Thank you for your responses Michael, Rosie, Philip and Graham , with a few issues raised :-
Few specific foods or drinks have been convincingly shown to raise or lower the risk of cancer - clearly it’s hard to design studies accurately looking at single items of diet, as our diet is so complex and varied.
We do know that being overweight raises the risk of several diseases including two of the most common cancers ( breast and bowel ), and several other types ( womb, stomach, gullet, and pancreas ). Extra body fat has various harmful effects on our cells, such as producing hormones and growth factors. Up to a tenth of cancers could be prevented through " healthy diets " including fruit and vegetables ; with limited salt, processed and red meat. It’s increasingly thought that a range of diets may help weight loss - provided they are maintained.
There have indeed been concerns about the health effects of dietary sugars - especially obesity and diabetes. All cells in our body are " programmed " to die, ideally making way for new healthy cells to grow. Cancer cells tend to avoid programmed cell death, using a faster metabolism at the expense of other cells in the body, which is why cancer patients lose weight. While all cells need sugar, cancer cells increase sugar consumption - but I’m not aware of good evidence that starving patients of sugar gets rid of cancer, or that sugar causes cancer ( other than indirectly through obesity ).
Screening for bowel cancer from the age of 60 ( 50 in Scotland ) is sensible on balance ; having your doctor look at ( and perhaps remove for microscopic diagnosis by a pathologist ) worrying skin lesions very sensible ; and giving up smoking has well known benefits .
Doctors’ primary job is to make people better ( with advice, not orders ) ; after accurate diagnosis which often involves pathology tests ( my specialty ).
Screening for evidence of illness and listing risk factors for possible diseases in people who have no symptoms is of secondary importance ( http://filipinaroses.com/showthread....cks-worthwhile ).