How Much Vitamin A Is Too Much?

What is Vitamin A?

Vitamin A is an essential nutrient also known as retinol. It is important for maintaining immunity, eye health, reproduction, and growth.¹ 

It is common for children and pregnant women to be vitamin A deficient, which can cause prolonged infections, anaemia and blindness.¹ 

To combat this, more individuals are beginning to take vitamin A/retinol supplements. The question is, how much vitamin A do you need? And, how much is too much?

The role of vitamin A

Vitamin A is a nutrient necessary for a healthy life. The benefits and roles of vitamin A are extensive as it is involved in many processes within the human body.

Benefits of vitamin A

The benefits of vitamin A include:^2,4

• Helping your immune system

Taking enough vitamin A helps your immune system to fight off infections. This means vitamin A helps to prevent infection as well as speed up how quickly you recover from an infection.¹

• Helping vision in dim sources of light and general eye health

The common phrase ‘carrots help you see in the dark ’ has some truth to it! Vitamin A is an essential component for the synthesis of a light-sensitive protein in the eye called rhodopsin that responds to light entering the eye.⁴ 

• Cell communication and cell growth

Vitamin A is necessary for cells to communicate with one another, as well as helping your cells to divide into more specialised cells fit for a specific purpose in a process called differentiation. 

• Helping maintain the skin, as well as the mucosal lining of some body parts 

Retinol (vitamin A) is a commonly used ingredient in skincare products due to its anti-aging properties. It is generally used in the form of retinoic acid and works by stimulating the synthesis of collagen to reduce the appearance of wrinkles and sun damage. Vitamin A also contains antioxidants, which are good for your skin.⁵

These mucosal linings of body parts include that of the nose and intestines. The mucosal lining of the nose acts as a further defense against pathogen entry and infection as part of your primary immune response.

Deficiency

Pregnant women require more vitamin A for normal fetal growth and development, meaning they are at an increased risk of deficiency.⁴ If a mother has insufficient vitamin A levels during lactation, the baby will not receive the required vitamin A levels and would also consequently  develop vitamin A deficiency.

Children and infants are at the highest risk of vitamin A deficiency due to either:²

• A low intake of vitamin A-rich foods
• Low absorption rates (Malabsorption) of vitamin A from foods due to certain diseases/disorders such as cystic fibrosis
• A combination of the two

Sources of vitamin A 

Important natural sources of vitamin A you can obtain from your diet include:²

• Liver or liver products (e.g. pâté)
• Eggs
• Cheese
• Oily fish

A more extensive list of foods high in vitamin A can be found at Havard Nutrition Sources.

Another way to increase your vitamin A intake is by consuming foods rich in beta-carotene. Beta-carotene is an example of a pigment in plants called provitamin A carotenoids. Foods rich in beta-carotene can be converted to vitamin A during metabolism in the intestine.

Examples of foods rich in beta-carotene are:

• Vegetables such as carrots, sweet potatoes and leafy greens
• Fruits such as apricots and mango

As a general rule, fruits and vegetables with red, orange and dark green colouration are rich in beta-carotene.

Vitamin A can also be obtained from dietary supplements in the form of preformed vitamin A. It is important to note that antioxidants in supplements are not as plentiful as in natural sources of vitamin A.

How much vitamin A is too much

The upper threshold of vitamin A that you may consume safely is 3 mg per day (or 3,000 mcg) however this volume is not recommended as it can have side effects and interfere with vitamin D.³ 

Vitamin supplements are in the form of tablets or capsules. You can buy them at your local health food shop, pharmacy or supermarket. It is important to consult with your GP before you take vitamin A supplements if you are trying to get pregnant, are pregnant, or are of an older age.

Recommended dosage

The daily recommended dose for individuals between the ages of 19-69 are:^2,3

• 600-700 micrograms per day for females
• 700-900 micrograms per day for males

This daily allowance can be obtained through diet or supplements. If you are able to do so, it is recommended to obtain vitamin A through diet alone. Before beginning to take vitamin A supplements, it is advisable to check with a health professional.

If you are a post-menopausal woman or an older man it is recommended to regularly consume less than 1.5 mg of vitamin A per day. This is because these individuals are at an increased risk of osteoporosis.² To maintain this, it is important to remember:

• You should avoid eating liver or liver products more than once per week. For pregnant women, liver should be completely avoided
• If you eat liver/liver products you are advised to not take vitamin A supplements including fish liver oil tablets
• Be aware that multivitamins include vitamin A. Do not take vitamin A supplements or eat liver when taking a multivitamin

Signs of overconsumption 

Serious overconsumption of vitamin A can cause hypervitaminosis A if the dosage of vitamin A is over 100 times the recommended daily allowance (RDA). This is also known as vitamin A toxicity. As vitamin A is fat soluble, it can be stored within the body for long periods of time meaning the vitamin A levels can continue to rise.

Potential signs and symptoms of hypervitaminosis A include:⁴

• Nausea
• Dizziness
• Blurred vision
• Headache
• Coordination issues

Despite being a vitamin, overconsumption can still cause serious side effects. Pregnant women or women lactating should take caution with vitamin A supplements as high dosages can cause birth defects and abnormalities.⁴ Dosages should not exceed 1.5 mg per day.

However, it is completely safe for these individuals to consume higher levels of provitamin A carotenoids such as beta-carotenes in their diet. The only side effect may be a yellow-orange colouration of the skin that disappears with the reduction of beta-carotene in the diet. 

Complications 

If an individual repeatedly overconsumes vitamin A, they may develop chronic hypervitaminosis A. The side effects of this condition include painful muscles and joints, liver damage, depression and dry skin.⁴ 

Over many years, overconsumption of vitamin A may weaken your bones meaning they are more likely to fracture.² Those already at risk of osteoporosis may experience some severe consequences. Therefore it is important to control your dose and avoid consuming over the daily recommended allowance. 

Remember, all things in moderation are still true for vitamins.

Summary

• Vitamin A is an essential nutrient for the regulation of immune function, eye health, cell growth and many other bodily functions
• Sufficient levels of vitamin A can be obtained from food alone for most people but you may take supplements if you require them
• The daily dosage of vitamin A supplements should not exceed 1.5 mg
• Taking too much vitamin A can cause some uncomfortable side effects
•  Controlling vitamin dosage is just as important as with other medications