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FUNCTIONAL FOODS AND NUTRACEUTICALS



This article is taken from www.foodsciencecentral.com, the website of IFIS Publishing, market-leading information providers in the areas of food science, food technology, and food-nutrition.

Functional Foods And Nutraceuticals

Rotimi Aluko
Associate Professor, Department of Human Nutritional Sciences,
University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2

1. Introduction

It is common knowledge that foods provide nutrients that help to nourish our bodies and keep our systems in proper working condition. However, from early in human history, it was also known that certain foods confer additional health benefits to humans such as prevention and treatment of various types of diseases. "Let food be thy medicine" is a popular quote from Hippocrates that emphasizes the role of foods in disease prevention and recognizes a separate role for foods in addition to their being simply nutrient providers. Recently, scientists have become focused on the health-promoting effects of foods and there is now abundant evidence that supports the role of various foods/food components in promoting human health. Such health-promoting foods or compounds are generally classified into 2 major categories:

    Functional foods are often conventional foods that are consumed as part of a usual diet, but apart from supplying nutrients they can also reduce the risk of chronic diseases such as cancer, hypertension, kidney malfunction, etc. A typical example of a functional food is tomato, which is rich in the antioxidant lycopene and helps to remove toxic compounds from our bodies, thereby preventing damage to essential organs. Other typical examples of functional foods include soybeans, fish, oat meal, cereal bran (wheat, rice), and tea (green and black). Apart from traditional foods, there are also functional foods that are produced through food processing such the antihypertensive sour milk that has been shown to reduce blood pressure in humans.

    Nutraceuticals are health-promoting compounds or products that have been isolated or purified from food sources and they are generally sold in a medicinal (usually pill) form. A good example is a group of compounds called isoflavones that are isolated from soybean seeds and packaged into pills that women can use instead of synthetic compounds during hormone replacement therapy. Other examples of nutraceutical products include fish oil capsules, herb extracts, glucosamine and chondroitin sulfate pills, lutein-containing multivitamin tablets and antihypertensive pills that contain fish protein-derived peptides. It is important to note that the efficacy of some of these products is still a subject of continuing debate and research within the scientific community; therefore, consumers should consult with their physicians or health providers before using such products, especially if they are already on physician-prescribed medications.

Let us now take a closer look at a few specific examples of foods and/or compounds that have been shown to have potential beneficial health effects in humans.

2. Lycopene

This is a compound that is very abundant in tomatoes and other brightly coloured foods such as papaya, watermelon, carrot, pink guava and pink grapefruit. For the best source of lycopene, consumption of concentrated tomato products such as tomato paste, canned pizza sauce, spaghetti sauce, barbecue sauce and ketchup are highly recommended. In addition, consumers should note that cooked tomato products provide better availability of lycopene than raw tomato products. Lycopene provides health benefits by neutralizing hazardous waste products such as reactive oxygen species (ROS) that our bodies normally produce during conversion of nutrients into energy. ROS are dangerous compounds that can damage DNA and promote cancer formation. They also damage lipids that are vital to keeping our hearts and blood vessels functioning properly; such damage can lead to development of hypertension. Research has shown that increased consumption of lycopene-containing food products can reduce blood pressure in hypertensive patients by reducing plaque development (hardening of blood vessels). Previous studies have also shown that men who ate 10 or more servings of tomato products (pizza sauce, tomato sauce) per week or those with high levels of lycopene in their blood were substantially less likely (about 34%) to develop prostate cancer than those who consumed little or no tomato products.

3. Lipids (Fatty Acids)

Fish oil has long been recognized as a functional food because of its ability to reduce blood pressure and lower the risk for other cardiovascular disorders such as abnormal heart beat and blockage of blood vessels by cholesterol. The health-promoting effect of fish oil is now known to be due to the omega-fatty acids, especially omega-3 and omega-6. The main omega-3 fatty acids in fish oil are docosahexaenoic (DHA) and eicosapentaenoic acids (EPA). DHA in particular has been shown to be an important structural component of the brain and contributes to improved memory functions. Recently, increased incorporation of DHA into margarines and baby foods has been promoted to enhance brain memory development; a role in reducing the severity of Alzheimer's disease has been suggested for DHA. Other omega-fatty acids such as linoleic and linolenic acids also provide increased cardiovascular benefits; they are abundant in fish oil, vegetable oils (canola, soybean, and sunflower) and nuts such as peanuts and almonds. Consumption of nuts is highly recommended since they are also packed with high levels of antioxidants that help maintain integrity of organs, blood vessels and genes. Apart from the omega fatty acids, conjugated linoleic acid (CLA) is another important lipid that has been shown to positively impact human health. CLA is found mostly in dairy products or meat products derived from ruminant animals (cow, goats and sheep). It has been shown to improve glucose tolerance, which is associated with type 2 diabetes. CLA also reduces development of adipose fat and it may play a role in weight loss, although this has not yet been thoroughly proven in human trials. Research with rat models also suggests that CLA can reduce progression and severity of chronic kidney disease, which could reduce the need for and frequency of dialysis.

