Vitamin A is a general term that describes a group of compounds with similar functions in the body. They play a vital role in human health, from reproduction and development to immunity, eyesight, and more.
Here’s our complete guide to vitamin A benefits, dosage, side effects, and more.
What Is Vitamin A?
The term vitamin A describes a group of fat-soluble nutrients with many physiological functions.
Although they are essential for good health, our bodies cannot synthesize them, and we must obtain them from our diets.
There are two types of vitamin A in food. Preformed vitamin A, also known as retinol or retinyl ester, is found in meat, eggs, and dairy products. Meanwhile, fruit and vegetables contain provitamin A in the form of compounds called carotenoids.
The body can convert some, but not all, carotenoids into vitamin A. The most commonly consumed form of provitamin A is a carotenoid called beta-carotene. It is a pigment that gives yellow and orange fruit and vegetables their vibrant color.
Vitamin A supplements might contain beta-carotene, preformed vitamin A, or a combination of the two.
Now, let’s explore some of this nutrient’s many benefits.
Vitamin A is essential for the development and maintenance of healthy tissues, including the skin. Therefore, the benefits of vitamin A for skin are numerous.
Doctors prescribe natural and synthetic vitamin A analogs called retinoids to treat various skin conditions.
For example, a retinoid called acitretin may help relieve psoriasis symptoms. Additionally, a topical retinoid called tretinoin and its oral counterpart, isotretinoin, are effective acne treatments.
Retinoids are vitamin A analogs that have anti-inflammatory properties and regulate the growth and development of skin cells.
These medicines have anti-inflammatory properties and regulate the growth and development of skin cells. They may also reduce sebum (oil) production, which is why they are popular among acne patients. One downside is that retinoids can cause congenital disabilities, making them unsuitable for use during pregnancy.
Another related compound called retinol has received FDA approval as an anti-wrinkle agent. As well as regulating the skin cell cycle, it promotes the production of new skin cells. It also strengthens the skin’s barrier function, helps to retain moisture, and prevents collagen breakdown.
Therefore, retinol has become a common ingredient in cosmetic preparations. However, it can cause several side effects, including red skin, burning, itching, and peeling. It also increases sensitivity to ultraviolet light, meaning users should avoid excessive sun exposure.
Healthy Growth and Reproduction
Vitamin A plays a role in reproduction, growth, and development. It regulates the generation and specialization of almost every cell type in the body. Therefore, it is essential for healthy organ formation, including the brain, heart, kidneys, lungs, eyes, and more.
The nutrient is also involved in both male and female fertility. For example, vitamin A benefits for men include maintaining the reproductive organs and promoting sperm production.
In women, it is involved in conception and pregnancy, including fertilization, implantation, placenta maintenance, and normal embryonic development. During pregnancy, either vitamin A deficiency or excess may lead to congenital disabilities.
Healthy Immune System
Vitamin A is responsible for the development and maintenance of many structures and cells involved in immunity.
Firstly, it is essential for healthy skin and mucous membranes. These tissues act as a first-line defense against potential threats, such as bacteria and viruses. It is also necessary for the production and activity of many different immune cells and plays a role in the inflammatory response.
Vitamin A deficiency could increase the risk of developing serious infections, including tuberculosis, measles, and acute pneumonia. It could also increase the risk of mortality from gastric or respiratory infections.
Therefore, vitamin A is essential for immune system function and preventing infections.
There is a complex relationship between vitamin A and the bones. Although the nutrient is necessary for normal skeletal development, consuming too much could have negative effects.
There is some evidence suggesting that excessive vitamin A intake could reduce bone mass and increase the risk of fractures. This is likely due to its impact on the bone remodeling cycle. It seems that vitamin A increases the activity of cells that break down bone while decreasing the activity of those that replenish it.
However, studies on the subject of vitamin A for bone health have produced mixed results. While many show that vitamin A supplementation adversely affects bone mass, others indicate no effect or a protective influence.
Several different factors are likely involved. For example, other nutrients, such as vitamin D are critical to the bone remodeling process. There is also no evidence that beta-carotene consumption alone has a negative impact.
Vitamin A is also crucial for healthy eyes and vision. It is necessary for the formation of a protein called rhodopsin in the retina. Its function is to convert light particles into nerve signals to send to the brain.
One of the key symptoms of vitamin A deficiency is reversible night-blindness. It can also cause various other eye problems, such as dryness and corneal damage.
Several other carotenoids may also help to promote healthy vision. For example, there is some evidence that lutein and zeaxanthin could slow the progression of age-related macular degeneration.
Notably, these two compounds are not forms of provitamin A. However, they appear to have powerful antioxidant properties that could complement the benefits of vitamin A for the eyes.
Maximizing the Benefits of Vitamin A
Vitamin A is good for us for many reasons, but how much do we need? Unfortunately, the answer is not straightforward.
The standard measurement for vitamin A used to be international units (IU). However, it recently changed to a unit known as retinol activity equivalent (RAE). This alteration may confuse consumers since some sources still list the recommended daily intake in IU while others use RAE.
Advice from the National Institutes of Health states that adult men should consume 900mcg RAE daily, while adult women should consume 700mcg.
The IU equivalent depends on whether the vitamin A is from retinol or beta-carotene. For example, one IU is 0.3mcg of retinol or 0.6mcg of beta-carotene. Therefore, consumers will need to calculate the RAE of foods and supplements accordingly.
The best food sources of retinol include:
- Meat, especially liver
- Dairy products
- Fish oil
Sources of beta-carotene include:
- Orange and yellow fruit and vegetables
- Leafy greens
Vitamin A is fat-soluble, so adding some oil or fat to meals will aid its absorption. Cooking can also help to break down fruit and vegetables’ cell walls to release more beta-carotene.
Some people also choose to take a daily vitamin A supplement. However, this is unnecessary for most and can cause serious side effects. We discuss these in detail below.
Can You Have Too Much Vitamin A?
The liver stores vitamin A and consuming too much can have adverse effects. This phenomenon is known as hypervitaminosis A.
The daily upper limit for preformed vitamin A is 3000mcg RAE for adults over 19. The upper limit for provitamin A, including beta-carotene, has not been established.
The side effects of too much vitamin A include:
- Increased intracranial pressure
- Skin irritation
- Joint and bone pain
- In severe cases, coma and death
However, these side effects only occur due to overconsumption of preformed vitamin A (retinol). While excessive beta-carotene intake can cause the skin to turn orange or yellow, this side effect is harmless and reversible.
Please note that some medications can interact with vitamin A and increase its levels in the bloodstream. Therefore, individuals should consult a healthcare provider before considering supplementation.
Final Thoughts on Vitamin A Benefits
Vitamin A is essential for good health. It is involved in reproduction, development, immunity, eye health, bone health, and more. However, despite the many benefits of vitamin A, consuming too much could be harmful.
Individuals should aim to get adequate vitamin A from dietary sources rather than supplements to decrease the risk of overdose. Anyone considering supplementation should consult a physician or dietician beforehand.