We've known for a while the risk factor for heart disease is serum SFA levels, not necessarily SFA consumption. What has never been shown is that consuming SFA raises serum SFA; instead, it's been an understood truism held in place by policy and demagoguery. This study is small, but evidence convicting saturated fats was extremely weak to begin with, and we are now seeing positive evidence exonerating it.
If you are interested in learning more about the history of nutrition, I highly recommend Nina Teicholz book The Big Fat Surprise. As others have mentioned, Phinney and Volek's books are a great overview off the science as of a few years ago. Phinney has been doing research on this for 40 years, quite an accomplishment, given how hard it has been to get funding for research that contradicts the policy line of "carbs are critical to survival and fat must be avoided".
Well, originally thought was valid. If we eat something, there must be more of it in body. Of course, now we see that body is more complicated in case of SFA, but generally assumption works for other cases.
If a cat entered a house, you generally might expect that cat should be inside the house. The reality, as we see, is more complex than that, but generally assumption works, and worked for most of the cases.
I just want to say that please don't blame scientists and policy makers. Everyone's smart after the fact.
If it were just incomplete science, I'd have no problem with the path we've taken, but it wassn't just a case off incomplete science. It was a case of a handful of scientists deciding on a hypothesis, then fitting data to it. When others rightly complained, a campaign of personal attacks began. Those same scientists got themselves into important positions with organizations like the AHA, giving their arguments a strong appeal to authority, not to mention giving them a huge soap box. Even that probably would have self-corrected, except politicians got involved. In the late 70s, the McGovern commission decided everybody needed a low-fat diet, which eventually entrenched the dogma in all NIH-funded studies as well as government provided food programs like school lunches and food stamps.
The really unfortunate thing is these scientists will likely be remembered for this misguided direction, rather than the huge steps they took in figuring out how to even approach nutritional studies in large populations.
As Feynman said, you have to make sure you aren't fooling yourself, and you are the easiest person to fool. I would argue there was (and continues to be) a lot of self-fooling going on in the field of nutrition. Fortunately, it seems to be getting better, perhaps because of the influence of biochemistry and physiology.
Well... with sugar for example we know for a long time that there is only about 50deciliters*80mg/DL=4grams of glucose in blood in average healthy adult.
As people are eating tons of sugar a day (snickers bar has 27g, half a liter of cola has ~50g, half of it fructose but still) it's clear stuff doesn't just go into bloodstream as we would all die before finishing that snickers bar. Somehow though fat magically getting into blood and clogging arteries was something which was accepted as common sense.
I do blame policy makers and scientists as healthy amount skepticism was clearly missing.
> Well, originally thought was valid. If we eat something, there must be more of it in body.
Sadly we replaced saturated fats (eg butter) with trans-fats (eg margerine). We know that trans-fats are terrible. That possibly caused some confusion. We knew people we still having heart attacks, we just thought that they were the group still eating saturated fats.
And now we may have gotten worse: instead of trans fats (really bad!), we now get highly oxidized poly-unsaturated fats as restaurants have moved to seed oils for frying, which don't handle the temperatures nor the time in use very well. Oxidized fats do nasty things in the body, perhaps worse than trans fats.
Bring back the stable saturated fats like coconut oil, palm oil (if sustainably produced), lard and tallow.
Unless you esat a lot, then your body makes relatively little. I love the way our bodies manage cholesterol, including dumping it into the intestines and recycling it if necessary. It's a beautiful example of how well our bodies regulate themselves when fed and tested well. My body has told me it needs 236mg/dL of total cholesterol right now. You couldn't pay me to mess with that.
If you eat a cat, do you then contain a cat? No, you contain products of digesting a cat. The supposed cause/effect looks like magical thinking in hindsight.
I think the original analogy refutes itself. If a strange cat enters your house, you remove it. Likewise, the human body has plenty of methods for regulating fats, sugars, sodium, etc. Of course, you can overwhelm those regulatory methods, but in general the assumption that there's a linear relationship between what you consume and the chronic levels seems pretty naive.
-- and if multiple strange cats enter your house, you start to think about closing the door.
Interesting that you mention sodium. I've wondered whether the common advice to restrict sodium to reduce blood pressure actually has any effect. It would only work if your kidneys were not effectively regulating your blood sodium.
Anecdote, my father has had blood pressure trouble due to both high sodium and low sodium in the past. In the first episode of low sodium, he kept reducing his salt intake thinking that would help. A visit to ER helped fix that notion.
According to this (there's a study linked within) salt's effect on blood pressure and other indicators of heart disease seem to follow a j-curve - too little or too much and you're at increased risk.
Nina Teicholz's book "The Big Fat Surprise" has gotten good reviews, but so has Thomas Campbell's book "The China Study" ... they both seem well researched, but very at odds with each other.
