Os Beef Gtrsse Bsd for You

Researchers recently unearthed some decades-old data that will surely add fuel to the ongoing controversy about the fat in our diet.

The study, published April 12 in the BMJ, focuses on the effects of fatty foods on cardiovascular health and mortality. The researchers reanalyzed data that was gathered 45 years ago for a study on what happens to people's blood cholesterol, and their risk of heart disease and death, when they substituted one type of fat for another.

For the randomized controlled trial, which was conducted in Minnesota between 1968 and 1973, one group replaced saturated fat (which typically comes from meat and dairy sources) with vegetable oils, while a control group followed a diet rich in saturated fat from meats, dairy, as well as trans-fat rich margarines, and shortenings.

The researchers who did this meta-analysis of old data discovered something intriguing: The study participants who got a diet rich in vegetable oil indeed had lowered cholesterol levels — but this did not improve their overall health outcomes. In fact, they had a higher, rather than lower, risk of death at the end of the study compared to the other group.

But there were a few major problems with the research. The study involved men and women of an average age of 52 who had been admitted to a nursing home and six state mental health hospitalsbecause they were sick. The researchers who conducted the meta-analysis note the "results are not necessarily generalizable to populations without mental illnesses or living outside nursing homes. "

Another issue: The study followed 9,423 women and men, but only a quarter of the participants followed the diets for more than a year. Altering one's diet for a short period of time — especially in old age — would not necessarily affect one's long-term health risks.

The bottom line

What we know:

It's not how much fat you eat that's important — it's what kinds. As best scientists can tell, trans fats (found in foods like margarine) contribute to cardiovascular diseases, whereas unsaturated fats (found in vegetable oils and fish) actually have the opposite effect — lowering the risk of cardiovascular disease. Saturated fats (found in butter and red meat) fall somewhere in between.

What we don't know:

Some of the biggest controversies surround saturated fats. Scientists disagree about the extent to which saturated fats contribute to important health outcomes like heart disease, stroke, and cancer. The available research does suggest, however, that there are health benefits from replacing saturated fats with unsaturated fats in the diet, and that eating lots of nutrient-poor carbs (like sugary cereals, soda, and white bread) instead of fat is a bad idea.

What this means for you:

Stay away from foods that are high in trans fats. And you're likely better off eating foods rich in unsaturated fat instead of saturated fat. But there doesn't seem to be any need to worry about your total fat intake. So as long as you're eating a variety of real foods and not too many calories, you're doing well.

Welcome to Show Me the Evidence, where we go beyond the frenzy of daily headlines to take a deeper look at the state of science around the most pressing health questions of the day.

Even so, the study serves as a reminder that the debate about the effects of dietary fat on the body is still very much alive among researchers, and that a lot of the thinking about "good fat" and "bad fat" over the past several decades may have been wrong.

Dietary fat is one of the most confusing — and controversial — food topics around. And no wonder: Americans have been hearing bizarrely mixed messages about whether it's okay to eat fat for more than half a century.

In the 1950s and '60s, saturated fat — the stuff found in red meat and butter —began acquiring a bad reputation. Back then, researchers were finding that people with diets lower in saturated fat appeared to be healthier. Public health officials worried that eating too much saturated fat could lead to heart disease, a major killer in the United States.

This specific concern about saturated fats eventually mutated into a generalized panic about all types of fat. In the 1980s, the official US dietary guidelines began warning Americans to cut their total fat intake. This recommendation wasn't very scientifically grounded, since it didn't distinguish amongtypes of fat (at the time, researchers were also finding that unsaturated fats, such as those found in vegetable oils and fish, had health benefits). But as Marion Nestle describes in Food Politics, the meat industry didn't want the government telling people to eat less red meat, a huge source of saturated fat. So the message became the vague "eat less fat, period."

Those warnings helped spur the "low-fat" diet craze of the past couple of decades. They also had a number of harmful unintended consequences. Food manufacturers began replacing the fat in their products with sugar — think Snackwell's cookies — and marketed them as healthy alternatives. This turned out to be a bad idea: Those sugars and refined carbohydrates were often just as bad for health. Worse still, food manufacturers and consumers started moving away from saturated fats and toward artificial trans fats — as seen in the switch from butter to margarine. This, too, was a disaster, since trans fats turned out to be very bad for the body.

