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Comment by randomsearch | Hacker News Reader

“The World Cancer Research Fund report Food, Nutrition, Physical Activity and the Prevention of Cancer provided advice on red and processed meat in 2007.

The organisation said the evidence that red and processed meats are causes of bowel cancer is convincing. It advises that people eat no more than 500g of red meat a week (around 70g a day) and avoid processed meats.”

https://www.nhs.uk/live-well/eat-well/red-meat-and-the-risk-...

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So how much did they weight the utility of eating red meat in order to conclude that severely restricting it would be worth the .074% decrease in death risk? Because that doesn't seem like a significant risk.

https://www.cancerresearchuk.org/health-professional/cancer-...

Genuinely curious, where did you see the "0.074% decrease in death risk?"

From the page you linked to: "13% of bowel cancer cases in the UK are caused by eating processed meat.

Bowel cancer risk is 17-30% higher per 100-120g/day of red meat intake, meta-analyses have shown.

Bowel cancer risk is 9-50% higher per 25-50g/day of processed meat intake, meta-analyses have shown; however bowel cancer risk was not associated with processed meat intake in a pooled analysis of UK case-control studies. Colon cancer risk is 12% higher per 1mg/day of haem iron intake, a meta-analysis showed; though bowel cancer risk was not associated with dietary iron intake in a pooled analysis of UK cohort studies.

Serrated bowel polyp risk is 23% higher in people with the highest versus lowest levels of red meat intake, a meta-analysis showed."

https://www.cancerresearchuk.org/health-professional/cancer-...

Ok let's run this scenario (please check my math here, I'm not positive I'm doing the probability right). Let's assume we're talking about a man, bc men are more likely to be affected. Your lifetime risk of developing bowel cancer is 7% for males [1]. Bowel cancer risk is 17-30% higher if you eat a quarter pound of red meat per day [2]. But let's go ahead and assume someone does eat that much meat and use 30%. If you get bowel cancer, you have a 25% chance of dying [3]. That means...

lifetime_risk_no_meat = 0.07

lifetime_risk_yes_meat = 0.07 + (0.07*.3)

risk_of_death_given_cancer = 0.25

(lifetime_risk_yes_meat - lifetime_risk_no_meat) /risk_of_death_given_cancer ==> 0.084

So an 0.084% increase in risk of death if we use the most risky scenario available.

[1]: Lifetime risk of bowel cancer https://www.cancerresearchuk.org/health-professional/cancer-...

[2]: https://www.cancerresearchuk.org/health-professional/cancer-...

[3]: Persons-> Crude rate -> UK https://www.cancerresearchuk.org/health-professional/cancer-...

I believe that your math is wrong because some of your numbers are percents and some are not, and because you divided instead of multiplying. If you are interested in the chance of death, you take the chance of cancer and multiply it by the chance of death given cancer.

lifetime_risk_no_meat = 7% lifetime_risk_yes_meat = 7% + (7%30%) = 9.1% risk_of_death_given_cancer = 25% (lifetime_risk_yes_meat - lifetime_risk_no_meat) risk_of_death_given_cancer = 2.1%*25% = 0.00525 = 0.525%

So by this math, eating a quarter pound of red meat a day causes men in this worse case scenario to die 0.525% more often, which is a sixteen times higher rate than your calculated value.

Of course, that’s not how to actually do the relevant calculations, since (assuming no significant technology changes), everyone will eventually die. Thus you instead need to do calculations based on life expectancy, or better yet on QALY (quality adjusted life years), which adjusts for the quality of life that people live in addition to their age.

>Genuinely curious, where did you see the "0.074% decrease in death risk?"

I was generously assuming that if I follow their advice, I eliminate bowel cancer risk entirely. Since only .074% of the population has it (74 per 100k), that’s the max change in risk of death.

But you’re right, I really only decreased my risk by 13% of that .074% by eliminating red meat. Still don’t see the enormous upside.

That makes sense, I should have caught that the harm reduction was not in total mortality but just of the bowel cancer subset.

