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“Saturated fat is not so bad for you that you can replace it with anything and get benefit.” Dr. Dariush Mozaffarian, Brigham and Women’s Hospital and Harvard Medical School (CNN.com)
“I agree strongly with the notion that rather than focusing on further reductions in saturated fat…we should be thinking much more seriously about finding ways of increasing our intake of polyunsaturated fat.” Dr. Ronald M. Krauss, Children’s Hospital Oakland Research Institute, Oakland, California (CNN.com)
Cutting Saturated Fat Alone Not Enough
Replace Bad Fat with Good Fat
I have come to appreciate the need for dietary fat more over time .
In 1998, my total cholesterol/HDL ratio improved from "very good" to "excellent" after I added a small amount of vegetable oil (olive and then flaxseed) to each of my meals and snacks. My total cholesterol dropped below 200 for the first time in years, perhaps ever. My triglycerides dropped 50 percent, from 153 to 76. For full details: http://www.cbass.com/TRIGLYCE.HTM
My diet was already low in saturated fat. I was eating very little processed food. My carbohydrate intake was almost all from whole foods. I thought my diet was just about perfect. But something was missing. That something, it seems, was vegetable oil, which is generally low in saturated fat, and high in poly- and mono-unsaturated fatty acids.
As time went on, I learned about the benefits of omega-3 polyunsaturated fatty acids, found mainly in fatty fish. Last year (2009), I started taking three fish oil capsules a day, with meals. (I was already having salmon several times a week.) My HDL “good” cholesterol skyrocketed to 78. It went from a very good 60 to stunning; 45-70 is the reference range for men. For details: http://www.cbass.com/FishOil.htm
Slowly but surely, I stopped trying to cut fat, and started striving for an optimum balance of fats. New research suggests that I’m on the right track.
Two new studies have added more pieces to the good fat-bad fat puzzle. There’s more to learn, but we’re making good progress.
The first study was a shocker. A group of researchers from the Children’s Hospital Oakland Research Institute in Oakland, California and the Departments of Nutrition and Epidemiology at Harvard School of Public Health analyzed the results of 21 studies involving 347,747 initially health participants. During a 5 to 23 year follow-up, 11,006 developed cardiovascular disease (heart or stroke). No significant evidence was found that dietary saturated fat is linked to increased risk of heart disease or stroke.
Say what? Saturated fat is okay after all? Think red and processed meat, butter, cheese, ice cream, egg yoke, cookies, and pastries.
Could it be that all of our efforts to cut down on saturated fat were for naught? That would be going too far. Studies have shown that saturated fat can increase LDL “bad” cholesterol, which is a known risk factor for heart disease and stroke. We’ve been headed in the right direction, but apparently have another lap or so to go.
The new findings should not be interpreted as a license to go on a bacon cheeseburger binge, according to the researchers. (You wouldn’t do that, would you?)
What we do need is more study on what foods should replace saturated fat. The second study explores that issue.
Researchers from Brigham and Women’s Hospital and Harvard Medical School, both in Boston, found evidence that replacing saturated fat with polyunsaturated fat does appear to reduce the risk of cardiovascular disease.
This is BIG news! Let’s dig into the details of both studies and see what else we can learn.
The first study was reported in the American Journal of Clinical Nutrition (March 2010). The researchers, led by Patty W. Siri-Tarino and Ronald M Krauss, simultaneously issued a background paper, which is published in the same issue.
No Significant Connection
Even though cutting back on saturated fat has generally been acknowledged to improve cardiovascular health, Siri-Tarino and her colleagues were unable to find a significant connection between saturated fat consumption and cardiovascular risk.
They reached this conclusion by performing a meta-analysis of earlier studies. In a meta-analysis, results from different studies on a specific topic are collected and jointly analyzed in order to reach a general conclusion. The combined data from numerous studies allows for a more detailed and statistically powerful analysis. Differing investigators and methods can be problematic at times, however.
Siri-Tarino and her team did find some studies suggesting that replacing saturated fat with polyunsaturated fat reduces cardiovascular risk, by 42% in one case, but not enough data to meet the criteria for meta-analysis. They called for additional research on the effect of replacing saturated fat with either polyunsaturated fat or carbohydrate.
In their background paper, the researchers made the case for further study.
