In 2003, it was estimated by the World Health Organisation (WHO) that up to a third of cancers could be prevented by a change in diet. That means 2.1 million lives a year could be saved and instead of 20 million people suffering from cancer worldwide, the figure could be 14 million (or 7 million if smoking was banned). And it isn't just cancer that could be prevented by making better dietary choices, heart disease, diabetes, Alzheimer's and depression are just some of the conditions that could be affected.

Balance is the key to any healthy diet, think of the superfoods below as an illness-busting booster for your body and then make sure you include all of the main food groups into your diet as well. No food is a guarantee that you won't ever get ill, but knowing the ones that give your body a much-needed helping hand might just turn out to be the best thing you ever do.

Blueberries

Blueberries or brain berries, as some nutritionists like to call them, really are the darlings of the healthy eating world. They have extraordinarily high levels of vitamin E and C, which help to keep the mind in tip-top shape and are therefore an essential addition for those feeling the mental strains of modern life.

Broccoli

Nutritionists have longed hailed broccoli as a superfood. Along with cabbage, Brussels sprouts and pak choi, they are collectively known as ‘brassica’ or ‘cruciferous’ vegetables. This class of vegetables is particularly rich in phytochemicals, which are believed to protect against cancer. They contain high levels of vitamins A, C and E that eliminate oxygen particles that can damage body cells. These oxygen particles are known as free radicals.

Butternut squash

Rich in zinc, this member of the gourd family is great for boosting your immune system and combating the effects of stress. Zinc is also the most important nutrient for fertility and is necessary for the body to hold reproductive hormones, oestrogen and progesterone. High levels of selenium found in butternut squash are important for optimum sperm formation and testosterone production, making this an essential addition to your diet if planning a family.

Garlic

Otherwise known as the stinking rose, garlic has been used for thousands of years to treat ailments. It contains sulphur, amino acids, minerals, such as selenium and zinc, and vitamins A, B and C. Its anti-bacterial and anti-viral properties give it its reputation as the perfect food to keep the common cold at bay.

Nuts

Although high in fat, nuts are very good for the body. The key is the fat they contain is largely unsaturated, which works to keep blood cholesterol levels down. In America, packets of walnuts now carry the government's Food and Drug Administration seal of approval for their health-giving properties.

Salmon

Recommended by many nutritionists as the top fish you can eat, salmon has confirmed its status as a superfood in the last few years. It contains high levels of omega-3 essential fatty acids, which keep the blood flowing through small blood vessels, slow the build-up of fatty material on the inner walls and steady the heart's rhythm. Research has shown that one serving a week may decrease the risk of heart disease by 40 per cent.

Soy

It has taken the Western world a long time to wake up to the benefits of soy. Now, finally people have cottoned on to what everyone in Asia has known for centuries. Soy is a good source of protein and iron and has been proven to reduce cholesterol levels. It also has high levels of a plant compound (phytochemical) called isoflavone. This may help to relieve menopausal symptoms as it interferes with oestrogen synthesis. Good sources? Tofu, miso soup and soy milk.

Tea

No food is a guarantee that you won't ever get ill, but knowing the ones that give your body a much-needed helping hand might just turn out to be the best thing you ever do.

Research has shown that the benefits of your daily cuppa may range from boosting your memory to protecting against ovarian cancer. A team of Swedish researchers recently claimed that drinking two cups of your favourite brew a day could cut the risk of ovarian cancer by nearly 50 per cent. Green tea has also been shown to increase the body's ability to burn fat, so may be useful for weight-loss.

Tomatoes

Tomatoes are little gems that contain lots of properties to improve your health. High in vitamins A and C, they help build up the body's resistance to infection, so are an essential weapon to have in your diet. They also contain lycopene, which is said to help reduce the risk of prostate cancer. Lycopene is the substance that makes tomatoes red and can be found in tomato ketchup.