Many different, and chemically unrelated, phytonutrients exist in plant-based foods, including carotenoids, polyphenols, phytosterols and others. All of these have been studied for their potential bioactivity in relation to health, initially due to interest in the antioxidant properties of many of these compounds.
The carotenoids are found in coloured vegetables and fruit, and are often responsible for the red, orange and yellow colours in these foods. Over 600 carotenoids have been identified, but only 20 are found in human plasma and tissue, and these are from five classes: lycopene, alpha-carotene and beta-carotene, beta-cryptoxanthin, lutein and zeaxanthin. Lycopene is predominately found in tomato and tomato-based products, while the others are found in varying quantities across leafy green vegetables, orange-fleshed vegetables and fruit, and maize products. Lutein and zeaxanthin can als be found in egg yolk derived from the chicken’s feed. Beta-cryptoxanthin, alpha- and beta-carotene all have pro-vitamin A activity, whereas lycopene, lutein and zeaxanthin do not. Promising areas of research on bioactivities of the carotenoids relate to eye and skin health, limiting DNA damage and cardioprotection (3-5). The polyphenols are divided into flavonoids, hydroxyl-cinnamates, hydroxy-benzoates, stilbenes and lignans. Over 9000 flavonoids alone have been identified, and this grouping can be further sub-divided – the six main classes include: flavonols, flavones, flavanones, flavanols, isoflavones, anthocyanidins. Recent research focus for many of the polyphenols is on cell signalling pathways, inhibition of oxidative enzymes, increasing endothelial nitric oxide synthase (eNOS) activity, and decreasing adhesion molecules and platelet aggregation (6-8).
A recent study in the United States found that intakes of phytonutrients (carotenoids and flavonoids) were significantly lower amongst adult individuals who consumed less than the daily amounts of fruit and vegetables recommended in US Department of Health and Human Services dietary guidelines (9). Food-based dietary guidelines have been established for many regions and countries across the world and are collated by the FAO (10). In Europe, although some individual countries may be encouraged to consume more than six portions of fruit and vegetables per day (11), the EU supports the WHO recommendation for at least 400 g per day. Fruit and vegetable consumption patterns may be expected to vary widely between global geographic regions depending on food availability and culture. As a consequence, the degree to which national phytonutrient intakes relate to compliance with local dietary guidance can be expected to vary. The current study determined population intake of specific phytonutrients in relation to fruit and vegetable consumption across Europe (12).
The data analysis showed that the proportion of the population that appear to be meeting nutritional guidelines can vary from as few as one third to as much as two thirds. There is also considerable variation within populations so that some individuals appear to report very little or no consumption, whereas others appear to consume as much as three times or more than the amounts recommended by international authorities (2). To a large extent phytonutrient intakes correspond to consumption of fruit and vegetables and so higher consumers of fruit and vegetables are more likely to obtain the benefits of greater phytonutrient intakes. However, this is not always the case and there are situations where processed foods may contain high levels of phytonutrients or particular national preferences may result in higher intakes. The seasonal availability of food is probably less important in recent years as food production becomes more global. However, there may still be significant effects, particularly for low-income groups who are unable to afford out-of-season fruit and vegetables.
Using Food Balance Sheets (FBS) data, total fruit and vegetable consumption was estimated for 45 countries across eastern, central and western Europe (13). The average amount of fruit and vegetables consumed ranged from 192 g/day in Latvia to 824 g/day in Greece. The overall average consumption was 429 g/d, which exceeds the WHO Countrywide Integrated Non-communicable Disease Intervention (CINDI) Dietary Guide recommendation of 400 g/day (14). Twenty-five countries had fruit and vegetable consumption equal to or greater than 400 g/day and 20 had less than that amount. Fruit and vegetable consumption was highest in southern Europe (600 g/day) followed by northern Europe (434 g/day), western Europe (387 g/day) and lowest in eastern Europe (310 g/day). Total fruit and vegetable consumption data excludes starchy foods such as potatoes and pulses, which may be valuable sources of phytonutrients. The food consumption data does take some processing into account but not wastage in the home (e.g., vegetable peeling) and so tends to over-estimate true consumption. Products processed and then re-exported in other foods such as the manufacture of juice-based drinks would not be identified.
Using the European Food Safety Authority (EFSA) data, European countries have been ranked according to the degree to which the international guidelines for fruit and vegetable consumption are met by consumers (15). Consumption of fruit and vegetables ranged from zero to nearly 1400 g/day. However, extremes of consumption probably reflect the short-term duration of surveys and are probably not sustained in the longer term. Average consumption was 375 g/day, with nine out of 14 countries consuming on average less than recommended amount. The percentage of the population who consumed less than 400 g/d ranged from less than 36% in Spain and Italy to over 70% in Ireland, Latvia, The Netherlands, Sweden and the UK.
Using the data of the UK National Diet and Nutrition Survey (NDNS) of 2008/9 with 1,007 adults, total consumption of fruit and vegetables ranged from less than 1 to 1400 g/day and averaged at 310 g/day (16). For UK adults, 73% were found to consume less than 400 g/day of fruit and vegetables and had an average consumption of 220 g/day. The 27% who consumed more than 400 g/day had an average intake of 559 g/day. There were no apparent differences in BMI between the two groups and there were no significant differences in fruit and vegetable consumption between males and females in those who did, or did not, meet the dietary guidelines.
A US survey (17) determined the intake of phytonutrients in high and low fruit and vegetable consumers in the US population. The results obtained from the NDNS survey on the UK population are comparable to the USA population for all the carotenoids, except lycopene which is three times higher in the USA compared to the UK for both the high and low fruit and vegetable consumers. A difference suggested to be attributed to higher intake of lycopene from raw tomatoes in the UK and from pasta sauces in the USA (18). For the polyphenols, the anthocyanins and ellagic acid were also approximately 3-5 times higher for the USA population in both high and low fruit and vegetable consuming adults. However, flavanones and flavonols were higher in the UK population. This may be a result of higher citrus juice and tea consumption in the UK respectively.
Overall, intakes of phytonutrients are highly variable suggesting that whilst some individuals are regularly consuming advised amounts, there may be others who may not obtain all of the potential benefits associated with phytonutrients in the diet.”
Based on: Tennant D. R. et al. Phytonutrient intakes in relation to European fruit and vegetable consumption patterns observed in different food surveys. British Journal of Nutrition. Published online September 2014.