Two new studies suggest sugar is harmful - not just because of weight gain but because the substance directly harms the body. One study, conducted by the MD Anderson Cancer Centre in the US, suggests sugar promotes breast tumour growth.The other, released yesterday by the University of Leicester, shows sugar may increase the contraction of hard blood vessels, raising blood pressure.The studies raise the question of whether sugar is harmful in and of itself or only when eaten in excess.Excess sugar intake is known to lead to obesity and Type 2 diabetes, as well as other diseases linked to weight gain.But sugar itself is not believed to be harmful as long as it is taken in small quantities."Are there other sugar-specific concerns beyond dental cavities? I am not sure," said Derek Yach, professor of the Vitality Institute.In a study conducted by the Cancer Centre, published in the journal Cancer, half of mice fed on diets high in sugar developed tumours compared with a third on a different diet.Mice fed a diet high in two forms of sugar, sucrose or fructose, also had a significantly higher risk of the cancer spreading to their lungs.In the University of Leicester study, scientists found high sugar levels in the blood changed the behaviour of blood vessels, making them contract more strongly than normal and increasing blood pressure.Richard Rainbow, lecturer in cardiovascular cell physiology at the University of Leicester, said: "This could result in higher blood pressure, or it could reduce the amount of blood that flows through vital organs."However, Yach said because the one study involved animals and the other study appeared to be too small and experimental, he was not convinced one should act on the basis of the results.He said the "overwhelming evidence" was still clear. Sugar is bad in high quantities.The World Health Organisation recommends no more than six teaspoons of sugar a day for an adult...