Does Saturated Fat Affect Your Cholesterol?

Krauss isn’t the first doctor to question the role of saturated fat in CVD. Many others have, but they’ve often been dismissed.

“More than 20 studies have shown that heart patients don’t eat more saturated fat compared with people who don’t have heart disease,” says Uffe Ravnskov, M.D., Ph.D., of Lund, Sweden. “Eight studies have shown that people with stroke have eaten less saturated fat than healthy people. And no dietary study has succeeded in lowering heart disease deaths by reducing intake of saturated fat,” he adds.

For several decades, medical and nutritional advice boiled down to this: too much dietary saturated fat leads to higher levels of blood cholesterol and an increase in CVD risk.

Many people have believed that a high-protein, low-carb diet was the worst thing a person could eat because it was presumed to contained lots of saturated fat and cholesterol. (Not all animal protein, however, is rich in saturated fat.) But over the past 10 years, numerous studies have given scientific credence to high-protein, low-carb diets – not just for losing weight, but also for improving multiple CVD risk factors.

“As a predictor of CVD risk, total blood cholesterol has limited value. That’s because half of the people who suffer a heart attack have normal cholesterol levels,” says Ron Hunninghake, M.D., chief medical officer of the nutritionally oriented Riordan Clinic in Wichita, Kansas.

To make sense of the often convoluted relationship between blood cholesterol levels and heart disease risk, researchers have studied cholesterol fractions, such as the “bad” low- density lipoprotein (LDL) and “good” high-density lipoprotein (HDL). These lipoproteins happen to be one of Krauss’ top areas of expertise. Although LDL is widely regarded as the bad cholesterol, it’s not just one nasty glob. It has both bad and good forms.

To explain, “pattern B LDL” consists of small dense particles that are more likely to infiltrate blood-vessel walls and set the stage for blockages, leading to a heart attack or stroke. In fact, Krauss says that high blood levels of pattern B LDL are currently the best predictor of CVD risk. In contrast, high blood levels of “pattern A LDL,” which consists of large fluffy particles, are associated with a low risk of CVD.

Now here’s the mind-blower: Saturated fat does increase LDL levels. But Krauss’ research shows that, if you’re eating a moderately low-carb diet, this increase is mostly in the good pattern A form of LDL. In other words, eating saturated fat while on any kind of low-carb diet has either a neutral or protective effect against CVD. Furthermore, saturated fat boosts levels of HDL cholesterol.

In contrast, diets high in refined carbs (e.g., cereals, pizzas, pastas, breads, muffins, bagels, and sweets) boost the dangerous pattern B LDL and lower HDL cholesterol – thereby increasing the risk of CVD – especially when combined with a sedentary lifestyle. Consider a European study that tracked almost 48,000 people. Those who cut back on saturated fat, but ate more refined carbs and sugars, developed dyslipidemia, a high-risk pattern of blood cholesterol and triglyceride. They also gained weight and became more likely to have signs of prediabetes. ³

Origins of the Sat-Fat-Is-Bad Theory

There’s no denying that scores of studies have shown a link between saturated fat and CVD. Krauss says that most have been the result of “publication bias,” meaning that medical journal editors favored publishing research on the potential risks of saturated fat, while ignoring findings that challenged the prevailing view. He also believes that many of the saturated-fat-is-bad studies have not accounted for diets containing a lot of sugars, refined carbs, and trans fats.

The link between saturated fat and cholesterol and the risk of CVD grew largely out of studies by the late Ancel Keys, Ph.D., a researcher at the University of Minnesota. Keys was originally skeptical of the idea that saturated fat caused heart disease and that blood cholesterol could predict risk. But once Keys embraced both of those ideas in the early 1950s, he cherry-picked research to support his argument. For example, Keys focused on the eating habits linking saturated fat to CVD in seven European nations that supported this theory, while ignoring contradictory data from 15 other nations, including France. In the so-called French paradox, people ate a lot of fat but had a low incidence of CVD.

The big push against saturated fat actually came from Senator George McGovern, who, based on Keys research, recommended in 1977 that Americans adopt diets low in saturated fat and high in carbohydrates to lower the risk of heart disease. Since then, Americans have decreased their consumption of saturated fat from 13.5 percent to 11 percent of total calories by 2000. In 2006, the American Heart Association recommended that people reduce their saturated fat intake to just 7 percent of calories, thereby increasing total intake of carbohydrates. But until recently, few officials distinguished between refined grains – calorie-rich starches – and whole grains and the complex carbs found in vegetables.

What Do You Replace Saturated Fat With?

When a person eliminates a significant amount of calories from the diet, he typically replaces it with some other source of calories (unless the person is simply trying to reduce calories). When doctors began recommending reductions in saturated fat intake, processed-food companies responded by marketing thousands of low-fat and zero-fat foods. To maintain taste, sugars and hydrogenated vegetable oils replaced the saturated fat.

