Vitamin A: The Ultimate Guide
You often hear about vitamin C; most of us know exactly where to find it and why it’s good for us. It’s even likely that the mere sight of the words immediately evoke the image of an orange in your mind’s eye. Thanks to the COVID-19 pandemic, vitamin D has also enjoyed some time in the spotlight, due to its purported capacity to help defend us against the ubiquitous virus we’ve been up against this year. Needless to say, both these vitamins are of crucial importance to ensuring you are receiving the correct amount of nutrients to maintain your health in various ways. Nevertheless, today we’re going to be shedding some light on one of the vitamins that receives less attention than it ought to: vitamin A. For a full overview of this vitamin, what it does, where to find it and how to dose it, you’ll want to keep reading!
What is vitamin A?
Vitamin A is a fat-soluble vitamin that is naturally present in many foods. It is involved in immune function, vision, reproduction and cellular communication. It is an essential component of rhodopsin, a protein that absorbs light in the retinal receptors, making it critical for vision. It also supports the normal differentiation and functioning of the conjunctival membranes and cornea.
There are two different types of vitamin A: preformed vitamin A and provitamin A. Preformed vitamin A is found in meat, poultry, fish and dairy products. Provitamin A is the other type and is present in fruits, vegetables and other plant-based foods. Beta-carotene is the most common type of provitamin A in both foods and dietary supplements.
How is it good for us?
Vitamin A does a number of things to our health. Firstly, it helps to keep our immune system working optimally. It also helps keep our vision sharp, especially in dim lighting (were you ever told to eat your carrots so you could see in the dark? That’s why!).
This vitamin also keeps skin healthy, like the lining of some parts of the body, such as the nose. Furthermore, it helps with reproduction and fertility.
Vitamin A boosts cell growth and differentiation, ensuring the heart, lungs, kidneys and other vital organs function properly.
Where can I find this vitamin?
Good sources of vitamin A include:
Cheese, eggs, oily fish (such as salmon), fortified low-fat spreads, milk and yoghurt, liver and liver products such as liver pâté (a particularly rich source of vitamin A, so if you have liver more than once a week, you may be at risk of having excessive amounts of vitamin A. Pregnant women should also avoid eating liver or liver products). Other organ meats aside from liver are rich in vitamin A (but also high in cholesterol, so eat them in moderation). Green leafy vegetables like kale and rocket, as well as other green, orange and yellow vegetables, such as broccoli, sweet potato and squash are also great sources of vitamin A, along with fruits like melon, apricots and mangos. Dairy products also supply good amounts of vitamin A. Some breakfast cereals do, too.
Vitamin A can also be garnered in your diet by including good sources of beta-carotene, as the body can convert this into retinol. Beta-carotene is mainly found in foods like yellow, red and green (leafy) vegetables such as spinach, carrots, sweet potatoes and red peppers. It is also present in yellow fruit, such as mango, papaya and apricots.
How much vitamin A is the right amount?
The vitamin A content of a food is usually expressed in micrograms (µg) of retinol equivalents (RE).
The amount of vitamin A thought to be necessary for adults aged between 19 and 64 is:
- 700 µg a day for men
- 600 µg a day for women
This dose does change if you are a pregnant or lactating woman. In those scenarios, see the tailored quantities below:
- 770 µg per day for pregnant women
- 1,200 µg per day for lactating teens
- 1,300 µg per day for lactating women
You should be able to get all the vitamin A you need from your diet, for example, by eating five servings of fruits and vegetables per day, which provides about 50% to 65% of the adult recommended dietary allowance (RDA) for vitamin A.
Any vitamin A that your body deems unnecessary for immediate use is stored for future use. This means you do not need this vitamin every day.
Can I overdose on Vitamin A?
There is the possibility of taking too much vitamin A, and high amounts of this vitamin may pose harm to your wellbeing. Research tells us that exceeding an average of 1.5 mg (1,500 µg) a day of vitamin A over a prolonged period (years) may have adverse health effects. So, if you take supplements containing vitamin A, make sure your daily intake from food and supplements does not exceed 1.5 mg (1,500 µg), and here’s why.
Excess preformed vitamin A (usually from supplements or certain medicines) can cause dizziness, nausea, headaches, comas- even death. Too much preformed vitamin A in pregnant women can also cause birth defects in their unborn baby, so women who might be pregnant should not take high doses of vitamin A supplements. As we said before, pregnant women should also avoid foods especially rich in vitamin A for this reason.
Furthermore, excess preformed vitamin A can have significant toxicity (known as hypervitaminosis A). It could also lead to increased intracranial pressure, skin irritation and pain in the joints and bones. Although hypervitaminosis A can be caused by excessive intake via food, the condition usually takes place when one consumes too much preformed vitamin A from supplements or therapeutic retinoids. Chronic excessive vitamin A consumption may mean a person’s tissue levels take a long time to fall after they discontinue their intake, resulting in liver damage that may not be reversible.
