What can high-carotenoid foods do for you?
- Protect your cells from the damaging effects of free radicals
- Provide a source of vitamin A
- Enhance the functioning of your immune system
- Help your reproductive system function properly
What events and lifestyle factors can indicate a need for more high-carotenoid foods?
- Smoking and regular alcohol consumption
- Low intake of fruits and vegetables
Food sources of carotenoids include carrots, sweet potatoes, spinach, kale, collard greens, and tomatoes. To maximize the availability of the carotenoids in the foods listed above, the foods should be eaten raw or steamed lightly.
For serving size for specific foods, see Nutrient Rating Chart below at the bottom of this page.
What are carotenoids?
Carotenoids represent one of the most widespread groups of naturally occurring pigments. These compounds are largely responsible for the red, yellow, and orange color of fruits and vegetables, and are also found in many dark green vegetables. The most abundant carotenoids in the North American diet are beta-carotene, alpha-carotene, gamma-carotene, lycopene, lutein, beta-crpytoxanthin, zeaxanthin, and astaxanthin.
What are the functions of carotenoids?
Preventing Vitamin A Deficiency
Until late in the 20th Century, the functions of carotenoids were discussed only in terms of their potential vitamin A activity. Certain members of the carotenoid family, approximately 50 carotenoids of the known 600, are called "provitamin A" compounds because the body can convert them into retinol, an active form of vitamin A.
As a result, foods that contain carotenoids can help prevent vitamin A deficiency. The most commonly consumed provitamin A carotenoids are beta-carotene, alpha-carotene, and beta-cryptoxanthin, but gamma-carotene and beta-zeacarotene also have provitamin A activity.
Antioxidant & Immune-Enhancing Activity
In recent years, carotenoids have received a tremendous amount of attention as potential anti-cancer and anti-aging compounds. Carotenoids are powerful antioxidants, protecting the cells of the body from damage caused by free radicals. Carotenoids, and specifically beta-carotene, are also believed to enhance the function of the immune system.
Promoting Proper Cell Communication
In addition to their antioxidant and immune-enhancing activity, carotenoids have shown the ability to stimulate cell to cell communication. Researchers now believe that poor communication between cells may be one of the causes of the overgrowth of cells, a condition which eventually leads to cancer. By promoting proper communication between cells, carotenoids may play a role in cancer prevention.
It is also believed that carotenoids participate in female reproduction. Although the exact function of carotenoids in female reproduction has not yet been identified, it is known that the corpus luteum has the highest concentration of beta-carotene of any organ in the body, suggesting that this nutrient plays an important role in reproductive processes.
What are deficiency symptoms for carotenoids?
A low dietary intake of carotenoids is not known to directly cause any diseases or health conditions, at least in the short term. However, if your intake of vitamin A is also low, a dietary deficiency of the provitamin A carotenoids (beta-carotene, alpha-carotene, and beta-cryptoxanthin) can cause the symptoms associated with vitamin A deficiency.
In addition, long-term inadequate intake of carotenoids is associated with chronic disease, including heart disease and various cancers. One important mechanism for this carotenoid-disease relationship appears to be free radicals. Research indicates that diets low in carotenoids can increase the body's susceptibility to damage from free radicals. As a result, over the long term, carotenoid-deficient diets may increase tissue damage from free radical activity, and increase risk of chronic diseases like heart disease and cancers.
Due to low consumption of fruits and vegetables, many adolescents and young adults do not take in enough carotenoids. In addition, if you smoke cigarettes and/or drink alcohol, you may have lower than normal blood levels of carotenoids. Statistically speaking, smokers and drinkers eat fewer foods that contain carotenoids. Also, researchers suspect that cigarette smoke destroys carotenoids. However, if you do smoke or drink, use carotenoid supplements with caution (see Toxicity section).
What are toxicity symptoms for carotenes?
A tell-tale sign of excessive consumption of beta-carotene is a yellowish discoloration of the skin, most often occurring in the palms of the hands and soles of the feet. This condition is called carotenodermia, and is reversible and harmless. Excessive consumption of lycopene can cause a deep orange discoloration of the skin. Like carotenodermia, lycopenodermia is harmless.
High intake of carotenoid-containing foods or supplements is not associated with any toxic side effects. As a result, the Institute of Medicine at the National Academy of Sciences did not establish a Tolerable Upper Intake Level (UL) for carotenoids when it reviewed these compounds in 2000.