But the resulting shift toward refined carbohydrates set the stage for dramatic increases in overweight, obesity, prediabetes, and type-2 diabetes. Two of every three Americans are now overweight or obese, around 100 million have prediabetes, and some 25 million have type-2 diabetes. And excess weight and blood sugar problems raise the risk of CVD.

In a study of more than 35,000 men and women over 12 years, Danish researchers reported that people were more likely to suffer a heart attack if they cut back on saturated fat and replaced it with high-glycemic foods such as white breads, muffins, potatoes, and desserts. However, if the people in the study replaced saturated fat with high-fiber vegetables, fruits, and grains, they were less likely to have a heart attack.⁴

Still other studies echo the beneficial effects of diets with relatively large amounts of protein and saturated fat and small amounts of carbs. In one of the studies, Gary D. Foster, Ph.D., of Temple University in Philadelphia, reported that people eating a high- protein, low-carb diet benefited from lower blood pressure, reductions in LDL cholesterol, and increases in HDL cholesterol – all of which would lessen the risk of CVD. ⁵

Another study of 322 men and women found that a high-protein, low-carb diet helped people lose more weight, compared with people on Mediterranean or low-calorie high- carb diets. Blood sugar levels improved, and the subjects following a high-protein, low- carb diet averaged a 23.7 decrease in triglycerides and a 29 percent decrease in levels of C-reactive protein (CRP) levels, both strong risk factors for CVD.⁶

The key then is not so much about limiting saturated fat, but avoiding insulin-provoking foods such as refined carbs and sugars. “It just doesn’t make sense to focus on just one feature of the diet, such as saturated fat, while ignoring the health effects of the overall diet,” Krauss says.

So, What Should You Eat?

Eating habits often gain a quasi-religious aura, with advocates of one or another approach developing a stridency and, in some cases, a zealotry. But the ancient human diet, sometimes called the Paleolithic diet, provides clues to what might be the best diet for most people.

“Given our ancestral diet, meal plans fairly high in quality proteins and low in processed carbohydrates would seem to be what most people are best suited to,” says Loren Cordain, Ph.D., a professor at Colorado State University in Fort Collins. “Our genes are virtually identical to those in people living 20,000 years ago, and our genes evolved with us eating lean proteins and vegetables. Eating a lot of processed grains and sugars is a total mismatch for our genetic heritage.”

• Saturated fat. Krauss doesn’t see any point in obsessing about saturated fat. Eggs and dairy are fine, and cheese might actually provide heart benefits. He suggests that red meat be eaten in moderation, because it may boost the risk of heart disease and cancer for reasons unrelated to saturated fat (e.g., don’t eat red meat at every meal).
• Vegetables. Eat your veggies, lots of them, because their role in disease prevention is so well established. “Multiple servings, preferably at every meal,” Krauss advises.
• Carbohydrates. Cut back on carbs, but don’t eliminate them. Best source: veggies and fruits. If you eat bread, Krauss suggests eating whole-kernel bread, in which the seeds (cracked and whole) are visible and abundant.

Hunninghake generally concurs, but adds, “I generally suggest that people tailor their carb intake to their weight, blood sugar, and activity level. If they’re good on all three counts, they can probably consume a little more in the way of carbs. But if they’re overweight, have high blood sugar, and are couch potatoes, they should be getting their carbs from high-fiber vegetables, not grains.”

References

1. Siri-Tarino PW, Sun Q, H FB, Krauss RM. Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease. American Journal of Clinical Nutrition, 2010;91:535-545.
2. Siri-Tarino PW, Sun Q, H FB, Krauss RM. Saturated fat, carbohydrate, and cardiovascular disease. American Journal of Clinical Nutrition, 2010;91: 502-509.
3. Sieri S, Krogh V, Berrino F, et al. Dietary glycemic load and index and risk of coronary heart disease in a large italian cohort: the EPICOR study. Arch Intern Med, 2010;170:640-647.
4. Jakobsen MU, Dethlefsen C, Joensen AM, et al. Intake of carbohydrates compared with intake of saturated fatty acids and risk of myocardial infarction: importance of the glycemic index. American Journal of Clinical Nutrition, 2010; epub doi 10.3945/ajcn.2009.29099
5. Foster GD, Wyatt HR, Hill JO, et al. Weight and Metabolic Outcomes After 2 Years on a Low-Carbohydrate Versus Low-Fat Diet: A Randomized Trial. Annals of Internal Medicine, 2010; 153:147-157.
6. Shai I, Schwartzfuchs D, Henkin Y, et al. Weight loss with a low-carbohydrates, Mediterranean, or low-fat diet. New England Journal of Medicine, 2008;359: 229-241.