A new study has found an association between fructose consumption and high blood pressure — a finding that has rekindled the debate about the health consequences of our American love affair with eating sugary things.
Especially highly processed sugary things. (I’m sorry. I find it difficult to call soft drinks and all that other sugar-laden, nutrient-deprived stuff on grocery shelves foods.)
For, yes, fructose is found naturally in fruits. But the vast majority of the fructose consumed by Americans comes from the table sugar (sucrose) and/or high-fructose corn syrup (a combination of sucrose and fructose) that manufacturers add to soft drinks, fruit-flavored drinks, bakery products, candies and other processed “foods.”
Particularly soft drinks.
In fact, the authors of this new study, which appears in the July issue of the Journal of the American Society of Nephrology, framed their findings in soft-drink terms: They reported that consuming the equivalent of 2.5 sugary soft drinks (74 grams of fructose) daily was “independently and significantly” associated with higher blood pressure — even in people without a history of high blood pressure.
The researchers (all from the University of Colorado in Denver) specifically found that taking in that much fructose daily was associated with a 77 percent increased risk of having a systolic blood pressure of 160 or higher. Systolic BP is the first number in a blood pressure reading. It measures how hard the blood is pushing against the artery wall while the heart is contracting, or beating. According to the National Heart Lung & Blood Institute, an optimal (healthy) blood pressure reading is one that’s less than 120/80 mmHg, while high blood pressure (hypertension) is a reading of 140/90 mmHG or above. Readings in between are considered borderline, or pre-hypertensive.
Why would fructose have an effect on blood pressure? Animal research, the Colorado researchers point out, suggest several possible mechanisms. The fructose may increase sodium absorption in the gut, or it may stimulate the sympathetic nervous system, or the endothelial nitric oxide synthase system, or the body’s production of uric acid – all factors involved in the regulation of blood flow and the health of the cardiovascular system.
Data for the current study was collected from more than 4,500 adults who filled out questionnaires from 2003 to 2006 as part of the ongoing National Health and Nutrition Examination Survey. The survey included questions about all sources of fructose, not just soft drinks. (Earlier studies involving fructose tended to focus on soft drink consumption alone.)
Interesting, but …
Now, this was an observational study, so it can’t prove cause-and-effect. The dietary data was self-reported (not always reliable), and although the researchers crunched the data to rule out potential confounding dietary factors like alcohol, salt, total carbohydrates and potassium intake, some other as-yet-unidentified factor may explain the increased risk for hypertension that the study uncovered.
Still, the findings are interesting — and troubling when you couple them with the fact that 31 percent of American adults have high blood pressure (up from 5 to 10 percent of adults 100 years ago). Hypertension is also becoming alarmingly more common among adolescents. “The rise in the incidence and prevalence of hypertension has been linked to adaptation of Western diets and culture,” write the study’s authors. “In particular, fructose consumption has increased dramatically in industrialized nations including the United States since the 1900s.”
But again, an association between two things doesn’t mean one causes the other. Clinical trials, of course, are needed to really determine if our ever-increasing passion for fructose-rich soft drinks and other “foods” has anything to do with our rising rate of hypertension. According to a report in Science News, the Colorado researchers intend to conduct such a study: one in which people’s blood pressure will be followed as they decrease their intake of fructose.
In the meantime, the American Heart Association recommends that women take in no more than 100 calories of added sugar daily and men no more than 150.
That’s less than you’ll find in a single can of most soft drinks.
That’s more than in one bottle of Starbucks frapuccino too. The American Heart Association says a “prudent upper limit of intake is half of the discretionary calorie allowance” which leaves me with about three teaspoons or thirteen grams per day. Time to enroll in sugar class at the co-op.