However, the results of two research studies indicate that those who smoke heavily and drink alcohol regularly, may increase their chance of developing lung cancer and/or heart disease if they take beta-carotene supplements in amounts greater than 20-30 milligrams per day.
How do cooking, storage, or processing affect
carotenoids?
In certain cases, cooking can improve the availability of carotenoids in foods. For example, the availability of lycopene from tomato products is increased when the foods are processed at high temperatures. As a result, your body absorbs the lycopene in canned, pasteurized tomato juice more easily than the lycopene in a fresh tomato. In addition, lightly steaming carrots and spinach improves your body's ability to absorb the carotenoids in these foods.
It is important to note, however, that in most cases, prolonged cooking of vegetables decreases the availability of carotenoids by changing the shape of the carotenoid from its natural trans-configuration to a cis-configuration. For example, fresh carrots contain 100% all-trans beta-carotene, while canned carrots contain only 73% all-trans beta-carotene.
What factors might contribute to a deficiency of
carotenoids?
Carotenoids are fat-soluble substances, and as such require the presence of dietary fat for proper absorption through the digestive tract. Consequently, your carotenoid status may be impaired by a diet that is extremely low in fat or if you have a medical condition that causes a reduction in the ability to absorb dietary fat such as pancreatic enzyme deficiency, Crohn's disease, celiac sprue, cystic fibrosis, surgical removal of part or all of the stomach, gall bladder disease, and liver disease.
What medications affect carotenoids?
The cholesterol-lowering medications referred to as bile acid sequestrants (Cholestyramine, Colestipol, and Colestid) lower blood levels of carotenoids. In addition, margarines enriched with plant sterols such as Benecol and Take Control, may decrease the absorption of carotenoids. Olestra, a fat substitute added to snack foods, may also decrease the absorption of carotenoids.
How do other nutrients interact with carotenoids?
Beta-carotene supplements reduce blood levels of lutein, suggesting that carotenoids may compete with each other for absorption.
Supplementing your diet with pectin may decrease the absorption of carotenoids.
What health conditions require special emphasis on carotenoids?
Carotenoids may play a role in the prevention and/or
treatment of the following health conditions:
- Acquired Immunodeficiency Syndrome (AIDS)
- Age-related macular degeneration
- Angina pectoris
- Asthma
- Cataracts
- Cervical cancer
- Cervical dysplasia
- Chlamydial infection
- Heart disease
- Laryngeal cancer (cancer of the larynx)
- Lung cancer
- Male and female infertility
- Osteoarthritis
- Photosensitivity
- Pneumonia
- Prostate cancer
- Rheumatoid arthritis
- Skin cancer
- Vaginal candidiasis
What forms of carotenoids are found in dietary
supplements?
In dietary supplements, carotenoids are available as synthetic all-trans beta-carotene, beta- and alpha-carotene from the algae Dunaliella, and mixed carotenes from palm oil.
It is important to note, however, that, due to the inconsistent results from research studies aimed at evaluating the health benefits of beta-carotene supplements, the National Academy of Sciences cautions against taking high dose carotenoid supplements, except as a method for preventing vitamin A deficiency.
What foods provide carotenoids?
The orange-colored fruits and vegetables including carrots, apricots, mangoes, squash, and sweet potatoes contain significant amounts of beta-carotene, alpha-carotene, and beta-cryptoxanthin.
Green vegetables, especially spinach, kale, and collard greens, also contain beta-carotene, and are the best sources of lutein.
Lycopene is found in tomatoes, guava, and pink grapefruit. Salmon, shellfish, milk, and egg yolks also provide carotenoids.
The contribution of spices to available carotenoids in the U.S. diet has increased steadily, making spices a great choice for upping your carotenoid intake. Cayenne pepper and chili pepper are worthy of special mention here.
What are current public health recommendations for
carotenoids?
To date, no recommended dietary intake levels have been established for carotenoids. In an effort to set such recommendations, the Institute of Medicine at the National Academy of Sciences reviewed the existing scientific research on carotenoids in 2000.
Despite the large body of population-based research that links high consumption of foods containing beta-carotene and other carotenoids with a reduced risk of several chronic diseases, the Institute of Medicine concluded that this evidence was not strong enough to support a required carotenoid intake level because it is not yet known if the health benefits associated with carotenoid-containing foods are due to the carotenoids or to some other substance in the food.
However, the National Academy of Sciences supports the recommendations of various health agencies, which encourage individuals to consume five or more servings of fruits and vegetable every day. This level of intake of fruits and vegetables provides approximately three to six milligrams of beta-carotene.
