Diets Debunked

Vitamin A is one of those nutrients you’ve probably heard about but might not fully understand. It’s often associated with good eyesight, but its role in the body actually goes far beyond that. From supporting your immune system to keeping your skin healthy, vitamin A is a true multitasker; but like. many micronutrients, you can have too much of a good thing.

What is Vitamin A?

Vitamin A is a fat-soluble vitamin, which means it’s stored in the body’s fatty tissues and liver, and requires a little fat to be eaten with it in order for it to be properly absorbed.

The property of a vitamin being fat-soluble is what means you can get too much. Essentially, water-soluble vitamins such as the B vitamins and vitamin C can be excreted if you get too much, meaning you won’t experience any build up in your body even if you overdose on them. The fat-soluble vitamins however (Vitamins A, D, E and K) will be stored in your fatty tissues, and cannot be excreted easily. This allows a build up to occur, and we can get what is known as hypervitaminosis, or a vitamin overdose.

Vitamin A isn’t just a single compound; it’s a group of related substances that include retinol, retinal, and retinoic acid (collectively known as retinoids), as well as carotenoids like beta-carotene. These different forms have unique roles in the body, which we’ll explore in more detail.

The two main forms of Vitamin A

1. Preformed Vitamin A (Retinoids):
   This is the active form of vitamin A, found in animal products such as liver and other animal tissues. It includes retinol, retinal, and retinoic acid. Retinoids are readily used by the body and are particularly important for vision, immune function, and cell growth. Retinoids can cause hypervitaminosis.
2. Provitamin A (Carotenoids):
   These are found in plant-based foods and need to be converted into active vitamin A in the body. The most well-known carotenoid is beta-carotene, which gives carrots, sweet potatoes, and other vegetables their vibrant orange colour. While not as immediately usable as retinoids, carotenoids are powerful antioxidants and play a key role in protecting cells from damage. Because carotenoids need to be converted into retinoids to have activity and fulfil their use within the body, it would be very unlikely that you would experience hypervitaminosis with carotenoids, as your body will simply not convert them to retinoids if it doesn’t need them.

What does Vitamin A do in the body?

Vitamin A is involved in a wide range of bodily functions, making it essential for overall health. Its key roles include:

1. Vision:
   Vitamin A is crucial for maintaining good eyesight, particularly in low-light conditions. It helps produce rhodopsin, a pigment in the retina that allows you to see at night. A deficiency in vitamin A can lead to night blindness and, in severe cases, even total blindness. The legend of “carrots help you see in the dark” is based off of this fact; British propaganda leaked to the Germans in WWII suggested the reason that the Allies were able to accurately target the enemy in the dark was due to their consumption of carrots, to throw them off of the scent when it came to the radar which was actually the reason they were so accurate!
2. Immune function:
   Vitamin A supports the immune system by maintaining the integrity of the skin and mucous membranes, which act as barriers to infection. It also plays a role in the production and function of white blood cells, which help fight off pathogens.
3. Skin health:
   Retinoids promote cell turnover and help keep skin smooth and healthy. This is why many anti-aging skincare products contain retinol, retinal or other retinoids; topical application also works to help maintain smooth and supple skin. Vitamin A also supports wound healing and reduces inflammation.
4. Growth and development:
   Vitamin A is essential for normal growth and development, particularly in children. It supports bone growth, reproduction, and the development of vital organs like the heart and lungs.
5. Antioxidant activity:
   Carotenoids like beta-carotene act as antioxidants, protecting cells from damage caused by free radicals. This can help reduce the risk of chronic diseases like cardiovascular disease and certain cancers.

What happens if you don’t get enough Vitamin A?

Vitamin A deficiency is rare in developed countries but remains a significant public health issue in parts of the world where access to nutrient-rich foods is limited, such as in Sub-Saharan Africa and South-East Asia. Children are disproportionately affected, with approximately 1/3 of children under the age of 5 having the deficiency. This leads to failure to thrive, which causes delayed growth and development in children, and if left untreated, this, along with blindness, can be permanent. Children with Vitamin A deficiency are also more likely to get ill or develop infections, due to a weakened immune system, which can cause further issues.

Image 1: Prevalence of Vitamin A deficiency across the world.

