What is Beta-Carotene?
Beta-carotene is a type of carotenoid found in many foods. Carotenoids are pigments found in plants, algae, and some bacteria. There are over 600 different types of carotenoids, with beta-carotene being one of the more common examples. About fifty carotenoids can be converted into vitamin A. The major carotenoids in humans are beta-carotene, alpha-carotene, lycopene, lutein, and beta-cryptoxanthin. Beta-carotene is yellow to orange to red in color and gives many fruits and vegetables their characteristic bright colors ranging from green to orange, red, and purple. Examples include carrots, sweet potatoes, pumpkins, dark leafy greens, cantaloupe, romaine lettuce, red bell peppers, broccoli, butternut squash, and apricots. The color of beta-carotene in dark green vegetables is masked by the chlorophyll in the plants.
Beta-carotene serves as a provitamin (or precursor) to Vitamin A in the body. This means that the body uses beta-carotene to make Vitamin A. Vitamin A is an important fat-soluble vitamin with a variety of functions in the body. Provitamin A (in the form of carotenoids, with beta-carotene being one of them) is only found in plants, whereas preformed Vitamin A (a group of retinoids) is found in animal foods such as dairy products, fish oils, eggs, and meat (especially liver). The Vitamin A your body makes from beta-carotene does not accumulate in the body to toxic levels, whereas preformed Vitamin A from animal sources can.
All carotenoids, including beta-carotene, serve as antioxidants in the body. Antioxidants are critical molecules that help to protect us from harmful free-radicals by neutralizing them, stopping their damaging chain reactions. This helps to protect us from developing a number of chronic diseases and health issues, ranging from cognitive decline to cancer.
Health Benefits of Beta-Carotene
As mentioned above, Vitamin A (that we can make from beta-carotene) has a number of important functions in the body. It helps cells reproduce correctly, is essential for good vision, helps ward off cancer, protects our brain health, and is needed for proper development of an embryo and fetus during pregnancy. It also helps keep the skin and mucous membranes that line various cavities of the body healthy. Vitamin A also plays a role in growth, bone formation, reproduction, wound healing, and the functioning of our immune system.
Vision. Vitamin A is critical for good vision. It is a component of rhodopsin, a protein that allows the eye to see in low-light environments. It is well established that a deficiency in Vitamin A can lead to night blindness.
Vitamin A is also important for proper functioning of the cornea, the protective outer layer of the eye. When Vitamin A is deficient, eyes produce too little moisture to stay lubricated. Prolonged deficiency of Vitamin A can lead to xerophthalmia, the leading cause of blindness among the world’s children in developing countries, many of which die within a year of losing their sight. In this preventable condition, the eyes become very dry, damaging the cornea and retina, eventually making the eyes themselves very crusty and unable to function. Simply ensuring adequate intake of Vitamin A or beta-carotene-rich foods prevents these serious eye problems and possible death, especially among children.
Furthermore, research shows that those who eat a diet rich in beta-carotene (or Vitamin A) are less likely to develop age-related macular degeneration, and have a lower risk of developing cataracts.
Immunity, Pregnancy Outcome, and Children. Vitamin A deficiency impairs immunity by hindering normal reproduction of mucosal cells. These cells line cavities and openings of the body, including all parts of the digestive tract including the mouth, and also the nose, sinuses, bronchial tubes and lungs, vagina, urethra, and anus. The mucosal cells form barriers helping to prevent infectious microbes from entering the body. When a Vitamin A deficient barrier is damaged by invading microbes, the function of our immune cells (specifically, neutrophils, macrophages, and natural killer cells) is hindered. These cells function in innate immunity. Vitamin A is also needed for adaptive immunity, where the development of T-cells and B-cells are needed to recognize the same invading microbe in the future. In this function, Vitamin A deficiency reduces antibody-mediated responses, reducing our ability to fight the microbe in future infections.
Because of its role in the immune function, Vitamin A deficiency is believed to account for many deaths among infants, young children, and pregnant women around the world. The deficiency lowers the body’s ability to fight infections, leading to respiratory and gastrointestinal infections, slower growth rates and bone development in children, and a lowered rate of survival with serious illness. Simply eating more beta-carotene-rich foods can prevent such tragedies.
Antioxidant Protection. Beta-carotene, like all carotenoids, as an important antioxidant in the body. An antioxidant is a compound that inhibits the oxidation of other molecules, protecting the body from harmful free radical molecules. Free radicals damage the body by robing healthy cells of electrons. This damage can lead to a number of chronic diseases, including cancer and heart disease. Antioxidants are capable of donating electrons to free radical molecules, stopping their destructive damage. In the process, antioxidants themselves are not damaged. Studies have shown that those who eat at least four servings a day of beta-carotene-rich fruits and vegetables have a lower risk of developing cancer or heart disease.