Research has been focused on lowering LDL “bad” cholesterol. Prevention of cardiovascular disease has been inferred from lower LDL concentrations. Evidence from trials that actually studied heart disease events has been mixed. Importantly, saturated fat has also been found to reduce insulin sensitivity and increase inflammation, both bad.
Moreover, the benefit of reducing saturated fat below 9% has not been evaluated. This is a concern, because efforts to go below 9% may see saturated fat replaced by carbohydrate, often refined carbohydrate. That’s a problem because carbohydrate, especially refined, can worsen cholesterol ratios and increase triglycerides. (See below)
“Evidence that supports a reduction in saturated fat intake must be evaluated in the context of replacement by other macronutrients,” the researchers opined.
“Clinical trials that replace saturated fat with polyunsaturated fat have generally shown a reduction in cardiovascular disease events,” they report.
Unfortunately, the same cannot be said for carbohydrates. “Replacement with a higher carbohydrate intake, particularly refined carbohydrate, can exacerbate the atherogenic dyslipidemia associated with insulin resistance and obesity that includes increased triglycerides, small LDL particles, and reduced HDL cholesterol.” That’s not good. They don’t recommend it.
“This is of particular concern with regard to the implications of further restrictions in total and saturated fat beyond prevailing US dietary guidelines, which call for levels [of saturated fat] no higher than 10% of total energy,” the researchers warn. They believe this guideline should be re-examined.
This brings us to the second study, led by Dariush Mozaffarian and published March 23, 2010 in the journal PLoS Medicine. Also a meta-analysis, this study focuses on replacement.
Swap Bad Fat for Good
Dr. Mozaffarian and his colleagues identified and analyzed the results of eight controlled trials in which 13,614 people replaced dietary saturated fat with polyunsaturated fat for a year or more; mean duration of the studies was 4.25 years. During the course of the trials, participants suffered 1,042 coronary events. Polyunsaturated fat consumption on average accounted for 15 percent of total calories consumed by the intervention participants; among the control groups, polyunsaturated fat accounted for only five percent.
Participants in the intervention groups had a 19% reduced risk of having a coronary event, compared to those in the control groups. Put another way, each 5% increase in the proportion of energy obtained from polyunsaturated fat reduced coronary risk by 10%. Importantly, the researchers also found that the benefits associated with polyunsaturated fat consumption increased in the longer trails; the longer participants stayed on diets high in polyunsaturated fat the more they benefited.
“These findings provide evidence that consuming polyunsaturated fat in place of saturated fat reduces coronary heart disease events,” the researchers concluded. “This suggests that rather than trying to lower polyunsaturated fat consumption, a shift toward greater…polyunsaturated fat consumption would significantly reduce rates of coronary heart disease.” (Some experts have argued that upping polyunsaturated fat could actually increase heart disease.)
It’s important to note that this study does not distinguish between the benefits of reducing saturated fat and the benefits of increasing polyunsaturated fat. It seems likely that the participants benefited from both dietary changes.
Keep in mind too that polyunsaturated fats come primarily in three forms: nuts, vegetable oils, and fatty fish. Benefits vary and are not fully understood. A mix of all three forms is probably best. (I include all three forms in my diet almost every day. My favorite vegetable oil is canola; Carol prefers olive oil.)
Balanced Diet Best
Dr. Mozaffarian and Dr. Ronald Krauss (a co-author of the first study), give us the take-home message.
Krauss concurs that the concentrated should be on replacing saturated fat with polyunsaturated fat. “I agree strongly with the notion that rather than focusing on further reductions in saturated fat…we should be thinking much more seriously about finding ways of increasing our intake of polyunsaturated fat.”
“With all the focus on fat and saturated fat and cholesterol, we’ve put a lot of junk in our diet instead,” Dr. Mozaffarian added. “What a person needs to do is to eat the appropriate amount of calories, and eat a healthy, balanced diet.”
Dr. Krause elaborates: "An overall eating pattern that emphasizes whole grains rather than refined carbs such as white flour, along with foods high in polyunsaturated fats, such as fish, seeds, nuts, and vegetable oils, is of more value for reducing coronary heart disease risk than simply aiming to further reduce saturated fat."
Eat a healthy, balanced diet—and exercise. As George Sheehan once wrote, when you pass on they’ll have to beat your heart into submission with a stick.
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