Golden rice: the wonder-food which could save the vision of thousands of children

Oryza sativa, or golden rice, is an example of how genetically-modified foods can help prevent malnutrition in areas which are most prone. It is a type of rice which has been modified to not only be high in carotenoids, but also to be resistant to crop failure through blights. It has been deemed as safe for human consumption by the US, Canada, Australia and New Zealand, and if approved in countries which have high rates of Vitamin A deficiency, could be key to helping prevent failure to thrive and blindness. However, at this point in time, no countries are officially using it within their population.

Can you have too much Vitamin A? The story of Mawson and Mertz

While vitamin A is essential, it’s possible to have too much of a good thing. Because it’s fat-soluble, excess vitamin A can build up in the body and lead to toxicity. This is more likely to occur from overconsumption of supplements or animal-based sources of retinoids, rather than plant-based carotenoids.

It is believed that a build up of Vitamin A in the body from consuming dog livers caused the mysterious illness that befell Douglas Mawson and Xavier Mertz on their Australasian Antarctic Expedition in 1912.

Mawson, Mertz, and Lieutenant Belgrave Ninnis, begun their journey to survey George V Land on 10th November 1912. They had spent 5 weeks making fantastic progress, mapping the coastline and collecting samples, when they begun their journey over the Ninnis Glacier. Whilst making their journey, unfortunately Ninnis, along with 6 dogs and most of the parties rations and supplies, fell into a crevasse.

Following the unfortunate accident, Mawson and Mertz turned back immediately, but they were 480km away from their base, and as such, ran out of food fast. This meant they had to improvise; with no other choice, they were forced to kill some of their sled dogs in order to have some sustenance to give them any hope of getting back to base.

The meat was horrible; tough, stringy and sinewy, as to be expected from an animal which is a working dog. Mawson, realising how horrible the meat was, decided to give Mertz the majority of the most appetising part; the liver.

Within a few days, both men experienced significant deteriorations in their condition; dizziness, nausea, stomach pain, jaundice, hair and skin loss, amongst other issues. Mertz experienced the worst of it. He also developed diarrhoea, and had a significant deterioration in his mental state. Violent raging and mood swings followed, to the point that Mawson had to sit on him to prevent him damaging the rest of the supplies they had. Unfortunately, Mertz was too far gone at this point; he experienced seizures, and slipped into a coma and died on the 9th January, 1913.

Mawson survived the ordeal, and despite falling into a crevasse himself, was rescued and lived to tell the tale.

Unbeknownst to the men and the medical community at the time, the men had suffered with hypervitaminosis A, or vitamin A toxicity. The husky liver that was eaten contained huge levels of the vitamin; leading to the symptoms experienced.

• Nausea and dizziness
• Headaches
• Skin irritation
• Joint pain
• Liver damage

Excessive vitamin A intake (which is not fatal) can also lead to more serious complications like bone thinning and birth defects during pregnancy. This is why it’s important to stick to recommended daily allowances and avoid over-supplementing unless advised by a healthcare professional.

Where can you find Vitamin A in your diet?

Vitamin A is found in a wide variety of foods, making it easy to incorporate into your diet.

1. Animal-Based Sources (Retinoids):

• Liver (beef, chicken, or pork)
• Fish liver oils (e.g., cod liver oil)
• Dairy products (milk, cheese, butter)
• Eggs

1. Plant-Based Sources (Carotenoids):

• Carrots
• Sweet potatoes
• Spinach and kale
• Butternut squash
• Red peppers
• Mangoes
• Apricots

To maximise the absorption of carotenoids, it’s a good idea to pair them with a source of fat, such as olive oil or avocado. Cooking vegetables can also help release more beta-carotene, making it easier for your body to use.

How much Vitamin A do you need?

The recommended daily intake of vitamin A varies by age, sex, and life stage. In the UK, the NHS provides the following guidelines:

• Men: 700 micrograms (mcg) per day
• Women: 600 mcg per day

Pregnant and breastfeeding women may need slightly more, so it’s always best to consult with a healthcare provider if you’re unsure.

Final Thoughts

Vitamin A is a powerhouse nutrient that plays a vital role in everything from vision to immune health. While deficiency is rare in the UK, it’s still important to ensure you’re getting enough through a balanced diet rich in both animal and plant-based sources. On the flip side, be mindful not to overdo it, especially with supplements, as too much vitamin A can be harmful.

By including a variety of colourful fruits, vegetables, and nutrient-dense animal products in your meals, you can easily meet your vitamin A needs and support your overall health. So, next time you’re enjoying a plate of roasted sweet potatoes or a spinach salad, remember—you’re not just eating for taste, you’re nourishing your body with one of its most essential vitamins.

Cheers to good health!