Cancer. A number of research studies have shown an association between diets high in carotenoids, especially beta-carotene, and a reduced incidence of many types of cancer, including cancers of the breast, lung, pancreas, colon, esophagus, cervix and skin (melanoma). The antioxidant properties of carotenoids appear to be the reason for this effect. Also, researchers have found that beta-carotene can lower the rate of chronic diseases in addition to cancer. It is believed that beta-carotene enhances immune cell function, and this effect is especially seen in the elderly.
Healthy Skin. Beta-carotene can help to boost the health of skin. This effect appears to be most likely due to its antioxidant properties. A study reported in the November 2012 issue of the American Journal of Clinical Nutrition reported that an optimal amount of antioxidant nutrients in the skin increases basal dermal defense against UV irradiation, supports longer-term protection, and contributes to overall maintenance of skin health and appearance. However, the researchers noted that dietary antioxidants such as beta-carotene or lycopene can offer some degree of sun protection, although it is lower than that of a typical sunscreen.
Vitamin A compounds (retinoids) regulate the growth and differentiation of many types of cells in the skin. Deficiency leads to abnormal keratinization. Keratinization is a process where cells are filled with keratin, which is a type of protein filament that forms tough, resistant structures such as hair and nails. Keratin also helps to provide structure to and contributes to the function of soft tissues, such as skin and mucosal membranes. Deficiency of Vitamin A leads to abnormal epithelial keratinization, which can show up as dry, scaly, tough skin, and hindered wound healing of damaged tissue.
Cognitive Decline. Researchers have shown that those who have a long-term high beta-carotene intake are far less likely to develop cognitive decline then those who did not consume a lot of beta-carotene. Oxidative stress is believed to be a key factor in cognitive decline. The antioxidant properties of beta-carotene, when ingested in high amounts over time, appear to help prevent the deterioration of brain function, including memory. Antioxidants, like beta-carotene may be helpful in reducing the symptoms of Alzheimer’s disease.
Symptoms of Vitamin A Deficiency
Symptoms of a serious deficiency of Vitamin A include dry eyes (which can lead to xerophthalmia, a condition where the eyes become completely dried and thickened, leading to irreversible blindness), night blindness, diarrhea, skin problems, and impaired immunity. Vitamin A deficiency may also contribute to impaired immune function (leading to gastrointestinal and/or respiratory tract infections), poor pregnancy outcomes, and slow growth and bone formation in children.
Keratinization of the skin can occur in Vitamin A deficiency. Keratin is used by the body to form hair and nails (and feathers in birds). When keratinization of the skin occurs, the skin can develop thick, tough, dry, and scaly areas. Examples include the development of corns and calloses. Keratinization can also occur in mucous membranes in the respiratory, gastrointestinal, and urinary tracts from a severe Vitamin A deficiency.
Should You Take Vitamin A Supplements?
Vitamin A supplements may contain only provitamin A (such as beta-carotene), preformed Vitamin A (usually retinyl palmitate, from animal foods or from fish oils), or a combination of both.
Hypervitaminosis A (Vitamin A Toxicity). Hypervitaminosis A is a condition where a person has too much Vitamin A in their body. This can happen when a person takes too many (preformed) Vitamin A supplements or uses some acne creams over a long period of time.
A wide range of symptoms can be indicative of hypervitaminosis A. If a person has taken a large dose of preformed Vitamin A in a short period of time, symptoms of Vitamin A toxicity can include irritability, drowsiness, nausea, abdominal pain, a feeling of pressure on the brain, and vomiting.
Symptoms of chronic Vitamin A toxicity, where a person has taken preformed Vitamin A over a long period of time where it slowly accumulated in the body include mouth ulcers, bone swelling, cracked fingernails, bone pain, loss of appetite, cracks in the corners of the mouth, vision problems, dizziness, nausea and vomiting, sensitivity to sunlight, skin problems (rough, dry, peeling, or itchy skin), jaundice, hair loss, confusion, or respiratory infection.
Taking large supplemental doses of beta-carotene is generally not recommended. Even though large doses are not known to be toxic to the general public, they can be harmful to specific groups of people, including smokers. Smokers who take high doses of beta-carotene supplements have been found to be at a greater risk of developing fatal lung cancer. This same precaution also applies to individuals who have been exposed to asbestos, or who consume excessive alcohol. In such cases, beta-carotene supplements have been linked not only to lung cancer, but also heart and liver disease. Other than the serious risk to these groups of individuals, taking long-term large supplemental doses of beta-carotene may cause the skin to turn orange-yellow. However, this can be corrected by simply discontinuing the supplements.
A study reported in the February 1999 issue of Free Radical Research found that the greatest antioxidant protection associated with beta-carotene and lycopene (a type of carotenoid found in tomatoes, watermelon, red grapefruits, and papayas), was at the concentration found in foods. When greater amounts (as would occur from supplementation) of these compounds were tested, researchers found the antioxidant protection was quickly lost and may have actually increased DNA damage, taking on a prooxidant effect. Similar effects were found when testing the protection of cellular membranes. This suggests that supplementation with individual carotenoids, such as beta-carotene, significantly raises blood and tissue levels with little to no benefit, and may actually be harmful.
