The saying “Eat your greens” is getting challenged by the rising nutritional profile of purple foods, writes Jane Carstens.
Purple foods get their colour from anthocyanins, which Delia McCabe, who has a masters in Clinical Psychology and is the author of Feed Your Brain and Feed Your Brain: The Cookbook, defines as a family of potent antioxidant compounds found in the purple/blue pigment of fruits and veggies Based on their pH, foods in this colour category can appear red as well. McCabe is a particular fan of purple/blue foods like blueberries because of their powerful brain-health benefits, a subject she has researched at length.
“Anthocyanins are potent antioxidants that are very important in keeping the tissues and organs that use a lot of oxygen healthy. For example, the brain benefits because every fourth breath we take goes to this vital organ. That means a lot of free radical activity occurs in the greedy, oxygen-demanding brain as well as in other tissues and organs,” explains McCabe. “Anthocyanins supply free radicals, which are unstable compounds, with electrons to make them stable again. This stops them from looking for electrons from healthy cells, which stops a potential cascade of cellular damage.”
McCabe says anthocyanins also protect mitochondria, which are the energy-producing powerhouses found in all of our cells. “Mitochondria produce and attract free radicals, and purple and blue foods step in to stop them being damaged,” she explains. “This is especially important for the brain because its mitochondria never rest.” Purple/blue foods also have an anti-diabetic effect: by helping with insulin production, they improve our blood-brain barrier integrity, while bilberry extract is excellent for the eyes. “Bilberry extract is good for visual health because of the eyes’ high concentration of DHA, which is a sophisticated omega-3 essential fat,” says McCabe. “Essential fats are easily oxidised so antioxidants are very helpful in protecting ‘fat-rich’ organs and tissues such as those found in the eyes and brain. Blackberries are also good for eye health for this reason.”
Anthocyanins bestow antimicrobial benefits by inhibiting the growth of food-borne pathogens, and they also influence anti-inflammatory pathways. One study, published in the Journal of Agriculture & Food Chemistry, reported that polyphenol compounds in fruits produced anti-inflammatory activity in humans, with anthocyanins regarded as the most notable of these compounds. This study’s authors noted that inflammation is a major contributing factor in the development of cardiovascular diseases (CVD), type 2 diabetes, cancer, and Alzheimer’s disease. Excess body fat, particularly around the gut, is also associated with low-grade inflammation. “Berry fruits contain appreciable amounts of flavonoids [plant pigments], particularly anthocyanins, which are responsible for the distinctive red-blue-purple colouring of berries,” wrote the study’s authors. “A diet rich in plant flavonoids is associated with a lower risk of chronic disease development, and specifically CVD mortality in men and women. Moreover, a higher intake of diet-derived anthocyanins is associated with lower risk of hypertension [high blood pressure], myocardial infarction [heart attack], type 2 diabetes and cancer.”
The great protector
The antioxidant capability of anthocyanins often steals the spotlight, but there’s another side to these compounds that’s quite astounding. McCabe says they help the body produce new blood vessels and stop bad blood vessels being created, which has an anti-cancer and anti-tumour effect. “Anthocyanins help replace blood vessels where they are needed by producing endothelial cells, but they also notice when blood vessels start going to places where they’re not needed, such as to feed a tumour, and stops these blood vessels from forming. It’s a powerful example of the balance of food and nature.”
Resveratrol is a polyphenol that seems to behave like an antioxidant. It’s present in peanuts and berries, and in the skin of purple and red grapes, which is why red wine is considered ‘healthy’. While this claim is still widely debated, McCabe says resveratrol also helps improve immunity and stabilise blood pressure. It has also been linked to a gene that is believed to protect the body against the effects of the diseases of ageing and obesity. One study, published in Menopause, also cautiously linked resveratrol treatment to reducing chronic pain in age-related osteoarthritis, and its consumption has the potential to boost perceptions of wellbeing in postmenopausal women.
Put purple on your plate
Purple foods are not restricted to berries and beetroot. They include plants that are red-purplish, as well as red-to-blue-coloured fruits, leaves, flowers, roots, and grains. There are the obvious choices like plums and purple cabbage, but don’t forget to try purple potatoes, cauliflower, asparagus, corn, sprouts, basil, and black rice to mix it up a bit more. You also need to eat the skin of purple foods that have a different coloured flesh, such as eggplants, to receive the benefits of purple power. McCabe advises eating foods in season as much as possible when their healing properties are at their peak, but there are exceptions. “I am a fan of organic frozen berries when fresh berries are out of season,” she says.
Fruit and vegetables fall into five different colour categories of red, purple/blue, yellow/orange, green, and white/brown. The best part is that nature colour-coded them for a reason. Each colour matches a set of unique disease-fighting phytochemicals that give the different fruits and vegetables their colour and healthful properties. So, if you eat the rainbow, you are also getting the disease-fighting benefits each colour offers.