Why Nutrition Advice Flip-Flops All The TimeOr Does It?

These are baffling times for health-conscious Americans. It seems that as soon as the implications of the latest diet study sink in, another comes along to contradict it. For example: Eggs are bad, eggs are okay; fiber is good, fiber doesn’t matter; margarine is the better spread, margarine is as bad as butter. These flip-flops are enough to get even the most conscientious eater fed up. And that has detrimental consequences.

In a recent survey of 1,750 adults, the more muddled they were about dietary recommendations, the more likely they were to eat high-fat diets and skimp on fruits and vegetables.

Why the confusion? The ever-evolving “gray” nature of science conflicts with human nature, which craves black-and-white finality. But nutrition science unfolds slowly and its movement is seldom unidirectional. If it seems like the experts are always changing their minds, it’s because they are, explains David Klurfeld, Ph.D., of Wayne State University in Detroit. “Dietary advice is based on what is known today. Tomorrow may contradict today; that’s the nature of science.”

Of Reporters and Researchers. Much of the confusion is compounded because headline writers have different goals than nutrition researchers. Reporters highlight unusual findings to grab your attention. Researchers, on the other hand, view each new study as a stepping stone to the truth, well aware that the latest finding may not stand the test of time. It is the total body of evidence?confirmed and reconfirmed?not the latest headlines, that should influence food choices.

The Making of a Flip-Flop. Uncertain science?especially when mishandled by the media?is often at the core of a seeming flip-flop. For example, last year’s shocking headlines that fiber does not prevent colon cancer misrepresented the research findings as the final word on a diet-disease relationship that is still uncertain. The research in question looked at whether colon polyps?which can turn cancerous?reappeared after eating fiber, but did not even study whether those polyps became cancerous. Perhaps fiber is protective after all or maybe something else in fiber-rich fruits, vegetables or whole grains keeps cancer at bay. For this and other reasons (see chart), you should still aim to eat more high-fiber foods.

Often, what seems like a flip-flop is really just a shift in emphasis for scientists. For example, researchers have known for years that too much fat?especially saturated fat?is not good. It now appears that for some people, a moderate amount of fat?especially if much of it is monounsaturated?may be heart-healthier than a very low-fat diet. Moreover, while saturated fat used to be considered the worst culprit, trans fats are now known to be just as bad. So the fat message didn’t really flip-flop; it became more complex, requiring nutritionists to refine the message.

Advice to Live By. One thing is certain. As scientific knowledge advances, dietary advice will change. To keep today’s advice in perspective, EN recommends the following:

  • Be cautious of overzealous reporting that flies in the face of conventional wisdom. Controversial news sells, but don’t rely on it for advice.
  • Read beyond the headlines. Perspective on how a study fits in with previous research may be found in a later article or more in-depth TV report.
  • Maintain a healthy skepticism about new research findings. Wait for additional evidence to accumulate before making significant changes to your diet. Listen to what the majority of experts are saying, not just the researchers of the study making news.
  • Realize there are no simple answers to preventing disease. Adopt lifestyle strategies best suited to you.
  • EN‘s advice? Stick with the tried and true?a varied diet of minimally processed foods. Choose plenty of fruits, vegetables and whole grains. Go easy on saturated and trans fats and salt plus practice portion control.

