What is Vitamin A and how does it work?

Vitamin A is the generic term for a group of fat-soluble compounds highly important for human health. It is essential for many processes in your body, including maintaining healthy vision, ensuring the normal function of your immune system and organs and aiding the proper growth and development of babies in the womb. It’s recommended that men get 900 mcg, women 700 mcg and children and adolescents 300–600 mcg of vitamin A per day (Trusted Source).

Vitamin A compounds are found in both animal and plant foods and come in different forms: Preformed vitamin A and Provitamin A

- Retinol is the main active form of vitamin A in the blood. Retinyl palmitate is the storage form of the vitamin.

- Beta-carotene is a provitamin, or a precursor of vitamin A. Beta-carotene is, in itself, an antioxidant, but the body can also convert it into vitamin A as needed.

These compounds are converted to the active form in your body. For example, beta-carotene is converted to retinol - an active form of vitamin A, in your small intestine (Trusted Source).

Food sources
The form of vitamin A will depend on the source (Trusted Source). For example, ready-made retinol, which is the active form of vitamin A, only comes from animal sources. The richest sources of retinol include: organ meats, such as liver; fatty fish, such as tuna and herring; milk and cheese; eggs

Plant-based foods contain carotenoids, which are antioxidant forms of vitamin A. The body converts these into retinol as it needs. Carotenoid is an orange pigment that contributes to the color of certain fruits and vegetables. They include: pumpkin, carrots, squash, sweet potato, red peppers, cantaloupe, apricot, mango

Plant foods that are rich in beta-carotene include dark green leafy vegetables, such as broccoli, spinach, turnip greens

6 BENEFITS FROM VITAMIN A

Protects Your Eyes From Night Blindness and Age-Related Decline
Vitamin A is essential for preserving your eyesight. It is needed to convert light that hits your eye into an electrical signal that can be sent to your brain.

In fact, one of the first symptoms of vitamin A deficiency can be night blindness, known as nyctalopia (Trusted Source). The vitamin A is a major component of the pigment rhodopsin that is found in the retina of your eye and extremely sensitive to light. People with this condition can still see normally during the day, but have reduced vision in darkness as their eyes struggle to pick up light at lower levels.

In addition to preventing night blindness, eating adequate amounts of beta-carotene may help slow the decline in eyesight that some people experience as they age (Trusted Source). Age-related macular degeneration (AMD) is the leading cause of blindness in the developed world. Though its exact cause is unknown, it’s thought to be the result of cellular damage to the retina, attributable to oxidative stress (Trusted Source).

Lower Your Risk of Certain Cancers
Cancer occurs when abnormal cells begin to grow or divide in an uncontrolled way. As vitamin A plays an important role in the growth and development of cells, its influence on cancer risk and role in cancer prevention is of interest to scientists (Trusted Source).

In observational studies, eating higher amounts of vitamin A in the form of beta-carotene has been linked to a decreased risk of certain types of cancer, including Hodgkin’s lymphoma, as well as cervical, lung and bladder cancer (Trusted Source). Yet, though high intakes of vitamin A from plant foods have been associated with a reduced risk of cancer, animal foods which contain active forms of vitamin A aren’t linked in the same way (Trusted Source).

Similarly, vitamin A supplements haven’t shown the same beneficial effects(Trusted Source). In fact, in some studies, smokers taking beta-carotene supplements experienced an increased risk of lung cancer (Trusted Source).

At the moment, the relationship between vitamin A levels in your body and cancer risk is still not fully understood. Still, current evidence suggests that getting adequate vitamin A, especially from plants, is important for healthy cell division and may reduce your risk of some types of cancer (Trusted Source).

Supports a Healthy Immune System
Vitamin A plays a vital role in maintaining body’s natural defenses. This includes the mucous barriers in eyes, lungs, gut and genitals which help trap bacteria and other infectious agents.

It’s also involved in the production and function of white blood cells, which help capture and clear bacteria and other pathogens from bloodstream.

This means that a deficiency in vitamin A can increase your susceptibility to infections and delay your recovery when you get sick (Trusted Source). In fact, in countries where infections like measles and malaria are common, correcting vitamin A deficiency in children has been shown to decrease the risk of dying from these diseases (Trusted Source).

