Beta-carotene: The Precursor for Vitamin A
Beta-carotene is a carotenoid, a highly pigmented (red, orange, yellow), fat-soluble compound. It is naturally present in many plants including common fruits and vegetables. It provides the orange coloration in many green plants, but is especially present in carrots, sweet potatoes, apricots and squash. Grains and oils may also contain beta-carotene. Beta-carotene is a precursor to vitamin A, meaning that this is a substance that the body converts to vitamin A. Even so, a feedback system limits its rate of conversion to the level needed by the body.1
One of the forms of vitamin A is retinol. It is essential for vision. Thus, without it vision will begin to fail. Yet increasing amounts of vitamin A will only improve vision if the body was deficient of retinol in the first place. Retinol can be converted to retinoic acid. This substance is involved in the growth of cells and their differentiation. Retinoic acid is a vital factor in maintaining healthy skin and is thought by many to be useful in dealing with skin conditions including acne. Vitamin A is an antioxidant and helps to reduce free radicals that cause the aging of cells. Claims have been made that it enhances cognition, and reduces damage from sunburn. Nevertheless, these claims have yet to be proven.
For the body to absorb beta-carotene it requires some dietary fat. But the amount of fat necessary is not large and is often provided by the vegetables themselves. The body has the best access to beta-carotene in vegetables when they are cooked, chopped, pureed, or juiced. The Mayo Clinic recommends 5 servings of fruits and vegetables daily to provide 6-8 milligrams of beta-carotene2. Children need 3 to 6 milligrams per day.
Golden rice was developed by Doctors Potrykus and Beyer within the European Union.3 They inserted two genes from a daffodil and one gene from a bacterium into a particular variety of rice (Taipei 309). The effect was to get the grain to contain beta-carotene. The vision of these scientists was to help populations living in poverty, dependent on rice, to have a ready source of beta-carotene, a component lacking in many diets. This type of rice has been grown in many regions of the world and has shown what bio-engineering can do to improve the lives of millions.
Should people be taking beta-carotene supplements? The fact is, most people can get sufficient beta-carotene in their diet by eating the recommended amounts of fruits and vegetables. However, not everyone eats properly and having a ready supply of beta-carotene can come in handy. Although beta-carotene is vital as a precursor to vitamin A, excessive amounts do not seem to impart any beneficial effects. In fact, it can be just the contrary. Some studies have shown that excessive amounts of beta-carotene can contribute to cancer in those at risk for lung or prostate cancer.4. It also may be harmful to those who consume large amounts of alcohol5. For those wishing to take beta-carotene supplements, they are available in both capsule and gel forms. To get the full effect of supplements they should be taken at meal times to ensure the fullest possible absorption.
Beta-carotene overdose and toxicity can be caused by excessive use of supplements or actually ingesting too many carrots or other beta-carotene rich foods. This can cause a condition called carotoderma. This is characterized by dizziness, and yellowing of the skin, especially the palms, hands, and soles of the feet6. Fortunately, there are no known severe symptoms of carotoderma. The condition is completely reversible by merely lessening the intake of beta-carotene. However, carotoderma itself may be an indicator of thyroid problems caused when the thyroid is unable to convert beta-carotene into vitamin A7.
Since beta-carotene imparts a yellow color and is perfectly safe to eat, it is commonly used as a food coloring especially for margarine. The coloring that is commercially available can be made synthetically or it can be extracted from palm oil. It can also be found in algae, or fungi.
Beta-carotene is vital for the functioning of the human body, aiding in vision and skin regeneration. It is also a vital antioxidant. It is found in many fruits and vegetables, and can be taken as a supplement. Those at risk for lung cancer or who consume large amounts of alcohol should be cautious about intake. Excessive consumption can cause carotoderma.
- Feedback System
- Mayo Clinic Beta-carotene Recommendation
- Golden Rice
- US Gov on Cancer Trials
- Carotoderma: Oregon State University