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Red meat causes heart disease. Except when it doesn’t?

One study says reduce red meat consumption; another says enjoy. Which should we believe?

Red meat causes heart disease. Except when it doesn’t?
  • A recent meta-analysis found red and processed meats increased the risk of developing heart disease by 3–7 percent.
  • The study comes just months after an infamous review claimed Americans did not need to change their meat-eating ways.
  • The problem is not scientific consensus, but how specialists analyze risk when proffering public guidelines.


Americans love meat. Love it! Worldwide, a person consumes on average 92 pounds of meat per year. The average American flesh-eater devours more than 265.

Most of that meat is poultry, which has dominated the dinner table slot since about the turn of the century. When you consider that the average chicken weighs 6 pounds at the time of slaughter, that's, wow, so many dead birds.

That isn't to say that Americans have given up on red or processed meats. Since the 1950s, red meat has been a symbol of American prosperity, and while our consumption has declined steadily since the beef lust of the 1970s, we still maintain our love of grilled steaks, juicy burgers, and cold-cut mountains sandwiched in bread. A majority of those polled in a 2012 survey said they eat red meat one to four times a week, a figure that excludes poultry and fish.

But even that may be too much. According to a meta-analysis published in JAMA Internal Medicine, just two servings of red meat and processed meats a week is associated with an increased risk of cardiovascular disease and death. And poultry isn't an entirely benign alternative, either.

A red meat menace

Red meat is associated with an increased, though slight, risk of developing heart disease.

(Photo: Kaleb Snay/U.S. Air Force)

The researchers analyzed six cohort studies, totaling 29,682 participants. The participants were surveyed about their eating habits and health. Baseline data were collected from 1985 to 2002 with follow-ups conducted until August 2016.

The researchers found two servings of processed meats a week to be associated with a 7 percent higher risk of developing cardiovascular disease — or an absolute risk difference of about 2 percent. Two servings of red meat were associated with a 3 percent higher risk — or about 1 percent absolute risk — and poultry was associated with similar risk. Fish consumption showed no increased risk.

The researchers then looked at all-cause mortality. They found a 3 percent higher risk of premature death for servings of red and processed meats, but no difference for poultry or fish.

"Modifying intake of these animal protein foods may be an important strategy to help reduce the risk of cardiovascular disease and premature death at a population level," lead study author Victor Zhong said in a release.

In the heart or in the head?

But a meta-analysis published last year said that Americans don't have to change their meat habits.

(Photo: Pixabay)

You may now be thinking, "Wait! Wasn't there a study last year that said it was okay to eat red meat?' Yes, yes there was.

That meta-analysis, published in the Annals of Internal Medicine in October, was based on four systematic reviews of trials and studies looking at the link between red and processed meat consumption and cancer, cardiovascular disease, and mortality.

In one review, the researchers looked at 12 trials — totaling 54,000 participants — and found no significant association between meat consumption and the risk of heart disease or cancer. In the other three, they looked at studies of all-cause mortality, totaling four million participants. They found a very small reduction in risk but an uncertain association.

The researchers ultimately concluded that the links were small, the risks low, and the quality of evidence lacking. As a result, they recommended that adults continue to eat red and processed meats at their current levels and saw no reason to reduce consumption for health.

"This is not just another study on red and processed meat, but a series of high-quality systematic reviews resulting in recommendations we think are far more transparent, robust and reliable," Bradley Johnston, an epidemiologist at Dalhousie University and the study's corresponding author, said in a release.

However, many nutritionists and organizations like the American Heart Association and the American Cancer Society came out against the study and pushed for its publication to be withheld.

"This new red meat and processed meat recommendation was based on flawed methodology and a misinterpretation of nutritional evidence," Frank Hu, chair of the Department of Nutrition at Harvard, said. "The authors used a method often applied to randomized clinical trials for drugs and devices, which is typically not feasible in nutritional studies."

Nutritional data and you

What should we take away from this back-and-forth between nutritionists? First, both studies found that people who reduce red and processed meat consumption lowered their risk of premature mortality. They also found that the risk reduction was small.

The difference lies in how they believe that risk should be communicated to the public and how people should navigate their daily diets.

"The standards of evidence for the [scientific conclusions] are scientific matters and should not depend on extra scientific considerations" David Allison, dean of the Indiana University School of Public Health, told the New York Times added. "The standards of evidence for the [recommendations] are matters of personal judgment or in some cases legislation."

Red meat and processed foods are associated with a low risk of developing cancer and heart disease. That's a scientific consensus. That's not the same as saying whether individual people should or should not consume those meats.

