Raw vs cooked
Is raw always the healthier option? Nutritionist Kerry Torrens explains which foods benefit from a little heat and which should be left as nature intended...
With the summer focus on salads and 'no-cook' meals, you might be forgiven for thinking that eating your fruit and vegetables raw is always the healthier option. After all, some vitamins are sensitive to heat, for example, cooking tomatoes for just two minutes decreases their vitamin C content by 10%. However, while cooking may cause the loss of some valuable nutrients, like vitamin C, there are some vegetables which offer useful health benefits when they're cooked.
Heat it up
These include carrots, asparagus and even tomatoes, because cooking makes it easier for our bodies to benefit from some of their protective antioxidants, specifically ferulic acid from asparagus, and beta-carotene, which we convert to vitamin A, from carrots. Similarly, when you cook tomatoes - whether you roast them slowly or make a cooked sauce - it helps to break down the plant cell walls, allowing us to better absorb the antioxidant lycopene. All these nutrients help to safeguard our cells from environmental damage, may protect us from certain cancers and are heart-friendly.
Keep it raw
On the other hand, there are certainly some veg, which benefit from being eaten raw. These include broccoli and watercress (both members of the cruciferous family). When these veg are heated an important enzyme is damaged, which means the potency of helpful anti-cancer compounds called glucosinolates, are reduced. Similarly, cooking makes the herb garlic less potent because heat reduces the amount of health-promoting allicin, so it's best to add your garlic just before you finish cooking rather than at the start. For those watching their weight, eating some fruit and veg raw can help fill you up because raw fruit and veg tend to be bulkier and have a higher water content.
Make the most of it
Although some nutrients are sensitive to heat there are others, like the fat-soluble vitamins (A, D, E and K), which are unaffected. So whether you choose to eat your fruit and vegetables raw or cooked follow these tips to get the most out of them:
- Buy local produce, because some vitamins are lost during transportation and storage.
- Store fruits like tomatoes at room temperature rather than in the fridge - this optimises the ripening process and increases levels of valuable lycopene.
- Prepare your fruit or veg just before you need them.
- Avoid losing water-soluble vitamins like the vitamin B group as well as vitamin C, by choosing cooking methods which use the minimal amount of water or preferably no water at all, like roasting. When you boil or steam save the cooking liquor for making sauces or soups.
- Increase your absorption of fat-soluble vitamins by eating your veggies with a little oil. Enjoy a spinach salad with vinaigrette dressing, roast vine tomatoes with a drizzle of olive oil or quickly stir-fry spring greens.
- At certain times of year it's worth considering frozen produce. That's because these fruit and veg are frozen quickly after picking which means they retain more nutrients than some supposedly 'fresh' produce.
- Finally, balance your intake. Enjoy crunchy raw veg to top up on immune-busting vitamin C, and cook others for their mix of protective antioxidants.
Kerry Torrens is BBC Good Food magazine's nutritional therapist.