These naturally occurring colorful compounds have gained quite a reputation in the health world. Between 500 and 600 carotenoids have been identified; most of them are found in fruits and vegetables, but only a handful are found to any significant degree in your body. The major ones are alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein, lycopene, and zeaxanthin.
All have antioxidant capabilities that protect cells from free radical attack, which has been linked to aging, cancer, atherosclerosis, cataracts, age-related macular degeneration, and a whole host of degenerative diseases. Both animal and human studies suggest that carotenoids also enhance the immune system. There are currently no officially recommended intakes for any of the carotenoids.
Three of the carotenoids mentioned here -- alpha-carotene, beta-carotene, and beta-cryptoxanthin -- are converted by the body to vitamin A. Their role as vitamin A precursors is independent of their role as antioxidants. If you take more than 30 milligrams of carotenoids a day, you may notice your skin turning a yellowish-orange color. It's harmless and will disappear if you cut back on your intake.
Whether you take supplements or choose to get your carotenoids from food, take them with a bit of fat; for example, have orange juice along with breakfast or have pasta sauce with olive oil. Because carotenoids are fat-soluble, the body absorbs them better when oil is in the mix. They are destroyed by light and oxygen, so sliced or cut fruits and vegetables can lose some carotenes if they are stored.
Strange though it may seem, many carotenoids are actually made more available when the carotenoid-containing food is cooked. That's because some of the carotenoids are trapped within the plant cell walls, and cooking breaks them open, releasing the carotene inside.
A lesser-known relative of the more famous beta-carotene, alpha-carotene is found in many of the same foods, mainly fruits and vegetables. Though not as extensively studied as beta-carotene, it has been linked to a reduced risk of lung cancer.
In fact, some researchers believe that earlier analyses may have misidentified beta-carotene as the beneficial compound reducing disease risk, when in fact it was alpha-carotene. There is no recommended intake for alpha-carotene, but the box above lists some of the richest sources of the carotenoid.
The most well-known of the carotenoid clan, beta-carotene has the greatest vitamin A potential. It is also the most widely studied of the carotenoids. A great deal of research has linked high intakes of foods rich in beta-carotene with reduced risk of several kinds of cancer, including cancer of the skin, cervix, uterus, mouth, stomach, lung, and bladder.
It also appears to increase the activity of natural killer cells, specialized cells of the immune system that help protect against infections and cancer. There is, however, a sour note among all the good news. A few years ago, two clinical trials testing synthetic beta-carotene supplements actually found an increased risk of lung cancer among smokers and former smokers. Would natural beta-carotene, such as that found in foods, have made a difference?
No one knows for sure. What we are sure of is that most of us are getting little beta-carotene in our diets. One estimate says that the average daily intake is only about 1.5 milligrams (mg) a day. While no official recommendations for intake have been made, some experts have suggested that a good goal to strive for would be an intake of 6 mg a day. No safe upper limit has been set for beta-carotene.
However, two large studies found that taking 20 to 30 mg a day for several years actually increased the risk of lung cancer among smokers. It isn't known whether such high doses might be harmful to nonsmokers. Though beta-carotene is converted to vitamin A by the body, the conversion slows down as beta-carotene intake increases. So, you don't have to worry about getting too much vitamin A if you increase your beta-carotene intake.
Beta-cryptoxanthin is little-known carotenoid that the body can convert to vitamin A and it is probably the least studied of the major carotenoids. But high intakes have been associated with a decreased risk for cervical cancer. There is no recommended intake for beta-cryptoxanthin.
Lutein and Zeaxanthin
Two more of those amazing carotenoid cousins, lutein and zeaxanthin, are found in corn and green, leafy vegetables, such as kale, spinach, broccoli, mustard greens, and collards.
They are the only carotenoids found in the macula of the eye, and it appears that people whose diets contain a lot of lutein-rich foods have as much as a 57 percent lower risk of developing macular degeneration, an eye condition that can lead to blindness, compared to those whose diets contain few.
The antioxidant properties of lutein may help protect the macula from free-radical damage. Research shows that high concentrations of lutein along with zeaxanthin may help prevent macular degeneration and cataracts.
These carotenoids serve as free-radical scavengers and as filters of harmful light that enders the macula. The forms of these two nutrients in the eyes are identical to the forms found in fruits and vegetables.
Tomatoes never looked so good. That's because tomatoes and tomato-based products are the uncontested winners when it comes to lycopene content. Why is that important? Because researchers now believe that lycopene, a lesser-known cousin of beta-carotene, may play an important role in reducing the risk of prostate cancer and heart disease.
A recent review of lycopene research done by a researcher at Harvard University found that high intakes of tomatoes and tomato-based products are consistently associated with a lower risk of several kinds of cancer. The evidence is strongest for cancers of the lung, stomach, and prostate. It is less certain, but still a possibility, that it helps prevent cancers of the cervix, breast, mouth, pancreas, colon, and esophagus.
Lycopene is the main carotenoid in the blood and in the prostate gland. How much is enough? You may need to eat about 5 to 7 servings a week of lycopene-rich foods such as tomatoes, tomato paste, pasta sauce, and tomato juice, though some studies suggest as little as three a week may provide some protection. Other foods with lesser amounts of lycopene include red and pink grapefruit, red peppers, and watermelon.
But you need to take your lycopene with a little bit of fat, which aids in its absorption. Drinking a cup of tomato juice in between meals, for example, may not provide you with much absorbable lycopene, despite the fact that tomato juice is one of the richest sources of the carotenoid. Here's another tip: Cooked tomato products, like tomato sauce and tomato paste, provide more lycopene than raw tomatoes.
That's because heat breaks open the plant's cell walls during cooking or processing, releasing more lycopene. There are also a number of lycopene-based supplements available to choose from. If you just can't stomach tomatoes and decide to go the supplement route, bear in mind that all the research so far has been done with tomatoes and tomato-based foods, not supplements.
Many of the supplements are just concentrated sources of lycopene, with none of the other phytochemicals found in tomatoes that may be important for their cancer and heart-disease fighting powers. Your best bet is to look for a lycopene supplement that contains tomato extract or tomato oleoresin. These should contain the full phytochemical portfolio found in tomatoes.
This naturally occurring plant compound is especially concentrated in raspberries, grapes, and nuts. It is also found in strawberries, pomegranates, and cranberries. Several studies have found that it may possess cancer-fighting potential. Studies suggest it inhibits the growth of tumors and actually triggers cell death in cancer cells.
In the next section, learn about the different types of flavonoid supplements for seniors.