids have been shown to provide protective action against cardiovascular disease. [7]

In addition, retinoic acid – an active metabolite of vitamin A – has been extensively studied for the management of diabetic complications. [9]

  • Bone Health

Vitamin A has been extensively studied for its role in bone health. According to a review published in 2021, it seems that both vitamin A and its provitamin are likely to act protectively and help maintain healthy bones. [8]

 

Maria Malteza

Malteza Maria, MSc, BSc Dietitian - Nutritionist, specializing in Clinical Nutrition, Nutritional Evaluation and Nutritional Supplements.

MORE

Disclaimer

The content of this blogspot is not and can not be considered as medical advice, diagnosis or treatment. All information is provided to readers solely for informational purposes. There is no intention to substitute this content for personalized medical advice, diagnosis, prognosis or treatment.

Featured Articles

Leave a comment

Newsletter

Subscribe to our Newsletter and be the first to know about news and offers.