4. Catechins

From epidemiological studies we now know that people who consume tea on a regular basis have fewer incidences of chronic diseases than non-tea drinkers. The active component has been identified as catechin, which is very abundant in green tea, although black tea also contains sufficient quantities. For tea drinkers to reap maximum benefits, it is important that the tea is boiled for several minutes to extract high quantities of catechins into the liquid beverage. Catechins are strong antioxidants that inhibit damage to DNA and blood vessels, thereby reducing the risks of cancer development and cardiovascular diseases, respectively. Cranberry juice contains high levels of epicatechin polymers that prevent adhesion of viruses and bacteria to the urinary tract; regular consumption of cranberry juice or cranberry concentrate tablets has been shown to reduce antibiotic requirements in women experiencing urinary tract infection.

5. Proteins And Peptides

Proteins are long-chain polymers of amino acids while peptides represent the shorter forms. Proteins in our foods can act as health promoters in 2 ways, firstly, by acting as indigestible substances in our digestive tract, they trap and expel (through faeces) toxins and bile, thereby reducing the re-absorption of cholesterol from the large intestine. Buckwheat and soybean proteins are known to contain substantial amounts of indigestible proteins and their increased consumption is beneficial to maintaining a clean and healthy gut. Secondly, proteins can be converted into peptides during digestion and are then absorbed into the blood circulatory system. Some of these bioactive peptides, especially from soybean proteins, have been shown to be capable of preventing the production of cholesterol by liver cells, which can lead to lower levels of cholesterol in the blood. Peptides can also be made by custom-designed enzyme digestion of proteins in a reaction vessel. Ingestion of such peptides either as part of a food or drink or in pill form has been shown to reduce blood pressure in hypertensive patients. A sour milk drink product that contains bioactive peptides is widely sold in Japan and some European countries. In the USA, a milk powder that contains antihypertensive peptides is also available as a functional food for blood pressure reduction. Milk is also fractionated into alpha-lactalbumin (which is rich in tryptophan), which has been shown to ameliorate sleep disorders and help sustain alertness in the morning after overnight sleep. Dairy whey protein fractions (sold as whey powder), obtained during cheese-making, contains compounds that can boost our natural immunity, decrease the risk of cancer formation, reduce the severity of muscle tissue degeneration associated with liver diseases, and reduce susceptibility to diarrhoea.

6. Indigestible Carbohydrates

Dietary intake of plant fibres is important for maintaining a healthy gut and reducing glucose absorption, which can be beneficial to diabetic patients. Plant fibres are highly concentrated in the bran of seeds and this has led to promotion of whole grain consumption as a way of maintaining a healthy lifestyle; such fibres are also abundant in fruits and vegetables. Consumption of insoluble fibres such as cellulose and hemicellulose, as found in bran, leafy vegetables or fruit skins (e.g. apples and pears), serve as roughage and help to reduce the caloric value of diets, which is important in obese and diabetic conditions. Soluble fibre (also called gums and pectin) is abundant in whole grain barley and oats, as well as in fruits such as ripe strawberries and bananas; this type of fibre forms a viscous indigestible mass in the gut and helps trap digestive enzymes, cholesterol, starch, glucose, and toxins that are then expelled through the faeces. In this way, soluble fibre can help obese people reduce the amount of calories they absorb from their food and help diabetics by reducing the rate of starch digestion and glucose absorption.

7. Conclusion

A significant body of scientific evidence exists that demonstrates the health benefits of foods beyond their basic function of providing nutrients and nourishment. The foods mentioned in this article is by no means exhaustive and several other compounds/foods have been identified as health-promoting agents. Development of novel functional foods and nutraceuticals is an emerging science that could provide substantial health benefits especially in the prevention and/or treatment of acute and chronic human diseases.

8. Acknowledgement

The research programme of Dr. Aluko receives financial support from the Natural Sciences and Engineering Research Council of Canada (NSERC) as well as the Advanced Foods and Materials Network (AFMnet)

F.A.C.S. Scientific Director. Posted May 2006.


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