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Antioxidants play a vital role in your body, helping protect against the degeneration of cells, and against cancer, stroke and heart disease. Antioxidants may also help delay the ageing process, reduce the formation of ‘bad’ LDL cholesterol and prevent the formation of cataracts.

They sound like miracle workers… but what exactly are antioxidants, and how do you pack them into your diet?

Hw do antioxidants work?

Think of antioxidants as fire fighters, putting out fires in your body created by unstable particles, called free radicals.

A free radical is an atom in your body that is damaged and missing one or more electrons, making it unstable. Free radicals roam around, searching for other atoms from which to steal electrons. When a stable atom has an electron stolen, it in turn becomes an unstable free radical. This starts a chain reaction of electron-stealing throughout your body.

Enter the fire fighters, in the form of free radical scavengers! These atoms contain extra electrons which they donate to free radicals, stopping this chain reaction. Antioxidants are a major source of free radical scavengers.

Free radicals can damage mitochondria (the energy powerhouse of your cells), rupture cell membranes and damage DNA, essentially altering or destroying cell function.

Your body can cope with low levels of free radicals, but high levels may initiate or contribute to premature ageing, atherosclerosis (a disease of the arteries) and heart disease, cancer, cataracts, arthritis, infertility in men and other degenerative diseases.

Surprisingly, while oxygen is essential to life, it can also damage cells. The chemical process that occurs when oxygen damages cells is called oxidisation and it’s this process which creates free radicals.

You can observe oxidisation in action in your kitchen when fats become rancid, or the flesh of an apple turns brown. This process is occurring in your body too.

Oxygen is not the only substance which causes oxidisation. These also contribute to the process:

  • Environmental pollution
  • Cigarette smoke
  • X-rays or radiation
  • Sunlight

Considering all of these factors are frequently present in our contemporary lifestyles, it’s virtually impossible to prevent the production of free radicals in your body. What you can do, however, is replenish your antioxidant levels to combat the activity of free radicals and therefore help prevent disease. However, antioxidants can’t prevent diseases on their own; hereditary and other factors can contribute to the development of disease.

Oxidisation and cholesterol

Antioxidants, such as Vitamin E, beta-carotene and lycopene (the red pigment in tomatoes) may help prevent damage occurring to your blood vessel walls by preventing the oxidisation of cholesterol within your body.

Oxidisation of ‘bad’ LDL cholesterol in your bloodstream is thought to play a key role in the development of fatty streaks and atherosclerosis in artery walls – and the associated increased risk of angina, heart attack and stroke.

Antioxidants are found in certain vitamins, minerals, enzymes and nutrients. They are also found in carotenoids, the pigments in fruits and vegetables giving them their red, yellow and orange colours. Another source of antioxidants are phytochemicals – non-vitamin compounds found in all fruits and vegetables.

Research estimates the risk of heart disease and cancer is considerably lower in people who consume five to seven serves of antioxidant-rich fruit and vegetables every day.

To make sure you’re getting enough carotenoids and phytochemicals in your diet, aim to eat three different colours of fruit and vegetables every day to provide you with a range of colour pigments and boost your antioxidant intake.

Vitamins

Vitamin Antioxidant action Food sources
Vitamin A Helps prevent the formation of free radicals by bonding to oxygen molecules. Promotes germ-killing enzymes, destroys carcinogens and is necessary for healthy mucous cells. The carotenoid beta-carotene is a form of Vitamin A, and is one of the most powerful antioxidants. Carrots, broccoli, squash, melon, spinach, other deep yellow and orange fruits and vegetables and green, leafy vegetables. The brighter the colour of the fruit or vegetable, the higher the carotenoid content.
Vitamin C Protects against harmful reactions occurring within cells and traps free radicals before they enter cells. Recommended dosage is between 600 and 1,000 mg per day. Citrus fruits and juices, strawberries, kiwi fruit, tomatoes, broccoli, spinach, potatoes and capsicum.
Vitamin E Improves the use of oxygen within the body and protects the coating around cells from free radical attack. Between 200 and 600 IU recommended daily. Vegetable oils, seeds, nuts, wheat germ, whole grain breads and cereals, green leafy vegetables.

Minerals

Mineral Antioxidant action Food sources
Selenium Stimulates increased antibody response to germ infection. Works well in conjunction with Vitamin E. Between 100 and 200 mcg recommended per day. Brewer’s yeast, meat, oysters, salmon, tuna, cashews and whole grains.
Zinc Required for protein synthesis and collagen formation. Promotes a healthy immune system. Between 25 to 30 mg recommended per day. Fish and other seafood, legumes, soy products and whole grains.

