It is defined as any food or food ingredients that may provide a health benefit beyond the traditional nutrients present in it. Traditional nutrients refer to vitamins and minerals. Functional foods don't differ from conventional food, in appearance and are consumed as part of usual diet. They are not pills or capsules but contain bioactive compounds such as antioxidants, antimicrobial, antiviral, anti aging, anticancer and low cholesterol substances.

Bioactive compounds are naturally occurring chemical compounds present in or derived from plant, animal or marine source, that exert beneficial effect on human health. Common examples of bioactive compounds are omega 3 fatty acid in fish oil and β glucan in oat and barley.
Though adequate nutrition can be obtained from the food containing carbohydrate, protein, fat, vitamins and minerals, but the functional food provides optimal nutrition for the health promotion. Functional foods may be whole, fortified, enriched, or enhanced foods.

Fortified foods
• Juices with calcium reduces risk of osteoporosis, reduces hypertension , help maintain healthy bones.
• Juices with added fibre reduce the risk of certain cancers and heart disease; reduce cholesterol, hypertension, and constipation.
• Grains fortified with folic acid reduce risk of heart disease and neural tube birth defects.
• Milk with vitamin D helps maintain healthy bones and reduces risk of osteomalacia and osteoporosis .

Enriched foods
Processed foods to which vitamins and minerals are added are called enriched foods. This is done to replace nutrients lost during processing; to make them more comparable to other foods. Vitamins A and D are added to margarines to make them comparable to butter.

Classification of functional food
• Biodefensive function --- Allergy reducing and immune defensing food, Lymphatic system enhancing food
• Disease preventing function-- High blood pressure preventing food, Diabetes preventing food, Congenital metabolic disorder preventing food, Antitumor food
• Disease recovery function--- Cholesterol controlling food , Blood platelet aggregation preventing food
• Physical rhythm controlling function---- Central nervous system stimulating food Peripheral nervous system stimulating food, Food intake regulating food, Absorptive function regulating food
• Aging suppressing function--- Lipid peroxide formation controlling food.

Green tea and green tea catechin:
It possesses the bio-defensing function by preventing cancer through fortification of the immune system, (ii) disease preventing function by preventing high blood pressure or diabetes, (iii) disease recovery function by inhibiting the rise of cholesterol, (iv) physical rhythm-controlling function by stimulating the central nervous system with caffeine and (v) aging suppressing function by providing the body with antioxidants. Green tea is, therefore, rich in possibilities as a functional food beverage

Oat as functional food
The outer layer of oats contains insoluble fibre that has the capacity to improve colonic functions. Its active component is a type of soluble fibre called β glucan that is reported to reduce low density lipoprotein (LDL) cholesterol. Each 0.026mmol/L increment in LDL-cholesterol causes an increase in coronary risk of 1 per cent. It reduces the LDL in blood plasma, lowers blood pressure and allows slow release of glucose into the bloodstream.
Milk with nutrients and functional components

Whey protein is a carrier of vitamins, minerals and fatty acids. Lactoferrin have anticancer and antibacterial properties. Lactoperoxidase also has antibacterial properties Bioactive peptides alleviate hypertension. Oligosaccharide compete against inulin

Some Natural Functional Foods
• Wheat bran contains insoluble dietary fibre that reduces the risk of colon or breast cancer
• Psyllium contains soluble dietary fibre and it protects against heart disease and reduces total cholestrol.
• Oat is an excellent soluble dietary fibre, it is essential for healthy gut function
• Rice bran oil contains oryzanol that is an antioxidant and is reported to be ten times stronger than vitamin E. This phenolic antioxidant scavenges oxygen free radicals and prevents their formation inside our body metabolic process. The antioxidant activity provides prevention against cancer, and heart disease by maintaining optimum cholesterol level and other factors like combating respiratory problems, diabetic health etc. This particular unsaponifiable material is considered to be an important factor in hypocholesterolemic and hypolipidemic action of rice bran oil.
• Soya contains Isoflavonoids that helps in reduction of certain cancers, cardiovascular and skin diseases, osteoporosis and obesity,
• Flaxseeds may lower the rate of prostate cancer and are a wonderful stool softener, reducing the risk for constipation.
• Fermented milk products contain probiotics, the beneficial bacteria that live in the gut, Consuming probiotics in diet can help to alter the composition of intestinal flora and can be beneficial for immune system
• Whey protein, derived from milk, is a good supplement for those who have a low intake of protein.
• Cheese and meat products contain conjugated linoleic acid as the functional component responsible for improving body composition and decrease risk of certain cancers.
• Fruits and vegetables contain fibre carotenoids
• Garlic reduces risk of heart disease and certain cancers and also reduces cholesterol
• Brocoli contains sulforaphane, an antioxidant and stimulators of natural detoxifying enzymes.
• Grape wine contains Resvertol, a powerful antioxidant that helps in cancer prevention, protection of the heart and brain from damage, reducing age-related diseases such as inflammation, reversing diabetes and obesity.
• Fish contains omega fatty acid
• Nuts are the source of phytosterol
• Almond prevent the absorption of cholestrol, lower the level of prostrate cancer and also have the ability to affect the sphingolipase.
Although functional foods are often used to prevent illness, it should be noted that they should not be used to treat disease.

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