A few weeks ago, I finally got around to finishing up the last of the macronutrients in my new series Nutrition 101. In the past couple of months I’ve gone into detail about carbs, protein, and fat. Now that you’re a pro on those, I figured I’d give you some info about some important micronutrients (aka vitamins and minerals). Where better place to start than at the beginning of the alphabet with good ol’ Vitamin A!
What is Vitamin A?
Vitamin A is a fat-soluble vitamin that can be found in two forms. The first form is called retinol, or pre-formed vitamin A, which is found in animal products, most specifically in animal fat. The second is provitamin A, which includes alpha- and beta-carotene, which is found in colorful fruits and veggies. I will be focusing on provitamin A.
Provitamin A interacts with an enzyme in the body, which converts it to retinal, which is used to perform many functions within the body.
The most commonly known function of vitamin A is the promotion of eye health. Vitamin A helps to build your retinas, which helps your eyes adjust to light, prevents night blindness, prevents cataracts and age-related macular degeneration (two of the leading causes of blindness), and helps to keep your eyes lubricated.
Vitamin A is also great for building up your skin, the lining of your organs, and mucus membranes! This is a major benefit for your immune system, since these are your first line of defense against infections. Vitamin A helps them to stay moist and resist damage, keeping pathogens out!
It also helps out your immune system by contributing to the development of lymphocytes, one of the types of cells that fights off intruders in your body, by stimulating the thymus gland, where the cells are formed.
Vitamin A, especially in the form of beta-carotene, may also help to prevent cancer and heart disease, although it is not proven, since studies have shown mixed results. It has been shown to be especially helpful in the prevention of prostate cancer. Strange fact, though: high amounts of beta-carotene has actually been shown to increase the risk of lung cancer in smokers! Time to kick the habit!
Beta-carotene’s free-radical fighting power doesn’t stop at cancer prevention, it might also be beneficial in the prevention and treatment of rheumatoid arthritis. Patients with rheumatoid arthritis have been shown to typically have lower blood levels of the provitamin, and high amounts of free-radicals in the region of their affected joints.
What are the best sources of vitamin A?
- butternut squash
- sweet potatoes
- red peppers
Dark leafy greens
- beet greens
- collard greens
- green leaf lettuce
- mustard greens
- red leaf lettuce
- turnip greens
How much vitamin A should I be consuming?
According to the National Institutes of Health, females should be consuming about 2310 IUs of vitamin A each day, and males should be consuming about 3000 IUs each day.
Personally, I wouldn’t waste the time and energy stressing over numbers. Just eat a couple of items from the list of good sources each day and you should be set. The majority of the foods on that list contain many times the amount vitamin A (in the form of beta-carotene) that the body requires.
You may be worrying about toxicity when eating so far beyond the requirements of a nutrient, but don’t. High levels of vitamin A are only toxic in the form found in animal products. I remember a professor telling us once that polar bear liver can be quite toxic because of the high levels of vitamin A that it contains! Beta-carotene, on the other hand, can be consumed freely, without concern for toxicity.