Nina's is different. Campbell's was trying to prove what you should eat; Teicholz' followed the history of the science to see where it went. The difference is subtle, but significant. Based on what I've seen and read of Campbell, I think he would expect his work to be the last word on nutrition; I think Teicholz would see hers as a beginning.
I recognize my own bias here, though. I think there are serious flaws in the China Study where Campbell reached beyond where the science illuminated. Teicholz isn't trying to prove a conjecture in the same way, so she isn't forced to do that (I think Robert Ludtig and David Perlmutter both did the same thing, so it's not just a function of vegetarian or not).
Edit: I say read them both and decide for yourself. Don't accept either of their conclusions, but follow the science they reference and evaluate it for yourself.
It's funny, but not surprising, to see the "I love science" crowd on HN so eagerly buy into the "all scientists have been wrong about heart disease" myths propagated by journalists like Gary Taubes and later by Nina Teicholz.
Here are some reviews of Nina Teicholz's shoddy work.
But Teicholz just follows in Gary Taubes' footsteps. See the numerous problems with that journalist's interpretation of health and dietary science beginning here:
One interesting thing to note is that the title Doubling Saturated Fat in the Diet Does Not Increase Saturated Fat in Blood does not logically contradict the notion that radically reducing saturated fat in the diet decreases saturated fat in blood. It's possible that once you reach a certain consumption point you're doing as much as you can do.
I'd want to read the study in detail before commenting further. I'm a little surprised they started with people with metabolic syndrome, which could mean a lot of things and lead to a lot of craziness.
Unfortunately, it's probably not too much of a stretch to think metabolically disordered people may outnumber those who aren't, if not now, then soon. But, realistically, it was probably necessary to target sick people to get the grant.
not that this negates the finding of the article, but i think it is important to highlight that: "This work was supported by the Dairy Research Institute, the National Cattlemen’s Beef Association and the Egg Nutrition Center."
Doesn't necessarily negate the findings, but I still don't trust it now that I read that. I want to see an academic medical center do a non-industry funded study before I accept this result.
I would be very careful about taking anything in this study at face value. Be sure to look at available responses before taking advice from the Atkins, Inc. folks.
Palmitoleic acid is a MUFA and while it may be true that it can act as a biomarker, there is an insanely huge amount of research against there being any direct deleterious mechanism of action for this fatty acid. To the contrary, palmitoleic acid is often shown to have protective, insulin sensitizing effects. More on that later, but come on. How can you write that when even perusing Wikipedia should cause pause!
But let me ask you this. When was the last time you heard that saturated fat caused an increase in the saturated fat circulating in your blood and that THIS was the cause of heart disease? Answer: Never!
It would be quite surprising. I concur with @elsewhen that the people funding this research must have been quite pleasantly surprised: "This work was funded by a grant from Dairy Research Institute, The Beef Checkoff, the Egg Nutrition Center, and the Robert C. And Veronica Atkins Foundation."
* Which SFAs (Saturated Fatty Acids) have been gone up in plasma by a carbohydrate diet? Only palmitoleic acid, or also other ones? And what's the percentage of these acids compared to all SFAs?
* If you only check people with metabolic syndrome are the results not typical of a metabolism which is screwed up? Don't you at least wanna know what it does in healthy people?
* If there is momentarily plasma palmitoleic acid response on dietary intake of carbohydrates, are those SFAs there so the body can get rid of them? What's the mechanism here? If you want to loose fat, it will need to go through the plasma at some time...
16 adults is quite good.
If you polled them well (that is randomly) and you obtained some result in all of them then it's significant evidence that that the result is true for very significant part of the population.
Sure, you can't show that it's true for everybody but having a result like: "only 0.1% chance that it occurred by random if 2/3 of the population reacts this way and way less if it's half of the population" is very nice result to have.
If something occurs for 16 randomly chosen people (or even 15/16 or 14/16) you are virtually certain it occurs for very significant part of the population which is often the goal of the study - to justify further research.
How important is it that this study had no control (and thus no randomisation or blinding) and had a small sample size, and that some of the authors have written books about this diet?
What would a control group have added? If you boil water in a beaker, do you need a control beaker where you monitor the temperature but don't light the Bunsen burner?
Also, how would you run a double-blind test of the foods people are eating? It's pretty hard to disguise steaks ;-)
Most nutritional studies are observational, so the numbers are not very reliable. In this case, "subjects were provided with all food for 18 wk, which was prepared and packaged by staff in our research kitchen." That's one reason why the numbers were so small, though it would have been better if they'd been bigger.
The most reliable evidence would come from controlling what people ate and what they did. I'd have thought this would be something that could be done with volunteer prisoners.
