What the colours of veges mean
You’ve probably heard the phrase ‘‘eat a rainbow’’, but just how important is this? Sure, having some colour on your plate may be more visually appealing, but does it really matter as long as you’re eating some vegetables each day? Well, yes, actually.
Eating a wide variety of plant foods is associated with so many health benefits, so if you’re eating the same two or three vegetables with dinner most nights and you stick to your favourite piece of fruit year-round, you may be missing out on some of these benefits.
Here’s why: fruit and vegetables are packed full of micronutrients (vitamins and minerals), as well as superstar substances known as phytochemicals (beneficial plant chemicals). Some of these phytochemicals are what give plant foods their colour, so different colours equal different nutrients and antioxidants.
To ensure you get a good spread of these nutrients and antioxidants, enjoy foods from each of these colours regularly.
Red
Red or pink foods such as tomatoes and watermelon contain a carotenoid called lycopene, which is a potent antioxidant. Lycopene is thought to help protect LDL cholesterol against oxidation, and it has anti-cancer properties.
Yellow/orange
Yellow or orange-coloured vegetables contain carotenoids such as beta-carotene, lutein and zeaxanthin, all of which are beneficial for eye health. Lutein and zeaxanthin are powerful antioxidants, and they filter and protect the eyes from blue light (the type of light that is emitted from screens – think smartphones, tablets, laptops and TVs). Betacarotene can be converted into vitamin A, which is essential for many processes in the body, including healthy vision.
Carrots, pumpkin and kumara are rich in beta-carotene. Lutein is found in corn, pumpkin and yellow squash, and zeaxanthin is found in corn and orange capsicums. Carotenoids are fatsoluble, so they are better absorbed in the presence of fat.
Green
Our glorious green leafy vegetables are especially nutrientdense. Their green colour comes from chlorophyll, a substance that contains magnesium. This mineral is essential for helping the body to relax and is important for bone health, too. Green leafy vegetables also contain beta-carotene (the yellow/orange pigment is masked by the green from the chlorophyll), as well as folate, a vitamin that is particularly important in the lead up to and during pregnancy.
Green vegetables from the Brassica family (such as broccoli, kale, cabbage and brussels sprouts) contain glucoraphanin, which is converted into the ultrasuperstar substance sulforaphane. Sulforaphane has anti-cancer properties and is a potent antioxidant. Eat more greens!
Purple/blue
Purple or blue-coloured fruits and vegetables such as eggplant, red cabbage, blackcurrants and blueberries contain anthocyanin, a substance with antioxidant and anti-inflammatory properties.
Beetroots contain substances known as betalains, which protect against oxidative damage. They also contain nitrate, which is converted into nitric oxide in the body. This helps to widen blood vessels, allowing more blood and oxygen to be sent to your muscles, so it may improve physical performance.
White/brown
Although they’re not as bright as other vegetables, white plant foods still have their benefits. Anthoxanthins, the compounds responsible for their white colour, have antioxidant properties. Potatoes, mushrooms and bananas are also a good source of potassium, which supports proper nerve and muscle function.
Garlic contains allicin, a substance with antimicrobial properties, and garlic and onions contain prebiotics (food for our gut bacteria). However, some people don’t tolerate garlic and onions well, so pay attention to how you feel when you eat these and be guided by the messages your body is sending you.
Remember, what’s nourishing for one person isn’t necessarily nourishing for everyone, so embrace eating a rainbow, but above all, choose real, whole foods that nourish you.
❚ Dr Libby is a nutritional biochemist, best-selling author and speaker. The advice contained in this column is not intended to be a substitute for direct, personalised advice from a health professional. Join Dr Libby in Christchurch for one weekend to change your life: November 25 and 26. More info at drlibby.com.