The health benefits of fruit and vegetables are more than skin deep, but it usually pays to eat the peel as well
The peel: contains d-limonene, a natural solvent which University of Arizona researchers have linked to protection against squamous cell carcinoma, the second most common form of skin cancer, when eaten regularly.
To eat: include orange zest in baking recipes and when you're juicing, include the whole fruit, peel and all. Alternatively, start eating cumquats, a citrus fruit with sweet, edible skin.
Boost the health package: by eating blood oranges. All oranges contain betacarotene, but blood oranges also contain anthocyanin, the antioxidant responsible for the fruit's red-tinged flesh.
The peel: is where you'll find more of the fruit's antioxidants compared to the pulp. Japanese scientists have also discovered a substance in kiwifruit skin that has an antibacterial action.
To eat: choose a gold or yellow-fleshed variety. All types of kiwifruit have edible skin but the peel of the golden-coloured fruit is smoother.
Boost the health package: by eating a bowl of iron-fortified cereal with a gold kiwifruit for breakfast.
While it's well known that vitamin C enhances the absorption of iron, a New Zealand study recently confirmed that two carotenoids – lutein and zeaxanthin – also play a role. Because gold kiwifruit have all three nutrients, when eaten with an iron-rich food, they improve a person's iron status significantly.
The peel: has a hepatoprotective effect, protecting against liver damage. And Korean researchers uncovered proteins in pumpkin rind that inhibit the growth of Candida albicans, the fungus that causes thrush.
To eat: cook with varieties that don't need to be peeled, including butternut, sweet dumpling and orange manikin.
Boost the health package: by picking a pumpkin with deeply coloured flesh. Created by the vegetable's betacharotene content, the deeper the colour, the more the pumpkin contains.
The peel: has as many as 10 times more antioxidants than a potato's flesh. It's also a valuable source of dietary fibre.
To eat: choose a variety designed to be eaten with its skin, such as kipfler or new potatoes, which are harvested early before their sugars completely turn to starch, resulting in thinner skins. Cooking potatoes in their jackets or making homemade wedges are other options.
Boost the health package: by choosing purple-skinned potatoes. Their peels contain anthocyanis, the same antioxidants that are found in blueberries.
The peel: contains 10 times the amount of falcarindiol, a compound found beneath the skin of carrots that has been found to have a protective effect against cancer.
To eat: pick Dutch, or baby carrots, which are sweeter, smaller and have thinner skins than regular carrots, so you won't need to peel. And never peel a carrot before juicing it.
Boost the health package: by cooking carrots whole. Cooked carrots contain 34 per cent more antioxidants than raw ones, but dicing increases the surface area that's exposed to heat or water, allowing more nutrients to leach out during cooking.
The peel: contains nasunin, an anthocyanin that gives the vegetable its vivid purple colour and increases intensity after cooking.
To eat: grill, barbecue pan-fry or roast eggplant with its skin. The bigger the eggplant, the tougher the skin, so choose smaller or Lebanese varieties, which have thinner peels.
Boost the health package: by picking a fresh eggplant. It should be heavy for its size because as eggplants age they lose moisture, which makes them lighter. And choose one with firm, unwrinkled skin, free of bruises and soft spots.
The peel: is a good source of chlorophyll, a green-coloured pigment with an anti-cancer action.
To eat: buy a continental, sometimes called 'telegraph' or Lebanese cucumber, rather than a green or common type. These have thinner, more palatable skins, as well as smaller, sweeter seeds inside, which is what dictates a cucumber's flavour: the older and bigger the cucumber, the more bitter the seeds become.
Boost the health package: by choosing a cucumber with a deep green colour, a sign that it has recently been picked. If a cucumber is dull or yellowed, it's old.
The peel: contains more lycopene, which protects against heart disease and cancer, and vitamin C than the seeds and pulp. The New Zealand-based researchers who made the discovery say removing a tomato's skin, as some recipes recommend, results in a significant loss of antioxidants.
To eat: pick your favourite variety and eat it raw, which doesn't require peeling first. But because cooking increases a tomato's lycopene content, with levels doubling after just two minutes of heat, try cooking methods such as grilling, roasting and sauteing, where the skin can be left on.
Boost the health package: by cooking tomatoes in olive oil. According to Deakin University researchers, the level of lycopene absorbed from those cooked in olive oil is significantly higher, because the oil makes the carotene more 'bioavailable' during digestion.
The peel: has an antioxidant activity that's nine times greater than the fruit's flesh. In fact, as well containing 75 per cent of an apple's fibre, researchers have discovered a dozen compounds in apple peel that inhibit or kill cancer cells.
To eat: choose an apple with a thinner skin if you don't like the texture of apple peel. Pink Lady apples are perfect and, naturally rich in sugar, they're also ideal for baking, peel and all.
Boost the health package: by stocking your fruit bowl with darker, pink and red-skinned apples.
The peel: contains the highest concentration of the vegetable's antioxidants, say Finnish researchers, who also identified the antioxidant present in the skin: called betacyanin, it's responsible for beetroot's colour and protects against heart disease and stroke.
To eat: go for baby beetroot, which has thinner skin that doesn't need to be removed after cooking.
Boost the health package: by turning beetroot – skins and all – into juice. While researchers in London discovered that it lowers blood pressure, Exeter-based scientists say beetroot juice can increase stamina and athletic performance.
Both are thanks to the vegetable's nitrate content, which widens blood cessels and reduces the amount of oxygen muscles require during exercise.