Reduces Your Risk of Acne
Acne is a chronic, inflammatory skin disorder. People with this condition develop painful spots and blackheads, most commonly on the face, back and chest. These spots occur when the sebaceous glands get clogged up with dead skin and oils. These glands are found in the hair follicles on your skin and produce sebum, an oily, waxy substance that keeps your skin lubricated and waterproof. Yet, the exact role that vitamin A plays in the development and treatment of acne remains unclear (Trusted Source).

Supports Bone Health
The key nutrients needed for maintaining healthy bones as you age are protein, calcium and vitamin D. However, eating enough vitamin A is also necessary for proper bone growth and development, and a deficiency in this vitamin has been linked to poor bone health.

In fact, people with lower blood levels of vitamin A are at a higher risk of bone fractures than people with healthy levels (30Trusted Source). Additionally, a recent meta-analysis of observational studies found that people with the highest amounts of total vitamin A in their diet had a 6% decreased risk of fractures (Trusted Source). Yet, low levels of vitamin A may not be the only problem when it comes to bone health. Some studies have found that people with high intakes of vitamin A have a higher risk of fractures as well (Trusted Source).

This means that currently, the link between vitamin A and bone health is not fully understood, and more controlled trials are needed to confirm what has been seen in observational studies. Bear in mind that vitamin A status alone does not determine your risk of fractures, and the impact of the availability of other key nutrients, like vitamin D, also plays a role (Trusted Source).

Promotes Healthy Growth and Reproduction
Vitamin A is essential for maintaining a healthy reproductive system in both men and women, as well as ensuring the normal growth and development of embryos during pregnancy.

Rat studies examining the importance of vitamin A in male reproduction have shown that a deficiency blocks the development of sperm cells, causing infertility (Trusted Source). Likewise, animal studies have suggested that vitamin A deficiency in females can impact reproduction by reducing egg quality and affecting egg implantation in the womb (Trusted Source).

In pregnant women, vitamin A is also involved in the growth and development of many major organs and structures of the unborn child, including the skeleton, nervous system, heart, kidneys, eyes, lungs and pancreas.

Yet, though much less common than vitamin A deficiency, too much vitamin A during pregnancy can be harmful to the growing baby as well and may lead to birth defects (Trusted Source). Therefore, many health authorities recommended that women avoid foods that contain concentrated amounts of vitamin A, such as pâté and liver, as well as supplements containing vitamin A during pregnancy.

Risks of dose
Preformed vitamin A can be toxic when people consume too much, either through their diet or through supplementation. The tolerable upper intake level for vitamin A varies by age. The upper intake level is the amount above which vitamin A intake may be toxic. The list below details the upper intake levelsTrusted Source for preformed vitamin A by age:
up to 3 years: 600 mcg per day
4–8 years: 900 mcg per day
9–13 years: 1,700 mcg per day
14–18 years: 2,800 mcg per day
19+ years: 3,000 mcg per day
It does not appear that a person can consume too much beta-carotene, as the body will only convert it into vitamin A as necessary. 

Vitamin A toxicity
Consuming too much preformed vitamin A can lead to vitamin A toxicity. Symptoms can include: changes in skin color, peeling on the palms of the hands and soles of the feet, cracked skin on the fingers, psoriasis, allergic contact dermatitis, ectropion, which affects the skins around the eyes, dry lips, mouth, and nose, which can increase the risk of infection, reduced sebum production.

Long-term overuse can lead to: changes in bone formation, high cholesterol levels, liver damage, nervous system changes leading to headaches, nausea, and vomiting.

During pregnancy, consuming too much retinol can increase the risk of an infant being born with: cleft palate, heart problems, microcephaly, hydrocephalus, or water on the brain, problems with the thymus gland, which produces white blood cells.

The use of the topical treatment retinol may also increase vitamin A levels to an unhealthy level. Topical products can have adverse effects on the skin, though these will likely be less severe than those resulting from oral overconsumption. However, people should avoid using them during pregnancy.

The highest risk of overconsumption is with supplements. A healthful, balanced diet is unlikely to lead to toxic levels of vitamin A. It should also provide enough vitamin A without needing supplements

Compiled and penned by Crocus Media