Vitamin A is an essential vitamin for human health and is a fat-soluble vitamin that is naturally found in many foods. It is needed for:
- Vision,
- The immune system,
- The reproductive system
- Helps maintain the:
- Heart,
- Lungs,
- Kidneys, and
- Other organs of the body
The first type of vitamin A, called preformed vitamin A is found in meat, poultry, fish, and dairy products. The second type of vitamin A, called provitamin A is found in fruits, veggies, and other plant-based products. The wide variety of vitamin A containing food makes it relatively easy to get the necessary dose, however, vitamin A supplements are also widely available. Most commonly, the provitamin A beta-carotene is added to multi-vitamins, which are very popular.
Recommended Daily Intake of Vitamin A
Acute Toxicity
While vitamin A is needed for proper nutrition and wellness, it can become toxic if too much is ingested. Symptoms of acute vitamin A toxicity include:
- Dry lips,
- Cheilitis,
- Dry oral, ophthalmic, and nasal mucosa,
- Rough skin,
- Rash,
- Headache, and
- Coarse hair
These can result from decreased sebum production, reduced epidermal thickness, and altered barrier function, seen in acute vitamin A toxicity.
Chronic Toxicity
Chronic toxicity of vitamin A can cause bone spurs, calcinosis, and bone resorption, which would then result in hypercalcemia, which is too much calcium in the blood. These symptoms can contribute to osteoporosis and hip fractures. Other symptoms include, headache, nausea, and vomiting. Also hyperthyroidism, renal dysfunction with elevated creatine, and pseudotumor cerebri syndrome can be seen in more extreme cases. Hypertriglyceridemia with elevated LDL levels can lead to acute hemorrhagic pancreatitis and eruptive xanthomas, and elevated serum transaminases can lead to liver damage. There are added potential harmful effects for pregnant women, since vitamin A has possible teratogenic effects. Too high levels of vitamin A during pregnancy can cause the baby to have a cleft lip or palate, and cardiac, thymic, and central nervous system abnormalities.
Safety
Even with these possible adverse effects, vitamin A supplements are not considered dangerous because very high levels are needed for any toxic effects. The upper safe limit for adults is 3,000 micrograms, which is much more than what is normally found in balanced diet.
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