Beta carotene
Carotenes, especially beta-carotene, occurs abundantly in the natural plant world. It is estimated that nearly more than 500 different carotenoids such as ?-carotene, α -carotene, lutein, cryptoxanthins, zeaxanthins, etc distributed throughout the plant and algae kingdoms. Although many of these have proven independent functions, around 50 or more can be metabolized to vitamin-A inside the human body. ?-carotene is the most prevalent carotenoid in the plant sources of the food chain and, for the same reason, is also known as pro-vitamin A.
Roughly, 6 μg (range varies widely 6-18 μg) of ?-carotene is equal to 1 RE (Retinol equivalents) or 3.33 IU of vitamin-A.
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| Fruits and vegetables rich in ?-carotene. |
Health benefiting role of beta carotene
Being an important flavonoid compound, beta-carotene has powerful antioxidant functions that help the body scavenge free radicals, and thereby limiting damage to cell membranes, DNA and protein structures in the tissues.
Research studies suggest that dietary intake of foods high in ?-carotene has a positive association with decreased risk of cardiovascular disease as well as oral cavity and lung cancers.
Up on conversion to vitamin-A by the enzymes in the intestinal wall, it performs all the functions of vitamin-A such as visual cycle, reproduction (gametes production), maintenance of epithelial functions, growth and development.
Natural sources of beta-carotene
Almost all the green-yellow-orange (GYO) vegetables and fruits are rich sources of beta-carotene. Some of the common vegetables/fruits/herbs/nuts per 100 g of weight with the highest content of ?-carotenes are:
| Vegetables: | ?-carotene/100 g |
| Brussel sprouts | 450 μg |
| Butternut-squash | 4226 μg |
| Carrots | 8285 μg |
| Collard greens | 3842 μg |
| Endive | 1500 μg |
| French beans | 379 μg |
| Kale | 9226 μg |
| Lettuce | 5226 μg |
| Mustard greens | 6300 μg |
| Pumpkin | 3100 μg |
| Spinach | 5626 μg |
| Sweet potato | 8509 μg |
| Swiss chard | 3647 μg |
| Tomato | 449 μg |
| Watercress | 1914 μg |
| Fruits: | |
| Apricots | 1,094 μg |
| Cantaloupes | 2,020 μg |
| Guava | 374 μg |
| Mango | 445 μg |
| Orange | 71 μg |
| Papaya | 276 μg |
| Persimmon fruit | 253 μg |
| Plums | 190 μg |
| Watermelon | 303 μg |
| Herbs: | |
| Basil | 3,142 μg |
| Cilantro | 3,930 μg |
| Parsley | 5,054 μg |
| Thyme | 2,264 μg |
| Nuts and seeds: | |
| Pistachio | 332 μg |
| Walnuts | 12 μg |
(Source: USDA National Nutrient Database).
Beta carotene supplements?
The benefits of beta carotene supplements, however, has surprisingly unexpected results. Two large-scale prospective randomized studies on high-risk cigarette smokers; 1. ?-carotene (α-tocopherol, ?-carotene (ATBC) Cancer Prevention Study and, 2. the ?-carotene and retinal efficacy trial (CARET) found that ?-carotene supplementation indeed increased the rate of lung cancer in the group.
On the contrary, as mentioned above, high dietary intake of foods rich in ?-carotene is associated with decreased risk of cardiovascular disease and cancers. However, ?-carotene supplementation appears harmful to health, especially in high-risk smokers.
Carotenemia
The consumption of excess plant sources of beta-carotene result in the deposition of carotenes in the skin, and tissues could lead to a harmless condition known as carotenemia. The state recedes in itself once foods rich in carotenes withdrawn from the diet. (Medical disclaimer:
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Further reading and References:
Stanford School of Medicine Cancer information Page- Nutrition to Reduce Cancer Risk.