So says Dr. Robert Lustig, Professor of Pediatric Endocrinology and director of the children’s obesity program at UCSF. His talk – Sugar: The Bitter Truth – has been watched over a million times on Youtube; I will try to summarize his points in this column.
The obesity epidemic in the US has been growing steadily since the public was told in the 1980s to decrease fats in their diet. The introduction of low-fat processed foods, laden with sugars for palatability, and devoid of fiber, laid the groundwork for our weight gain. Roughly half of teenage boys drink more than two six-packs of soft drinks every week. Today, one in 50 adults is severely obese (with a BMI of 40 or higher) and 34% of us are obese (BMI 30 or higher). The share of obese children has tripled in that time, to 17%. This is more than double the percentages of 30 years ago. Someone whose height is 5’6” is obese at 186 pounds; a 6’ person is obese at 221 pounds.
Understanding sucrose, glucose, fructose and starch: Sucrose is derived from sugar cane and sugar beets. It is 50% glucose and 50% fructose. High fructose corn syrup is 55% fructose and 45% glucose. From the point of view of the liver, they are about the same – neither is good for us. The fructose in whole fruit is fine, because it is encased in fiber, which slows its absorption. Whole fruits also have many beneficial compounds for health. Starch is a complex carbohydrate, made up of joined glucose molecules, used by many plants for energy storage. Our digestion easily breaks down most starch to glucose.
Glucose digestion: When we eat plants, from cabbage to potatoes, we break down their starch to glucose; this travels in the bloodstream to all our body cells for energy use. About a quarter of the glucose goes to the liver, where it makes glycogen – a useful and necessary storage compound for energy. A small amount is translated into fat.
Fructose digestion: When we eat or drink sugar (sucrose) or high fructose corn syrup (HFCS), the 50% or 55% that is fructose goes to the liver, as only the liver can metabolize it. This is in contrast to glucose, used by all our body’s cells. Some fructose is broken down into uric acid and excreted by the kidneys. Uric acid increases the risk of gout, and also elevates blood pressure. Much of it is metabolized to fat, leading to a problem called non-alcoholic fatty liver – rarely if ever seen before the recent sugar craze. Some of it goes into the blood stream as triglycerides, which become fat. As triglycerides rise, and body fat increases, cells become resistant to insulin. Insulin, produced by the pancreas, causes cells in the liver, muscle and fat to take up glucose from the blood, for energy production and storage. When blood glucose rises, due to the cells’ insulin resistance, diabetes results. A diet high in fructose also is associated with ‘leptin resistance’ – the body does not respond to the hormone called leptin that cuts off appetite. The eater keeps on eating.
Alcohol digestion: Alcohol is fermented sugar. When it enters the liver, it is digested in a way that is similar to fructose, resulting in high blood pressure, fat deposition in the liver (ultimately cirrhosis) and increased triglycerides in the bloodstream. Alcohol also leads to obesity (beer belly), insulin resistance and possible addiction. A small amount of alcohol, especially as red wine, is heart-healthy (1 five ounce glass for women, 2 for men). However, even small amounts of alcohol raise women’s risk for breast cancer.
What to do!
Here is the formula that Dr. Lustig gives to the families with children in his obesity clinic: He says it works – they lose weight – if they can follow it and stay off of soda.
1.Only drink water or plain milk
2.Eat carbohydrates with their natural fiber.
3.Wait 20 minutes before seconds.
4.Buy screen time minute for minute with physical activity. Screen time includes TV, DVDs, computer games, et al.
Look at 2 in this table. This would mean avoiding all foods made with sugar – cakes, cookies, pies, candy, ice cream, jam, syrup, the works. These foods were occasional treats one hundred years ago, and now they are everywhere, and often cheaper than real food. It also means eating whole grain pasta, 100% whole grain bread, and brown rice. Even Dr Lustig admits to an occasional dessert, and lets his kids eat ice cream on Sunday (according to another Youtube video). However, he still labels sugar a ‘toxin’ and would like FDA regulation. Others are calling for a tax on high-sugar soft drinks, which would decrease use and help pay for health care reform. Stay tuned for a discussion of this proposal. In the meantime – opt for water, unsweetened coffee and tea, and an orange for dessert!
Sadja Greenwood, MD, MPH back issues on this blog