Long-derided saturated fats -- associated with an array of health problems such as heart disease -- caught a break Friday when research revealed their intake could be doubled or even nearly tripled without driving up their level in a person's blood.
Carbohydrates, meanwhile, are associated with heightened levels of a fatty acid linked to increased risk for diabetes and heart disease, the same study showed.
"The point is you don't necessarily save the saturated fat that you eat, and the primary regulator of what you save in terms of fat is the carbohydrate in your diet," senior author Jeff Volek of Ohio State University, said in the report.
To conduct the study, which appeared in the journal PLOS ONE, scientists put 16 participants on a strict dietary regime that lasted four and a half months.
Every three weeks their diets were changed to adjust carbohydrate and total fat and saturated fat levels.
The scientists found that when carbs were reduced and saturated fat was increased, total saturated fat in the blood did not increase, and even went down in most people.
The fatty acid called palmitoleic acid, which is associated with "unhealthy metabolism of carbohydrates that can promote disease," went down with low-carb diets and gradually increased as carbs were re-introduced, the study said.
An increase in this fatty acid indicates that a growing proportion of carbohydrates is being converted into fat instead of being burned by the body, the researchers said.
"When you consume a very low-carb diet your body preferentially burns saturated fat," Volek said.
"We had people eat two times more saturated fat than they had been eating before entering the study, yet when we measured saturated fat in their blood, it went down in the majority of people," he said.
The finding "challenges the conventional wisdom that has demonized saturated fat and extends our knowledge of why dietary saturated fat doesn't correlate with disease," Volek added.
By the end of the trial, participants saw "significant improvements" in blood glucose, insulin and blood pressure and lost an average of 22 pounds (10 kilograms).
"There is widespread misunderstanding about saturated fat. In population studies, there's clearly no association of dietary saturated fat and heart disease, yet dietary guidelines continue to advocate restriction of saturated fat. That's not scientific and not smart," Volek said.
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Good carbs for your body:
cookbookman17/FlickrKidney, pinto, black, garbanzo -- just about any type of bean provides a hearty dose of fiber and little sugar. An ounce of black beans, for example, contains 7 total grams of carbs, 2 of which are fiber.
Of course, beans have the additional benefit of providing protein, and one study found that bean eaters weighed less (but ate more!) than people who avoided beans, WebMD reported.
levork/FlickrSquash, like butternut here, is another low-sugar, high-fiber source of carbs. A cup of cooked butternut cubes contains nearly 22 grams of carbohydrates, more than 6 of which are fiber.
The bright hue of butternut and other squashes signifies the presence of carotenoids, a type of disease-fighting antioxidant.
sweetbeetandgreenbean/FlickrThe particular type of fiber in oats has been linked to improved heart health and weight management, as well as lower cholesterol. Just don't overdo it on the sugar-sweetened toppings!
Alan Cleaver/FlickrIn some of the greatest news: Popcorn is a whole grain. Stick to the air-popped variety so you don't overdo it on fat and sodium -- one cup has 6 grams of carbs, 1 of which is fiber, and has only 31 calories.
emmadiscovery/FlickrNot only does one cup contain 5 grams of fiber, but quinoa is also a complete protein. That means it contains all nine of the essential amino acids, which cannot be made by the body and therefore must come from food.
cseeman/FlickrAny potato (with the skin on!) is a great source of fiber-rich carbs, but sweet potatoes are loaded with those same colorful carotenoids as squash. Sweet taters boast some vitamin C, protein and potassium, to boot.
keepon/Flickr"Nature's power bar" rivals sports drinks when it comes to providing athletes with energy (i.e. carbs) thanks to those natural sugars. But a medium banana also contains 3 grams of fiber and a hearty dose of vitamin B6, crucial for more than 100 different functions in the body.
@rsseattle/FlickrJust about any variety will deliver some fiber and a whole host of vitamins and antioxidants. Blueberries are one of our favorite picks, since an entire cup will only set you back 84 calories. Plus, eating just one serving of the tiny superfruit a week has been linked with warding off cognitive decline as we age.