포화 지방은 ‘나쁜지방’ 아니에요 Study: Doubling Saturated Fat in the Diet Does Not Increase Saturated Fat in Blood

美 연구진 “탄수화물 섭취량 증가가 더 문제

 

 

[포화 지방 Saturated Fat]

포화 지방은 주로 동물성 기름(육류, 삼겹살, 피자, 햄버거, 치즈, 쇠기름, 유제품)에 많이 들어있다.

상온에서 고형상태이며 인체에서 분해가 잘 안되어 나쁜 콜레스테롤을 증가시킨다. 엔하위키

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​ ‘나쁜 지방’으로 알려진 포화 지방이 심장병과 당뇨를 유발하는 주된 원인은 아니라는 연구 결과가 나왔다.   제프 볼렉 미국 오하이오주립대 교수팀은 포화지방 섭취량이 2~3배 증가해도 혈중 포화지방산 농도가 높아지는 것은 아니라는 연구 결과를 내놨다.   상온에서 딱딱하게 굳는 성질을 가진 포화지방은 심장병과 당뇨 등의 질병을 유발하는 것으로 알려져 있다. 소고기와 돼지고기 기름이 포화지방에 속한다.   하지만 최근 심장병과 당뇨를 유발하는 물질은 포화지방 자체가 아닌 피 속에 녹아 있는 포화지방산이라는 연구 결과가 속속 나오면서 포화지방에 대한 오해가 조금씩 풀리고 있다.   볼렉 교수팀은 포화지방 섭취량과 혈중 포화지방산 농도는 상관관계가 없으며 오히려 탄수화물 섭취량이 증가할 때 혈중 지방산 농도가 높아진다는 사실을 확인하고 미국 공공과학도서관 학술지 ‘플로스원’ 21일자에 발표했다.   연구진은 16명의 참가자들에게 3주마다 1회씩, 총 18주간 6회에 걸쳐 탄수화물의 양은 차츰 높이고 전체 지방량과 포화지방량은 낮춘 식사를 제공했다. 실험 기간 내내 전체 식사 칼로리는 동일하게 유지했다.   실험 기간 동안 참가자들의 혈중 포화지방산 농도를 주기적으로 측정한 결과 포화지방 섭취량과 포화지방산 농도는 유의미한 상관관계가 없었다. 반면 탄수화물 섭취량이 많아질수록 비만과 당뇨 등 다양한 질병을 유발하는 혈장 팔미톨레산 농도가 높아지는 것으로 나타났다.   볼렉 교수는 “모두에게 평소 먹던 양보다 2배 정도 많은 포화지방을 먹게 했지만 오히려 혈중 포화지방산 농도가 낮아지는 경우도 있었다”며 “소고기와 돼지고기에 들어 있는 포화지방이 무조건 몸에 나쁘다는 인식은 편견”이라고 말했다. 동아사이언스 최영준 기자 jxabbey@donga.com

 

Study: Doubling Saturated Fat in the Diet

Does Not Increase Saturated Fat in Blood

 

Selections from the lowest-carb study diet

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New research links diabetes, heart disease risk to diet high in carbs, not fat