Controls are always essential in this type of research. Placebo effects abound. Maybe the people knew they were on an increased fat diet and so exercised more?
Nutrition studies will often use people as their own controls because of the significant variability between people. Nobody is willing to fund nutrition research with "perfect" studies, so researchers do what they can (especially when they are known to have hypotheses counter to the orthodox view).
On their books, I think that would be a ridiculous thing to reject people's findings for. Almost every academic has written a book at some time. Instead, we need to recognize the possibility of a bias inherent in every researcher and look to the study design, execution, and conclusions to see if they hold. Phinney and Volek are in a different class when it comes to their books and their ideas than is, say, Robert Lustig.
Whatever, I give it at most two years before some other study directly contradicts this one (just as this one directly contradicts conventional wisdom based on other studies which themselves contradicted the generally-accepted status quo before them).
I would take that bet. Phinney and Volek have a long history of doing pretty good science. I haven't seen any of their work directly contradicted over Phinney's 35+ year career[0]. Also, there is scant evidence that this is actually showing a different result than other studies. The diet-heart hypothesis never had good, controlled studies[1] to back it up; we are just now seeing the good science testing it, and it's not holding up well.
I will agree that nutrition science has been, and, in many cases, continues to be, lacking. It is getting better, though. We are moving past epidemiology being the be-all-end-all and starting to see well controlled trials asking interesting questions. Unfortunately, those are really expensive and hard to do.
0. I could be wrong here; I've read a lot but not everything. Still, they've had enough detractors that I'm sure people would have trumpeted it.
1. Lots of epidemiological studies, but causation shouldn't have ever been inferred from them. Unlike with smoking, risk factors were never 20x, more like 1.2x.
You basically nailed the problem: the generally-accepted status quo is based on flimsy evidence. Our metabolism is complicated and it will likely take decades before we fully understand it, not to mention that different people process calories differently.
Luckily, it's very easy to detect when your diet is having a negative impact on your health and you have time to make changes before heart disease or type 2 diabetes strikes. There's no excuse for not keeping track of your weight and not getting regular blood work to look for risk factors. When these risk factors emerge, very simple changes like eating more vegetables and spending more time walking can be enough to reverse them. Easier said than done of course, but we do have reliable science that shows this.
Well, the sample is quite small, and just because a measure of fats in blood did not increase, it is probably not justified to conclude that a high intake is safe.
High anything is probably not wise. However a somewhat different story from that to which we're accustomed, is emerging.
Am J Clin Nutr. 2010 Mar;91(3):535-46. doi: 10.3945/ajcn.2009.27725. Epub 2010 Jan 13.
Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease.
CONCLUSIONS:
"A meta-analysis of prospective epidemiologic studies showed that there is no significant evidence for concluding that dietary saturated fat is associated with an increased risk of CHD or CVD. More data are needed to elucidate whether CVD risks are likely to be influenced by the specific nutrients used to replace saturated fat."
We've been running some basic experiments that suggest the opposite to these findings: http://hema.vu/1vA0sHR . But again, this is hardly conclusive (our sample size is much smaller).
Your experiment doesn't really look like the same thing at all. From your link, it doesn't look like you are controlling carbohydrates and your participants are just eating lots of fast food. The study started with low carb high saturated fat. I would argue that fast food is high carb and high fat. Interesting research though either way.
Yes, it's time we stop reflexively dismissing every study with a small sample size as if that made it worthless. This is the latest meme in a sequence that includes "correlation is not causation" and "the plural of anecdote is not data". It's a generic dismissal and has a de-interesting effect on discussion. It has more in common with internet reflexes like "First" and "Betteridge" than with reflective thought.
One way to catch oneself before doing this is to ask if you're tacitly assuming that the people doing the work are idiots. The odds—and the Principle of Charity [1]—suggest they're not. Comments that imply this generically are usually low-quality.
If the people doing the work really are dumb, then it almost certainly has more specific flaws (e.g. "this way of measuring glucose isn't reliable", to make something totally up) that it would be far more helpful to point out.
It's not just a meme. There have been multiple articles and papers the last few years on how a great number of clinical trials are statistically underpowered and therefore suspect; this includes a 2005 paper entitled "Why Most Published Research Findings Are False", which analyzes "49 of the most highly regarded research findings in medicine over the previous 13 years" and finds that a worrying number of them hasn't stand replication.
And when people talk about underpowered studies, it's mentioned less than 100 individuals, not less than 20.
Oh I know. You're preaching to the choir, believe me! But that's not the meme. The meme is invoking it to dismiss a study with no further thought and no specific content.
Small samples get overinterpreted, many published findings are false, etc.—it's all true and the community here is well aware. But it's a gross overreaction to dismiss small-sample experiments wholesale. Even a few seconds' reflection is enough to see that.
