According to Danish researchers, cooking carrots whole before chopping them has been shown to preserve more of the potentially cancer-busting supernutrient falcarinol. But carrots are not the only vegetable that can benefit from some special treatment in the kitchen. The same guidelines apply to preparing and cooking everything from garlic to broccoli, says Amanda Ursell
Cooking for the shortest possible time, in minimal water, preserves the folate, which, as well as keeping the nervous system in good shape, for pregnant women reduces the risk of babies being born with spina bifida. In some people it also lowers homocysteine, a substance in the blood which, like cholesterol, helps to block arteries and cause heart disease. Stir-frying, microwaving and short steaming are the best options.
Boiling tomatoes down to a rich sauce has been shown to release the nutrient lycopene — which studies have shown is linked with lower levels of prostate and lung cancer. Our bodies find it hard to extract the lycopene from raw tomatoes because it is bound up in the plants’ cell walls and fibres. Adding a little oil will further increase the body’s ability to absorb lycopene.
Raw broccoli may not be to everyone’s taste but cooking destroys the enzyme myrosinase, which converts supernutrients into sinigrin. Studies have suggested that this chemical triggers pre-cancerous cells to, effectively, commit hara-kiri. Even if you do cook broccoli, our bodies have digestive enzymes that can take over this conversion process.
Health-wise, it is better to crush raw garlic cloves between your teeth than it is to cook them. When the raw bulb is crushed or chewed, the sulphurous supernutrient alliin is converted into allicin, which appears to make our blood less sticky and therefore less likely to clot.
Asparagus is an excellent food for the B vitamin folate, which we need for a healthy nervous system. You can conserve maximum amounts of folate by steaming the asparagus upright in a little water, in a pan with the lid on, until just tender. Thankfully, cooking does not destroy fructo-oligosaccharides, a special type of fibre that helps to produce good probiotic bacteria, which aid digestion.
To get the most from your lettuce, tear rather than chop it, preferably just before eating it. Cutting with a knife damages the cellular structure, releasing oxidising enzymes which destroy vitamin C. This is true of most salad leaves — avoid pre-packed salads that contain chopped leaves. Lollo Rosso is one of the most nutrient-rich lettuce varieties. With its red “frill” at the top of the leaves, it delivers high levels of the supernutrient quercetin, which is linked to lowering bad cholesterol, and vitamin K, which is needed for strong bones.