New Health Protecting Compounds In Plant Foods Biology Essay


Just as vitamins were discovered in the first half of the 20th century, scientists are now revealing a wealth of new health-protecting compounds in plant foods which have been named as phytochemicals - from "phyto" meaning plant. "In plants, phytochemicals act as a natural defense system for host plants and provide colour, aroma and flavour." [1] These compounds have been described as "biologically active non-nutrients." In other words, although they are not considered as nutrients (like carbohydrates, lipids, proteins, vitamins and minerals) they can act in ways which help prevent cancer and heart disease.

1.2 Why are phytochemicals important for us?

1.2.1 They defend the body against cancer. How? Mimic the hormone oestrogen

Phytoestrogens, which are a group of phytochemicals, are similar in structure to the hormone oestrogen and therefore they may copy the effects of oestrogen in the body. Preventing or slowing down the production of oestrogen may inhibit cell replication in GI tract, reduce the risk of breast, colon, ovarian, prostate, and other oestrogen-sensitive cancers as well as reduce cancer cell survival. Moreover two other classes of phytochemicals, lignans and indoles, act in relation to oestrogen, by blocking oestrogen activity in body cells which could possibly reduce the risk of breast, colon, ovary and prostate cancers. Furthermore indoles may also elicit the production of enzymes that block DNA damage from carcinogens. Prevent carcinogens from forming and inhibit enzymes that activate carcinogens

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Free radicals, which are chemically unstable molecules missing an electron, can damage cell membranes and mutate genes in their search for electrons. Compounds that prevent or reduce the formation of free radicals, remove these from the body by donating electrons or repair some of their damage after it occurs, are called antioxidants. Various phytochemicals act as antioxidants, acting against the damge caused by free radicals, including carotenoids, flavonoids, phytic acid and tannins. Flavonoids have yet another important function that of binding to nitrates (food preservatives) in the stomach and thus prevent the conversion of nitrates into the cancer-causing agents, nitrosamines. Similarly to the role of the previously described phytochemicals there are other phytochemicals including curcumin, organosulphur compounds and isothiocyanates which inhibit enzymes that activate carcinogens. Boost enzymes that detoxify carcinogens

Isothiocyanates also trigger the production of enzymes which detoxify carcinogens and render them harmless together with monoterpenes while organosulphur compounds may speed production of the carcinogen-destroying enzymes. Act on cells that have already been exposed to carcinogens, slowing the development of cancer

In order for cancer cells to spread these must activate a set of enzymes known as proteases which enable them to dissolve the substances between cells and then migrate through normal tissues. Protease inhibitors may suppress enzyme (protease) production in cancer cells, slowing tumour growth and possibly prevent cancer spread. In other ways, monoterpenes and tannins may inhibit cancer promotion. In addition saponins may interfere with DNA replication, preventing cancer cells from multiplying as well as stimulating immune response.

1.2.2 They defend the body against heart disease. How?

The previously mentioned free radicals do not only alter DNA and damage cell membrane contributing to cancer but free radical attacks also contribute to cardiovascular disease when free radicals within the lining of the arteries oxidize low-density lipoproteins (LDL), changing their structure and function. "The oxidised LDL then acceralate the formation of atery-clogging plaques. These free radicals also oxidize the polyunsaturated fatty acids of the cell membranes, sparking additional changes in the artery walls, which impede the flow of blood." [2] 

Therefore phytochemicals which act as antioxidants may protect against CVD. For example, flavonoids, a large group of phytochemicals, "are powerful antioxidants that may help to protect LDL cholesterol against oxidation and reduce blood platelet stickiness, making blood clots less likely." [3] Carotenoids are also linked with defending against CVD especially lutein and lycopene (two compounds of the carotenoid group). "It has been found that adequate intake of lycopene can reduce incidence of heart attacks by 50% by antioxidant activity and possibly by lowering LDL blood cholesterol levels." [4] 

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Phytosterols and lignans may protect against heart disease in another way additional to them being antioxidants. Since these plant-derived compounds are similar in structure to cholesterol, they can compete with cholesterol for absorption into the intestinal cells. As a result, they help lower LDL cholesterol levels and reduce the absorption of cholesterol by body cells.