High intakes of beta-carotene and other provitamin A carotenoids, however, do not cause birth defects or the other more serious effects that may accompany excess preformed vitamin A. Consuming high amounts of beta-carotene or other forms of provitamin A can give the skin yellow-orange tinge, but this is a harmless condition.
Long-term use of large amounts of vitamin A might also cause symptoms like fatigue, irritability, changes in mental health, stomach discomfort, nausea, vomiting, mild fever and excessive perspiration. For women who have undergone the menopause, excessive vitamin A could increase the risk of osteoporosis and hip fracture.
Can I be Vitamin A-deficient?
Mostly, vitamin A deficiency is not likely, as this vitamin can easily be obtained in your diet. There are, however, some that are more vulnerable to vitamin A deficiency than others; namely, premature infants and infants, young children, pregnant women and lactating women in developing countries, as well as people suffering from cystic fibrosis. The reasons for the vulnerability of these particular groups are numerous: people with cystic fibrosis often suffer from pancreatic insufficiency, increasing their risk of vitamin A deficiency due to their difficulty absorbing fat. Several studies have determined that a significant proportion of patients with cystic fibrosis have vitamin A deficiency. Lactating women in developing countries with vitamin A deficiency have low levels of vitamin A in their breast milk, which are therefore not sufficient to maintain adequate vitamin A stores in infants who are exclusively breastfed, meaning infants also become deficient.
Some of the possible symptoms of vitamin A deficiency may include:
Xerophthalmia and general declination of vision
Xerophthalmia is perhaps the most common symptom of vitamin A deficiency in young children and pregnant women. Indeed, the World Health Organisation (WHO) proposes that 9.8 million pregnant women around the world have xerophthalmia due to vitamin A deficiency. Xerophthalmia is an eye condition that renders a person unable to see in low light. In extreme cases, vitamin A deficiency can lead to total blindness or dying corneas, which are characterised by marks called Bitot’s spots.
Dry eyes, or an inability to produce tears, is another telling sign of vitamin A deficiency. Young children in developing countries, whose diets are often lacking in vitamin A, are most at risk of developing dry eyes. Studies have found that children and infants taking vitamin A supplements for a prolonged period had decreased prevalence of dry eyes by 63%.
Vitamin A is important for skin regeneration; it stimulates the creation and repair of skin cells. It also helps fight inflammation that causes skin conditions. As such, not enough vitamin A may be responsible in some cases for the development of eczema and other inflammatory skin conditions. Indeed, studies have demonstrated the efficacy of one prescription medication given to eczema sufferers which happened to contain vitamin A, known as alitretinoin. One trial that focussed on this drug showed that there was a 53% reduction in symptoms of chronic eczema.
Due to vitamin A’s capacity to promote skin regeneration and fight inflammation, it may help prevent or treat the proliferation of acne. A number of studies have noted a correlation between low vitamin A levels and the presence of acne. In one study, vitamin A levels in those with acne were considerably inferior to those without the condition. Topical and oral vitamin A, then, may treat some cases of mild to moderate acne, as shown in one piece of research, where creams containing vitamin A reduced the number acne spots by as much as 50%. In fact, one of the common oral acne medications for severe cases is isotretinoin or Accutane. This medication is made up of vitamin A but does have side effects like mood changes and potential birth defects.
Vitamin A deficiency has also been linked to worse or slower wound-healing, such as wounds from injury or surgery. Since vitamin A promotes the creation of collagen, an important component of healthy skin, a lack of such will leave your skin without the tools to repair itself. Research indicates that both oral and topical vitamin A has the ability to strengthen skin. Moreover, one study investigating rats saw that oral doses of vitamin A improved collagen production, while another found that treating skin with topical vitamin A appeared to prevent wounds associated with diabetes.
Research in humans has shown similar results.
Increased throat and chest infections
Recurrent chest and throat infections may be one sign of vitamin A deficiency. It's possible that vitamin A supplements could help reduce these, as illustrated in one study that looked at underweight children in Ecuador with respiratory infections. Its findings were substantiated by a study of elderly people, which found that high blood levels of the provitamin A carotenoid beta-carotene may shield them against respiratory infections.
There are conflicting beliefs about this vitamin, though. Some studies contest that vitamin A supplements help with chest and throat infection recurrence, asserting that this vitamin actually increases susceptibility in children.
Since vitamin A is important for the full and proper development of the human body, lack of such could result in stunted growth.
Several studies conducted on children in developing nations have shown that vitamin A supplements, alone or with other nutrients, can improve growth. However, it appears that in terms of growth, vitamin A supplements produce better results when taken in collaboration with other nutrients, rather than in a pure form.
