How Do These Antioxidant Nutrients Benefit the Body?

By Asst. Prof. Dr. Ratchanee Kongkachuichai, Ajarn Rin Charoensiri, Assoc. Prof. Dr. Apichart Vanavichit, Mr. Siriphat Ruengphayak  Institute of Nutrition, Mahidol University; Rice Science Center, Kasetsart University, Kamphaeng Saen

How do these nutrients benefit the body? Vitamin E is a name covering a group of 8 antioxidants: 4 tocopherols, namely alpha, beta, gamma and delta tocopherol, and 4 tocotrienols, namely alpha, beta, gamma and delta tocotrienol. Alpha-tocopherol is the only form of vitamin E that plays an important role in metabolic processes in the human body, so alpha-tocopherol is found in the greatest amount among the vitamin E forms in the bloodstream and tissues.

Roles and functions of vitamin E The main function of alpha-tocopherol in humans is to act as an antioxidant. Free radicals arise from the human body's own metabolic processes and may also come from the environment, such as cigarette smoke, exhaust fumes and toxins contaminating food. Fats, which are part of the cell membrane, are easily damaged by oxidation from free radicals. Alpha-tocopherol is a fat-soluble vitamin, so it can block oxidation by free radicals and protect the fats in the cell membrane from damage. Besides keeping cell membranes throughout the body intact, alpha-tocopherol also protects the fats in low density lipoproteins (LDLs) from oxidation, and LDLs oxidized by free radicals are one factor contributing to cardiovascular disease. Several studies say that eating more vitamin E can reduce the risk of heart attack and death from heart disease.  

Other functions of alpha-tocopherol include inhibiting the activity of protein kinase C, which is involved in immune system function and cell inflammation. Alpha-tocopherol also inhibits platelet aggregation and helps dilate blood vessels.

Carotenoids are a group of more than 600 pigments occurring naturally from plant synthesis, and these pigments give vegetables and fruits their yellow, orange and red colors. Fruits and vegetables are an important source of carotenoids in our diet. The carotenoids most commonly found include alpha-carotenoid, beta-carotenoid, beta-cryptoxanthin, lutein, zeaxanthin and lycopene.

Roles and functions of beta-carotene 1. It is a vitamin A precursor (provitamin A carotenoid), meaning it can be converted into vitamin A after being absorbed into the body. 12 micrograms of beta-carotene convert to 1 microgram of vitamin A. 2. It acts as an antioxidant, able to quench the activity of free-radical oxygen. In addition, test-tube tests have found that carotenoids can inhibit lipid peroxidation. Epidemiological studies have found that eating vegetables and fruits high in carotenoids helps reduce the risk of cardiovascular disease and some cancers. 3. Carotenoids stimulate the synthesis of the protein connexin, which forms pores or gaps in the cell membrane, enabling communication between cells by exchanging small molecules. This cell-to-cell communication is important in the cell division process, and this property is lost in cancer cells.

Role of gamma-oryzanol in rice 1. Lowers bad cholesterol (LDL) and lowers triglyceride levels Gamma-oryzanol binds to cholesterol in bile, increasing bile excretion into the intestine, and then prevents it from being reabsorbed. Gamma oryzanol consists of sterol and ferulic acid. Rosenbloom and colleagues reported in 1992 that gamma oryzanol helps increase the production of the hormone testosterone in men and also stimulates the brain to secrete more endorphin, the happiness chemical. 2. Several research studies have found that gamma-oryzanol helps increase good cholesterol (HDL) levels 3. Helps lower the risk of diseases caused by atherosclerosis

Polyphenols and anthocyanidins The role of this group of compounds is as antioxidants. 1. Inhibit oxidation of bad cholesterol (LDL) 2. Inhibit platelet aggregation, which reduces the risk of fat blockage in blood vessels and coronary artery hardening 3. Reduce the risk of cancer 4. In addition, a 2002 research report by Dr. Morimitsu found that anthocyanidins in colored rice help inhibit cataract formation in diabetic patients 5. This group of compounds helps slow cell degeneration