One of the first things you'll hear in the emotionally loaded conversation about diet and health is a soft whisper in your ear that white sugar is poisonous. It's such a common refrain that you don't hesitate to accept its truth.
Sugar scrambles normal thoughts and feelings, rots you from the inside like a dental cavity and blows out your pancreas. It revs up bacteria and yeast, is bad for the immune system and speeds up the growth of cancer cells. Parents roll their eyes with resigned agreement that children go wild after eating sugar and then crash.
Sugar demonizers tell us pure sugar was found in nature only rarely back in the prehistoric dinosaur days when our metabolism evolved, but now it's everywhere. We have created a candy-coated theme park based on concealed greedy economic interests bent on destroying our insides. The more refined and simple sugar we take in, the faster our pancreas sounds the alarm and pumps insulin into our bloodstream, causing sugar to be stored as fat and blunting our brains' understanding that we've had enough to eat. Gorging on sweets makes us keep eating more and more, we get fat, we get diabetes and that gives us heart disease.
Fascinating and terrifying. But what does the scientific basis for this story look like?
Sugar science has tended to focus on "glycemic index" (GI) and "glycemic load" (GL), mathematical abstractions secondarily related to what sweet and starchy food does to blood sugar. High GI/GL food like non-diet Coke causes it to rise quickly; low-GI/GL foods ("healthy" carbohydrates like brown grains) cause it to creep up slowly.
The uniquely prestigious Cochrane Collaboration has done several reviews of dietary GI/GL. Conclusions: For heart disease, people fed sweet white sugary diets were not shown to have any greater likelihood of heart disease than people fed "healthy" brown grains and fibre.
For obesity, although reliable research suggested obese people lose more weight with low GI/GL, there was no real health-outcome result from drinking sugar-sweetened beverages and eating rock candy as opposed to the same energy content derived from tofu and multigrain bread.
Cochrane reviewers and other authors did find complex carbohydrate in the diet may help diabetics control their blood sugar. But recent evidence suggests it may not be worth their trouble: Intensive lifestyle intervention probably doesn't reduce the rate of cardiovascular events in overweight or obese adults with type 2 diabetes.
For the non-diabetics among us, the total outcome of Cochrane's recent large, carefully-done meta-analyses of high-quality trials on GI/GL shows no advantage to avoiding simple sugar if you are healthy and if "advantage" means not getting sick.
In other words, eating sweets of any kind and avoiding stone-ground grains, and "natural" carbohydrates doesn't cause diabetes, coronary heart disease or obesity.
I found nothing in my own literature review to contradict Cochrane, and more evidence that avoiding simple sugar doesn't affect dental health, colon cancer, attention-deficit disorder, dementia, depression, other cancers and even obesity.
There was one study showing sugar in the diet lined up with several illnesses. But it relied on the strange manoeuvre of comparing people who ate massive quantities of simple sugar with others who ate almost none. This might support the idea that big sugar-eaters and complex-carbohydrate fans are fundamentally different kinds of people, but it also says the only way you could make a difference to your risk of illness with a low-sugar diet would be to start out as a massive sugar-eater and immediately start eating nothing but brown rice. Even then, the difference would be tiny.
The American Heart Association tells us in the face of this evidentiary vacuum to limit our daily intake of added sugar to nine teaspoons for men and six teaspoons for women. No big surprise that many bakeries and restaurants, fulfilling their expanded role as guardians of public health and at the same time responding to public demand, sell us pastries and desserts that taste like cardboard or flour-and-water paste.
It's only human for us to worry that our lives are falsely frosted with undeserved goodies and for this to find resonance in the idea that sweetness is dangerous. The only trouble with this representational food mythology is that when we go looking for scientific proof, it isn't there.
John Sloan is a family physician and a clinical professor in the department of family practice at the University of British Columbia. He is the author of the forthcoming, Delusion for Dinner: Unmasking the myth of healthy eating.