Did you know that fruit and vegetables can be classified into groups according to the phytochemicals (plant nutrients) they contain? Phytochemicals are simply biological compounds; and different combinations of these and nutrients give fruit and vegetables their distinctive colours and smells. Some phytochemicals are antioxidants, others have antibacterial action or otherwise interact with the cells of the human body, thus providing health benefits.
Broadly speaking, fruits and vegetables can be classified into five different colour groups (some sources recommend seven, and include a red/purple and a yellow group as well) – green, red, orange and yellow, blue and purple, and white/brown.
Green includes the obvious leafy vegetables such as spinach and kale, together with asparagus, celery, lettuce, peas and watercress. Fruits include avocados, green apples and grapes, limes and kiwi fruit, and pistachio nuts. This group generally contains fibre, calcium, vitamins C and K, folate and the antioxidants lutein and beta-carotene, together with the chlorophyll that gives them their distinctive green colour. Foods from the ‘green’ group can help lower blood pressure and LDL cholesterol levels, boost immune system activity, fight free radicals and assist with digestion.
The red group includes beets, red onions, radishes and tomatoes, and fruits such as raspberries, strawberries, cranberries, pomegranate and watermelon. These contain the antioxidant lycopene, vitamin C, folate, and flavenoids, another branch of antioxidant. These nutrients can help reduce the risk of prostate and some other cancers, reduce the risk of heart attacks, and reduce inflammation in arthritis cases.
Yellow/orange vegetables include corn, carrots, sweet potatoes and butternut squash; and fruits such as lemons, peaches, pineapple and oranges. These contain potassium, vitamin C, beta-carotene and lycopene, and together can promote healthy joints, lower blood pressure and cholesterol, improve immune function and work with magnesium and calcium to support healthy bones.
Blue/purple is a relatively small group, containing eggplant (aubergine) and black olives, and and fruits including plums, raisins, blackcurrants, black- blue- and elderberries, and purple grapes. Their colour is due to anthocyanins, a type of antioxidant that is particularly good for the heart and may help support healthy blood pressure. This group contains fibre, antioxidants such as flavenoids, and lutein and thus supports healthy digestion, improves mineral absorption, fights inflammation and can limit the activity of cancer cells.
The final group, white/brown, includes cauliflower, garlic, mushrooms, parsnips, potatoes and turnip, and fruits including dates and bananas. The nutrients in this group tend to be immune-system boosters as they activate natural killer T and B cells (not as scary as it sounds – these are the white blood cells that search out and fight infections without our bodies) and thus reduce the risk of some cancers as well as helping to balance hormone levels.
Of course, no system of categorisation is 100% correct, and there are some fruits and vegetables that don’t fit neatly into these categories, and some that have health benefits that far exceed the broad lists mentioned here. So the important thing is to make sure that, while you are eating your greens, you remember to eat your reds, blues and yellows as well!