What Is Vitamin A?

Vitamin A is a fat-soluble substance readily available in many foods, and plays a crucial role in eye health and clear vision. Keep reading to find out what you need to know about this essential vitamin, including how to recognise signs of a deficiency.

What exactly is vitamin A?

Vitamin A is one of many essential substances our body uses to support key biological processes; however, it doesn't occur naturally in humans.^[1] Instead, the body's inability to produce vitamin A means we need to consume naturally rich sources to reap its benefits—benefits that extend to eyesight, cell proliferation, skin health, and more.

We'll cover the best sources of vitamin A shortly, but first, let's take a closer look at the compound's chemical structure and various metabolites. In truth, the term vitamin A actually refers to two main forms:

• Preformed vitamin A (retinol and retinyl ester)
• Provitamin A (beta-carotene)

Fortunately, both types are converted into retinal and retinoic acid, the metabolites needed to support various biological functions. Vitamin A may seem confusing at first glance, but the main takeaway is you don't need to worry about which type you're consuming, as both end up providing the same benefits.

Before we explore the vitamin's benefits, it's helpful to know which foods contain which types of vitamin A, as you might be getting more or, in some cases, less than your body needs to support well-being. And as we'll soon discover, a vitamin A deficiency can lead to a host of debilitating health conditions.^[2]

What are good sources of vitamin A?

The best sources of preformed vitamin A are animal foods, namely meat, fish, and dairy.

Foods to focus on include:

• Fatty fish (tuna, salmon, and mackerel)
• Cow's milk (whole, skim, and reduced-fat)
• Cheese (goat, cheddar, and mozzarella)
• Eggs

The best sources of provitamin A come from fruits and vegetables. Technically, these foods contain a precursor to vitamin A called beta-carotene, but this antioxidant is converted into vitamin A automatically by the body.

Plant-based products to focus on include:

• Mango
• Red peppers
• Sweet potato
• Carrots
• Broccoli
• Spinach

Of course, if you struggle to maintain a balanced diet or aren't a fan of the foods listed above, you can choose multivitamins and other supplements to achieve your recommended daily intake.

How vitamin A helps the body

Now that we know which foods to focus on to ensure we're getting enough vitamin A, it makes sense to cover how, exactly, vitamin A can benefit the body.

Eye health

Vitamin A plays a crucial role in overall eye health, including helping to maintain normal vision and clarity at night. Moreover, some research suggests the compound may help with age-related cataracts and macular degeneration.

In 2001, a study examined the influence of vitamins on three different types of cataracts in over 2,800 elderly patients.^[3] Researchers concluded that the long-term use of group B & A vitamins may strongly influence cortical cataracts. This positive outcome goes hand in hand with a 2005 paper that saw similar results in AMD (age-related macular degeneration) using a blend of beta-carotene, vitamin C, and zinc.^[4]

Cell activity

The role of retinoic acid (RA) has long been associated with normal cell differentiation (the transformation of simple cells into complex tissue or cell types). Researchers first published the impact back in 1992, before more recent studies explored the compound’s specific influence on cell activity in the small intestine.^[5]

By replicating conditions in vitro, a 2007 paper "revealed the potential of RA to induce cell differentiation".^[6] However, the authors did note that a better understanding of "regulatory mechanisms" should be the focus of future research to better understand the implications on human health.

Immune system

Another notable benefit of vitamin A is its proposed contribution to the normal functioning of the immune system. In Mexico, the School of Natural Sciences found that a vitamin A deficiency may increase the inflammatory process, which contributes to chronic inflammation and a plethora of non-communicable diseases.^[7]

Vitamin A deficiency

Having briefly touched on the topic of vitamin A deficiency, now seems a good time to dive deeper into the implications. First, some positive news: vitamin A deficiency is rare compared to other vitamin deficiencies.

That is, of course, provided your habitual diet includes a balance of foods we highlighted earlier, something that can be difficult for children to achieve in developing countries. In such cases, a vitamin A deficiency to lead to:

• Xerophthalmia (night blindness)
• A greater risk of mortality from infections
• Increased severity of measles and diarrhoea

Encouragingly, cases of vitamin A deficiency in developed countries are rare. Focusing on a healthy and balanced diet is one of the best ways to ensure you get enough vitamin A, alongside the various other vitamins, minerals, and antioxidants whole foods provide.

Side effects of vitamin A

We've talked extensively about the benefits of vitamin A and how to make sure you're getting enough; but can you have too much of a good thing? Thankfully, side effects from excessive vitamin A intake are rare, and from a global perspective, the impact of vitamin A deficiency far outweighs the acute effects of vitamin A toxicity.

However, cases of vitamin A toxicity can still occur, especially with abuse of vitamin supplements. Common side effects of excessive vitamin A include:

• Nausea/vomiting
• Dizziness
• Lethargy/drowsiness

Despite the risk of side effects, you shouldn't worry too much about vitamin A toxicity, as the threshold is far beyond what you'd receive from food alone.

How much vitamin A should I take?

The ideal amount of vitamin A differs according to lifestyle, age, and sex. And for the most part, you'll get all the vitamin A you need from your diet.^[8] In fact, the body will even store excess vitamin A, using it as and when required. Still, if you want to focus on keeping levels topped up, then the recommended daily amounts are:

• Men (700µg)
• Women (600µg)

Calculating daily intake can get a little complicated as the different forms of vitamin A (provitamin and preformed) convert to retinol at differing rates. However, to give you an idea of what 600µg of vitamin A looks like, you would only need to consume one whole sweet potato to meet the daily guideline.

Vitamin A joins dozens of other vitamins and minerals to positively influence well-being. Its beneficial impact on eyesight, the immune system, and cell activity make it a substance undoubtedly worth focusing on. That said, most people will get all the vitamin A they need from a balanced and varied diet, with supplements available for specific lifestyles or health conditions.

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