Conversely, some studies such as research reported in 2000 in the American Journal of Clinical Nutrition found that some individuals do not adequately convert beta-carotene from foods into the active form of Vitamin A. This may be due to inadequate enzymes necessary for the conversion, lack of adequate fat intake when beta-carotene is consumed, or a simultaneous zinc deficiency, since zinc is necessary for beta-carotene uptake and its conversion into the active form of Vitamin A.
If a person is not receiving adequate Vitamin A or beta-carotene in their diet, or for some reason cannot adequately convert beta-carotene to active Vitamin A, the Council for Responsible Nutrition considered supplements of 10,000 IU daily of preformed Vitamin A (retinol) to be generally safe. Those who routinely eat liver or organ meats may be getting enough from their diet and should use caution when considering Vitamin A supplements.
Foods That Contain Beta-Carotene
Foods that are rich in color are usually high in beta-carotene. Some examples include dark leafy greens (such as kale, collards, turnip greens, mustard greens, arugula, and spinach), sweet potatoes, carrots, broccoli, asparagus, butternut squash, cantaloupe, red and yellow bell peppers, apricots, peas, papayas, plums, mangoes, raspberries, and romaine lettuce. Some herbs and spices also contain beta-carotene. Examples include paprika, cayenne, chili pepper, parsley, cilantro, marjoram, sage, and coriander.
Effects of Cooking on Beta-Carotene in Foods
There is a great debate on whether it’s better to eat fruits and vegetables raw or cooked. The true answer is not simple. It depends on which nutrient you’re talking about, which food you’re considering, and also which cooking method you’re using vs eating something raw. Carrots are well-known for their high beta-carotene content. Whether they are cooked or raw, they supply plenty of beta-carotene. However, cooking carrots actually increases their beta-carotene content, especially when they are lightly boiled or steamed. This is because cooking opens the cell walls and releases more beta-carotene then when the carrot is raw. This same principal applies to raw vs cooked spinach and Swiss chard. Furthermore, we are able to absorb more of the beta-carotene from cooked carrots than we can from raw carrots, since the cell walls in carrots are softened when cooked, making them easier to digest. If you want to enjoy your carrots raw, chopping them well (and chewing them thoroughly) can help to break down the cell walls, releasing more of the beta-carotene then would be available if they were eaten whole.
Increasing Your Absorption of Beta-Carotene from Foods
A Little Fat Goes a Long Way. Beta-carotene along with preformed Vitamin A, are both fat-soluble nutrients, meaning that they are absorbed along with fats in the digestive tract. Having a little fat in your meal with foods high in beta-carotene (or including a food in the meal that naturally contains some fat) can help to enhance the absorption of the nutrient. This was demonstrated in a study conducted at Iowa State University where graduate students were recruited to eat green salads with tomatoes. Various types of salad dressings were used, ranging from fat-free to traditional Italian dressing made with oil. Students had IV lines inserted so researchers could test blood before and after the meals. Results clearly showed that students who were given fat-free or low-fat salad dressings did not absorb the carotenoids as well as those who ate the traditional dressings.
Cooked vs Raw Foods.
As detailed in the section above (Effects of Cooking on Beta-Carotene in Foods), beta-carotene is better absorbed from foods that have been cooked or finely chopped. This is because beta-carotene is bound tightly within plant cells. Finely chopping or cooking helps to break down the cell walls, releasing the beta-carotene so it can be absorbed more easily during the digestive process. Whether you enjoy beta-carotene-rich foods cooked or raw, be sure to chew them well to further release the beta-carotene from the foods.
Zinc Status. In the March 2003 issue of The Journal of Nutritional Biochemistry, an animal study was reported where subjects were fed the same diets, except for the levels of zinc. One diet was low in zinc, whereas the other contained adequate zinc. The findings demonstrated that a low intake or marginal deficiency of zinc resulted in decreased absorption of beta-carotene. The study suggested that adequate zinc status is an important factor in the absorption of beta-carotene. So, ensuring you have adequate zinc intake will help boost your absorption of the very important nutrient and antioxidant, beta-carotene.
Julia W. Klee (Judi) began her journey enjoying “all things food” in elementary school when she started preparing meals for her family. That love of food blossomed into a quest to learn more and more about health and wellness as related to nutrition. She went on to earn a BS Degree in Food and Nutrition, then an MS Degree in Nutrition. She has taught nutrition and related courses at the college level to pre-nursing and exercise science students. Her hunger to learn didn’t stop upon graduation from college. She continues to research on a regular basis about nutrition as it relates to health. Her hope is to help as many people as possible to enjoy foods that promote health and wellness.