Today the conventional wisdom is shifting yet again. Some critics now argue that saturated fat isn't actually that bad for you, and that we all made a terrible mistake switching to low-fat diets that were higher in sugar. In 2014, the former New York Times food writer Mark Bittman declared, "Butter is back," going through the research on how saturated fat wasn't nearly as harmful as we thought and arguing that we should ditch artificial foods (like margarine) in favor of natural foods (like, well, butter).

So what's the truth about fat?

I decided to sift through the available evidence, interviewing eight researchers and reading more than 60 journal articles on the subject. What I learned is that there's still a ton of controversy about fat — although there is also clarifying consensus in important areas.

The state of the science on fat

For starters, just about everyone agrees that the 1980s-era recommendations about switching to a low-fat diet were not supported by science. There isn't any high-quality evidence to back up that advice. In fact, researchers today generally don't think the total amount of fat you eat has much effect on obesity and heart health (so long as you're eating healthy foods and not consuming too many calories).

Instead, they focus on what types of fat we should eat. Not all fats are created equal. (More on that in the next section.) Artificial trans fats appear to be extremely harmful, which is why they're now being banned from foods. Unsaturated fats, like those found in vegetable oils and fish, appear to have some health benefits. Saturated fats fall somewhere in between. We've also learned that other types of ingredients, such as the highly refined carbohydrates that make up cookies and soda, can actually be just as unhealthy as "bad fats."

Now, this doesn't mean it's okay to eat a cheeseburger every single day. What it does mean, however, is that not all fats are bad and that fat can most certainly be a part of a healthy diet. These revelations have also triggered a debate among researchers about whether it's still useful to give dietary advice about macronutrients like fat and carbohydrates — or whether we should focus on actual foods instead.

There are three main types of fat — and it's crucial to distinguish them

Broadly speaking, there are three main types of dietary fats: saturated, unsaturated, and trans fats. Foods with fat contain some mixture of these three, and chemically they're all pretty similar (chains of carbon atoms attached with hydrogen atoms). But they seem to do different things to the body.

Saturated fats are usually solid at room temperature. They're found at high levels in animal-based foods such as red meat (beef, bacon), poultry, and full-fat dairy milks, butter, and cheese. Some plant-based foods, like coconuts and palm oil, are also high in saturated fat.

By contrast, unsaturated fats typically remain soft or liquid at room temperature. These are more likely to appear at high levels in fish and certain vegetables. There are two types: monounsaturated fats (found in olive, peanut, and canola oils, avocados, almonds, pecans, pumpkin, sesame seeds, etc.) and polyunsaturated fats (found in fish and seafood, sunflower, safflower, corn, soybean, and flaxseed oils, walnuts, and flaxseeds).

Finally, there are trans fats. These can appear naturally in some foods, such as beef and lamb. But the trans fats that doctors worry about tend to be industrially produced. They're made when vegetable oil goes through a process called hydrogenation, which involves adding hydrogen to liquid oil to make it more solid. Major sources of artificial trans fat include frozen pizzas, pie, margarine and spreads, ready-made frosting, coffee creamers, and some fried foods and snacks (such as microwave popcorn). Trans fats are also used in restaurant cooking, particularly in baking and frying, though that's been changing in light of government bans.

We need fat in order to live. It serves many vital functions, providing energy for the body and helping with the absorption of vitamins and minerals. But some fats are better for the body than others.

Trans fats are definitely bad for your health

Artificial trans fats have been around for more than a century, but they've risen in popularity since the 1950s because they're relatively inexpensive compared with solid animal fats. They can help increase the shelf life of food, and they taste good.

During the saturated fat panic of the mid-20th century, trans fats were billed as a healthy alternative. We now know this was a huge mistake. Evidence soon began mounting that even a small amount of trans fat appears to increase bad (LDL) cholesterol in the blood and decrease the amount of good (HDL) cholesterol — raising the risk of coronary heart disease and heart attacks. As this 2006 research in the New England Journal of Medicine shows, for every 2 percent of calorie intake that comes from trans fats, a person's heart disease risk increases by an incredible 23 percent.

That explains why the Food and Drug Administration has been working to phase trans fat out of the food supply and doctors recommend that people keep their consumption of it as close to zero as possible.

Unsaturated fats have health benefits

At this point, most scientists agree that unsaturated fat, relative to the other fat types, appears to be the least problematic for human health.

As Dariush Mozaffarian, an epidemiologist at Tufts University, describes in the journal Circulation, numerous studies have found that eating polyunsaturated fat (the kind found in fish, sunflowers, and walnuts) can decrease the amount of bad (LDL) cholesterol in the blood, raise the amount of good (HDL) cholesterol, and lower the risk of cardiovascular disease.