But they only appeal to the bowel cancer risk and don't list any other death risks that are associated with red meat, so I'm assuming that's the only (or the far-dominant) one.

Every single one of those recommendations as of 2007 was the result of correlational epidemiological studies. It cannot be emphasized enough that correlation is not capable of proving causation. Period. All that correlation (or the lack thereof) is capable of doing is disconfirming hypotheses, not confirming them. When it comes to confirming a hypothesis it's randomized, controlled trials or GTFO.

From your link:

>This is because there is probably a link between eating a lot of red and processed meat, and bowel (colorectal) cancer.

Probably? Link? "Link" as in "co-occurring but not necessarily causally related"? No references to the studies or methods? This is the same quality material that has been used to promote eating less fat for several decades, while obesity exploded to record levels.

This is the same quality material that has been used to promote eating less fat for several decades, while obesity exploded to record levels.

It’s a bit ironic you are questioning the study with regards to causality and then mention obesity exploding to record levels with an unsubstantiated, implied connection to the promotion of eating less fat. Your coment would have been perfect without the obesity comment since your comment is decrying linking things without sufficient causal evidence.

The person you're responding to is not saying that avoiding fat led to obesity. They're simply saying that the obesity epidemic is evidence against the hypothesis that consuming fats leads to becoming fat. Disconfirming a hypothesis is not the same thing as as proving a competing hypothesis.

Without further evidence/study one can’t conclude much. We have two facts:

1. There was a campaign against eating fats.

2. There was an obesity epidemic that started shortly after the campaign against eating fats.

Fact 2 is seductive because it’s natural to assume that 1) is the cause. But without further analysis and study one can’t conclude this. In a post decrying causal links without proper statistical evidence it’s ironic to fall victim to this seduction without proper statistical evidence.

There was an intervention (telling people not to eat fat) based on the "eating fats = bad" hypothesis and that intervention failed to have the effect that the hypothesis would predict. That is disconfirming evidence. You are correct that it's not conclusive, but it is disconfirming nonetheless.

That's all I am saying.

It’s not disconfirming since it’s possible that eating fats is bad but also that replacing fats with sugar is bad too or possibly even worse than eating fats. There are also other possibilities to explain why eating too many fats is bad even though when they were targeted for reduction health outcomes did not improve.

It disconfirms the original hypothesis. You have mentioned other, more complicated hypotheses which it does not disconfirm.

>The organisation said the evidence that red and processed meats are causes of bowel cancer is convincing. It advises that people eat no more than 500g of red meat a week (around 70g a day) and avoid processed meats.”

The previous recommendations (that got retracted) had "convincing" evidence at their time too.

The problem is the anti-egg science was convincing at the time as well.

It never was. There were afaik no studies ; basically the advice was given on the chain “dietary cholesterol -> serum cholesterol -> blocked arteries -> cardiac problems” of which the last was convincing, the middle mostly convincing at the time, though much less so now - and the first was just assumed but is now known to be essentially wrong.

Which would make it wrong, but at the time, a non-expert who was looking for advice from people like doctors or their government would hear that they should be cutting back on eating eggs. Which would count as legitimately "convincing", if you're not a researcher in the field. Just wrong.

I used to be convinced that I knew more about nutrition science than doctors do.

Then I found that my total cholesterol was v high (7.5 mmol/L). I got scared and followed my doctor's dietary advice (less saturated fat, basically), and it dropped significantly (to 5.7, still higher than recommended levels)

That's when I realised that the likelihood that I can come up with some health strategy for myself that is better "following the advice of professionals" is extremely low

I followed doctors’ advice for my asthma blindly for years (since age 0, practically, without question) and basically felt horrible most of the time - was basically unable to finish a 2km run until age 20.

Then I woke up one day with the feeling that this can’t be right; started experimenting, and within a couple of months got to 5k, and within less than a year to 15k, feeling much better all the time and with every objective measurement improved.

That’s when I realized I should look into things and not just trust “advice of professionals” most of whom follow others quite blindly, and whose incentives are very different than mine (in my case, their incentive that guided me for 20 years is to minimize their legal risk - it was not to improve my health).

