Introduction
Beta carotene is a pigment found in orange and yellow-coloured fruits such as apricots; papaya; squash; carrots; sweet potatoes; pumpkin; leafy greens; broccoli; etc. It is responsible for the colouration of various fruits and vegetables. Beta carotene has powerful antioxidant properties. It is also considered a provitamin A carotenoid; which means it is inactivated form of vitamin A and the body can convert it into active vitamin A (retinol). Carotenoids are primarily stored in adipose tissue.
Beta carotene has been considered one of the most promising chemopreventive agents in reducing cancer risk in humans. A study shows that a diet rich in vegetables and fruits contains a sufficient amount of carotenoids required to inhibit the transformation of premalignant lesions in the oral cavity and reduces the risk of developing cancers in specific sites such as the pharynx; colorectum; and breast. The frequency of Breast cancer; lung cancer; and liver cancer is increased with low concentrations of beta carotene. But Long term intake of beta carotene can lead to hypercarotenemia. The most frequently recorded non-serious adverse effect of antioxidant supplements was yellowing the skin in patients supplemented with beta-carotene known as Carotenodermia.
Action mechanism
●Beta carotene antioxidant property; able to inhibit the initiation and promotion of carcinogenesis.
●It also acts by blocking the pathway of carcinogenic processes. Beta-carotene reduces cell growth and induces apoptosis in a variety of cancer cells.
●Enhances macrophage function and natural killer (NK) cell cytotoxicity; and increases T-helper lymphocyte counts.
Beta-Carotene in Cancer
Carotene is the most widely tested antioxidant for cancer prevention. A study shows that beta-carotene does not have substantial anticarcinogenic properties in gastrointestinal cancers. Carotene alone only tends to increase mortality. However; beta-carotene combined with vitamin A and vitamin E significantly increased mortality. A recent study has suggested that beta-carotene might act as a co-carcinogen. There are also harmful effects of beta-carotene. There is no evidence of the beneficial effect of beta carotene in preventing lung cancer. A study done on men only shows that men who received beta carotene were more frequently found to have lung cancer than those who did not receive beta carotene.
The reduced risk of cervical cancer has generally been reported to be related to high intakes of carotenoids. Carotene has shown immunologic activities that prove to have essential functions for cervical disease through the antioxidant defence.
Growth-inhibitory effects of beta-carotene in the colon and prostate cancer cells have been reported. The study reveals that beta carotene may not be an active cancer-inhibiting component of fruits and vegetables, or the intake of beta carotene may be only a nonspecific marker for lifestyles that protect against cancer. There is a possibility that beta carotene may have harmful as well as beneficial effects.
In smokers who also consume alcohol; b-carotene supplementation promotes pulmonary cancer and; possibly; cardiovascular complications. Retinol and beta-carotene therapy must be considered when formulating treatments to correct vitamin A deficiency; especially in drinking populations.
Beta-carotene in other diseases
Several studies revealed that beta carotene supplementation increases specific immune cells in HIV patients.
A study confirmed that smokers and obese women had lower plasma concentrations of carotenoids. We also found that plasma; carotene; and lycopene were positively associated with LDL (low-density lipoprotein) cholesterol. Plasma lycopene is positively associated with Haemoglobin and inversely associated with HDL(high-density lipoprotein) cholesterol, and plasma-carotene is inversely associated with CRP (c-reactive protein).
Inverse associations were found between cataracts and blood antioxidants.
Oxidative stress by free radicals has been seen in diabetes pathogenesis, and thus antioxidants could protect against diabetes