Additionally, capsaicin regulates blood clotting, possibly reducing the risk of fatal clots in the arteries while resveratrol counteracts the artery-damaging effects of high diets rich is fat especially saturated fat.

1.3 Classes of phytochemicals and examples of locally available foods


Rich Food Sources


whole grain wheat


hot peppers



beta-cryptoxanthin [5] 


capsanthin [6] 



phytoene [7] 



deeply pigmented fruits and vegetables e.g. apricots








tumeric, a yellow-coloured spice; a significant ingredient in curry powder



ellagic acid

ferulic acid




rutin [8] 

taxifolin [9] 



black tea


citrus fruits

green tea



purple grapes

purple grape juice

soy beans

soy products


whole wheat



Cruciferous vegetables: e.g.


brussels sprouts



horseradish [10] 




wasabi [11] 


(including sulphoraphane)

as previous


flaxseed and its oil

whole grains



Perillyl alcohol [12] 


citrus fruit peels and oils

Organosulphur compounds




Phenolic acids

coffee beans











Phytic acid

whole grains


genistein and daidzein


soy products


Protease inhibitors

broccoli sprouts


soybeans and other legumes

soy products


red wine



alfalfa sprouts and other sprouts

green vegetables




black-eyed peas



red and white wine


1.4 How can a family include these different plant-derived compounds?

Keep fruits and vegetables available and in sight so that one can remember to use them.

Drink fresh fruit juice or blend a variety of fruits and vegetable to create a healthy drink, instead of soft drinks and other fruit-based beverages. In addition, adults can have a glass of red or white wine everyday. Different types of teas including black and green tea can be enjoyed as healthy hot drinks instead of hot chocolate and other powders added to milk.

Add chopped fruit, citrus fruit zest and ground flaxseeds [13] to cereal, porridge, milkshakes, pancakes, muffins, cakes.

Use fruits and vegetables as snacks for example carrots, raw pumpkin, sweet peppers, apples and pears.

Raw vegetables also go well with dips such as hummus and the traditional 'bigilla' which mainly consist of pulses. Dips also provide an opportunity to consume some hot peppers, garlic, horseradish and tumeric or curry as these can be used to add flavour. These dips can also be used in sandwiches as spreads.

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Use dried fruits such as apricots, raisins, blueberries and prunes as tasty treats instead of empty-calorie sweets.

In place of salt, use fresh herbs such as thyme and garlic to season food.

Start a meal with a healthy soup containing lentils and vegetables such as broccoli, potatoes, leeks, pumpkin and onions.

Always serve raw or cooked vegetables with meat, poultry and fish as well as with pasta and savoury pies. To give cooked vegetables a nuttier flavour, some ground flaxseeds can be sprinkled on top of the vegetables. Apart from being mixed in foods where a nutty flavour is appropriate, ground flax seeds may also serve as an egg replacement in baking by binding the other ingredients together (1tbsp of seeds : 3tbsp of water)

Substitute some meat with soy mince, for example in Bolognese sauce, and milk and milk products with soy drink, yoghurts and tofu.

1.5 How will I - as a future teacher - use this knowledge I gained about phytochemicals?

Now that I know more about the benefits of phytochemicals, I will be eager to pass this information to the students throughout the Home Economics lessons. I will be applying the knowledge about phytochemicals in a number of ways, but for certainty these compounds will be mentioned as another plus when discussing the importance of consuming the (minimum of) five servings of fruits and vegetables daily. I will also be giving some practical ideas of how to include foods containing phytochemicals with the aim of having students trying out some of these suggestions at home and passing on the message to other family members, especially the cook of the household.