Boost the nutritional quality of your diet - as well as your running performance - with these easy food swaps.

SWAP: Apple FOR: Orange Oranges contain nine times more immune-boosting vitamin C than apples - each has more than 100 per cent of the recommended daily amount. They can also lower cholesterol, protect your eyesight, and help fight cancer thanks to the potent antioxidant hesperidin. Oranges are also rich in folic acid, fibre and essential minerals.

SWAP: Potatoes FOR: Sweet potatoes Potatoes have a high glycaemic index (GI), which means their carbohydrates are fast-releasing. But sweet potatoes break down and release their carbohydrates more slowly, to provide longer-lasting energy. They are also rich in omega-3 oils (0.9g per 100g), vitamin A (as beta-carotene), vitamin C, iron, potassium and manganese.

SWAP: Sultanas FOR: Dried apricots Sultanas are high in sugar and handy for boosting blood sugar levels during a long run. However, you'll get more sustained energy pre- or post-run if you have dried apricots instead. They have a low GI (30, versus 56 for sultanas) and contain about half the sugar of sultanas. They are also packed with the potent, free radical-fighting antioxidant beta-carotene. Five dried apricots (100g) supply 6.3g of fibre (one third of your daily needs, and three times more than the same weight of sultanas) and also provide a quarter of your daily requirement of iron as well as potassium and folic acid.

SWAP: Lettuce FOR: Watercress Apart from water and a little potassium, there's not much going for round or iceberg lettuce. Upgrade your salad by choosing a dark-green salad vegetable like watercress instead. An average portion (80g) provides 42 per cent of your daily vitamin A needs (in the form of beta-carotene, which the body converts to vitamin A), 100 per cent of your daily vitamin C and 13 per cent of your iron. It also has high amounts of the compound phenylethyl isothiocyanate (which gives watercress its unique peppery flavour) that has been shown to protect against cancer.

SWAP: Bagels FOR: Wholemeal hot cross buns Despite their healthy image, bagels are no better for you than plain white rolls. For a high-octane snack, swap for a wholemeal hot cross bun, which provides significantly more insoluble fibre, iron, zinc, vitamin E and selenium. Whole-grain foods promote a healthy gut and also lower your risk of heart disease and stroke. Just four servings a day gives the same blood cholesterol-lowering benefits as statin drugs. They'll also cut your colon cancer risk due to their content of phytic acid.

SWAP: Herbal teas FOR: Black tea You might feel virtuous having a herbal fruit tea but most have no nutritional value and they can be bad for your teeth. Black tea is full of antioxidants called flavanols and is just as good as water for rehydrating you. Scientists have shown that blood levels of protective antioxidants rise significantly within 30 minutes of drinking tea. A study at Kings College, London found that drinking three or four cups a day can cut the chances of heart attacks and may protect against cancer.

SWAP: Apple juice FOR: Pomegranate juice A study by the University of California discovered that drinking a daily glass of pomegranate juice can cut the risk of prostate cancer. Pomegranates contain cancer-fighting polyphenols, immune-boosting tannins, and anthocyanins, which reduce inflammation and protect blood vessels. They are also rich in vitamins A, C and E and iron. Research in Israel also found that a glass a day can reduce the buildup of arterial plaque by 35 per cent, protecting against heart disease and stroke.