For example, if changing dietary habits reduces the risk of heart disease by 3 percent, that means only three in one hundred people would statistically see the benefits. The vast majority, 97 people, won't. That's the view of the Annals of Internal Medicine's recommendation: The current guidelines won't change much on an individual level.

On the other hand, spread that risk across an entire population, and the salubrious effects become staggering. For the U.S.'s 327 million people, a reduced risk of 3 percent means 9,810,000 fewer people suffering from heart disease. Since health recommendations are generalized for an entire population, it makes sense that experts target individual advice with the public in mind.

Aaron Carroll, a physician and author of the Bad Food Bible, has written and spoken a lot on this topic. His advice is as follows: "If you're eating multiple servings of red meat a day, then you may want to cut back. If you eat a couple of servings a week, then you're likely just fine."

Moving away from meat, nutritional research also agrees what the average person should eat on a daily basis. In an interview with Big Think, David Katz, director of the Yale Prevention Research Center, summed up the findings nicely:

You want to eat fish? Eat fish. You want to eat seafood? Eat seafood. You want to eat some lean meat? Do. You want to eat eggs? Do. You want to eat dairy? Do. But the bulk of your diet should be vegetables, fruits, whole grains, beans, lentils, nuts, and seeds. This is true all around the world where people do the best.

If you choose to eat meat, well, you do you. But you do you at your own risk.

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  • Quantum particles can tunnel through seemingly impassable barriers, popping up on the other side.
  • Quantum tunneling is not a new discovery, but there's a lot that's unknown about it.
  • By super-cooling rubidium particles, researchers use their spinning as a magnetic timer.

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Exactly why or even how quantum tunneling happens is unknown: Do particles just pop over to the other side instantaneously in the same way entangled particles interact? Or do they progressively tunnel through? Previous research has been conflicting.

That quantum tunneling occurs has not been a matter of debate since it was discovered in the 1920s. When IBM famously wrote their name on a nickel substrate using 35 xenon atoms, they used a scanning tunneling microscope to see what they were doing. And tunnel diodes are fast-switching semiconductors that derive their negative resistance from quantum tunneling.

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Steinberg is a co-author of a study just published in the journal Nature that presents a series of clever experiments that allowed researchers to measure the amount of time it takes tunneling particles to find their way through a barrier. "And it is fantastic that we're now able to actually study it in this way."

Frozen rubidium atoms

Image source: Viktoriia Debopre/Shutterstock/Big Think

One of the difficulties in ascertaining the time it takes for tunneling to occur is knowing precisely when it's begun and when it's finished. The authors of the new study solved this by devising a system based on particles' precession.

Subatomic particles all have magnetic qualities, and they spin, or "precess," like a top when they encounter an external magnetic field. With this in mind, the authors of the study decided to construct a barrier with a magnetic field, causing any particles passing through it to precess as they did so. They wouldn't precess before entering the field or after, so by observing and timing the duration of the particles' precession, the researchers could definitively identify the length of time it took them to tunnel through the barrier.

To construct their barrier, the scientists cooled about 8,000 rubidium atoms to a billionth of a degree above absolute zero. In this state, they form a Bose-Einstein condensate, AKA the fifth-known form of matter. When in this state, atoms slow down and can be clumped together rather than flying around independently at high speeds. (We've written before about a Bose-Einstein experiment in space.)

Using a laser, the researchers pusehd about 2,000 rubidium atoms together in a barrier about 1.3 micrometers thick, endowing it with a pseudo-magnetic field. Compared to a single rubidium atom, this is a very thick wall, comparable to a half a mile deep if you yourself were a foot thick.

With the wall prepared, a second laser nudged individual rubidium atoms toward it. Most of the atoms simply bounced off the barrier, but about 3% of them went right through as hoped. Precise measurement of their precession produced the result: It took them 0.61 milliseconds to get through.

Reactions to the study

Scientists not involved in the research find its results compelling.

"This is a beautiful experiment," according to Igor Litvinyuk of Griffith University in Australia. "Just to do it is a heroic effort." Drew Alton of Augustana University, in South Dakota tells Live Science, "The experiment is a breathtaking technical achievement."

What makes the researchers' results so exceptional is their unambiguity. Says Chad Orzel at Union College in New York, "Their experiment is ingeniously constructed to make it difficult to interpret as anything other than what they say." He calls the research, "one of the best examples you'll see of a thought experiment made real." Litvinyuk agrees: "I see no holes in this."

As for the researchers themselves, enhancements to their experimental apparatus are underway to help them learn more. "We're working on a new measurement where we make the barrier thicker," Steinberg said. In addition, there's also the interesting question of whether or not that 0.61-millisecond trip occurs at a steady rate: "It will be very interesting to see if the atoms' speed is constant or not."

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