It’s essential for healthy immune function – and particularly for protection against respiratory viruses such as the seasonal flu. Boost your defences by learning how it works and how to get enough.
It’s an essential nutrient for skin, eye and reproductive health. But to understand why the body needs Vitamin A to stop viral infections from taking hold, we need to understand what it does for our mucous membranes – the tissues that line the nose, eyes, mouth and throat.
Think of mucous membranes as a bit like roadblocks at the body’s key entry points. They cover body cavities exposed to air, and act to keep dirt and pathogens – such as viruses, bacteria, and fungi – out of the body. Some of them secrete mucus, a thick protective fluid that’s difficult for pathogens to pass through.
Certain immune cells also make a point of hanging out in the mucous membranes, ready to attack would-be invaders and send danger signals to the immune network, a team of highly specialised cells, proteins, and tissues that work together to fend off and destroy infections.
“Vitamin A helps to form healthy mucous membranes, which aid in creating a barrier against invaders,” explains Pietermaritzburg-based registered dietitian Tracy Sparrow. A lack of Vitamin A lowers resistance to infection, especially respiratory infection (in the breathing organs) and gastrointestinal infection (in the stomach and intestines). This is because when you’re deficient, your mucous membranes are much less successful at keeping viruses and bacteria out.
As well as helping to form healthy mucous membranes, Vitamin A is necessary for the production of effective immune cells called macrophages, which ‘eat’ microbes and clean up the debris and damage caused by infections. Neutrophils, a type of white blood cell that also works to resolve infections, are also enhanced by Vitamin A.
How do you get enough Vitamin A?
“Although Vitamin A is crucial to health and growth, it’s not usually prescribed – especially to adults – unless there’s a clear deficiency,” says Sparrow. This is because too much Vitamin A (especially in pre-formed, pill form as retinol) can be toxic. Overdoses are especially serious for pregnant women because they can lead to birth defects.
Instead, Sparrow recommends getting your Vitamin A from a variety of food sources, such as liver, eggs, fortified milk and cheese. Your body is also able to convert carotenoids, the pigments found in yellow fruit and vegetables – such as butternut, carrots, pumpkin, sweet potato, mango, peaches and apricots – into readily available supplies of Vitamin A. Broccoli, spinach and kale can provide decent doses of the compounds your body needs to make Vitamin A.
The recommended daily allowance (RDA) of Vitamin A for adults is 700 to 900 mcg daily, which is fairly easy to reach from a diet rich in whole foods. However, Sub-Saharan Africa has some of the highest rates of Vitamin A deficiency in the world. This, says Sparrow, is why South Africa launched a large-scale public health campaign in 2002, giving children periodic supplemental doses of Vitamin A to prevent faltering growth and respiratory infections.
Because Vitamin A is so important to so many immune responses, making a point to get enough will support your body’s fight against all types of infection, including flu.
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Also read: Are you getting enough of these 3 key vitamins and minerals?
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