Why You Should Care About Vitamin A Overdose

Getting enough vitamin A through diet (preferably) or supplements (carefully) is very important for growing children. In response to a reader comment to last week’s post 5 Things to Know About Vitamin A, I decided to write a follow up post on risks of vitamin A overdose and what you can do to protect yourself or your child.

Risks of vitamin A overdose

According to the 2nd edition of the PDR for Nutritional Supplements, overdose of vitamin A can be very serious in infants or children, and even adults:

A single dose of 25000 IU per kilogram of body weight causes acute toxicity – vomiting, high pressure in the brain and death may occur (recommended daily dose for children less than 4 years old is 2500 IU)
High amounts of vitamin A causes chronic toxicity – early signs are dry rough skin, cracked lips, sparse coarse hair and hair loss of the eyebrows. Late signs are irritability, headache, high level of liver enzyme in blood and liver disease.
Supplemental daily doses of 10,000 IU or more taken by pregnant women have been reported to increase the risk of birth defects.
Too much vitamin A can increase the risk of osteoporosis.

Clearly, you have to be careful not to exceed the recommended dosage and frequency if you are using a vitamin A supplement.

This is another reason why you should mainly rely on getting this nutrient from dietary sources such as carrots, sweet potato, cantaloupe, dairy products, eggs, green vegetables (spinach, collard greens), cod liver oil etc. Except cod liver oil, where it may be possible to get a lot of vitamin A at one time, all of these sources contain moderate amounts of provitamin A. There is no way you can get an overdose by consuming these sources.

Factors affecting vitamin A levels in the body

The amount of vitamin A finally delivered into your body from provitamin A depends on the type of provitamin A (beta carotene, alpha carotene or beta-cryptoxanthin). Carrots, sweet potato, spinach and collard greens are good sources of beta-carotene, which is the more effective form of provitamin A. For example, 1 IU is equal to 0.6 micrograms of beta-carotene and 1.2 micrograms of other mixed provitamin A. Here is a nice table showing amount per serving of vitamin A from different foods. 5 servings of a variety of fruits and vegetables will provide about 3 – 6 mg of beta-carotene a day, enough for maintaining healthy levels of vitamin A in the long run.

Another factor affecting the vitamin A level is the amount absorbed in the small intestine after eating these foods. Efficiency of absorption can range from 9 – 22%. That is, out of the 3-6 mg daily beta-carotene, only about a tenth or a fifth will be absorbed. You can improve it by cooking the food and adding a little fat to the recipe. Absorption can be severely affected by certain medical conditions such as cystic fibrosis (pancreas), Whipple’s disease (small intestine), Crohn’s disease (intestines), ulcerative colitis (large intestine) and chronic liver disease.

Many processed foods are fortified with vitamin A, that is they contain added vitamin A mostly in the form of retinyl palmitate and retinyl acetate. The efficiency of their absorption is much higher, typically around 60-90%.

A third factor that affects the amount of vitamin A levels is the amount stored in the body in the first place. Vitamin A is fat soluble and your body typically stores excess vitamin A in the liver. The half life of vitamin A is about six months, which means that it takes about 6 months for its level to fall down to half of the original levels. That is why it takes a long time of poor nutrition for vitamin A deficiency to show up.

5 actions you can take to be safe

Bottom line: vitamin A is vital for your child’s growth, but there are serious risks of accidental overdose or sustained high levels of vitamin A supplementation. Here are a few things you can do to be safe:

Rely on fruits, vegetables and dairy products to meet your growing child’s vitamin A needs. Check out these simple vitamin A rich recipes.
Reduce or limit processed foods, they are artificially fortified with vitamins (including vitamin A). While one serving of a particular food item may not have a lot of vitamin A, when you add all the processed food together, you can end up consuming a lot of them.
Check the nutrition facts label on your child’s multivitamin if you are using one. Vitamin gummy bears are very popular!
Talk to you doctor about a suitable vitamin A supplement if your child has a medical condition. Do not make this decision yourself and do not pick up any random over the counter supplement yourself.
Get an annual eye exam for both you and your child to catch early eye health problems

Are you using a vitamin supplement for your child? Have you checked the label? Share your thoughts and concerns in a comment below.

Spread the word