Enzymes, nutrients and fatty acids

Enzyme Antioxidant action Food sources
Alpha lipoic acid Your body produces its own alpha lipoic acid, a vitamin-like fatty acid which plays a large role in energy production within cells. Red meat, potatoes, carrot, spinach.
Gamma-Linoleic Acid (GLA) An omega-6 fatty acid. Hydrogenated vegetable oils, margarine or a high-fat diet can block your body’s ability to convert food to GLA. Your body creates its own GLA from linoleic acid, found in vegetable oils. Evening primrose oil, black currant seed oil and borage oil.
L-Cysteine Used by your liver and lymphocytes to detoxify the body. Works best when taken with vitamin E and selenium. Garlic.
L-Glutathione An amino acid which works as a detoxifier, ridding your body of free radicals produced from metals, drugs, cigarette smoke and alcohol. Studies have shown L-Glutathione levels aren’t improved by taking supplements. Present in most plant and animal food sources.
Superoxide dismutase (SOD) An enzyme which revitalises your cells and reduces the rate of cell destruction. Removes the most common free radical, superoxide, and your the body use zinc, copper and manganese. Studies have shown SOD is not increased in the body by taking supplements. Barley and wheat grasses, broccoli, Brussels sprouts, cabbage and most green plants.
Coenzyme Q-10 Helps your body produce energy at a cellular level. Protects and strengthens the heart and slows the shrinking of the thymus (one of the body’s main immune organs) which occurs with age. People over 35 may consider using a Coenzyme Q-10 supplement. Fish, red meat, eggs, spinach some grains and beans.

Carotenoids

These are the red, yellow and orange pigments found in fruits and vegetables. As well as having antioxidant properties, they’re thought to be potent cancer fighters. Beta-carotene (Vitamin A) is one of the most powerful antioxidants (see above).

Carotenoid Antioxidant action Food sources
Lycopene Gives tomatoes their red colour. Lycopene is linked to a lower risk of prostate cancer in men. In one study, men who ate at least ten servings of tomato-based foods every week had a 45% reduced risk of developing prostate cancer. May also reduce cholesterol oxidisation. Tomatoes, tomato sauce, tomato puree.
Lutein and zeaxanthin Linked to eye health in the elderly. Spinach and broccoli.

Phytochemicals

Phytochemicals are found in all fruits and vegetables. Early research is speculative but suggests the potential for phytochemicals to protect against cancer. They seem to interact with every step of the cancer process, by slowing, stopping or reversing cancers.

Phytochemical Antioxidant action Food sources
Flavonoids Help regulate cellular activity and fight off free radicals which cause oxidative stress to your body. They help your body function more efficiently, and protect against everyday toxins and stressors. Green and black tea, red wine, most fruits and veg.
Isoflavones Plant hormones whuch are very weak versions of the human hormone oestrogen (including phytoestrogens).  However, due to the way in which phytoestrogens in soy may react with certain treatment medications, people who’ve had breast cancer should always consult a doctor before eating soy products or other phytoestrogen-rich foods. Soy foods, such as tofu and tempeh.
Lignans Lignans are a type of phytoestrogen (see above). High lignan intake is associated with reduced rates of breast, prostate and colon cancer. Plant foods, soy beans, sesame seeds and flax seeds.

Other phytochemicals include indoles and isothiocyanates (mainly responsible for broccoli’s anti-cancer properties), organosulphur compounds in garlic and onions, monoterpenes in citrus fruits and caraway seeds, saponins in soybeans, nuts and chickpeas, and cruciferous chemicals with anti-cancer properties found in broccoli, cabbage, cauliflower and Brussels sprouts.

Supplements versus real food sources

Foods provide a range of antioxidants, and may be a better solution than taking single vitamin supplements in tablet form, such as vitamin E or vitamin C tablets. Antioxidants work together to assist each other in your body, so the combination of antioxidants obtained naturally from foods works more effectively than single supplements. You may choose an antioxidant supplement formula which contains a range of antioxidants, but remember vitamin supplements should never replace a healthy diet.

It’s also important not to go overboard. Studies have shown extremely high doses of antioxidants may damage cells in much the same way free radicals do!

Calorie King
CalorieKing's mission is to provide the best information, tools and education to Australians to help them conquer their weight.

CalorieKing is the brainchild of Allan Borushek, registered dietitian, co-found here at food.com.au and author of "Allan Borushek's Pocket Calorie & Fat Counter", Australia's best-selling calorie counter for over 30 years.
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