Low-fat diets have led to dangerously high carbohydrate consumption

[David Baxter PhD]

Recommended fat intake should increase, Canadian researchers say
By Nicole Ireland, CBC News
August 29, 2017

Low-fat diets have led to dangerously high carbohydrate consumption, study suggests

Global dietary guidelines should change to suggest people can eat more fat than previously thought, with a view to preventing overconsumption of carbohydrates, according to a new international study led by Canadian researchers.

"Our findings do not support the current recommendation to limit total fat intake to less than 30 per cent of energy," said the paper published in the Lancet on Tuesday. "Individuals with high carbohydrate intake might benefit from a reduction in carbohydrate intake and increase in the consumption of fats."

Scientists from McMaster University in Hamilton and other researchers used questionnaires to document the fat, carbohydrate and protein intake of 135,335 people in 18 countries, then followed them over an average of about seven years.

The research team, led by Mahshid Dehghan, a nutrition epidemiologist at McMaster, was set to present the results of the study at the European Society of Cardiology Congress in Barcelona on Tuesday.

The researchers looked at whether or not participants of the epidemiological study developed heart disease or stroke. They also documented the number of deaths due to cardiovascular disease as well as other causes, including cancer, and respiratory and infectious diseases.

Contrary to popular thinking over the last few decades, the researchers found no significant association between eating more than the recommended amount of fat and developing heart disease or having a stroke. In addition, a fat intake of about 35 per cent of total calories was associated with a lower overall risk of dying compared to a lower percentage of fat in the diet.

In contrast, people who ate a lot of carbohydrates (more than 60 per cent of their total calorie intake) were at higher risk of death overall, as well as death not related to cardiovascular disease.

"When you recommend lowering fat, by default, people increase their carbohydrate consumption," said Dehghan. "And increasing consumption of carbohydrates results in higher risk of mortality."

That's why nutritional guidelines around the world need to change, Dehghan told CBC News.
"Relaxing current restrictions on fat and emphasizing on carbohydrate intake ... is more likely to be beneficial."

The study did not find that a certain type of fat — saturated or unsaturated — had any significant impact on cardiovascular disease. In fact, both saturated and unsaturated fats were associated with a lower risk of total mortality and stroke.

However, the authors note that they were unable to specifically measure trans fat consumption — a potentially important limitation in the study. Cardiologists have recognized the specific danger of trans fats, which are artificial and also known as partially hydrogenated oils. Canada is moving toward banning trans fats — something New York City has already done in its restaurants and bakeries.

There has been mounting scientific evidence over the last five years challenging the long-held notion that fat is to blame for cardiovascular disease and death, said Richard Bazinet, of the Department of Nutritional Sciences at the University of Toronto, who was not involved in the Lancet-published study.

In the last couple of decades, that notion led to a slew of low-fat and fat-free products on grocery store shelves.

The problem, Bazinet said, is many of those products contain high levels of sugar and carbohydrates, substituting other sources of calories that pose health risks.

"We're seeing that play out maybe with people thinking that things like juices are fine and sweetened, you know, foods that say low in fat are a great choice. A cookie's still a cookie even if it doesn't have saturated fat or high fat content."

Dehghan, the study's lead author, emphasized that the research looked solely at cardiovascular disease and mortality, and did not look at the effects of fats and carbohydrates on obesity — a health issue of particular concern in North America.

According to Statistics Canada[/URL], more than half of adult Canadians were overweight or obese, based on body mass index (BMI), in 2014.

Although Bazinet largely agrees with the study's findings, he said the constant onslaught of research focused on specific nutrients like fat or carbohydrates and "blaming one versus the other" may be "missing the mark" in educating the public on how to make healthy food choices.

"Moderation" is the solution, he said. "Don't eat too much of any single thing."

 

[David Baxter PhD]

The demise of a dietary dogma?

The demise of a dietary dogma?
By Kelly Crowe, CBC News
Sept. 2, 2017

A new study was released in The Lancet challenging the dogma of the diet-heart hypothesis. For decades, that dogma has stated that eating less saturated fat will lower the risk of heart disease and death.

Headlines quickly flashed the surprising findings: Thousands of people in the Prospective Urban Rural Epidemiology (PURE) study who ate more fat — even saturated fat found in meat and cheese — had a lower risk of death. And people who ate more carbohydrates had a higher death rate.

Immediately, the Twitterverse lit up with reasons why the new study is flawed:

• It spanned 18 countries with vast differences in health care and access to nutritious food, which meant differences in diet might have reflected differences in wealth and poverty
• It used a food questionnaire that depends on people accurately reporting what they ate, and they only filled it out once, at the beginning of the seven-year study
• The researchers didn't count calories, and they didn't report what types of food were consumed

"Does it have limitations? Of course, all studies do," said Richard Bazinet, associate professor at the University of Toronto. He wasn't involved in the research, but Bazinet said it's the latest in a series of studies that have complicated the dietary fat story.

"This is seven years of big studies coming in that don't fit," Bazinet said. "It's getting hard to say there's nothing to see here."

Bazinet is a nutrition scientist who studies the effect of dietary fat on the brain. He believes he's seeing a major shift in the dietary fat dogma that he was taught as a graduate student in the 1990s.

"I was trained in a field where this was taught to everybody. Saturated fats are bad. They raise your cholesterol. They raise your risk of heart disease. And now my honest opinion is that's at least oversimplified, if not wrong."

The dietary fat dogma started more than a century ago with some meat-eating rabbits.

Back in 1908, scientists noticed that rabbits who were fed high cholesterol diets (meat, eggs, milk) developed plaque in their arteries. It was the beginning of a diet-heart hypothesis that reached full flower in the 1950s, when researcher Ancel Keys convinced the world that diets high in saturated fat increased the risk of heart disease.

But gradually the scientific pendulum has started swinging in the other direction, as a series of studies and meta-analyses suggest the fat/carb diet/health equation is much more complicated.

In one dramatic twist to the whole fat story, two large randomized trials from the early '70s were never published. Later, when the data was recovered, it became clear why. Both studies failed to support the diet-heart hypothesis.

• The case of the missing data
• Benefits of switch from saturated fat to corn oil for longer life challenged

A few months ago, a group of British researchers dared to suggest that the dogma was dead. We reported on the dietary dust-up that followed in an April edition of Second Opinion.

"As nutritional scientists, we've been watching this develop for almost 10 years," Bazinet said. "Maybe we're reworking the diet-heart hypothesis, maybe we're tweaking it, but something is going on."

It will take a well-designed randomized controlled trial to ultimately resolve the uncertainty about diet and health. In an accompanying commentary in The Lancet, one researcher had this advice: "Until then, the best medicine for the nutrition field is a healthy dose of humility."

What about the rest of us, raised on the dogma that fats are bad? That story hasn't changed.

"The recommendation from our study is moderation in both carbohydrate and fat intake," said PURE study author Mahshid Dehghan, from the Population Health Research Institute at McMaster University.

The human body needs a balance of fats, protein and carbohydrates to fuel its complex metabolic processes. So the basic nutritional advice remains the same: control calories, eat both fats and carbohydrates in moderation and aim for as much fresh food as possible.