Where's the sugar?
Naturally occurring sugars are found in fruits, vegetables, and dairy products. Because these foods contain only modest amounts of sugar and have plenty of important nutrients, they are healthful.
Added sugars are the syrups and granules added to foods during processing or preparation or at the table. The most popular added sugar these days is high fructose corn syrup. It's produced from corn syrup (nearly pure glucose) that is treated with enzymes to convert some of the glucose to fructose; at the end, glucose is added back in, so the final product has a mix of glucose and fructose that is very similar to table sugar.
Naturally occurring sugars are healthful, but added sugars are another matter. If they help increase consumption of healthful foods like yogurt or milk, they can be an asset, but when they are used to sweeten candy, baked goods, or beverages, they do much more harm than good.
Added sugars add up
According to the U.S. Department of Agriculture, the average American consumed the equivalent of 25 teaspoons of sugar a day in 1970, but the number rose to nearly 29.8 teaspoons a day by 2005. That corresponds to a 19% increase in daily caloric intake (400 to 476), much of it from high-fructose corn syrup. Not coincidentally, America's waistline began to expand during this period, fueling our worrisome epidemic of diabetes. The table shows the major sources of added sugar; although all are a concern, soft drinks and other sugar- sweetened beverages stand out. In fact, the average American increased consumption of caloric soft drinks by 70% between 1970 and 2000.
Added sugar in the American diet
Percentage of all added sugars
Candy and table sugar
Cakes, pies, cookies
Ice cream, sweetened yogurt, flavored milk
Various grains (cinnamon toast, etc.)
Source: Johnson et al. Circulation (Aug. 24, 2009), Vol. 120, pp. 1011–20.
Sugar, risk factors, and the heart
It's clear that America has a sweet tooth, and new evidence suggests that sugar is bad for the heart. Although the culprits are simple sugars, their relationship to cardiovascular disease is not so simple, since it depends on cardiac risk factors.
Obesity is strongly linked to many health problems, ranging from heart disease and hypertension to arthritis and prostate cancer. In all, obesity and overweight account for about 300,000 deaths in the U.S. each year; that's about one of every 10 deaths. Obesity is a complex problem, with many possible causes. Still, there's no denying that excess caloric consumption is a prime contributor to obesity, and that added sugar is a major source of excess (and empty) calories. Between the 1970s and the 2000s, the average American adult's caloric intake jumped by some 500 calories a day, more than enough to account for the rise in obesity that occurred during these same years. The increased consumption of sugar accounts for more than 15% of the extra calories. Sugar-sweetened beverages (soft drinks, fruit drinks, energy drinks, and vitamin water drinks) are particularly culpable, since consumption has tripled over the past 30 years.
Type 2 diabetes has increased in parallel with obesity, and sugar sweetened beverages appear to play an important role. Three large studies that collectively evaluated over 160,000 women for up to 18 years provide the clearest evidence of the link. As compared with people averaging less than one sugar-sweetened beverage a month, those consuming one to three a day were 24% to 83% more likely to develop type 2 diabetes. And a 2011 Harvard study of more than 40,000 men linked a high intake of sugar-sweetened beverages to a 24% increase in the risk of type 2 diabetes; the increased risk did not depend on obesity or total caloric intake.
Like obesity and diabetes, cholesterol is a major cardiac risk factor. In this case, though, there is only modest evidence that sugar boosts the leading suspect, LDL ("bad") cholesterol. But there is lots of evidence that a high intake of sugar is linked to two related risk factors, since it both lowers HDL ("good") cholesterol and raises triglycerides.
The major dietary cause of 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 disrespect it deserves, but two new studies should change that. A 2011 study of 2,696 adults in the U.S. and U.K. linked each daily serving of a sugar-sweetened beverage with a 1.6 millimeters of mercury (mm Hg) rise in systolic and a 1.1 mm Hg rise in diastolic blood pressure readings. And a 2010 study of 810 adults found that the trend can be reversed. Over an 18-month period, people who cut out just one 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 valid even after the researchers took body weight, caffeine, and other factors that influence 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%.
The 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.
To be diagnosed with the metabolic syndrome, a person needs to have just three of the following: abdominal obesity (waist circumference of 40 inches or more in men, 35 inches or more for women), high triglycerides (150 milligrams per deciliter [mg/dL] or higher), low HDL cholesterol (below 40 mg/dL for men, below 50 mg/dL for women), a blood pressure of 135/85 or higher, and insulin resistance (a fasting blood sugar of 100 mg/dL or higher). Since sugar contributes to each of these problems, it's no surprise it increases the risk of the risky metabolic syndrome. In fact, a study of 6,039 middle-aged men and women found that people 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.
It's clear that large amounts of sugar are linked to an increase in cardiac risk factors. But does that translate into actual clinical events?
It does. A 24-year Harvard study of 88,520 female nurses tells the story. The women were between the ages of 34 and 59 and none had been diagnosed with heart disease when the study began. As compared with women who had fewer sugary drinks, women who averaged one a day were 23% more likely to have heart attacks, while those who consumed over two a day had a 35% higher risk. The results held up even after researchers accounted for other cardiac risk factors.
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