What do sweet potatoes and grapefruits have in common? If you answered that they both contain vitamin A, you are correct. Vitamin A is absolutely vital for a variety of reasons, yet many know almost nothing about it. Did you know that vitamin A is in fact not one vitamin, but a broad group of related nutrients? To start with, there are retinoids, which are found in animal foods, and then there are carotenoids, which are found in plant foods. However, the complexity of vitamin A doesn’t end there.
In the retinoid family we have retinol, retinal, retinoic acid, and retinyl esters. The carotenoids are further broken down into 2 classes, carotenes and xanthophylls. The carotenes consist of alpha-carotene, beta-carotene, gamma-carotene, delta-carotene, epsilon-carotene, and zeta-carotene. In the xanthophyll class we have astaxanthin, beta-crypto-xanthin, canthaxanthin, fucoxanthin, lutein, neoxanthin, violaxanthin, and zeaxanthin. How many of those words did you know before you read them? I’ll bet the answer is ‘not many’.
What Does It Do?
Vitamin A plays special roles in the body and brain. Some of its most important functions are to help form and maintain healthy skin, teeth, soft tissue, mucus membranes, and skin. Sometimes vitamin A is referred to as retinol due to its production of pigments in the retina of the eye. In fact, vitamin A is somewhat synonymous with eye health in general.
Besides vision health, vitamin A plays a key role in support of immune and inflammatory functions. Throughout life, our digestive tract can often become exposed to unwanted substances and unwanted micro-organisms. This is where immune and inflammatory systems come in. Vitamin A helps to make and release antibodies, as well as keeping both systems in equilibrium.
Besides these functions, vitamin A is required for regular cell growth and development. The mechanisms involved are not fully clear yet but retinoic acid is one of the key players involved. Glycoproteins control cellular adhesion and retinoic acid is required for their synthesis. Retinoic acid is also required for the production of red blood cells. Some researchers even hope that they can understand development and growth problems from the synthesis of retinoic acid.
Preformed vitamin A is mainly found in animal products. This means preformed vitamin A can be found in meat, fish, poultry and dairy. Preformed vitamin A is also referred to as retinoids. Retinoids are chemically different from the type of vitamin A found in plants. They also provide different health benefits. Pregnancy issues are closely related to the retinoid form of vitamin A. Then there are the relations to night vision, red blood cell production, and infectious diseases. Retinoid forms of vitamin A are required for simple, normal human function, as well.
The type of vitamin A found in plants is more commonly referred to as carotenoids. Carotenoids perform different functions, such as being involved in antioxidant and anti-inflammatory activities. Interestingly, carotenoid forms of vitamin A can sometimes be converted into the retinoid form of vitamin A. This does not apply to all individuals, however. There are a multitude of factors which may impair a person’s ability to convert the plant form of vitamin A into the animal form. Genetics is one key aspect that may impair conversion. Then there is the use of high dose supplementation, with vitamin D and vitamin A sometimes causing problems. Even an imbalance in gut microbiota can impair the conversion of carotenoids to retinoids.
Though it is interesting to understand the differences between the forms of vitamin A, one does not base their diet solely around individual forms of individual vitamins. Instead, one looks at the big picture as a whole, eating a well-rounded diet that contains many essential vitamins and nutrients. This then brings us to the question of the best foods to eat, which will help in acquiring both forms of vitamin A, and also provide the most bang for your buck, nutrient density wise. It should not come as a surprise to most in the health world that sweet potatoes are one of the best foods to consume, not only in regards to vitamin A, but for overall health benefits.
Sweet potatoes contain over 200% of the daily value of vitamin A, as well as potent doses of vitamin C, copper, manganese, vitamin B6, and other B vitamins. Sweet potatoes can help to regulate blood sugar, as well as help perform antioxidant functions in the body. Sweet potatoes have also been shown to exhibit anti-inflammatory properties. The level of researched detail currently available in the scientific community regarding both of these properties, is truly fascinating.
Sweet potatoes contain genes called IbMYB1 and IbMYB2. These genes help to produce antioxidant activity in the flesh of the sweet potato. Specifically, two enzymes, named catalase (CAT) and copper/zinc superoxide dismutase. (Cu/Zn-SOD). It is interesting to think about all of the enzymatic and molecular activity happening while you are eating what you might otherwise deem an “ordinary” meal!
Besides sweet potatoes, there are many other great food sources of vitamin A. Carrots are another interesting example. Containing over 400% of the daily value of vitamin A in one serving, carrots are also high in biotin, vitamin K, fiber, potassium, and other nutrients. Beta-carotene was in fact named after carrots. This is due to the obvious fact that carrots supply a rich amount of beta-carotene per serving. This may be unique in both food and nutrients, as I can’t recall a single other example of a nutrient being named after a food.
Interestingly, there are many studies regarding the cardiovascular benefits of carrots. In one study, the very color of food helped to show that orange and yellow foods seemed to be the most protective against cardiovascular events. This plays into the adage that one’s diet should be colorful, like a rainbow. The polyacetylenes are another healthful, somewhat unique, benefit to eating carrots. They are phytonutrients made from the metabolism of fatty acids, and the two most well-researched are falcarinol and falcarindiol. These phytonutrients show anti-inflammatory activity, as well as other health benefits.
Unfortunately I do not have the time to delve into all of the unique properties of foods which contain vitamin A. But besides the choices already listed, one can consume spinach, kale, Swiss chard, winter squash, tuna, beef liver, broccoli, herring, eggs, salmon and many other foods to get their daily dose of vitamin A. With all of those choices, it may be hard to believe that some people will want to supplement with vitamin A. But, believe it or not, this is sometimes the case.
Supplementation with vitamin A can occur due to a variety of reasons. A deficiency in vitamin A, though rare in the United States, would be the main reason. One of the first signs of this problem is night blindness. People who drink lots of alcohol may also become deficient in vitamin A. It can get confusing, however, as there are many different forms of vitamin A available to supplement with. There is retinyl acetate, retinyl palmitate, beta-carotene, or some form of combination of these choices. Ask your doctor before supplementing, and listen to their advice, as too much vitamin A can be toxic.
Since we covered deficiencies of vitamin A, it is also important to understand that one can have too much vitamin A. Since the vitamin A that comes from animals is fat soluble, it is fairly easy to take too much supplemental vitamin A. Confusion, hair loss, and many other negative side effects can occur when one takes too much. Taking plant-based precursors, like beta-carotene, is one tip that can help you avoid toxic amounts of vitamin A.
I hope you’ve seen that there is a lot more to vitamin A than most realize. A seemingly random and small element to your diet – can have a big impact on your health. From vision, to antioxidant effects, to hair loss, vitamin A plays an important role in many physiologic functions. There are clearly a multitude of fairly easy ways to get enough vitamin A in the diet, and hopefully I’ve made that clear.
Eating one sweet potato a day is in fact enough to do the trick. When you add eggs, liver, spinach, kale and more great foods to the list, it becomes extremely easy to get enough of this essential vitamin. While you may not need to remember all the forms of vitamin A, and all their different health benefits, I hope you’ve learned something, and look at certain foods in an entirely new light.
Do you have questions about vitamin A? Do you eat enough of it? Let me know in the comments!