Because of their antioxidant activity, it has been suggested that beta-carotene and other carotenoids might protect against atherosclerosis by preventing oxidative damage to serum cholesterol. However, research is conflicting in this area. One thing is clear—carotenoids are significantly less effective in protecting against damage to serum cholesterol than is vitamin E. While feeding people beta-carotene has been shown to prevent oxidative damage to cholesterol in some trials, other studies have reported that beta-carotene does not protect cholesterol from oxidative damage.
Carotenoids are also found in green vegetables but their color is masked by chlorophyll, a more predominant pigment. Foods such as these form a large part of the healthy Mediterranean diet, and while scientists have yet to establish precisely how they protect health, one theory gaining support is that the carotenoids they contain may well provide more than just their color.
Due to the hydrophobic character, carotenoids are associated with lipid portions of human tissues, cells, and membranes. In general, 80-85% of carotenoids are distributed in adipose tissue, with smaller amounts found in the liver, muscle, adrenal glands and reproductive organs. Approximately 1% circulates in the serum on high and low density lipoproteins.
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 are the benefits of carotenoids?
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.
Beta-Carotene provides the major source of vitamin A in the body. Serum levels correlate inversely with a variety of cancers and deficiency is associated with blindness particularly in third world countries. beta-Carotene exhibits potent antioxidant activity and can be found in carrots, pumpkin, papaya, peaches prunes, squash, sweet potato, apricots, cabbage, lima beans, green beans, broccoli, brussel spouts, kale, kiwi, lettuce, peas, spinach, tomatoes, pink grapefruit, honeydew melon and oranges.
Lycopene, a carotenoid found in tomato products, prevents oxidation of low density lipoprotein (LDL) cholesterol and reduces the risk of developing atherosclerosis and coronary heart disease
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.
There is growing evidence linking individual carotenoids withparticular sites in the body, suggesting that the most effective all-round protection comes from a mix of carotenoids, rather than large doses of single carotenoids.
What are the deficiency symptoms of carotene?
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.
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.
Symptoms of high intake
Excessive consumption of beta-carotene can lead to 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.
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.
Experts estimate that the levels of beta-carotene associated with lowest risk of disease are between 8 and 10 mg a day. In sharp contrast, the current average intake of beta-carotene (and lycopene) in Europe is only 2 mg a day. The figures for other carotenoids are less well researched.
Prevalence in Food, Effects of Cooking and Differences in Absorption
Approximately 80-90% of the carotenoids present in green, leafy vegetables such as broccoli, kale, spinach and brussel sprouts are xanthophylls, whereas 10-20% are carotenes. Conversely, yellow and orange vegetables including carrots, sweet potatoes and squash contain predominantly carotenes. Up to 60% of the xanthophylls and 15% of the carotenes in these foods are destroyed during microwave cooking. Of the xanthophylls, lutein appears to be the most stable. Effects of freezing and other storage conditions are unknown.
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.