Sugar has always been a target for the "food police," who warn that it leads to tooth decay, diabetes and obesity. So far that's failed to curb America's appetite for sweets. But new research links sugar with an increased risk of heart disease. This may make it harder to stay sweet on sugar.
According to the U.S. Department of Agriculture, the average American consumed the equivalent of 25 teaspoons of sugar a day in 1970. By 2005, the number rose to nearly 30 teaspoons a day. That adds an extra 76 calories a day, much of it from high-fructose corn syrup.
It's no coincidence that America's waistline began to expand during this period, fueling our worrisome epidemic of diabetes.
Americans also increased their consumption of caloric soft drinks by 70% between 1970 and 2000.
So what are the top sources of added sugar in Americans' diets?
- Candy and table sugar
- Cakes, pies and cookies
- Fruit drinks
- Ice cream, sweetened yogurt and flavored milk
- Sweetened cereals and breads
(Source: Johnson et al. "Dietary sugars intake and cardiovascualr health: a scientific statement from the American Heart Association." Circulation. 2009; 120:1011.)
By itself, sugar doesn't harm the heart. But that doesn't mean it's safe. Sugar is bad for you because it increases problems that lead to heart disease. These include:
Obesity adds to many health problems, ranging from heart disease and high blood pressure to arthritis and prostate cancer. In all, obesity and overweight account for about 216,000 deaths in the United States each year; that's about one of every 10 deaths.
Obesity is a complex problem with many causes. Still, there's no denying that excess calories contribute to obesity, and that added sugar is a major source of excess (and empty) calories. Between the 1970s and the 2000s, the average American man's diet added 500 calories a day, more than enough to account for the rise in obesity that occurred during these same years. Fifteen percent of the extra calories comes from sugar, especially sugar-sweetened drinks (soft drinks, fruit drinks, energy drinks, and vitamin water drinks).
Type 2 diabetes has increased in parallel with obesity. Sugar-sweetened drinks appear to play an important role. A Harvard study of over 40,000 men linked a high intake of sugar-sweetened drinks to a 24% increase in the risk of type 2 diabetes.
Like obesity and diabetes, cholesterol is a major cardiac risk factor. Although there is only modest evidence that sugar raises LDL ("bad") cholesterol, there is strong evidence that it lowers HDL ("good") cholesterol and raises triglycerides.
4. Blood pressure
The major dietary cause of high blood pressure (hypertension) is excessive sodium, or salt. Large amounts of alcohol and low amounts of calcium and potassium also play a role. Until recently, sugar has not gotten the blame it deserves. Two major studies should change that.
One linked each daily serving of a sugar-sweetened beverage with a 1.6 mm Hg rise in systolic and a 1.1 mm Hg rise in diastolic blood pressure. The other found that the trend can be reversed. Over an 18-month period, people who cut out just 1 sugary drink a day lowered their systolic blood pressure by an average of 1.8 mm Hg and their diastolic pressure by 1.1 mm Hg. The benefit remained even after the researchers took other factors that affect blood pressure into account. These blood pressure improvements may not seem like much, but in an earlier study of dietary sodium and blood pressure, similar blood pressure reductions reduced the risk of cardiovascular events by 25% to 30%.
5. Metabolic syndrome
Individual cardiac risk factors are bad enough, but combinations are even worse. The metabolic syndrome is just such a cluster of risk factors, and it signals a sharp increase in the risk of heart attack and stroke. A study of 6,039 middle-aged people found that those who averaged more than one soft drink a day were 44% more likely to develop the metabolic syndrome than those averaging less than one soft drink a day.
6. Heart attack
Lots of sugar can increase many cardiac risk factors. But does that translate into actual heart attacks? It does. A 24-year Harvard study of 88,520 people tells the story. People who averaged 1 sugary drink a day were 23% more likely to have heart attacks, compared with people who drank no sugary drinks. Those who had 2 or more sugary drinks per day had a 34% higher risk. The results held up even after researchers accounted for other cardiac risk factors.
The American Heart Association says that a man consuming 2,200 calories a day should have no more than 36 grams of added sugar a day. That's 9 teaspoons a day. That's just about a third of what the average American guy is getting today.
You don't have to give up all sweets to be healthy, but you should limit your consumption of added sugars to about 7% of your total calories. But it's not enough to cut down on table sugar (sucrose). To protect your heart, remember that "natural" or "brown" sugar is no better than white sugar.
When you decide to cut down, sugar-sweetened drinks are the place to start. The average 12-ounce can has 10 teaspoons of added sugar. Because the sugar is in liquid form, it's rapidly absorbed. And the high-fructose corn syrup that's used in so many drinks produces a double whammy. The spike in the blood glucose level triggers a rush of insulin, which increases cardiac risk. In addition, the jolt of fructose stimulates the liver to churn out triglycerides, another bad thing. And some studies suggest that a high intake of sugar may increase oxidative stress and inflammation, which can damage arteries in the heart and other parts of the body.
Here are some ways to help cap your sweet tooth.
- Give up sugar-sweetened drinks. Instead, quench your thirst with water; ordinary tap water will do just fine. If you really miss soda, switch to non-caloric artificially sweetened brands. Despite early worries generated by animal studies, these appear safe for humans. If you miss the caffeine in energy drinks, take some coffee or tea (easy on the sugar, please).
- Eat fruit instead of drinking fruit drinks. And don't even worry about making up for the vitamins in vitamin water; your normal diet will provide all the vitamins you need.
- If you use sweeteners for coffee, tea or cereal, consider artificial sweeteners. They can help you cut down on sugar, but don't rely on them for weight control. That requires a long-term commitment to diet and exercise.
- Switch up dessert. Instead of a steady diet of cake and pie, experiment with fresh or dried fruit, low-fat yogurt or low-fat frozen desserts that don't have a lot of added sugar.
- Re-think snacks and treats. Instead of candy or cookies, try fruits, nuts (unsalted, please), yogurt or frozen desserts made without added sugar, or no-sugar-added frozen desserts. Fresh veggies with dip also make a good snack.
- Read food labels. Try to reduce your consumption of foods with added sugars in any form. Added sugar shows up on food labels as glucose, dextrose, fruit juice concentrates, maple syrup, molasses and high fructose corn syrup.
Sugar has always been part of the human diet, and it always will be. Doctors have no quarrel with naturally sweet foods, but they have important worries about the large quantities of sugar that are added to foods and drinks during manufacturing and processing. Fresh, unprocessed foods are natural and they can help make life healthy and sweet.
Harvey B. Simon, M.D., is an Associate Professor of Medicine at Harvard Medical School and a member of the Health Sciences Technology Faculty at Massachusetts Institute of Technology. He is the founding editor of the Harvard Men's Health Watch newsletter and author of six consumer health books, including The Harvard Medical School Guide to Men's Health (Simon and Schuster, 2002) and The No Sweat Exercise Plan, Lose Weight, Get Healthy and Live Longer (McGraw-Hill, 2006). Dr. Simon practices at the Massachusetts General Hospital; he received the London Prize for Excellence in Teaching from Harvard and MIT.