​ ​By: Emily Caldwell COLUMBUS, Ohio – Doubling or even nearly tripling saturated fat in the diet does not drive up total levels of saturated fat in the blood, according to a controlled diet study. ​ However, increasing levels of carbohydrates in the diet during the study promoted a steady increase in the blood of a fatty acid linked to an elevated risk for diabetes and heart disease. ​ 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,” said senior author Jeff Volek, a professor of human sciences at The Ohio State University.   “It’s unusual for a marker to track so closely with carbohydrate intake, making this a unique and clinically significant finding. As you increase carbs, this marker predictably goes up,” Volek said.The researchers found that total saturated fat in the blood did not increase – and went down in most people – despite being increased in the diet when carbs were reduced. Palmitoleic acid, a fatty acid associated with unhealthy metabolism of carbohydrates that can promote disease, went down with low-carb intake and gradually increased as carbs were re-introduced to the study diet.In the study, participants were fed six three-week diets that progressively increased carbs while simultaneously reducing total fat and saturated fat, keeping calories and protein the same. ​ When that marker increases, he said, it is a signal that an increasing proportion of carbs are being converted to fat instead of being burned as fuel. Reducing carbs and adding fat to the diet in a well-formulated way, on the other hand, ensures the body will promptly burn the saturated fat as fuel – so it won’t be stored. ​ “When you consume a very low-carb diet your body preferentially burns saturated fat,” Volek said. “We had people eat 2 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. Other traditional risk markers improved, as well.” ​ The research is published in the Nov. 21, 2014, issue of the journal PLOS ONE. ​ Volek and colleagues recruited 16 adults for the study, all of whom had metabolic syndrome, defined as the presence of at least three of five factors that increase the risk for heart disease and diabetes (excess belly fat, elevated blood pressure, low “good” cholesterol, insulin resistance or glucose intolerance, and high triglycerides). ​ After getting them to a baseline reduced-carb diet for three weeks, researchers fed the participants the exact same diets, which changed every three weeks, for 18 weeks. The diets started with 47 grams of carbs and 84 grams of saturated fat each day, and ended with 346 carb grams per day and 32 grams daily of saturated fat. ​ Each day’s meals added up to 2,500 calories and included about 130 grams of protein. The highest-carb level represented 55 percent of daily calories, which roughly matches the estimated daily percentage of energy provided by carbs in the American diet. ​ Compared to baseline, there were significant improvements in blood glucose, insulin and blood pressure that were similar across diets. Participants, on average, lost almost 22 pounds by the end of the trial. ​ When looking at palmitoleic acid, however, the scientists found that it consistently decreased on the high-fat/low-carb diet in all participants. The fatty acid then showed a step-wise increase in concentration in the blood as carbs were progressively added to the diet. Elevated levels of palmitoleic acid in the blood have been linked to obesity and higher risk for inflammation, insulin resistance, impaired glucose tolerance, metabolic syndrome, type-2 diabetes, heart disease and prostate cancer. ​ The study does not address what happens to palmitoleic acid levels when high carbs are combined with a diet high in saturated fat. Instead, Volek hoped to identify the carb-intake point at which participants began to store fat. ​ “That turned out to be highly variable,” he said. “Everyone showed increased palmitoleic acid levels as carbs increased, but values varied widely between individuals, especially at the highest carb intake. This is consistent with the idea that people vary widely in their tolerance to carbohydrates.” Participants’ existing health risks were not a factor in the study because everyone ate the exact same diet for 18 weeks. Their bodies’ responses to the food were the focus of the work. ​ “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. “But studies measuring saturated fat in the blood and risk for heart disease show there is an association. Having a lot of saturated fat in your body is not a good thing. The question is, what causes people to store more saturated fat in their blood, or membranes, or tissues? ​ “People believe ‘you are what you eat,’ but in reality, you are what you save from what you eat,” he said. “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. Since more than half of Americans show some signs of carb intolerance, it makes more sense to focus on carb restriction than fat restriction.” ​ Volek sees this palmitoleic acid as a potential biomarker to signal when the body is converting carbs to fat, an early event that contributes to what he calls “metabolic mayhem.” ​ “There is no magical carb level, no cookie-cutter approach to diet, that works for everyone,” he said. “There’s a lot of interest in personalized nutrition, and using a dynamically changing biomarker could provide some index as to how the body is processing carbohydrates.” ​ This work was supported by the Dairy Research Institute, the National Cattlemen’s Beef Association and the Egg Nutrition Center. ​ Co-authors include Brittanie Volk, Laura Kunces, Brian Kupchak, Catherine Saenz, Juan Artistizabal and Maria Luz Fernandez of the University of Connecticut; Daniel Freidenreich, Richard Bruno, Carl Maresh and William Kraemer of Ohio State’s Department of Human Sciences; and Stephen Phinney of the University of California, Davis. news.osu.edu

 

 

 

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