Oh sugar: fructose, the sweet white poison
Doctors are leading the charge against the deadly toxin present in processed foods, and warn we’re eating our way to bad health
Belly fat: excess fructose ends up as fat in the liver, which is extremely bad for our health. Photograph: George Doyle/Thinkstock
Forget the horsemeat food scandal. Our food is adulterated with a cheap, white and far more deadly toxin: sugar. So says Dr Robert Lustig, a top paediatrician in the US leading the charge against excessive sugar, who argues we should treat it as a poison.
And he has bad news for anyone thin and smug. One in five obese people will live perfectly healthy lives, but 40 per cent of thin people will develop metabolic diseases such as diabetes, which we associate with being fat.
“Subcutaneous or ‘big butt’ fat is completely benign,” says Lustig, a respected clinician at the University of California, San Francisco. “The problem is visceral or ‘big belly’ fat, the fat surrounding your organs and especially fat in the liver.”
Fructose, a sugar found in small quantities in fruit, is sweeter than glucose and often added to processed foods. Excess fructose ends up as liver fat. It’s the bad guy in this story. Large amounts impair our ability to control our weight.
It’s not that you get fat by eating too much or exercising too little, says Dr Richard Johnson, a leading kidney specialist at the University of Colorado. “You are gaining weight because you have changed your ability to regulate your diet.” And suffering metabolic syndrome means a raised risk of kidney, liver and heart disease as well as cancer.
Fructose causes obesity and metabolic syndrome by encouraging you to eat more and by clogging your cells’ energy generators, Johnson explains. “Our work also shows that sugar or fructose induces resistance to leptin,” which is the hormone the body uses to signal fullness to the brain. It also regulates how energetic we feel. Eating too much sugar, especially too quickly, eventually leads the brain to miss the “I’m full now” message.
Even when Johnson put lab animals, fed plenty of fructose, on a calorie-restricted diet, they still developed metabolic syndrome. Fructose primes the body: “When you eat fructose it makes [weight gain] real easy. The firewood is fat, but fructose is the fire,” is how Johnson explains this unhealthy fat-sugar duet.
“The problem is that sugar is incredibly pleasant and palatable and people can consume large amounts rapidly,” says Dr Carel le Roux, an obesity expert at UCD. “That is part of the problem with the fast-food industry. People can eat vast amounts before they feel satisfied.”
His colleague Dr Helen Roche, a professor of nutrition at UCD who studies genes and diet interaction, says genetics plays a strong role in obesity and our desk-bound lifestyle is also at fault. We can’t just blame the industry, she argues. We must take some personal responsibility.
Lustig, however, calls for the food industry to reformulate its products and argues it won’t be possible to educate us away from the problem. Asked how the food industry has reacted to his arguments, he says: “With venom”. He compares the industry to big tobacco, and says it will have to be made to comply for the sake of public health.
Increasingly fructose is viewed as “special”, but not in a positive sense. The body directs glucose from the gut to the liver or the bloodstream, as needed. But fructose goes straight to the liver. Small amounts are fine, but a glut clogs up our mitochondria, the power plants of our cells. It leads to an energy bottleneck in liver cells, which turns the excess into liver fat, and induces cellular distress and even inflammation.