Eat bananas when they're green and potatoes when they're cold Surprising advice that'll transform how you enjoy favourite foods

The type of food you heap on to your plate is not the only thing you need to think about. How you cook, prepare or eat it can dramatically affect its health benefits. Here, dietitian Juliette Kellow reveals the best ways to serve popular kitchen staples…


Canned sweetcorn still counts as one of your five a day. And, now, scientists from New York’s Cornell University have even found the heat treatment used to process canned sweetcorn increases the amount of antioxidants in it by a huge 44 per cent.

Antioxidants help to mop up the free radicals in the body, which can damage cells and raise the risk of health problems such as heart disease and cancer. This increase in antioxidants more than makes up for the loss of vitamin C from canning.

Unripe is right: A greener banana means you'll absorb fewer calories

Unripe is right: A greener banana means you'll absorb fewer calories


When potatoes are cooked, their starch cells swell and start to break down — a process known as gelatinisation. This allows them to be digested more easily.

But when potatoes are chilled after cooking, some of the gelatinised starch is converted into a more solid, crystalline form of starch that can’t be digested, called resistant starch.

This resistant starch, like fibre, ends up in the large intestine, where it’s thought to help improve bowel regularity. In a UK study, cooked potatoes were found to have 7 per cent resistant starch, increasing to 13 per cent when cooled.

But if you’re making potato salad, don’t undo all the good work by mixing them with mayonnaise. Instead, combine with fat-free Greek yoghurt, spring onions and chives.


Extra virgin olive oil is rich in omega-6 fats, which block the body’s response to inflammation in chronic conditions such as heart disease and arthritis. Many people use it to cook with in favour of other oils.

But as this type of olive oil is less processed than other oils, it has a low smoke point — the temperature at which the nutritional benefits are affected.

Once oils have reached this point, their chemical composition alters and they start to contain more free radicals — harmful molecules that can damage cells. So it is not a good choice for high temperature cooking and is best left for dressings and marinades.


Italian researchers have found that compared to raw and steamed carrots, boiled ones had the highest levels of carotenoids — anti-oxidants the body uses to make vitamin A, which is important for growth, reproduction, immunity, healthy skin, eyes and hair.

Per 100g, boiled carrots also contained 28mg vitamin C — only a little less than the 31mg in raw carrots and a lot more than the 19mg in steamed carrots.

Brew benefits: Tea contains polyphenols - antioxidants that protect cells in the heart

Brew benefits: Tea contains polyphenols – antioxidants that protect cells in the heart

Tea contains polyphenols — antioxidants that protect cells in the heart. Polyphenols are released only when tea is heated, and it takes one to four minutes sitting in hot water to do this, says nutritionist Carrie Ruxton.

According to a British Nutrition Foundation report, some studies have found that adding milk reduces the body’s absorption of polyphenols, but others say it doesn’t have an effect.


Pasta tends to have a low glycaemic index (GI), meaning it keeps you fuller for longer so you’re less at risk of hunger pangs. But to keep it that way it needs to be cooked al dente (firm).

When pasta is firm, the digestive enzymes in the gut take longer to break down the starch into sugars, so they’re released more slowly into the bloodstream, filling us up for longer and making it easier to control our weight. If it’s overcooked, the GI increases, so the starch is more readily broken down into sugars.

So start testing your pasta at least two to three minutes before the suggested cooking time to ensure you keep an al dente texture.


To get the best from your salad, use full-fat dressing made with oil. That’s because we need fat for our bodies to absorb important antioxidants linked to healthier hearts and a lower rate of cancer.

Research from Ohio State University found that eating fresh salad with fat helped the body to absorb antioxidants such as lycopene from tomatoes, beta-carotene from carrots and lutein and zeaxanthin from salad leaves. The more fat there is, the more antioxidants are absorbed.

As an alternative, top salads with avocado, which is rich in heart-healthy monounsaturated fat.


Grilling and barbecuing are often championed as low-fat methods for cooking meat. But the National Cancer Institute has found that cooking meat at high temperatures can create two harmful chemicals — heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs) — which have been linked to causing cancer in animals.

It’s healthier to cook dishes at lower temperatures and use methods that are unlikely to result in meat being charred, such as stews and casseroles. Meanwhile, add plenty of herbs and spices. Naturally occurring compounds found in rosemary, for example, have been shown to block the formation of HCAs by up to 92 per cent in meat that’s cooked at high temperatures and well-done.

And spices such as turmeric, coriander and cumin have been found to prevent HCAs from forming by up to 39 per cent, according to research from Kansas State University.

Healthy start: Organic milk contains more omega-3 fats which are good for the heart

Healthy start: Organic milk contains more omega-3 fats which are good for the heart

While most people know milk, including skimmed milk, is a rich source of calcium, what many people won’t realise is that it also contains omega-3 fats.

These are important for heart health: they reduce the stickiness of blood so it’s less likely to clot; keep the heart beating regularly; and protect small arteries.

A three-year study by the Universities of Liverpool and Glasgow suggest organic milk contains more omega-3 fats than standard milk. This is thought to be because of the cows’ diet of grass, while non-organically farmed cows rely on grains and proteins.

A recent study from Newcastle University has also found organic milk had 24 per cent more heart-healthy polyunsaturated fats, including conjugated linoleic acid (which has been found to lower ‘bad’ cholesterol) and eicosapentaenoic acid (an omega-3 fat), than conventional milk. But remember, it’s important to cut down on saturated fat for a healthy heart, so opt for semi-skimmed organic.


It’s a common misconception that ripe bananas contain more calories than unripe ones, but it’s true they taste sweeter. That’s because some of the starches are turned into sugars as banana ripens, but this doesn’t affect their calorie content.

But the degree of ripeness does affect how many calories you may get from the fruit. The less ripe a banana is, the more resistant starch it contains, and so the slower it is absorbed by the body and the lower its GI. This means more undigested starch passes into the large intestine, so a greener banana means you’ll absorb fewer calories.


Research confirms that drinking four to five cups of coffee a day is safe and may even benefit health — for example, helping to protect against heart disease and type 2 diabetes.

Better still, coffee counts towards the recommended daily fluid intake of 1 to two litres. That’s why it’s better to have a long coffee rather than an expresso.

Additionally, a large latte made with full-fat milk contains 225 calories — 11 per cent of a woman’s recommended daily amount. A large Americano with a splash of semi-skimmed milk has just 50 calories.