Carotenoids and Human
Health
i.e. Eat your fruits and vegetables!
What are
Carotenoids?
Carotenoids are red, yellow and orange pigments, which are widely distributed in nature and are especially abundant in yellow-orange fruits and vegetables and dark green leafy vegetables. They serve many functions. In plant life they are essential for photosynthesis. They also play a major role in the photoprotection of cells and tissues by neutralizing oxidants. Since a large part of the aging process is felt to be due to oxidation, carotenoids are, therefore, important.
Role in Human Health
The knowledge of the importance of carotenoids in human health is not new. For years it has been known that beta-Carotene plays an essential role as the main dietary source of vitamin A. Deficiency of vitamin A, particularly in the third world countries, accounts for blindness in 250,000 to 500,000 children a year according to estimates by the World Health Organization. More recently, protective effects of carotenoids against serious disorders such as heart disease, cancer and degenerative eye disease have been recognized stimulating intensive research into the role of carotenoids as antioxidants and possibly as regulators of the immune system.
Thus far there have been over 700 naturally occurring carotenoids identified and as many as 50 may be absorbed and metabolized by the human body. Of these, 14 carotenoids have be identified in the human serum. Common carotenoids include Lutein, Zeathanthin, Lycopene, beta-Carotene and alpha-Carotene.
Lutein and Zeathanthin
Lutein and Zeathanthin are found in the retina and compose the macular pigment. They function to protect photoreceptor cells from light-generated oxidants known as free radicals. Because of this they play a key role in the protection of a common form of blindness known as age-related macular degeneration (ARMD). Studies have been conducted demonstrating that the levels of both Lutein and Zeathanthin in the retina can been enhanced with foods rich in these compounds and that these levels correlate inversely with the incidence of ARMD. Dietary sources include kale, mustard greens, spinach, corn, celery, broccoli, lettuce, parsley and green peas.
Importantly, Lutein has recently been shown to be very important in the prevention of heart disease!
Lycopene
Lycopene is the carotenoid that imparts the red and pink colors to many of the fruits and vegetables we eat. It like the other carotenoids is a powerful antioxidant and displays chemoprotective properties. Serum levels have been inversely related to the risk of pancreatic, cervical and prostate cancer. More recently, serum levels have been shown to be inversely related to the risk of heart disease as well. Dietary sources of lycopene include tomatoes and tomato products, apricots, pink grapefruit, guava, skin of red grapes, papaya and watermelon.
beta-Carotene
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.
alpha-Carotene
alpha-Carotene is similar to beta-Carotene in its biologic activity with the exception that it is a more potent antioxidant and smaller amounts are converted to vitamin A. Serum levels are generally between 10 and 20% of beta-Carotene levels and like beta-Carotene are inversely associated with cancer. Dietary sources are much the same as for beta-Carotene.
Effects of
preparation and differences in absorption
Cooking: Cooking reduces the carotenoid content of food, but also disrupts cellular membranes and liberates nutrients. Carotenoids are, therefore, absorbed more efficiently from cooked versus uncooked foods.
Drying: Since dried fruits contain little water, they are by weight much higher in carotenoids than fresh fruit.
Processing: Processing food as in tomato juice releases nutrients as well. The lycopene content on a weight basis in tomato juice is over twice the content of raw tomatoes.
Supplements versus purified sources: Serum levels of beta-carotene were almost 20% higher in persons who consumed purified beta-carotene in a capsule compared to those ingesting an equivalent amount from cooked carrots.
Summary
In summary, the two epidemics in America today, heart disease and cancer, are to a large degree nutritionally related. Americans today are consuming less fruits, vegetables and whole grains than at any other time in history. It is my sincere hope that an increase in public awareness of the importance of proper nutrition will lead to changes in dietary habits that will have a significant positive impact on the health of all Americans. Now….eat your fruits and vegetables!
