Getting reliable information about nutrition can be a daunting challenge. For the most part, your nutrition information is likely to come from TV and radio talk shows or news, your daily newspaper, your favorite magazine, a variety of nutrition-oriented books, and the Internet. How can you tell whether what you hear or read is really right?
The people who make nutrition news may be scientists, reporters, or simply someone who wandered in with a new theory (Artichokes prevent cancer! Never eat cherries and cheese at the same meal! Vitamin C gives you hives!), the more bizarre the better. But several groups of people are most likely to give you news you can use with confidence. For example:
Consumer alert: Regardless of the source, nutrition news should always pass what you may call The Reasonableness Test. In other words, if a story or report or study sounds ridiculous, it probably is.
Want some guidelines for evaluating nutrition studies? Read on.
Can you trust this study?
You open your morning newspaper or turn on the evening news and read or hear that a group of researchers at an impeccably prestigious scientific organization has published a study showing that yet another thing you've always taken for granted is hazardous to your health. For example, the study says drinking coffee stresses your heart, adding salt to food raises blood pressure, or fatty foods increase your risk of cancer or heart disease.
So you throw out the offending food or drink or rearrange your daily routine to avoid the once-acceptable, now-dangerous food, beverage, or additive. And then what happens? Two weeks, two months, or two years down the road, a second, equally prestigious group of scientists publishes a study conclusively proving that the first group got it wrong: In fact, this study shows coffee has no effect on the risk of heart disease — and may even improve athletic performance; salt does not cause hypertension except in certain sensitive individuals; only some fatty foods are risky.
Who's right? Nobody seems to know. That leaves you, a layperson, on your own to come up with the answer. Never fear — you may not be a nutritionist, but that doesn't mean you can't apply a few common-sense rules to any study you read about, rules that say: "Yes, this may be true," or "No, this may not be."
Does this study include human beings?
True, animal studies can alert researchers to potential problems, but working with animals alone cannot give you conclusive proof.
Different species react differently to various chemicals and diseases. For example, although cows and horses can digest grass and hay, human being can't. And while outright poisons such as cyanide clearly traumatize any living body, many foods or drugs that harm a laboratory rat won't harm you. And vice versa. For example, mouse and rat embryos suffer no ill effects when their mothers are given thalidomide, the sedative that's known to cause deformed fetal limbs when given to pregnant monkeys — and human beings — at the point in pregnancy when limbs are developing. (And here's an astounding turn: Modern research shows that thalidomide is beneficial for treating or preventing human skin problems related to Hansen's disease [leprosy], cancer, and/or autoimmune conditions, such as rheumatoid arthritis, in which the body mistakenly attacks its own tissues.)
Are enough people in this study?
Hey, researchers' saying, "Well, I did give this to a couple of people," is simply not enough. The study must include sufficient numbers and a variety of individuals, too. If you don't have enough people in the study — several hundred to many thousand — to establish a pattern, there's always the possibility that an effect occurred by chance.
If you don't include different types of people, which generally means young and old men and women of different racial and ethnic groups, your results may not apply across the board. For example, the original studies linking high blood cholesterol levels to an increased risk of heart disease and linking small doses of aspirin to a reduced risk of a second heart attack involved only men. It wasn't until follow-up studies were conducted with women that researchers were able to say with any certainty that high cholesterol is dangerous and aspirin is protective for women as well — but not in quite the same way: In January 2006, the Journal of the American Medical Association reported that men taking low dose aspirin tend to lower their risk of heart attack. For women, the aspirin reduces the risk of stroke. Vive la difference!
Is there anything in the design or method of this study that may affect the accuracy of its conclusions?
Some testing methods are more likely to lead to biased or inaccurate conclusions. For example, a retrospective study (which asks people to tell what they did in the past) is always considered less accurate than a prospective study (one that follows people while they're actually doing what the researchers are studying), because memory isn't always accurate. People tend to forget details or, without meaning to, alter them to fit the researchers' questions.
Are the study's conclusions reasonable?
When a study comes up with a conclusion that seems illogical to you, chances are the researchers feel the same way. For example, in 1990, the long-running Nurses' Study at the Harvard School of Public Health reported that a high-fat diet raised the risk of colon cancer. But the data showed a link only to diets high in beef. No link was found to diets high in dairy fat. In short, this study was begging for a second study to confirm (or deny) its results.
And while we wait for that second and, naturally, third study, you can bet we're keeping an open mind. The nature of life is that things do change, sometimes in surprising ways. Consider dioxin, a toxic contaminant found in some fish. Consider Olestra, the calorie-free fat substitute that makes some tummies rumble. As you read this page, dioxin's still a bad actor, but in 2005 researchers at the University of Cincinnati and the University of Western Australia announced that eating foods containing Olestra may speed your body's elimination of — you guessed it — dioxin. A-maz-ing.
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