For example, assuming this experiment was rigorous, it didn't need more than 16 subjects to find that greater saturated fat in diet doesn't automatically cause greater fat in blood. Additional resources might be better spent on future samples (i.e. replicating the finding by other researchers) than on a larger single sample, which is probably a game of rapidly diminishing returns. And so on.
The point is that HN wants reflective discussions, not reflexive ones. It takes no work and no real thought to pick out one detail that people are currently primed to fuss over and make a post of it. That's not reflection, it's habit, and its payload is not learning, but reinforcement. Reflection requires engaging with the material—this specific material.
There are two ways to do that. One is to dig in and learn the material, think about it, and report your findings to HN. The other is to happen to know something about it in the first place. The first takes work, the second luck. Comments based on neither work nor knowledge are likely not to be substantive. That's why want to avoid generic dismissals as opposed to specific ones.
I have to strenuously disagree with you (respectfully, of course) on this issue, dang. My several years of participation in the University of Minnesota journal club on behavior genetics, in which we go over current papers, sometimes being amazed by the papers (especially the papers on the methodology of doing science right) and sometimes picking apart the papers line by line (especially the papers on social psychology), have taught me to the core that most scientists are doing a job narrowly conceived of as trying to get published. I think they mostly went into science because they also desire to seek truth and inform humanity, but institutional pressures sometimes keep them from achieving that ideal. A surprisingly huge percentage of working scientists, as John P.A. Ioannidis[1], Uri Simonsohn,[2] Peter Norvig,[3] and special issues of science journals[4] and methodological blogs[5] remind us, are actually working right at their own level of competence or even beyond their own level of competence in setting up experiments and observational studies to be validly generalizable. I do NOT assume that "that the people doing the work are idiots," but I do assume, based on huge numbers of historical and current events examples, that the people doing the work are fallible and subject to cognitive biases (as I am) and subject pressure to publish to stay funded. Moreover, announcements of results are subject to wishful thinking on the part of a university press office.
Until a preliminary study has been replicated, I don't take it to be a statement of facts about the world. Even Wikipedia, which accepts some very dodgy user-submitted content, declares a content guideline that Wikipedia articles should be based on SECONDARY sources[6] (that is, sources by authors who have thought about and digested the primary research findings) rather by preliminary primary research findings. (Of course, for lack of enforcement, many Wikipedia articles break this rule.) It's especially important to establish high standards of sourcing for statements about human health and medicine and nutrition.[7]
I genuinely think that many (too many) readers of Hacker News have no idea what an adequate sample size would be, for a given effect size, to validly infer from a preliminary study result a statement about the entire population. We should be talking about sample sizes all the time here (I agree, with more sophistication and nuance than we often do) as part of educating ourselves about basic science methodology in this community of intellectual discussion.
That said, I heartily agree that "Betteridge's Law" is a useless Internet meme, even though it was popularized here by our esteemed site founder pg. We can do better, and we can raise the level of discussion here. I cherish the participants here who can speak knowledgeably about experiment design, about effect sizes, about observational studies as contrasted with experimental studies, and so on. I also delight when participants here share links to the prior scholarly literature, and especially when something is submitted here that is a better source than a press release.[8] Besides decrying crap, I like to applaud thoughtful discussion, so I regularly upvote comments that point us beyond the headlines to what issues researchers have to grapple with as they try to figure out the complexity of the world.
I feel like the point may be getting lost here. If you're poring over a paper line-by-line, you're engaging with that specific material and are in a position to point out specific things about it. That's not a problem. The problem is generic dismissals—the ones that don't take work or thought. Those dilute discussion, especially when they're an internet reflex as this one is becoming.
Most published studies may well be false, but that's no basis for substantively discussing a specific one, any more than "most movies are bad" is a movie review.
The problem, dang, is that some of the submissions here are generic submissions (health is a chronic topic here, because we all desire to be healthy), and not submissions based on a line-by-line reading of a few different sources to see which one is worthy of discussion here. A university press release about a small-n preliminary research finding rarely deserves more dismissal than noting it is a publicity puff piece about an unsettled conclusion.
We only discuss what's submitted here. The first filter that distorts reality here is what never gets submitted, because it is thoughtful and nuanced and takes too much thinking to read and discuss.
There is a class of poor-quality science blogs that mostly lift content from elsewhere. We mostly don't ban them, because occasionally they do end up being the best popular article on a study. We do, however, penalize them.
If you are interested in learning more about the history of nutrition, I highly recommend Nina Teicholz book The Big Fat Surprise. As others have mentioned, Phinney and Volek's books are a great overview off the science as of a few years ago. Phinney has been doing research on this for 40 years, quite an accomplishment, given how hard it has been to get funding for research that contradicts the policy line of "carbs are critical to survival and fat must be avoided".