Carotenoids are a family of over 600 naturally occurring organic chemicals found in plants and some fungus, bacteria and algae. They function as both antioxidants and plant pigments and put the wonderful red, orange and yellow hues in fruits and vegetables. As antioxidants, carotenoids are created by plants to protect themselves from the cell damaging oxidative effects of free radicals found in sunlight. Carotenoids actually separate into two distinct groups – carotenes and xanthophylls.
Carotenes are the orange colored members of the carotenoid family and put the orange hue in carrots, squash, cantaloupe melon as well as many other plants. In fact the colorings of carotenes are not limited to plants but also color animals, mammals and birds. The pink color of lesser Flamingos for example is generated by the abundant amount of beta-carotene rich shrimp in their diets. Flamingos are naturally white in color, and white mixed with orange = pink!
Beta-carotene is one of the most well known carotenes for its ability to be converted to vitamin A in the body. Alpha-carotene is also another carotene that can be converted (although less efficiently) into vitamin A. Carrots are one of the best known food sources of beta-carotene and alpha-carotene and is therefore often referred to as a vegetable ‘high in vitamin A’. Lycopene is another antioxidant that is a carotene but does not convert in vitamin A. However, all carotenes are considered potent disease fighting plant chemicals regardless of whether they convert to vitamin A or not.
Research that has studied the diets of tens of thousands of people show that those with the most carotenes in their diet are generally at a much lower risk of developing cancer than those who have the least in their diets. Alpha-carotene has been shown to be especially effective at protecting us from lung cancer while lycopene is effective at protecting men from prostate cancer.
Xanthophylls are the other branch of carotenoids and include lutein, zeaxanthin and beta-cryptoxanthin. Xanthophylls are yellow based pigments and contribute to the yellow color in leaves as well as the yellow in egg yolks and even the yellow hue in our own fat and skin.
Lutein and zeaxanthin are the only antioxidants that are found in the lens and retina of our eyes where they protect the eye from oxidative damage induced by blue light. This protection helps to delay the aging of the eyes and protect them against eye disease like cataracts and macular degeneration. For this reason lutein and zeaxanthin are a common ingredient in most eye care vitamins.
Beta-cryptoxanthin is the only carotenoid of the xanthophyll family that converts to vitamin A and is also strongly associated with a reduced risk in lung cancer. People with diets high in beta-cryptoxanthin are actually 25% less likely to develop lung cancer than those with a low intake.
Health Benefits of Carotenoids
The health benefits of carotenoids as an overall group relates to all degenerative diseases that result from oxidation. Carotenoids strongly defend our cells from free radicals (the unstable oxygen based molecules that produce oxidation) and as carotenoids are fat soluble they are effective at protecting fat cells in particular. LDL cholesterol (a fat based substance) in the blood stream greatly contributes to the development of atherosclerosis when it is oxidized. This explains why high levels of carotenoids in the blood is a great indicator that a person is at low risk of heart disease. Atherosclerosis is a leading cause of heart disease.
Free radical cell damage is also a well known cause of cancer; such cell damage can mutate the DNA code in cells and develop into tumours.
Food Sources of Carotenoids
Alpha-carotene: carrot juice and pumpkin are the two best sources. Other good sources include carrots (cooked are better than raw), plantains, tomatoes, collard greens and tangerines
Beta-carotene: carrot juice, pumpkin, spinach and sweet potatoes (cooked) are the best sources of beta-carotene. Carrots (cooked are better than raw), collard greens, kale, cantaloupe melon and are good sources.
Beta-cryptoxanthin: pumpkins (cooked) and papayas are great sources. Red bell peppers, oranges, carrots and nectarines are good sources.
Lutein and zeaxanthin: spinach, kale, turnip greens and [ad#Commission Junction-2]collard greens are exceptionally rich sources. Squash, brussel sprouts, broccoli and yellow corn are good sources. These vegetables are a better source when cooked or juiced. Egg yolks are a great source of highly bio-available lutein.
Lycopene: processed tomato products such as tomato paste, tomato puree, tomato juice and tomato soup are by far the best sources of lycopene. Raw tomatoes, watermelon and pink grapefruits are a fair source.
Carotenoids and Digestion
You will notice in the above list of carotenoid food sources that processed foods are actually a better source of carotenoids than their raw and whole counterparts. This can be a little counter intuitive as most nutrients in fruits and vegetables actually get destroyed in the cooking process. So what is the deal?
Carotenoids are deeply embedded in the fibers of the fruits and vegetable in which they are found. So to be more effectively released for digestion, carotenoid rich foods generally need to be processed to ‘break the carotenoids free’. So cooking, pasting and juicing greatly enhance the bioavailability of carotenoids. Carrot juice is a much better source of beta-carotene than raw carrot (although still good). Lycopene is the toughest of the group and tomatoes are by far the most abundant source of lycopene that we know of. Even so the difference in bioavailability of raw tomatoes and processed tomato products is astounding. For example – 1 cup of raw tomato delivers 4.6mg of lycopene, 1 cup of tomato juice provides 22mg of lycopene while 1 cup of tomato paste delivers a whopping 75mg of lycopene!
There is also another factor that greatly enhances the bioavailability of carotenoids and that is fat. Carotenoids are fat soluble compounds so they are digested more easily when consumed with fats or oils. This is one of the reasons that the bioavailability of lutein in egg yolks is much greater than the bioavailability of lutein in raw spinach and kale. Research has shown that adding health fats like olive oil or avocado to salads greatly enhances the amount of carotenoids we will digest from the vegetables in them. For this reason I like to mix a little oil into the fresh vegetable juices I make at home.