Title: Fruit and vegetable intake

Key words: Free radicals, asthma, cancer, cataracts, diabetes, inflammatory disease, antioxidant, vitamin C, vitamin E, beta-carotene, flavonoids, ORAC, flavonoids, terpenes, limonoids, coumarins, isothiocyanates, ellagic acid, allium, lycopenes, cardiovascular disease, anaemia, fibre, potassium

Date: March 2001

Category: Macronutrients

Type: Article

Author: Kate Neil (NS3)


Fruit and vegetable intake

Free radicals have been implicated in a number of disease processes, including asthma, cancer, cardiovascular disease, cataracts, diabetes, gastrointestinal inflammatory diseases, and other inflammatory processes1. Radical oxygen species (ROS) are produced as a normal consequence of biochemical processes in the body and as a result of increased exposure to environmental and/or dietary xenobiotics1. ROS also exert beneficial effects in the body1. It is an imbalance in the oxidant versus antioxidant processes (oxidative stress) that is thought to cause the subsequent cellular damage leading to the disease processes1.

Eating a wide range of fruits and vegetables is associated with a high intake of antioxidant nutrients, vitamins C, E, and beta-carotene. Flavonoids, including anthocyanidins, are substantially more powerful as antioxidants than vitamin C and can be 50 times stronger than vitamin E2.

One study showed that the plasma oxygen radical absorbance capacity (ORAC) significantly increased when 10 pieces of fruit and vegetables were consumed daily compared to baseline measurements when the more usual 5 pieces a day were eaten3. Current guidelines are that we eat 5 portions of fruit and vegetables daily, a portion equalling 80grams.

Flavonoids, terpenes, limonoids, coumarins, isothiocyanates, ellagic acid, allium compounds, protease trypsin inhibitors, lycopenes found in a variety of fruits and vegetables have been shown to have a protective role in the incidence and/or progression of cancer4.

Vegetables and fruits contain very little fat, and are low in calories and can therefore protect against obesity and thus against the risk of cardiovascular-disease, as well as against those cancers associated with overweight and obesity5. Vitamin C may help maximise intestinal iron absorption, helping to prevent iron-deficiency anaemia5.

Fruits and vegetables are high in fibre, which may help control diabetes and high serum cholesterol levels and protect against digestive disorders5. The high potassium content of fruit and vegetables may help prevent or control hypertension and thereby reduce the subsequent risk of stroke and heart disease5.

Fruits and vegetables are rich in antioxidant nutrients, and although the evidence for a protective effect of specific antioxidants is incomplete, national and international recommendations to increase fruit and vegetable intakes to at least five portions a day form a sound basis for policy.

The policy to increase fruit and vegetables:

Potential problems in implementation:


1 Miller A, ND, Antioxidant Flavonoids: Structure, Function and Clinical Usage, Alternative Medicine Review, Vol 1, No 2, 1996, p103-111

  1. Christie S, Anthocyanidins – key members of the Flavonoid family. Their role in human nutrition. Lamberts Healthcare Bulletin.
  2. Cao G, et al, Am J Clin Nutr 1998;68:1981-1087
  3. Georgiou G, PhD, Dietary Management of Cancer, The Chemical Constituents of Food Related to cancer, Research Project
  4. Food, Nutrition and the Prevention of Cancer: a global perspective, World Cancer Research Fund, American Institute for Cancer Research, 1997

Other Sources of Information

1. At Least Five a Day, Strategies to increase vegetable and fruit consumption, National Heart Forum, 1997

2. Preventing coronary heart disease, The role of antioxidants, vegetables and fruit, National Heart Forum, 1997