Should saturated fat have a bad rap?

Taken from the Ottawa Citizen.

Should saturated fat have a bad rap?

A growing number of scientists don't think so

 

Melissa Arseniuk

The Ottawa Citizen


Friday, November 16, 2007

The low-carb Atkins-style diet may not be the rage it once was, but its core concept - that saturated fat is not necessarily bad for us and won't lead to weight-gain - is gaining momentum in some research circles.

Gary Taubes' current best-seller, Good Calories, Bad Calories, is making waves with the assertion that there's no real evidence that saturated fat is bad for us. The cover of the book shows a piece of toast with a pat of butter on it, except that contrary to what what we've been told for decades, Taubes claims it's the piece of bread that represents the "bad" calories, while the butter is symbolic of the "good."

He's not alone.

A growing number of experts insist that scientific studies show that it's starchy and sugary carbohydrates that are at the root of obesity, diabetes and heart problems, not saturated fat. In other words, it's not the burger that's bad for you - it's the bun.

Dr. Eric Westman of North Carolina's Duke University is one of the sat-fat believers. He led a 2004 study that showed obese participants on low-carb diets lost more body fat, lowered their triglyceride levels (triglycerides are the chemical form of fat in the body), and raised their "good" (HDL) cholesterol while lowering their "bad" (LDL) levels compared with low-fat dieters.

The low-carbers also lost more weight while on an unrestricted fat and protein regimen - an average of 26 pounds, or 12 pounds more than the average low fat dieter.

It was so surprising that Westman repeated the study the following year with similar results.
For six months, the low-carb group ate just  two cups of salad and one cup of non-starchy vegetables like broccoli per day - while eating unlimited amounts of eggs, meat, fowl, fish and shellfish. They could use as much butter and oil as they wanted, and were allowed four ounces of hard cheese per day. They were also given nutritional supplements.

Patients typically ate bacon and eggs for breakfast (no toast), a salad topped with cheese and meat (such as a chef's salad or a chicken caesar salad sans the croutons) for lunch, and meat and more veggies for dinner.

In contrast, the low-fat dieters ate more traditional meals where all four food groups were represented and limited their fat intake to no more than 30 per cent of total calories. Their calorie consumption was also restricted to 500 fewer calories per day than what their bodies required to maintain their body weight.

Although calories were not limited in the low-carb test group, Westman says the subjects ended up eating between 500 to 700 fewer calories than they usually did, for a total of about 1,500 per day.

"People restrict their food intake because they're not hungry," he says. He attributes  this to the satiating nature of the fats and proteins consumed.

The results were not what he was expecting, especially in terms of cholesterol. "It's fascinating," he says. "The science is just being done right now about the low-carb condition. There's something about carbohydrates that the body can't regulate well," but researchers don't know definitively what that is.

While it hasn't been proven how high-fat, carbohydrate-restricted diets lower blood fat and cholesterol, Westman and his colleagues think they have a pretty good idea.

"Most of the blood cholesterol is made by the liver," Westman explains. And it's the cholesterol our bodies produce in the liver that ends up lining our arteries, not the cholesterol that's in our food.

When we eat few carbohydrates and more fat, the liver adapts and begins to burn fat for fuel. When it does this, it produces ketones - a chemical that shows your body is breaking down fat. At the same time, the liver produces less cholesterol. So the body effectively shifts from using the glucose (or sugar) as fuel to burning dietary fat as energy.

"It's complicated, but I think the science marches on," Westman says. "I know this may come as a surprise, but I don't think we really know whether high amounts of saturated fat are harmful to people."

Like Taubes, Westman says there are no studies that that prove that eating less saturated fat results in better health.
"This is pretty controversial to say, but I think we just need better science to say that saturated fat is bad."
According to Taubes, a series of studies on fat funded by U.S. National Institute of Health in the 1970s gave saturated fat the thumbs down. But the science writer says  researchers got it all wrong and the evidence against sat fat was never proven. "And that 30-year-old science is what we've embraced ever since," Taubes told National Public Radio earlier this month.

Yet, low-carbohydrate regimens are commonly dismissed as ineffective fad diets.
Westman's findings, in particular, have been criticized because they are funded by grants from the Atkins Foundation, the organization founded by the late Dr. Robert Atkins and his wife. (Atkins published the The Atkins Diet Revolution in 1972, which advocated a diet high in protein and fat, with vegetable-based carbohydrates, and low in "empty carbs" like pasta, bread, potatoes and sugary desserts. It was a best-seller for years. It re-emerged slightly revised earlier this decade - again to huge sales - and spawned similar low-carb plans like The South Beach Diet.)

Westman says "he is an advocate for the science in this area, not the diet."
He adds that what he really wants is more research in the low-carb field. To date, there haven't been any conclusive studies on the long-term impact of the diet, which is why he doesn't recommend a strict low-carb diet long-term. (He also stresses that the diet be monitored by a qualified doctor.) One of the reasons for the lack of research, he says, is that there's a taboo, even among scientists, on studying higher fat diets.

Earlier this year, the Stanford Prevention Research Center released a large, year-long study that showed people on a low-carb, high-fat diet lost almost twice as much weight as those on a more traditional diet. It made headlines, but the head researcher was "worried" about the results, fearing people would "abuse" the findings.

There are other studies to back the low-carb theory. In trial after trial, low-carbohydrate diets have been found to improve cholesterol levels, weight, calorie consumption, hunger and insulin resistance.

(Very basic science lesson: Insulin is a vital hormone released into the bloodstream each time we eat. When we eat refined carbohydrates like white bread or sweets, our blood sugar levels rise. In response to the elevated blood sugar levels, our bodies release more insulin leading our bodies to store excess sugars as fat. Over time, our cells become more resistant to insulin, and needs to produce more of the hormone every time our blood sugar levels are elevated. Insulin resistance is associated with diabetes and an increasing number of other ailments.)

All of this comes in stark contrast to the longstanding recommendations from various health authorities.
Canada's Food Guide currently recommends a diet largely rooted in carbohydrates - six to seven servings of grain products per day, if you're a female aged 19 to 50, or eight servings if you're a middle-aged man - with just two to three servings each of meat and dairy products. Health Canada and most dietitians recommend fat represents no more than 30 per cent of all calories consumed.

Health Canada is not alone, not by a long shot. Just last month, the World Cancer Research Fund made headlines with its huge report, which proposed limiting red meat consumption as one of its 10 recommendations to avoid cancer. The list of suggestions came after researchers reviewed 7,000 studies, some dating back to the 1960s.

Westman was there for the World Cancer Research Fund announcement. He says the review included many short-term, non-clinical trials where varying levels of red meat consumption were compared and contrasted after being self-reported by participants.

"They have no testing of the recommendations at all," he observes. "You have to test something before you recommend it. A lot of this is on belief."

He says he would like to see large-scale, randomized trials follow people on both high- and low-meat diets over a longer period of time before making any firm recommendations regarding cancer.

"Diet is really powerful," he says. "There is so much we don't know."

© The Ottawa Citizen 2007

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