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Vitamin A: Functions and Evidence-Based Health Benefits

Vitamin A Benefits

It is quite normal to think about the eyes when vitamin A is mentioned. After all, we all have heard the association between vitamin A, carrots and better vision many times in our lives.

However, limiting this vitamin’s function only to eye health would become quite unfair given the fact that vitamin A is necessary for various physiological processes in the human body.

To put it simply; Vitamin A is an extremely important nutrient for the human body!

Now, you might be asking questions like  ” what makes this vitamin so special? “, ” what are the functions of vitamin A in the human body?” or ” what are the benefits of eating enough vitamin A?”.

In this article, we are going to investigate this essential nutrient thoroughly and provide answers to your potential questions.

But, firstly, let’s explain what this vitamin really is.

What is Vitamin A?

As mentioned above, vitamin A is an essential micronutrient that the human body needs to function properly (1).

So, what kind of nutrient is vitamin A? This is a fat-soluble nutrient, which means it can be stored in the liver and fatty tissues to be used later (2), (3).

The human body can’t produce vitamin A itself, so we need to take it from animal and plant foods (1).

One interesting fact about this micronutrient is that the term “vitamin A” doesn’t represent only one particular nutrient. It actually represents a group of fat-soluble compounds (1).

Vitamin A compounds have two forms namely preformed vitamin A and provitamin A.

As the name implies; preformed vitamin A (retinol) is used in the body just as it is. Therefore, it is called an active form of vitamin A. This form of vitamin is found in animal products (4).

On the other hand; provitamin A carotenoids ( alpha-carotene, beta-carotene and beta-cryptoxanthin) are converted into retinol ( the active form of vitamin A)  in the human body. This form is mostly found in plants (1), (4).

 

Vitamin A Functions in The Body

Above we have tried to explain what actually vitamin A is. Now, it is time to discover the functions of this vitamin in the human body. That will also explain why this vitamin is vital for your body.

As mentioned in the beginning; this vitamin plays a significant role in the various physiologic process in the human body.

Let’s be more obvious and explain its main functions. The followings are the main functions of vitamin A:

–  Vitamin A promotes good eyesight and helps vision in dim light (5), (6).

–  It has a role in healthy pregnancy and breastfeeding (5).

  It is necessary for cell growth and immune functions (4).

–  also helps form and maintain (5) :

  • Healthy teeth
  • Skeletal
  • Soft tissue
  • Mucous membranes

 

Health Benefits of Vitamin A

Now that we have understood what vitamin A is and its functions in the body, we can focus on the health benefits of getting enough of this vitamin.

Without further ado; here are the 6 evidence-based health benefits of Vitamin A.

 

1- May Supports Bone Health

Many of us know that vitamin D and calcium are crucial for healthy bones. Although vitamin A is not as important as these nutrients for bone health, it is also necessary for building healthy bones (7).

We know from scientific studies that vitamin A deficiency substantially increases the risk of bone fracture. This piece of information can give us a clue about how important this vitamin might be for the bones (8).

But what is interesting is that too much vitamin A in the body as well can increase the risk of bone fractures (7),(9).

So, the message is clear vitamin A level should be neither less nor more than it is needed. Otherwise, it may impact the bones negatively.

 

2- Supports The Immune System

The proven fact is that eating enough vitamin A strengthens the natural defence system of the body and, therefore helps protect the body against disease-causing pathogens such as bacteria, viruses and germs.

In what way vitamin A strengthens your body’s defence? In fact, vitamin A supports the natural defence system of the body in two ways:

1-) It supports mucous membranes that help prevents pathogens from entering the body (10).

2-) It helps the production and function of white blood cells, which are the key player for the immune system (11),(12).

Moreover, studies show that enough vitamin A intake decreases the morbidity and mortality of certain infections such as measles and malaria in children (13).

Vitamin A alone is not enough to protect the body against pathogens. However, when eaten sufficiently, it helps the body to remain strong against these disease-causing pathogens.

 

3- May Lower Cancer Risk

Scientific studies point out the positive correlation between higher intake of vitamin A and reduced risk of certain types of cancer such as cervical, lung, and bladder cancer (14),(15).

However, it is necessary to underline the fact that the inactive form of vitamin A – obtained from the plants – is thought to be effective for lowering cancer risk rather than the active form of this vitamin (16).

