Written by Dr Robert Verkerk
Many of the very compounds that protect plants from attack also have an immensely beneficial and protective effect on the humans that ingest them; these are phytonutrients. Read on to find out more.
Just like humans, plants have primary life processes (organic compounds known as primary metabolites) without which they wouldn’t be able to sustain life, and secondary life processes that, although not critical to life, do ensure their long-term survival. These secondary metabolites are ones that exist to help protect the plant from the ravages of pests and diseases. These range from insects and mites, to nematodes (root-infesting worms) through to pathogenic microorganisms, including particular types of bacteria, fungi and viruses.
What are phytonutrients?
We are increasingly aware that many of the very compounds that protect plants from attack may also have an immensely beneficial and protective effect on the humans that ingest them. We often refer to these compounds as phytonutrients. They help prevent damage to cells throughout the body, they regulate inflammatory responses in the body and genetic expression, and they protect our all-important genetic code, DNA. Compounds found in plants as diverse as turmeric root, grape skins and seeds, broccoli (and other cruciferous vegetables), leafy vegetables, garlic, carrots and many herbs and spices, have been shown to reduce the risk of cancer, heart disease, stroke, osteoporosis, Alzheimer’s and Parkinson’s disease. Experts believe that eating plenty of nutrient-dense, phytonutrient-rich foods promotes healthy aging.
Types of phytonutrients
Hundreds of thousands of phytonutrients have been identified across our vegetable, fruit and herb crops. Many of them have multi-target functions, unlike most synthetically-manufactured drugs. Well researched phytonutrients include:
- Carotenoids: These provide the yellow, orange and red colours in fruits and vegetables, such beta-carotene and other carotenoids in carrots (antioxidant), lutein in marigolds (helpful against macular degeneration and cataracts) and lycopene in tomatoes (protective against heart disease and some cancers).
- Curcuminoids: Found in turmeric root, a powerful antioxidant, immune modulator and anti-inflammatory and neuro-protective agent.
- Flavonoids: Such as catechins from green tea that may prevent some forms of cancer, hespiridins from citrus fruits that help to reduce inflammation and thereby chronic disease; and flavonols found in apples and berries as well as kale and onions that may be used to reduce the risk of asthma, some forms of cancer and coronary heart disease.
- Resveratrol: A well-known and popular one found in red grape skin and red wine, linked to reduced levels of heart disease
- Glucosinolates: From cruciferous vegetables like broccoli, cabbage and kale that have been to reduce cancer risk and high blood pressure.
Different varieties of the same crop can often contain quite different levels of secondary metabolites depending on where they have grown and when they were harvested. Unripe fruits and vegetables may often contain fewer secondary metabolites than ripe ones, and artificial ripening may prevent the development of the same, full complement of phytonutrients as compared with sun-ripened crops.
You can often taste the difference, the taste buds on your tongue being particularly sensitive to phytonutrients. If a fruit or veg is lacking in flavor or taste, chances are it’s got a low quotient of phytonutrients. If the flavor is full, the reverse may be true. This is particularly evident with crops like tomatoes.
With some crops, younger plants can have higher levels of phytonutrients. Broccoli sprouts, for example, contain much higher levels of the sulforaphane (a glucosinolate derivative) than mature broccoli heads.