The maximum safe dose of vitamin A in the form of retinol is 3,000 mcg a day. Consuming higher dosages, either from food, or supplements, can cause side effects. We can consume much higher doses of carotenoids, though!
Health benefits of vitamin A
Vitamin A is a fat-soluble vitamin. Most of it is stored in the liver. It’s well-known for its key role in vision. In fact, vitamin A helps absorb light in the retinal receptors, and it supports the normal functioning of the cornea.
In addition, vitamin A is necessary for the immune function, reproduction, and the normal functioning of the heart, lungs, kidneys, and other organs.
What’s the recommended daily intake?
It’s a bit tricky to set a recommended daily intake for vitamin A, as it’s absorbed in different rates, depending on the dietary source. Whatever the source, the body converts all dietary forms of vitamin A into retinol.
Actually, there are two forms of vitamin A:
- preformed vitamin A (retinol)
- provitamin A carotenoids
Retinol is more bioactive than carotenoids, though.
First, vitamin A from dietary supplements containing retinyl esters (a form of retinol), and vitamin A from animal source foods has the highest bioavailability. Retinol is easily metabolized by the body.
On the other hand, 1 mcg of supplemental beta-carotene is equivalent to 0.5 mcg of retinol. Beta-carotene (or provitamin A carotenoid) isn’t absorbed as effectively!
Moreover, beta-carotene from food is absorbed even less. 1 mcg of dietary beta-carotene is equivalent to 0.083 mcg of retinol. It’s 12 times less bioactive than retinol!
Other types of carotenoids, such as alpha-carotene or beta-cryptoxanthin are even 24 times less bioactive than retinol.
Actually, the recommended daily dose for vitamin A is referred to retinol. That’s what the RAE (Retinol Activity Equivalents) stands for.
|1–3 years||300 mcg RAE||300 mcg RAE|
|4–8 years||400 mcg RAE||400 mcg RAE|
|9–13 years||600 mcg RAE||600 mcg RAE|
|14+ years||900 mcg RAE||700 mcg RAE|
Practically, teens and adults need a daily vitamin A dose of:
- 900 mcg from retinol supplements, or
- 900 mcg from animal-based foods (beef liver, fish oils) or
- 1,800 mcg from beta-carotene supplements, or
- 10,800 mcg from plant-based foods
Only pregnant and lactating women need higher vitamin A doses of 770 mcg RAE and 1,300 mcg RAE, respectively.
What’s the maximum safe dosage of vitamin A from supplements?
We should be really cautious with consumed quantities of vitamin A. Vitamin A is a fat-soluble vitamin. Hence, the body stores excess amounts. This may lead to toxicity! Thus, you shouldn’t exceed the maximum safe dosage of vitamin A, unless your physician has advised you otherwise.
Actually, the maximum safe dosage of vitamin A is 3,000 mcg. In most cases, vitamin A toxicity may occur due to the overconsumption of:
- animal-derived foods high in retinol (beef liver and fish oil) or
- dietary supplements.
On the contrary, getting high amounts of beta-carotene, either from supplements, or food, is considered pretty safe, as it’s less bioactive.
How much vitamin A should I take from supplements?
Actually, there are vitamin A supplements containing doses up to 7,500 mcg. This dose is 833% of the recommended daily intake and 250% of the maximum safe dose for adults!
You shouldn’t take so high dosages without consulting your physician. As a rule of thumb, prefer vitamin A supplements with a smaller dose of 1,500 mcg, which is only half of the maximum safe dose.
Side effects of high vitamin A dosages from supplements
Chronic intakes of higher vitamin A doses than the recommended daily intake may lead to increased intracranial pressure, dizziness, nausea, headaches, skin irritation, pain in joints and bones, liver damage, birth defects, and even death.
Also, chronic high dosages of vitamin A may cause reduced bone mineral density, and increased fracture risk! This is particularly important for older people. Especially women, who are at increased risk of osteoporosis.
Moreover, pregnant women and women planning to become pregnant should avoid excess vitamin A intake in the retinol form, which is commonly found in vitamin A supplements, and animal foods, such as beef liver, and fish oil. Retinol doses higher than the maximum safe dosage seem to increase the risk of birth defects and may harm the fetus.
On the contrary, extremely high beta-carotene doses of 30,000 mcg a day, or diets high in carotenoid-rich foods for long periods have not been associated with vitamin A toxicity!
Always consult your physician before taking supplements or changing your diet.
Should I take vitamin A supplements?
Actually, vitamin A deficiency is rare. Healthy people who follow a well-balanced diet probably don’t need to take vitamin A supplements.
Can I get too much vitamin A from diet?
In fact, beef liver contains extremely high amounts of preformed vitamin A. It may cause side effects. You should avoid its regular consumption. Additionally, fish oil is pretty high in retinol. High amounts could cause toxicity.
Milk and egg contain smaller amounts of preformed vitamin A as well.
Practically, you can’t exceed the maximum safe dosage of vitamin A from food. Just avoid eating beef liver and consuming high amounts of fish oil.
Certainly, you could eat high amounts of plant-based foods rich in vitamin A. Plants contain carotenoids, which don’t cause vitamin A toxicity. Actually, there hasn’t been established a maximum safe dose for carotenoids!
Common foods high in beta-carotene and other carotenoids are sweet potatoes, carrots, turnip greens, dandelion greens, beet greens, spinach, kale, lettuce, red peppers, mango, papaya, pumpkin, and winter squash.