As for vitamin A supplements; there is no evidence that says the supplements may lower cancer risk. On the contrary, a long-term high dose of supplements is claimed to increase the risk of lung cancer (17).

Evidence suggests that the inactive form of vitamin A may lower certain cancer risks. However, more research is necessary to draw a certain conclusion on this issue.

 

4- Protect Eyes

Here is the most well-known health benefit of vitamin A. As most of us know vitamin A is essential for optimal eyesight and to maintain healthy eyes.

According to Healthline; this vitamin has a crucial role in vision as it maintains a clear cornea, the outside covering of the eyes (18).

As the vitamin is crucial for eye health, there must be consequences of insufficient intake of it.

The followings eye disorders can occur as a result of vitamin A deficiency (19):

If not reversed, vitamin-A deficiency can even lead to permanent blindness (20).

To sum up: eating enough vitamin A contributes to your eyes’ health.

 

5- Support Skin Health

Vitamin A offers a variety of benefits to your skin from reducing acne flare-ups to stimulating collagen production.

Yet, not only eating but also applying vitamin A to your skin topically can improve your skin quality.

Let’s start with scientific studies that show the potential benefits of vitamin A on the skin.

As per the findings of a 2010 study; topical application of retinoids (preformed vitamin A) can stimulate collagen production and also may reduce wrinkles (21).

In another study, it was found that dietary carotenoids (the inactive form of vitamin A ) can protect the skin against free radicals and avoid premature skin ageing (22).

What’s more; according to The American Academy of Dermatology; retinoids (an active form of vitamin A) can be used topically to treat acne in both adolescents and adults (23).

It appears that vitamin A is necessary for maintaining healthy skin.

 

6- Supports Hair

It is safe to say that vitamin A is one of the important nutrients for your hair.

It helps secretions of sebum that keeps the scalp moisturised and in this way it prevents hair breakage and hair loss (24), (25).

So what happens to your hair when your body lacks vitamin A?

Studies suggest that vitamin A deficiency can lead to several hair problems. One of them is hair loss.

However, experts warn that too much vitamin A as well can lead to hair loss (28).

To sum up; when your diet lacks vitamin A, you are more likely to encounter hair problems.

 

How Much Vitamin A Do You Need Per Day?

Thus far, we have examined the functions and health benefits of vitamin A.

While doing it we repeatedly underlined the fact vitamin A deficiency as well as too much vitamin A in the body can cause a variety of health problems.

So, the question is ” how much vitamin A do I need per day?”.

According to Mayo Clinic; the recommended daily amount of vitamin A is 900 micrograms (mcg) for adult men and 700 mcg for adult women (29).

National Institutes of Health Recommends (20):

  • 300 mcg of Vitamin A for 1-3 years
  • 400 mcg of Vitamin A for 4-8 years
  • 600 mcg of vitamin A for 9-13 years

 

Sings Of Low Vitamin A-Level in the Body

Vitamin A deficiency is rare in developed countries while many people suffer from vitamin A deficiency in developing countries.

Vitamin A deficiency can manifest itself with various signs and symptoms

The followings are the most common signs of low vitamin A level (19):

  • Dry Skin
  • Dry Eyes
  • Night Blindness
  • Infertility and Trouble Conceiving
  • Delayed Growth
  • Throat and Chest Infections
  • Poor Wound Healing
  • Acne and Breakouts

 

Harms of Too much Vitamin A In the Body

We have discussed the potential consequences of a low level of vitamin A intake. But, how about too much vitamin A presence in the body?

There are of course certain risks of ingesting too much vitamin A.

However, it is important to note that a high dose of preformed vitamin A intake can cause serious medical conditions rather than provitamin A.

According to the National Institutes of Health; getting too much-preformed vitamin A can lead to:

Note: Especially pregnant women should discuss their daily vitamin A intake with their doctors.

 

Foods That Are Rich In Vitamin A

The table below displays a list of foods that are high in Vitamin A (30).

FoodDaily Value
Carrots95%Per 100gr
Tuna84%Per 100gr
Butternut Squash62%Per 100gr
Sweet Potato107%Per 100gr
Spinach58%Per 100gr
Cantaloupe19%Per 100gr
Lettuce48%Per 100gr
Red Bell Peppers16%Per 100gr
Pink Grapefruit6%Per 100gr
Broccoli9%Per 100gr