“The question is whether saturated fat is harmful or is just a bystander,” Ronald M. Krauss, M.D. says. Krauss directs atherosclerosis research at the Children’s Hospital Oakland Research Institute, a major medical center. “Saturated fat may have an effect on cardiovascular disease (CVD) risk, but the effect is so small that we just can’t detect it. We shouldn’t be demonizing saturated fat,” he adds.

Krauss is mild-mannered and not contrarian by nature. He has held high-level positions in the American Heart Association, and he sticks to following the science, wherever it might lead. In 2010, he and his colleagues published two articles in the American Journal of Clinical Nutrition that questioned the mantra that too much saturated fat causes heart disease and other types of CVD. In one study, they analyzed 21 published studies involving almost 350,000 people who were tracked from five to 23 years. They found that people who consumed the most saturated fat did not have a higher risk of heart disease, stroke, or any other form of CVD. ^{1 2}

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 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 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 percentof total calories by 2000. The American Heart Association still recommends that people reduce their saturated fat intake to less than 10% of calories, thereby increasing total intake of carbohydrates.⁴

What Do You Replace Saturated Fat With?

When a person eliminates a significant amount of calories from the diet, they typically replace 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 highly processed vegetable oils replaced the saturated fat.

But the resulting shift toward refined carbohydrates resulted in dramatic increases in overweight, obesity, prediabetes, and type-2 diabetes. 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 lower glycemic index foods such as high-fiber vegetables, fruits, and whole grains, they were less likely to have a heart attack.⁵

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.⁶

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 mg per deciliter decrease in triglycerides and a 29 percent decrease in levels of C-reactive protein (CRP), both strong risk factors for CVD.⁷

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 should be eaten in moderation, because it may boost the risk of heart disease and cancer for reasons unrelated to saturated fat.
• 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.”

C15:0 – An Example of the Benefits of Saturated Fats

Limiting dairy consumption to limit saturated fat intake is often recommended for those at risk of cardiovascular disease, but multiple studies have found that those who eat a lot of dairy aren’t at greater risk of, and may even be protected from, major cardiovascular events.^{8 9 10} C15:0 (or pentadecanoic acid) may be one of the reasons why. C15:0 is an odd-chain saturated fatty acid that is mainly found in whole-fat dairy products such as whole milk, butter, cheese, and yogurt, and to a lesser extent in meat from ruminant animals. Meat and dairy from animals raised on pasture have been shown to have higher levels of C15:0 than conventionally raised meat and dairy.^{11 12} Blood levels of C15:0 correlate so strongly with the amount of dairy eaten that it is sometimes used as a blood marker for dairy intake. Epidemiological studies have found higher C15:0 blood levels to be associated with a lower risk of type 2 diabetes and heart disease as well as a lower total mortality risk.^{13 14 15 16 17 18}  In animal and in vitro studies, C15:0 shows anti-inflammatory and antifibrotic activity and improves mitochondrial function. It may do this in part by partially activating peroxisome proliferator-activated receptor-α (PPARα) and PPARδ, which play key roles in inflammation and metabolism homeostasis, and by activating adenosine monophosphate-activated protein kinase (AMPK), which regulates how energy is produced and used by the body.^{19 20} Overall, we still have much to learn about C15:0, including whether it is essential or if the body has the capacity to make it. However, available preliminary evidence points to a range of potential health benefits. In addition to obtaining C15:0 from whole-fat dairy foods, supplemental forms are also available and may help individuals achieve meaningful levels of this fatty acid.

References

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