Fruit and vegetables (FV) have a spectacular range of health effects which can be attributed to the numerous compounds such as vitamins, minerals, fibers, phytosterols, saponins, glucosinates and polyphenols that they contain. For the polyphenols, despite their beneficial effects on human health, especially for their antioxidant and chemo-preventive properties, no recommended daily intake has been established. This could be mainly explained by the current lack of knowledge on their biological activities, the inconclusive data on bioavailability and pharmacokinetics and the incomplete food composition data in regard to the numerous dietary phenolic structures.

As polyphenols are largely distributed in fruit and vegetables in derived products such as flavonoids, phenolic acids, stilbenes and lignans, this could be another valuable assertion for strengthening the positive image of these foods and recommendation for consumption.

The difficulty for quantifying the food composition of polyphenols

The International Network of Food Data Systems (INFOODS) has already created a programme to acquire and interchange food composition databases around the world. In conjunction with the work on the usual macro- and micronutrients, it would be relevant to improve the quality and availability of bioactive compounds data such as that on polyphenols. It could also be interesting to match up such information with the dietary patterns of each country, in order to improve the health status of vulnerable populations. For example, the health status of obese Mexican rural populations could be improved by the consumption of local fruits and vegetables-an important source of polyphenols with antioxidant properties and dietary fibre¹.

The assessment of dietary intake of polyphenols has already been done in some countries. Brazilians and US adults have a high dietary intake of polyphenols especially fl avonoids, with an estimation of 60-106 mg/day and 190 mg/day respectively. In Brazil this would be mainly attributed to the consumption of fruits and vegetables, with 70% coming from oranges, 8.9% from lettuce, and 5.8% from onions. These figures seem high when compared to the dietary intake in Finland (55mg/day) or Denmark (29 mg/day).

Polyphenols content and antioxidant activity in F&V

In the last few years, several bioactive compounds such as polyphenols have been reported in food composition databases. It appears that fruit and vegetables are the major source of polyphenols with levels such as black grapes (91.2 mg/100g), apples (56.3 mg/100g), guavas (126.4/100g), strawberries (97.6 mg/100g), broccoli sprouts (73.8 mg/100g) or artichoke (260.3 mg/100g).

Moreover it was found that the stage of ripening (immature, mature, ripe, and over-ripe) in fruit, such as Durian, may infl uence the amount of polyphenols and the antioxidant activities with higher levels being identified in over-ripe fruits².

Antioxidant activity has been found to be proportionate to the content of flavonoids. For example, in the litchi fruit, a positive correlation was demonstrated between its antioxidant property and fl avonoid content (28.8mg/100g). As well, proanthocyanidin tannins of the Feijoa fruit were responsible for its antioxidant activity³.

Biological activities and health benefits

The high antioxidant activity of polyphenols can prevent lipid peroxidation and DNA protein damage. In fact many dietary polyphenols are antioxidants capable of quenching ROS (reactive oxygen species) and toxic free radicals formed by the peroxidation of lipids and thus have anti-infl ammatory and antioxidant properties in human metabolism. Moreover, when specific foods are combined – such as fruits (raspberry, blackberry, and apple), vegetables (broccoli, tomato, mushroom, and purple caulifl ower), and legumes (soybean, adzuki bean, red kidney bean, and black bean) a synergistic antioxidant interaction could occur resulting in a more positive physiological effect on cardio-health⁴. Moreover diets supplemented with tropical fruit rich in polyphenols, such as Durian (309.7mg/100g) or mangosteen (190.3 mg/100g) could hinder the rise in plasma lipids and decrease in antioxidant activity.

Although some clinical observations using polyphenols showed positive outcomes for human health5, further research needs to be conducted to assess their bioavailability and thus their biological effects.