I’m certain that if you live in the United States — or probably any western country — you’ve heard these five dietary claims. More than likely, you’ve heard them over-and-over ad nauseam. Unless you seek alternatives to mainstream dogma, you may not know that current research renders each as myth.
- Avoid saturated fat because dietary cholesterol causes heart disease.
- Margarine is better for you than butter.
- Eggs cause heart disease.
- Eating too much salt will cause hypertension.
- A calorie is a calorie is a calorie.
1. Avoid saturated fat because dietary cholesterol causes heart disease.
Despite the mantra that eating foods high in cholesterol drives up blood cholesterol — a proposition first argued by Ancel Benjamin Keys in the 1950s — the science behind the claim has always been shaky.
In his “Seven Countries” study, Keys ostensibly made the case for restricting saturated fat intake. There were a few problems with the study, however. First, 13,000 men; no women. Second, countries with data that did not support the thesis weren’t included, such as high-fat-consumption folks in France, Sweden and West Germany. Keys started with Yugoslavia in 1958. He would eventually select only six countries out of 21 with available data; data from those other countries muddled his thesis.
Not only that, Keys missed the true diet of the Crete peasants chosen for being long-lived, an oversight not articulated until 2002 (pdf). 2002!
An almost endless number of observations and experiments have effectively falsified the hypothesis that dietary cholesterol and fats, and a high cholesterol level play a role in the causation of atherosclerosis and cardiovascular disease. The hypothesis is maintained because allegedly supportive, but insignificant findings, are inflated, and because most contradictory results are misinterpreted, misquoted or ignored.
In 1961, Keys joined the nutrition committee of the American Heart Association, where he persuaded the committee to overturn its reluctance to endorse his hypothesis. That same year, the AHA issued the the country’s first guideline targeting saturated fats (pdf).
Too much [saturated fat] tends to increase the cholesterol in the blood.
Twenty years later, the U.S. Department of Agriculture would follow. By 1993, the U.S. Food and Drug Administration required that saturated fat and cholesterol be listed on food labels.
Between the 1950s and today, lab technology improved. Back then, we had only one measurement for blood cholesterol. Today, we know that there is HDL (high density lipoprotein, the good guys) and LDL (low density lipoprotein, the bad guys). Their ratio is more important than total cholesterol.
But there is one more element in this puzzle: there are two types of LDL cholesterol: large, buoyant (type A) LDL particles (the good guys, linked to saturated fat) and small, dense (type B) LDL particles (the bad guys, linked to carbohydrate intake and heart disease). Research in the 1990s began focusing on this difference. In 2004, this heart specialist summarized (pdf):
A growing body of evidence suggests that LDL particles that are small and dense are more atherogenic than those which are large and “fluffy.”
In early 2014, researchers examined 72 studies focused on diet and heart disease (a meta-analysis). Their conclusions indict much of the public heath messaging of the second half of the 20th century:
They found no significant evidence that saturated fats increase the risk of heart disease and no significant evidence that omega-6 and omega-3 polyunsaturated fats protect the heart.
And in the fall of 2014, the Annals of Internal Medicine reported on a year-long study featuring a racially- and age-diverse group of 148 men and women without clinical cardiovascular disease and diabetes. One group ate “low-carb” and the other ate “low-fat.” Which was more healthy at the end?
The low-carbohydrate diet was more effective for weight loss and cardiovascular risk factor reduction than the low-fat diet.
Nevertheless, you’ll see claims that saturated fat = heart disease in bookstores, reputable websites, and, probably, in your doctor’s office.
2. Margarine is better for you than butter.
The emphasis on removing saturated fat from our diets led to substitutions like margarine for butter. Margarine was made primarily from partially hydrogenated oil, a manufactured product that we now know as transfats.
In 2013, the FDA began the process of labeling transfats as no longer “generally recognized as safe” as it began banning all transfats.
3. Eggs cause heart disease.
Eggs have been a victim of the “dietary saturated fat equals heart disease” myth. In the era of dietary-cholesterol-avoidance, the level of cholesterol in an egg yolk — about 200 mg for a large egg — was considered “high.”
By 2006, researchers were pointing out that eggs helped increase good cholesterol, HDL. Not only that, the research showed that “most people’s bodies handle the cholesterol from eggs in a way that is least likely to harm the heart.”
A 2012 meta-analysis examined the “dose response” relationship between coronary heart disease and stroke. The take-away: eating an egg a day does not increase your risk of coronary heart disease or stroke.
This flies in the face of the recommended American diet, where we are encouraged to substitute cereal for eggs in the morning. But in April 2014, JAMA Internal Medicine published research showing the breakfast culprit isn’t eggs. It’s sugared cereal and yogurt:
Most US adults consume more added sugar than is recommended for a healthy diet. We observed a significant relationship between added sugar consumption and increased risk for CVD mortality.
4. Eating too much salt will cause hypertension.
Nevermind that causation is very difficult to show; correlation is the more common research outcome. However, in 2011
Scientific American published the results of a meta-analysis of research on salt and diet; there were 6,250 subjects. The verdict?
[N]o strong evidence that cutting salt intake reduces the risk for heart attacks, strokes or death in people with normal or high blood pressure.
The 2011 research was the latest in a series of research reports exonerating salt.
Intersalt, a large study published in 1988, compared sodium intake with blood pressure in subjects from 52 international research centers and found no relationship between sodium intake and the prevalence of hypertension. In fact, the population that ate the most salt, about 14 grams a day, had a lower median blood pressure than the population that ate the least, about 7.2 grams a day…
One oft-cited 1987 study published in the Journal of Chronic Diseases reported that the number of people who experience drops in blood pressure after eating high-salt diets almost equals the number who experience blood pressure spikes; many stay exactly the same.
Yet the American Heart Association continues to insist that “sodium (salt) is your enemy” (October 7, 2014).
Is it any wonder that some Americans choose to ignore all medical and science news?
5. A calorie is a calorie is a calorie.
“SugarScience shows that a calorie is not a calorie but rather that the source of a calorie determines how it’s metabolized,” said pediatric endocrinologist Robert Lustig, a member of the SugarScience team and the author of Fat Chance: Beating the Odds Against Sugar, Processed Food, Obesity, and Disease.
The World Health Organization has reduced its recommendation that no more than 10% of an adult’s calories should come from added sugar or from natural sugars in honey, syrups and fruit juice. The new recommendation is 5%; for a 2,000-calorie diet, that’s 25 grams.
- Yoplait yogurt has as much as 26 grams of sugar per serving
- Dannon yogurt has as much as 24 grams of sugar per serving
- Pop-tarts have 17-34 grams of sugar per serving
- Some cereals are more than 50% sugar by weight
When it comes to breakfast cereal, FDA researchers estimate that “the average person eats 30 percent more than the serving size given on the boxes.” So label reading isn’t very helpful.
“When you exclude obviously sugar-heavy foods like candy, cookies, ice cream, soft and fruit drinks, breakfast cereals are the single greatest source of added sugars in the diets of children under the age of eight,” according to the the author of a 2014 Environmental Working Group analysis of more than 1,500 cereals.