What are phytochemicals ?

Phyto” is Greek for “plant“. Phytochemicals are protective, disease preventing non-nutritive compounds of plant origin.¬† These compounds are naturally present in fruits and vegetables.

Phytochemicals are commonly referred to as functional foods, phytonutrients and nutraceuticals. All these different terms explain the importance and role of these chemical compounds in the prevention of disease.

Types of phytochemicals

The common sources and some of the major benefits of various types of phytochemicals are represented in the following table :

Phytochemical Sources Benefits
Carotenoids Tomato, carrot, pumpkin, spinach, drumsticks, mangoes, papaya, cantaloupe and citrus fruits. Potent free radical scavenger.
Prevents acute macular degeneration.
Protects against cancer.
Enhances the immune response.
Flavonoids Soya beans, tofu, olives, onions, apples, kale, celery, broccoli, green tea and whole grains. Reduces the risk of cardiovascular diseases.
May protect against certain cancers (lung, skin etc.)
Strengthens blood capillaries.
Alpha tocopherol Whole grains, wheat germ, green leafy vegetables (spinach, asparagus), nuts (almonds, cashews and peanuts), wheat germ oil, linseed oil, palm oil and soyabean oil. Free radical scavenger
Prevents lipid peroxidation
Protects the skin
Alpha lipoic acid Red meat, liver, kidney, yeast, spinach and broccoli.
Aids the liver in removing harmful substances from the body.
Controls blood glucose.
Helpful in the treatment of Amanita poisoning (mushroom poisoning).
Allium compounds (allylic sulphides) Garlic, onion, leeks, chives. Anti-carcinogenic
Glucosinolates Cruciferous vegetables like broccoli, cabbage etc. Activate liver detoxification enzymes.
Prevent tumor growth.
Thiols (Indoles, Dithiolthiones and isothiocynates) Garlic, leeks, cabbage, turnip, broccoli, cauliflower and kale. Help to bind carcinogens (cancer causing chemicals) and hence reduce cancer risk.
Monoterpene (Limonene) Citrus fruits, nuts, seeds. Inhibits tumor growth.
Protects lung tissues.
Chemo-preventive (cancer preventing) agent.
Phenolic compounds (Ellagic acid, Ferulic acid) Fruits, vegetables, seeds, walnuts, strawberries, raspberries, cranberries and grapes. Anti oxidant.
Inhibits tumor growth.
Increases blood clotting and controls hemorrhages.
Block enzymes that cause inflammation.
Saponins Legumes and vegetables. Reduce cancer risk.
Lowers cholesterol levels and hence protects against cardiovascular complications.
Phytoestrogens (Lignans and Isoflavones) Cereals, legumes, soya beans, fruits and seeds. Anti-carcinogenic.
Boosts the immune system.
Reduces cholesterol levels.

Intake: Diet vs. Supplements

The field of phytochemicals or functional foods still needs to be explored to assess the efficacy or action of these foods in disease prevention. Until further research uncovers the adequate quantity, American Heart Association (AHA) recommends that eating a balanced meal consisting of a variety of fruits, vegetables and whole grain product ensures an optimum intake.

Also, research indicates that the benefits of phytochemicals can be best achieved by consuming a varied diet that includes a minimum of five servings of fruits and vegetables, rather than in a supplement form. Clinical trials have indicated that the beneficial effect of these phytochemicals can be obtained only when they are consumed in the form of a balanced meal and such effects are not demonstrated when individual nutrients are consumed  in a supplement form.

However, there are some disease states that require high levels of specific phytonutrients that cannot be given through diet. A classical example is the need for high dose vitamin E (d alpha tocopherol), a lipid soluble chemical present in oils of plant and vegetable sources. To give the required quantity would mean giving unacceptable amounts of oils and fats that would defeat the dietary balance.

Another example is the need for lutein and zeaxanthin, two members of the carotenoid family that protect the retina of eyes and the skin from damaging effects of the actinic rays of sun, by filtering the harmful part of the light spectrum. A person working outdoors and being exposed to excessive sunlight would need large amounts of green vegetables and fruits daily to supply the required amounts of carotenoids. This may affect the dietary balance of the individual, making the supplements a more practical and convenient alternative.