Changing Perspectives on Dietary Advice

What Experts Said What Experts Now Say EN’s Advice for Today
Don’t drink alcohol. Chronic drinking increases blood pressure and contributes to liver, pancreas and heart damage. Drinking alcohol in moderation may protect the heart by raising HDL’s, making blood less likely to clot and preventing LDL’s from clogging arteries. It may also lower the risk of ischemic stroke. However, alcohol may increase the risk of breast cancer and can be addictive. Moderate drinking’two drinks a day for men, one for women? may protect against heart disease. Do not drink if you are pregnant, have a history of alcohol abuse, have high blood triglycerides, liver disease or are at risk for breast cancer.
Caffeine increases the risk of heart disease, blood pressure, osteoporosis, miscarriage and raises blood cholesterol. Cut back on coffee, the greatest contributor to caffeine intake and which has been linked to pancreatic cancer. Coffee does not increase the risk of pancreatic cancer, nor does it appear to increase heart disease risk. Only nonfiltered coffee appears to raise blood cholesterol levels. Caffeine may raise blood pressure temporarily, if you?re not accustomed to it. Getting enough calcium offsets negative effects of caffeine on bones. Caffeine may reduce the risk of gallstones and symptoms of Parkinson’s disease. Effects on miscarriage are inconsistent. A moderate amount of caffeine?about 300 milligrams (the amount in two to three 8-ounce cups of coffee) a day?is considered safe. Caffeine’s link to Parkinson’s disease is too preliminary to act on. Women who are pregnant or trying to get pregnant should play it safe and limit or avoid caffeine.
Eat no more than three eggs a week, because high-cholesterol foods raise blood cholesterol levels. Eating eggs in moderation, up to one a day, may not increase risk of heart disease or stroke in most people. Saturated fats raise blood cholesterol far more than eggs. There’s no need for most people to avoid eggs, but don’t overdo it, either. Limit full-fat dairy foods, fatty meats and butter to help lower blood cholesterol.
Limit all types of fats, especially saturated fats like in butter, since they raise total cholesterol and LDL’s. A very low-fat diet may actually increase heart disease risk in some people. Monounsaturated fats are praised because they lower LDL’s and may raise HDL’s. Trans fats, found in most stick margarines and baked goods, are as (or more) harmful as saturated fats. Limit, but don’t try to eliminate, fat from your diet. Replace trans- and saturated fat-rich foods with mono-rich foods like olive and canola oils. Cut down on processed foods made with trans-containing hydrogenated oils. Buy trans-free margarine.
Fiber helps prevent colon cancer and lowers total cholesterol and LDL’s. Fiber may not protect against precancerous colon polyps or colon cancer. Fiber does help lower blood cholesterol and may help improve blood sugar levels. Fiber’s other potential benefits: prevents constipation, combats obesity and lowers the risk of other cancers, diabetes, heart disease and high blood pressure. Fiber itself may not prevent colon cancer, but it may work in concert with other substances in fruits, vegetables and whole grains to offer protection. Other benefits are reason enough to aim for 20-35 grams a day.
Too much sodium increases blood pressure. Since salt is the biggest source of sodium in the diet, it should be avoided. Reducing sodium may help lower blood pressure in some people, so cutting back is a good idea. Potassium, calcium, magnesium and fiber may also help lower blood pressure. A low-fat, high-produce diet that includes dairy foods can lower blood pressure. A high-sodium diet can leach calcium from bones, raising the risk of osteoporosis. Eat plenty of fruits, vegetables and low-fat dairy foods. Although not everyone is salt-sensitive, cutting back is a good idea because most people get far more than they need. Plus, excessive sodium may harm bones. Aim for 2,400 milligrams of sodium a day (one teaspoon of salt). Cut back on processed foods, where Americans get the most sodium.
Soy lowers blood cholesterol and heart disease risk plus it reduces the risk of breast and prostate cancers. Soy can eliminate hot flashes in post-menopausal women. Eat soy foods to get isoflavones, the active compounds. Soy’s effect on hormone-sensitive cells are inconsistent, leaving uncertainty about the safety of taking in large amounts of isoflavones if a person has or is at risk for a hormone-sensitive cancer (e.g. breast cancer). Limited evidence suggests isoflavones may help reduce the risk of osteoporosis. Evidence for whether soy has a small effect on relieving hot flashes is inconsistent. Include soy-based foods, such as soy milk, soy nuts, tofu and soy protein powder in your diet. People with or at high risk for hormone-sensitive cancers and those taking tamoxifen should avoid the large amounts of isoflavones in soy supplements and should limit soy foods to a few servings a week.
LDL’s = low-density lipoproteins (“bad” cholesterol)
HDL’s = high-density lipoproteins (“good” cholesterol)

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