I agree it is important to know the bounds of knowledge - both yours and the professionals - and also to realize the incentives.

Also, google “John ioannadis”, an MD, on nutrition science and research in general. His seminal work about not trusting published research is unrefined 13 years later.

So why didn't scientists come out in droves and push back on the anti-egg movement?

To a first approximation, nobody actually cares what scientists say. Scientists can publish press releases and hound journalists until they're blue in the face, but they're not getting on the news unless what they're saying fits into a pre-determined media narrative. They're little more than a useful prop, like the flashy "scientific" graphics in moisturizer commercials.

Fox News will wheel out anyone with a PhD who is willing to cast doubt on climate change, Vox will dredge up someone who'll say that NASCAR gives you cancer and we all end up less informed than grade-schoolers.

Scientists are largely powerless to "push back" against anything, because they don't control the institutions that disseminate information.

Some did. I worked in a lab for the woman whose papers were instrumental in getting the anti-egg recommendation reversed. There was a lot more money on the other side, unfortunately.

Because there's no research grants to be had by going against the prevailing fashionable beliefs in the field.

It's my understanding that disproving commonly accepted things is a way to become a superstar in the scientific field. Also, you don't need research grants to show that there is no research that shows a causal link between two things, which is what the poster above claimed was the problem with the anti-egg movement

Disproving stuff is a good way to "fan the flames" of your career but you have to have some reputation in the first place. Otherwise you're a quack amateur which doesn't work well with others, just like you'd be in any other field if you picked fights with the wrong people too soon.

It also turns out that validating people's preconceptions and getting grants is a great way to build credibility via "social proof".

The truly skilled PIs can develop a popular idea, make it accepted in the field, then dramatically disprove it once the "bad" researchers start piling on! These masters can usually be identified by massive grants, sending students places(careers) to build relationships/incur debt of favors over years, writing bestseller books (ghostwritten) etc. And these are the people whose ideas everyone repeats.

"disproving commonly accepted things is a way to become a superstar in the scientific field"

It doesn't necessarily follow that people will gamble grant money on the off-chance that you might turn out to be that superstar.

Studies of communities that have longitivtiy confirm this. For example, the "Ikaria" study, a university of Athen's study of the island of Ikaria, where males reach the age of 90 2.5 times more frequently than Americans, their diet consisted of hardly any red meat at all (and also hardly any sugar), but rather beans, legumes, wild local greens with lemon juice and olive oil, fish, honey, and red wine.

Was the study of this island controlled for climate, compared to a nearby island with different diets, or compared to a distant island with similar diets?

One of the points made by Ioannidis is that we’re far too easily swayed to believe what sounds plausible when no one has yet asked “Could this be for some other reason altogether that we aren’t testing for?” and then tests for those reasons. That flaw applies here: studying just one community automatically implies that the results are invalid, simply because there’s no evaluation of other communities that share various attributes that could be hidden factors for the benefit.

EDIT: Per one article, that study “would try to cut through the stories and establish the facts about Ikaria’s longevity”. It has succeeded in establishing that, factually, Ikaria’s longevity is a thing relative to other populations. It has not established which of the properties of Ikaria are responsible. (For example, perhaps the island is slightly radioactive, and old people thrive in a slightly higher radioactivity.) Extrapolating that their diet is responsible is an instance of the A/X error described in the above-linked article.

I think you could do worse than that diet, but this is a multivariate comparison. From the study abstract[0]

> Conclusion. Modifiable risk factors, such as physical activity, diet, smoking cessation and mid-day naps, might depict the “secrets” of the long-livers; these findings suggest that the interaction of environmental, behavioral together with clinical characteristics may determine longevity. This concept must be further explored in order to understand how these factors relate and which are the most important in shaping prolonged life.

It could be that the quantity red meat is solely responsible for their longevity, or has nothing to do with it, or plays some role with the many other confounding variables.

[0] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3051199/

The study you cite did not confirm the red meat hypothesis. It merely failed to disconfirm it. Those are two very different things, which nutrition researches and the general public seem to be incapable of wrapping their heads around.

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