Issues with fertility and conceiving
Vitamin A deficiency may be contributing to your struggle to conceive. Indeed, vitamin A is necessary for healthy reproductive functioning, so a deficiency could lead to infertility in both men and women. Vitamin A deficiency has also been cited in connection with recurrent miscarriage. Furthermore, studies on rats show that female rats with vitamin A deficiency have difficulty getting pregnant and may form embryos with birth defects.
It has been found that there are higher levels of oxidative stress in the bodies of infertile men. As such, there is a greater need for antioxidants, and Vitamin A is among the nutrients that function as an antioxidant in the body.
Vitamin A supplements
Vitamin A is available in the form of dietary supplements, usually as retinyl acetate or retinyl palmitate (preformed vitamin A), beta-carotene (provitamin A), or a combination of preformed and provitamin A. Most multivitamin-mineral supplements contain vitamin A. Dietary supplements that are exclusively vitamin A are also available.
The dangers of vitamin A supplements: Drug interactions
As with most supplements, you should take extra care if you are on medication for a health condition, as vitamin A is included in a number of prescription medications already, and so taking both could mean your vitamin A levels become too high. Some medications also leave you vulnerable to certain side effects, which may be exacerbated by regular vitamin A intake. Some of the medications that vitamin A supplements may interact with are as follows
- Orlistat (Alli®, Xenical®), a weight-loss drug, can reduce the absorption of vitamin A, causing low blood levels in some people.
- Prescription medications make use of several synthetic forms of vitamin A, such as in the psoriasis treatment acitretin (Soriatane®) and in bexarotene (Targretin®), a treatment that helps with the skin effects of T-cell lymphoma. These medications, combined with a vitamin A supplement, can cause a dangerous increase of vitamin A levels in the blood.
- Medications for skin conditions (Retinoids) interact with vitamin A. Taking vitamin A pills alongside these medications for skin conditions could result in too much vitamin A, as some medications already contain vitamin A.
- Antibiotics (Tetracycline antibiotics) interact with vitamin A. Taking very large amounts of vitamin A, with some antibiotics, can increase the likelihood of a serious side effect called intracranial hypertension. Some of these antibiotics are demeclocycline (Declomycin), minocycline (Minocin), and tetracycline (Achromycin). Taking normal doses of vitamin A along with tetracyclines, however, doesn't seem to cause this problem. Avoid taking large amounts of vitamin A if you are on a course of antibiotics.
- Hepatotoxic drugs (medications that can harm the liver) interact with vitamin A.
Consuming large amounts of vitamin A might harm the liver, and large doses of vitamin A combined with medications that might also harm the liver can increase the risk of liver damage. Avoid large amounts of vitamin A if you are already taking a medication that may harm the liver.
- Warfarin (Coumadin) interacts with vitamin A. Warfarin is used to slow down blood clotting. Large amounts of vitamin A can have the same effect. Taking both vitamin A and warfarin (Coumadin), then, can further slow blood clotting and increase the chances of bruising and bleeding. Ensure your blood is checked regularly and your dose of warfarin is assessed and changed if necessary.
Remember: always talk to a doctor if you are worried about a medication clash. Your doctor will know what cannot be taken in conjunction with your medication.
How can vitamin A help us long-term?
This vitamin could help us ward off some chronic health conditions, such as:
Cancer: Those who eat a lot of foods rich in beta-carotene might have a lower risk of certain kinds of Cancer, like lung cancer or prostate cancer. Studies to date have not shown any compelling evidence that vitamin A or beta-carotene dietary supplements can help prevent cancer or decrease the likelihood of dying from this disease. By contrast, studies seem to show that smokers who take high doses of beta-carotene supplements actually have an increased risk of lung cancer.
Age-Related Macular Degeneration (AMD) is the loss of our central vision as we get older and is one of the most common reasons for vision loss in elderly people. A supplement containing a blend of antioxidants, zinc and copper with or without beta-carotene has demonstrated the potential to slow down the rate of vision loss in people with AMD who are at high risk of developing advanced AMD.
Measles. When children with vitamin A deficiency contract measles (which only tends to happen in developing countries), the disease may be more severe. Supplements with high doses of vitamin A are believed to reduce fever and diarrhoea caused by measles. These supplements can also reduce the risk of death caused by measles among children living in third-world countries, where vitamin A deficiency is common.
Unlike some of the other vitamins, fortunately, vitamin A is not hard to come by in regular diets, meaning deficiencies are not so common and the need for supplements is relatively rare, compared to, say, vitamin D. That said, if you do feel you may be deficient, it is certainly worth checking it out with your GP. We always recommend having that all-important conversation with a professional before self-prescribing vitamin A, especially given the potential long-term health effects of chronic use.
In the meantime, don’t forget to eat your broccoli!