You can almost picture the news editors and producers jumping on this story:
“Eating three or more servings of blueberries and strawberries per week may help women reduce their risk of a heart attack by as much as one-third,” according to a study published in the American Heart Association clinical journal in Circulation.
Wow. Worried about a heart attack because your diet is less than ideal, or your lifestyle is a little too sedentary?
Not to worry. Just pick up a bag of berries at the supermarket, and your worries are over.
At least that’s the way the media—including CBS News, National Public Radio and CNN--is spinning what is, in reality, a study with a ton of variables that clouds its conclusions.
And they are some stunning conclusions, if one takes them at face value.
Eating three servings a week—a serving being one-half cup—of blueberries or strawberries reduces cardiovascular risk, because these fruits (and lots of others, by the way) contain high levels of dietary flavonoids. These compounds help dilate arteries, counter the buildup of plaque and provide other benefits, according to the study, which was funded by Britain’s National Institutes of Health and the Biotechnology and Biological Sciences Research Council.
“Blueberries and strawberries can easily be incorporated into what women eat every week,” Eric Rimm, D.Sc., senior author and Associate Professor of Nutrition and Epidemiology at the Harvard School of Public Health, stated in an HSPH news release. “This simple dietary change could have a significant impact on prevention efforts.”
Scientists from Harvard and the UK’s University of East Anglia conducted a prospective study among 93,600 women ages 25 to 42 registered with the Nurses’ Health Study II. That’s obviously a huge sample size, but here’s the problem: The women completed questionnaires about their diet once every four years for 18 years (emphasis added). Heck, most adults can’t remember what they ate last night, much less four years ago. And dietary recall studies are notorious for overestimating the quantity of “good” foods eaten, while seriously low-balling the “bad” foods.
This study found that women who ate the most blueberries and strawberries had a 32% reduction in their risk of heart attack, compared with women who ate berries only once a month or less, and the findings were independent of such risk factors as age, high blood pressure, family history of heart attack, body mass, exercise, smoking, caffeine or alcohol intake.
That all sounds impressive, but keep in mind that association—more berries being associated with fewer heart attacks—does not indicate causation. In fact, it’s not a leap of faith to suggest that people eating larger quantities of any fruit are likely to have an overall healthier diet, versus people who aren’t eating much in the way of fruits and likely relatively few vegetables, as well.
Plus, let’s not forget the standard prescription that AHA tacks onto virtually every news release concerning heart disease and nutrition: “AHA recommends eating a variety of foods as the most prudent way to ensure that you get the optimum amounts of both macronutrients and micronutrients. Use of foods containing plant sterols [ie, flavenoids] should be reserved for adults requiring lower total and lower LDL cholesterol levels because they are at high risk of—or have had—a heart attack.”
Why the qualifier? Because any alleged beneficial effects, at this point, remain speculative. Here is AHA cautioning against jumping on the flavenoid bandwagon:
“Large population studies have often shown links between the intake of vegetables and fruits and coronary heart disease that aren’t clearly attributable to major macronutrients or known vitamins and minerals. This suggests that other components of plants may be important in lowering risk of cardiovascular disease. Although the literature contains studies of numerous possible plant components, many of these studies are based on a small sample of subjects or were poorly controlled. Further, the notion itself has led to claims of ‘miracle’ ingredients with supposed beneficial effects on cardiovascular diseases and other chronic diseases.”
Hm-m-m-m . . . “Miracle” ingredient?
Let’s review: “[Eating berries] may help dilate arteries, counter the buildup of plaque, reduce their risk of developing Parkinson’s disease, reduce their risk of a heart attack by as much as one-third and reduce the risk of a heart attack later in life.”
That sounds like a pretty miraculous outcome merely as a result of eating strawberries or blueberries a few times a week.
Not to mention that nobody—well, virtually nobody—eats berries au naturel. Typically, they’re dumped on top of ice cream, mixed into yogurt or piled on top of cereal. Not that those foods are unhealthy, but it introduces a complicating factor, an uncontrolled variable, as researchers characterize it, that makes it less likely that any effects of a diet including berries can be attributed solely to the berries themselves.
The bottom line here is that eating fruits of any sort is generally a good thing, especially as part of AHA’s “balanced diet” recommendation.
But pretending that wolfing down berries trumps all the other things we’re supposed to be doing to protect our health is about as soft a conclusion as those fruits themselves.
The opinions expressed in this commentary are solely those of Dan Murphy, a veteran food-industry journalist and commentator.