Monounsaturated fats (found in olive oil, avocados, and almonds) have also shown similarly favorable effects on blood lipids and cardiovascular disease — they seem to decrease LDL cholesterol while maintaining HDL cholesterol. Though there's a caveat here: Mozaffarian and other researchers caution that long-term studies on monounsaturated fats show mixed results on cardiovascular disease. So they say, "Some caution is needed."

There's controversy surrounding saturated fats

Unlike unsaturated fat, saturated fat has been shown to increase LDL cholesterol (again, the bad kind), so some researchers have wondered whether eating a lot of this stuff must therefore increase the risk of cardiovascular disease.

Starting in the 1950s and '60s, that hypothesis was backed up by observational studies that looked at people who ate different diets and found a link between a diet heavy in saturated fat and cardiovascular diseases. This research was the basis for dietary guidelines that have long recommended people cut their saturated fat intake to stave off their risk of this leading killer.

More recent research, however, has suggested that the effects of saturated fat on health may not so clear-cut, says Tuft's Mozaffarian. It's true that saturated fat appears to affect blood levels, but the question of whether this alone truly ends up altering a person's cardiovascular disease risk remains controversial. (The BMJ analysis, published in March, finds lowering blood cholesterol by lowering the intake of saturated fats doesn't in fact translate to improved survival — but as noted above, the study had some serious limitations.)

There are two key reasons for the controversy. First, studying diet and its impact on health is really, really difficult. People don't consume macronutrients like fat. They consume food, which typically contains fats but also lots of other ingredients, and their diets change over time. "You're not going to get clean answers in the studies because you cannot separate the fat from the food," says Marion Nestle.

Maybe people who eat foods rich in saturated fats have poorer diets generally, and those who don't have lots of other healthy behaviors. This helps explain some of the mixed findings on questions about fat, such as these recent reviews of the observational research, which concluded that the evidence that saturated fat alone had a bad effect on the heart is weak and unconvincing.

Second, scientists have been finding that what you're eating besides saturated fat can be just as important for your health (more on this below). Many of the experimental studies on saturated fat asked people to swap saturated fat out of their diet for some other type of macronutrient. It turns out that people ended up with different health outcomes depending on what else they ate, leaving researchers to wonder whether fat or diet generally was the key variable here.

This 2015 Cochrane Review of long-term randomized controlled trials on saturated fat, for example, found that reducing one's saturated fat intake can reduce the risk of cardiovascular disease (including heart disease and stroke), but it really depends on what you replace that food with. People who replaced saturated fat with unsaturated fat got the most benefit.

So researchers generally don't disagree about the fact the unsaturated fat seems to be better than saturated fat for health. But they do disagree abut what to do with that information. Some, like Harvard's Frank Hu, continue to advocate saturated fat reduction as a way to better health. "Saturated fat — compared to unsaturated fat — is definitely an unhealthy or bad fat," Hu says.

But other researchers say the focus on fats is confusing and outdated. The panic over saturated fats in the past pushed many people to foods higher in sugar, which we now know is just as bad. "There's good evidence that refined grains and starches are worse for people than saturated fat," Mozaffarian said. "You can find foods that have saturated fat in them that are good for you, or foods that have no saturated fat in them that are bad for you."

(Timeline by Javier Zarracina/Vox)

Replacing saturated fat with unsaturated fat is fine. Replacing it with sugar isn't.

So it's probably helpful to think of various fats on a spectrum. Trans fats appear to be the worst for health, unsaturated fats the best, and saturated fats somewhere in between.

Even with the uncertainty, most doctors will suggest that you should replace saturated fats with unsaturated fats whenever possible. And there is a lot of good research to back this up.

Numerous studies have found that when people swap out their saturated fats for unsaturated fats (especially polyunsaturated fats, like those found in fish) they reduce their risk of coronary heart disease. (The new US dietary guidelines also recommend replacing saturated fat with polyunsaturated fat to reduce the risk of cardiovascular disease and mortality.)

This doesn't justify any "low-fat" diet, however. Studies have also found that when people swap out saturated fats for more refined carbohydrates, their health doesn't improve. So it's probably a good idea to replace a cheeseburger with fish or lentils. It's not necessarily a good idea to replace an egg with a low-fat muffin or bagel.

Cutting your total fat intake seems to have no effect on weight loss or heart health

It's a common misconception that eating fat makes you fat. But there's little evidence to back this up. Systematic reviews of all the studies comparing low-fat diets with other diets have repeatedly found that reducing fat consumption doesn't have an effect on weight loss.

