In the US and Canada dietary guidelines do not take into consideration the recent extensive scientific research into role of saturated fats.
Two generations of researchers have tried to prove that eating saturated fat (such as beef, pork, dairy, eggs, chocolate, and tropical oils) causes heart disease. This hypothesis is false.For proof look to multiple recent meta-analyses of large populations followed carefully for decades, examining what they eat and what they die of. All show no consistent association between dietary saturated fat intake and risk for heart disease or death from all causes.In fact some of these studies show just the opposite – they suggest that one’s risk for a coronary event increases when dietary saturated fat is reduced and replaced by carbohydrate.
By continuing to provoke fear about the harmful effects of saturated fat, the likely response is that people will seek out foods low in fat and higher in carbohydrate. In fact, according to a government-funded survey, Americans have decreased their consumption of saturated fat and replaced those calories with an even greater amount of carbohydrate. In the same time interval rates of obesity and diabetes have rocketed skywards.
Much of what we’ve been taught about dietary fat is wrong. How could this be – a good place to start would be to read Good Calories, Bad Caloriesby Gary Taubes andThe Big Fat Surpriseby Nina Teicholz, both highly regarded investigative journalists.
In short, 50 years ago diseased coronary arteries were found to contain buildups of cholesterol and saturated fat. Professor Ancel Keyes of the University of Minnesota hypothesizedthat too much of these two nutrients in the diet were the cause – i.e., his hypothesis was built on the flawed concept that you are what you eat. Then came well-done studies showing that blood levels of saturated fats predict future cases of heart disease and diabetes, thus appearing to support Keyes’ hypothesis. But this works only if you believe “you are what you eat”,a concept that doesn’t pass the common sense test.
Obviously, the key question here is, “what’s the precise relationship between dietary saturated fat and blood levels of saturated fat?”The scientific evidence clearly shows that dietary saturated fat intake has little to do with saturated levels in our blood, then what does? There is, in fact, sound evidence that dietary carbohydrate is a major determinant of serum saturated fat levels.
We know this because two respected research groups fed humans carefully measured, weight-maintaining diets either high in carbohydrate or moderate in carbohydrate. In both studies, blood levels of saturated fats went up dramatically on the high carb diets, even though they were very low in fat.
We (Virta) performed a weight loss study during which we fed diets varying from 32 up to 84 grams of saturated fat per day, with “healthy carbohydrate” making up the energy difference when dietary fat was reduced. In blood triglycerides and cholesteryl esters, saturated fat levels trended upwards when the high carbohydrate, very low fat diet was consumed, despite the diet being energy restricted, causing on-going body fat loss.
A high carbohydrate intake has two effects in the body that promote higher levels of saturated fat.
First, carbohydrates stimulate the body to make more insulin, which inhibits the oxidation of saturated fat. Thus, when insulin levels are high, saturated fat tends to be stored rather than burned as fuel.
Second, a high carbohydrate intake promotes the synthesis of saturated fat in the liver.
This is particularly problematic for individuals with insulin resistance, characterized as “carbohydrate intolerance” in our recent book, (Volek J, Phinney SD. The Art and Science of Low Carbohydrate Living. Beyond Obesity, May 2011.) Available through Amazonhttps://www.amazon.com/Art-Science-Low-Carbohydrate-Living/dp/0983490708
Insulin resistance makes it harder for muscles to take up and use blood sugar, thus causing a higher propensity for the liver to convert dietary carbohydrate into body fat.
This combination of decreased oxidation and increased synthesis of saturated fat therefore results in accumulation of saturated fats in the blood and tissues.The culprit then is clearly not dietary saturated fat, but rather consumption of more carbohydrate than an individual’s body can efficiently manage.This threshold of carbohydrate tolerance varies from person to person, and it can also change over a lifetime.
In addition to the studies mentioned above in which high carbohydrate feeding increased blood levels of saturated fats, we conducted a pair of studies allowing 6-12 weeks for adaptation to moderate carbohydrate or very low carbohydrate diets. Because these were not very low-calorie diets, the low-carb diets were naturally pretty high in fat, containing 2-3 fold greater intakes of saturated fat than the moderate carbohydrate diets used as controls.
The results were pretty striking: compared to low-fat diets, blood levels of saturated fat were markedly decreased in response to the low carbohydrate, high fat diets.Our data indicates that this occurred because the low insulin levels accelerated the oxidation of all fats (and particularly saturated fat); plus the relative few dietary carbohydrates meant there wasn’t much of it to be converted into saturated fats. Thus, from the body’s perspective, a low-carbohydrate diet reduces blood saturated fat levels irrespective of dietary saturated fat intake.
There is convincing evidence that dietary carbohydrate exerts an important influence on how the body processes saturated fat. Thus, saturated fat, whether made in the body or eaten in the diet, is more likely to accumulate when aided and abetted by high levels of dietary carbohydrate, particularly in insulin-resistant individuals (as in type 2 diabetes or metabolic syndrome*).
* Metabolic syndrome is a clustering of at least three of the five following medical conditions: central obesity, high blood pressure, high blood sugar, high serum triglycerides, and low serum high-density lipoprotein. Metabolic syndrome is associated with the risk of developing cardiovascular disease and type 2 diabetes. Source: https://en.wikipedia.org/wiki/Metabolic_syndrome
A one-size-fits-all recommendation to aggressively lower saturated fat intake with the expectation of lowering blood saturated fat levels is intellectually invalid and likely to backfire.
SOURCE: The Sad Saga of Saturated Fat by Jeff Volek, PhD, RD and Stephen Phinney, MD, PhD https://blog.virtahealth.com/the-sad-saga-of-saturated-fat/?fbclid=IwAR28z406CUcbrwZ-kdEWAoko7-gOMgPNJ4fgxy0HSeLkdLfZW1co244xP3cIn Categories: Science & Research. Please see the extensive list of studies under References.
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