Antioxidants in food

The process of oxidation in the human body produces unstable chemicals called free radicals. Free radicals are also known as reactive oxygen species (ROS). When free radicals accumulate, they may cause a state known as oxidative stress. This may damage DNA and other important structures in human cells.

Chronic oxidative stress can increase your risk of chronic diseases such as heart disease, type 2 diabetes and cancer. Antioxidants (or sometimes called free-radical scavengers) are substances that can prevent or slow damage to cells caused by free radicals.

Antioxidants are compounds in foods that scavenge and neutralize free radicals. Among nutrients with antioxidant activity: vitamin C, vitamin E, carotenoids, selenium, zinc, phenolic compound.

Eating a diet rich in antioxidants can help increase blood antioxidant levels to fight oxidative stress and reduce the risk of these diseases. Higher intakes of antioxidant-rich fruits, vegetables, and legumes are found to have associated with a lower risk of chronic oxidative stress-related diseases like cardiovascular diseases, cancer, and deaths from all causes.

The best antioxidant sources are fruits and vegetables, as well as products derived from plants. Some good choices include blueberries, raspberries, apples, broccoli, cabbage, spinach, eggplant, and legumes like red kidney beans or black beans.

Antioxidants β-carotene and other carotenoids can be found in apricots, asparagus, beets, broccoli, cantaloupe, carrots, corn, green peppers, kale, mangoes, turnip and collard greens, nectarines, peaches, pink grapefruit, pumpkin, squash, spinach, sweet potato, tangerines, tomatoes, and watermelon

Vitamin A: Dairy produce, eggs, and liver

Vitamin C: Most fruits and vegetables, especially berries, oranges, and bell peppers

Vitamin E: Almonds, avocado, sunflower seeds, oatmeal and legumes (beans, lentils, split peas)

Selenium: Eggs, tuna, salmon, brown rice, onions and many other vegetables
Antioxidants in food

Antioxidants in tea

The antioxidants work on protecting the various organs of the body, and also eliminate free radicals that can potentially damage blood cells, DNA and collagen.

Tea is a very rich source of a specific kind of antioxidant flavonoids:
*Flavonols – myricetin, quercetin, kaempferol
*Theaflavins – formed when black tea leaves are oxidized
*Catechins – found in green tea; epigallocatechin-3 gallate (EGCG) is the main form

The detoxifying effect of these antioxidants protects cells from free radicals, the damage that can lead to blood clot formation, atherosclerosis, and cancer.

The flavonoids found in green and black tea are very effective radical scavengers. The tea flavonoids may therefore be active as antioxidants in the digestive tract or in other tissues after uptake.

One study in rats examined the role of theaflavins in black tea and the risk of diabetes, obesity and elevated cholesterol. Results showed that theaflavins reduced cholesterol and blood sugar levels (Lipids Health Dis. 2018 Mar 27).

Since ancient times, tea has been used as a health product or medicine to prevent and treat various diseases. The first recording of tea described it as a medicinal beverage in China in the 3rd century AD. Merchants helped its popularity to spread quickly across continents.

It was recommended by experts that drinking three or more cups of black tea throughout the day may decrease the risk of heart attack, and drinking 4-5 cups may promote blood vessel relaxation.
Antioxidants in tea

The benefits of tea drinking

Tea (Camellia sinensis) originate from Southern China and is consumed by over two thirds of the world population.

Green Tea is produced by heating the leaves shortly after harvesting through a process of steaming or pan-firing to prevent oxidation from occurring, and then rolling and drying the leaves. Black and Oolong Tea undergo full or partial oxidation, which makes the leaves–and subsequent brew—darker in color.

Some review articles have reported the relationship between the tea consumption and the human cancer risk. A general overview of the pertinent epidemiological studies on tea consumption and cancer prevention in different organs such as bladder and urinary tract, breast, colon and rectum, esophagus, kidney, liver, lung, pancreas, stomach, and uterus is provided.

The powerful antioxidant properties of the tea are generally attributed to its flavonoid components; theaflavins, bisflavanols and theaflavic acids .These compounds are all potent antioxidant in vitro and, when consumed, may act as the free radical scavengers which remove endogenously generated superoxide, peroxyl and hydroxyl radicals.

The antioxidant property of tea is also associated with several other mechanisms e.g., depolarization of electrons, formation of intramolecular hydrogen bonds, rearrangement of the molecular structure. These compounds may also prevent oxidative reactions by chelating free copper and iron, which may catalyze the formation of reactive oxygen species in vitro.

Caffeine, 1,3,7-trimethylxanthine, is widely distributed in natural products, such as tea. Caffeine shows a variety of biological effects those have attracted the interest of pharmacologist and clinicians. Caffeine is regard as follows;
･ Diuretic
･ Cardiac muscle stimulant
･ Central nervous system stimulant
･ Smooth muscle relaxant
･ Elevates free fatty acids and glucose in plasma

In a prospective study of more than 74,000 subjects who were followed for 10 years, an inverse relationship was found between tea drinking and risk of stroke. During that time, 4,089 cases of stroke were recorded. After adjusting for other risk factors, tea consumption was associated with a significantly lower risk of stroke. Those who consumed four or more cups of tea per day had a 21 percent reduced risk of stroke compared to those who did not drink tea (Larsson SC, Virtamo J, Wolk A. Black tea consumption and risk of stroke in women and men. Ann Epidemiol. 2013 Mar;23(3):157-60).
The benefits of tea drinking