Functional foods can offer a variety of health benefits. Common health benefits that may be associated with functional foods include reductions in the risk of certain cancers, cardiovascular disease, diabetes and osteoporosis. Other possible benefits include a reduced risk of macular degeneration and gastrointestinal disorders, as well as improvements in memory.

In most cases, health benefits associated with functional foods may be attributed to several different sources within the food, rather than one specific substance. For example, tomatoes include folate, vitamins C, A and E, as well as numerous phytochemicals (including high levels of lycopene). Due to a lack of scientific evidence it is unclear to what extent any one particular substance is responsible for a specific health benefit. It may be that one substance acts in conjunction with the others to produce the associated benefit.

Additional examples include oatmeal, which offers numerous health benefits due to its fiber, antioxidants, amino acids and phytosterol content. Legumes (e.g., peas, beans) contain fiber as well as several different phytochemicals (e.g., isoflavones, saponins, protease inhibitors) that can perform different actions associated with different health benefits.

The health-benefiting substances in functional foods are referred to as bioactive food components (BFC). They may come from plant sources (phytochemicals) or animal sources (sometimes referred to as zoochemicals). The bioactive food components of functional foods include:

• Phytochemicals (sometimes referred to as phytonutrients). Non-nutrient compounds found in plant foods. Some are associated with specific health benefits, beyond basic nutrition. There are a large variety of phytochemicals, available in an even larger variety of food sources. Several different types of phytochemicals may be present simultaneously in the same food source.
  
  
• Dietary fiber. The part of plant foods a human body cannot digest. Dietary fiber is considered a type of carbohydrate but not a nutrient because it is not absorbed into the body and does not provide calories. It may help regulate digestion (e.g., preventing constipation) and lower cholesterol levels. Soluble fiber may be more effective at reducing the risk of heart disease than insoluble fiber because it dissolves in water, and can help absorb cholesterol from food in the intestines. Fiber may also reduce the length of time the colon may be exposed to certain carcinogens, potentially lowering the risk of colon cancer. Fiber can be found in oatmeal, oat bran, rice, wheat bran, barley, beans (e.g., kidney, pinto beans) and many different fruits and vegetables.
  
  
• Soy protein. Soy may be associated with numerous health benefits. Most studied are its effects in helping to lower cholesterol levels, although recent reviews have called into question the level of cholesterol reduction. Soy is also associated with reducing the risk of heart disease, cancer, osteoporosis and possibly alleviating menopausal symptoms (e.g., hot flashes). Soy products can be produced with soy protein or the entire soybean (a type of legume). Both the protein and bean may contain certain phytochemicals (e.g., isoflavones, protease inhibitors, saponins). Soy protein can be used as a meat substitute to make plant-based burgers. Additional types of soy products include soy milk, tofu, miso, soybean oil, soy sauce and soy flour.
  
  
• Plant stanols and sterols. Plant molecules that mimic the structure of cholesterol. When consumed, they compete with animal-based cholesterol for absorption into the body. Plant stanols and sterols are not naturally present in plant foods in an amount significant enough to have this effect on the body. Thus, they are modified to form a chemical compound called esters. In this form, they may be incorporated into foods containing fat (e.g., margarine) or developed into fat substitutes without losing the cholesterol-lowering effects. In ester form and in appropriate quantities, these compounds may inhibit absorption of cholesterol from food in the small intestine. Small amounts of stanols and sterols are also found in fruits, vegetables, nuts, seeds, cereals, legumes and vegetable oils (especially soybean oil).
  
  
• Prebiotics and probiotics. Prebiotics involve nondigestible substances (e.g., fructo-oliogosaccharides contained in shallots) and probiotics involve live microorganisms (e.g., lactobacilli contained in certain yogurts and cultured dairy products). Both help to manage the levels of microorganisms within the digestive tract, increasing levels of helpful bacteria and reducing levels of harmful bacteria. A growing body of evidence suggests that probiotics and prebiotics may aid digestion, boost the immune system and protect against gastrointestinal problems.  Probiotics can have an anti-diarrheal effect, and prebiotics may aid in the absorption of certain minerals (e.g., calcium, magnesium). Prebiotics can also be found in whole grains, onions, bananas, garlic, honey, leeks and artichokes. When probiotics are combined with prebiotics, it is referred to as synbiotics.
  
  
• Fatty acids. Certain fatty acids are associated with specific health benefits. These include:
  
  
• Omega 3 fatty acids. A type of polyunsaturated fat commonly known as “omega-3,” which may lower the risk of cardiovascular disease. The three types of omega-3 fatty acids are  alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).  EPA and DHA can be found in fatty fish (e.g., salmon, sardines, tuna) and fish oils. ALA is found in walnuts and certain vegetable oils (e.g., flaxseed oil, canola oil).
  
  
• Conjugated linoleic acid (CLA). A type of fatty acid found in dairy products and some meats (e.g., beef, lamb) that is associated with a decrease in the risk of cancer.