Carotene is a general name for biochemical compounds that play an important role in photosynthesis, and it has two well-known forms: alpha carotene and beta carotene. It can only be synthesized by plants. Other forms of carotene include delta, epsilon, gamma and zeta. These forms are all made up of hydrogen and carbon molecules, and are therefore called hydrocarbons. They do not contain oxygen, and this makes them hydrophobic, which means they “dislike” water. Therefore, all forms of carotene are insoluble in water, but soluble in fat. Three carotenes–alpha, beta and gamma–are also called provitamins, because your body can process and turn them into vitamin A.
Structure and Occurrence
Alpha carotene and beta carotene differ in the position of double bonds in their ring structures. Alpha carotene is less common than beta carotene. In fact, when a fruit or vegetable appears more orange, it has more beta carotene than alpha carotene.
Amount Converted into Vitamin A
As mentioned, both alpha carotene and beta carotene can be converted into vitamin A by the body. Vitamin A, also called retinol, is important for maintenance of visual acuity. According to research, intake of 1 microgram beta carotene dissolved in oil is equivalent to 0.5 microgram retinol, 1 microgram beta carotene from the diet is equivalent to 0.083 microgram retinol and 1 microgram alpha carotene from the diet is equivalent to 0.042 microgram retinol. Alternatively, these can be expressed in retinol activity equivalent (RAE).
If you consume alpha carotene in your diet, you will have to eat about 24 micrograms of alpha carotene or 12 micrograms of beta carotene in order to gain 1 microgram RAE. If you are a male, you need at least 900 micrograms vitamin A daily, while if you are a female, you need at least 700 micrograms. If you do a conversion of these amounts, a man would need 10,800 micrograms of dietary beta carotene or 21,600 micrograms of dietary alpha carotene. A woman would need 8,400 micrograms of dietary beta carotene or 16,800 micrograms of dietary alpha carotene to satisfy the recommended daily allowance of vitamin A.
Vitamin A Deficiency
Due to their conversion to vitamin A, both alpha carotene and beta carotene are important for the prevention of vitamin A deficiency, which could lead to blindness. These carotenes serve as powerful antioxidants. They also appear to boost the immune system, and help the body fight against foreign agents such as bacteria and viruses.
Where to Get Alpha Carotene
Alpha carotene is found in different vegetables and fruits such as carrots, spinach, collard greens, turnip greens, broccoli, tomatoes, cilantro, green beans, apples and avocados. Beta carotene is also found in green plants, vegetables and fruits such as apricots and cantaloupes. Consuming foods rich in alpha carotene is good for you. A tip is that you should eat these foods in the presence of dietary fat, because they are fat soluble and are absorbed better with fat. If you are taking cholesterol-lowering drugs, such as cholestyramine, your absorption of carotenes may become impaired. Therefore, avoid taking these drugs together with eating carotene-rich foods.