Most recently, a team of Harvard-affiliated researchers tried to sift through all the best available evidence and see whether low-fat diets — in which 30 percent or fewer of the total calories came from fat — work better than those that are higher in fat. In the study, published in The Lancet, the typical weight loss was about 7 pounds for all groups, an amount the researchers considered to be quite insignificant since most of the dieters had many pounds to lose.

Lead author Deirdre Tobias, a doctor at Brigham and Women's Hospital and Harvard Medical School, puts it this way: "The dogma has been that dietary fat makes you fat, and if you lower your fat you won't be fat. That message was pervasive for quite some time. But the evidence surrounding it was never really there."

Indeed, Tobias's conclusions square with those of other high-quality research on the subject. And it makes sense: After all, the past few decades have seen a surge in popularity for low-fat diets. Yet the obesity rate rose nonetheless.

So ... what should I be eating?

University of Auckland researcher Rod Jackson put all the current science on dietary fat in perspective. "The original message was to eat less saturated fat, which got dumbed down to, 'Eat less fat,'" he says. That was misguided. "But," he adds, "this latest craze to eat more fat is an equally bad message. The evidence actually says replace saturated fat with unsaturated fat."

In other words: Ignore the latest hype and magazine covers. Fat isn't bad. But certain types of fat are better for health than others.

Marion Nestle goes even further. "The science hasn't changed," she says. "But we need to move away from nutrients because nobody understands what they are and it's not how people eat." In other words, nutritionists should stop saying things like "eat more fat" or "eat less carbs" and instead focus on what types of foods to eat.

Nestle points out that all foods with fat contain some mixture of the three types and that you can't separate a conversation about fat from talk of food and calories. "People eat food, not nutrients," she said. And if you're getting too much energy from food, you'll gain weight and be worse off no matter what you're eating.

She also noted that the Japanese have great health outcomes, as do some Mediterranean countries and many other places in between — very different societies with vastly different diets. "As far as I can tell," she added, "the common thread through all of this is Michael Pollan's haiku: 'Eat food, mostly plants, not too much.' When people eat healthier diets they do better, and it doesn't have anything to do with how much carbohydrate or protein or fat they ate."

Key studies:

1960: Science — "The Relation in Man between Cholesterol Levels in the Diet and in the Blood." Researchers propose the amount of saturated fat in the diet alters the concentration of cholesterol in the blood.

1965: American Journal of Clinical Nutrition — "Quantitative Effects of Dietary Fat on Serum Cholesterol in Man." This early research explained the link between saturated fat in the diet and the concentration of cholesterol in the blood.

1970: Circulation — "Coronary Heart Disease in Seven Countries." Studying populations in seven countries, researchers found associations between diets high in saturated fat intake, cholesterol, and cardiovascular disease.

2005: New England Medical Journal — "Trans fatty acids and cardiovascular disease." This review of the evidence finds eating trans fats "provides no apparent nutritional benefit and has considerable potential for harm."

2010: PLOS Medicine — "Effects on Coronary Heart Disease of Increasing Polyunsaturated Fat in Place of Saturated Fat." This systematic review found that consuming polyunsaturated fat in place of saturated fat reduces cardiovascular disease events.

2011: Circulation — "Recent Advances in Preventive Cardiology and Lifestyle Medicine." Heart researchers suggest people focus on eating high-quality food instead of particular fat quantities.

2015: Cochrane Review — "Reduction in saturated fat intake for cardiovascular disease." This systematic review finds reducing saturated fat intake has "a small but potentially important reduction in cardiovascular risk."

2015: Journal of the American College of Cardiology — "Saturated Fats Compared With Unsaturated Fats and Sources of Carbohydrates in Relation to Risk of Coronary Heart Disease." This prospective cohort study found that unsaturated fats (especially polyunsaturated) and/or high-quality carbohydrates can be used to replace saturated fats to reduce cardiovascular disease risk.

2015: Lancet — "Effect of low-fat diet interventions versus other diet interventions on long-term weight change in adults." People on low-fat diets don't lose more weight.

2015: BMJ — "Re-evaluation of the traditional diet-heart hypothesis." Replacing poly-unsaturated fat with saturated fat does not seem to reduce the risk of mortality.

---

Vox Featured Video

buckinghamyind1946.blogspot.com

Source: https://www.vox.com/2015/11/24/9782098/dietary-fat-saturated-fat-good-or-bad

Share :