Saturday, March 26, 2011

Historical Context, Part 5 - Inadequate Evidence

Following in the McGovern Senate Select Committee's lead, the USDA drafted its first official Dietary Guidelines for Americans in 1980.  The recommendations were strikingly similar to those of McGovern's recommendations, despite the fact that many of the organizations involved in food and nutrition, like the Food and Drug Administration (FDA), the National Academy of Sciences (NAS), and the National Institute of Health (NIH), had considered the original Dietary Goals to be largely a political document instead of a scientific one.  Now, solid scientific evidence was needed to support the low-fat diets they were promoting (that's a little backwards, no?).  In the early 70's, NIH administrators decided against conducting a $1 billion clinical trial that would likely offer a definitive answer to whether or not low-fat diets prolong life.  Instead, they opted to conduct a half-dozen smaller observational studies, at a third of the cost, that they hoped would provide the evidence they were looking for.  The results of these studies were published between 1980 and 1984.

Four of these studies tried to establish relationships between dietary fat and heart disease.  They observed populations in Honolulu, Puerto Rico, Chicago, and Framingham, Massachusetts, and although some of the data suggested an association with fat and heart disease, the data involving all-cause death revealed a different story.  In the Honolulu study, the researchers followed 7,300 men of Japanese descent and found that those who developed heart disease ate slightly more fat and saturated fat than those who didn't.  However, the men who actually died tended to eat less fat and less saturated fat, so low-fat diets were associated with increased mortality.  Similar results were seen in Framingham and Puerto Rico.  The researchers' interpretation of these results is absolutely astounding.  They reported that because men in Puerto Rico and Honolulu who remained free of heart disease ate more starch, the studies suggest that Americans should follow the Dietary Guidelines and eat more starch.  Consequently, in order to avoid eating too many calories, Americans should also reduce fat intake.  WHAT??  Talk about twisting the results to support your hypothesis...

And it gets worse.  Also found in this data, with the exception of the Chicago study, was an association between cholesterol levels and cancer rates.  That is, low cholesterol predicts higher cancer rates.  This link was not abnormal.  In fact, by 1980, this association was showing up regularly in studies like this.  But this connection seemed to present a problem for the diet-heart hypothesis and was never publicized the way it should have been.  Just ask someone on the street today if they've ever heard that high cholesterol may be protective of cancer... they'll probably laugh and walk away.  Regardless, there is a strong link there.  In the Framingham study, men whose total cholesterol was below 190 mg/dl were three times more likely to get colon cancer as men with cholesterol over 220 mg/dl, and they were almost twice as likely to get any form of cancer than those with cholesterol over 280 mg/dl.  This is not an anomaly.  It is in fact very typical of these types of studies.  Those who have higher cholesterol tend to have a slightly greater risk of heart disease, but those with lower cholesterol clearly have a greater risk of cancer, and often times a greater total mortality rate as well.

The National Heart, Lung, and Blood Institute (NHLBI) also published two studies in the early 1980's that were supposed to provide support for the diet-heart hypothesis.  The first was the Multiple Risk Factor Intervention Trial (MRFIT), which collected a group of 12,000 men who were considered at imminent risk of having a heart attack; they all had a total cholesterol level over 290 mg/dl.  The men were randomly divided into two groups, a control group and an intervention group.  The control group was told to live, eat, and address their health problems however they wanted, while the intervention group was counseled to quit smoking, take medication to control their high blood pressure, and eat a low-fat, low-cholesterol diet.  The men were then followed for 7 years.  The results, announced in October 1982, showed that there had been slightly more deaths in the intervention group than in the control group.  Also of note, despite the fact that 21% of those in the intervention group quit smoking compared to only 6% in the control group, the intervention group had more lung cancer.  The researchers attributed this to the fact that those on the low-fat diet had lower cholesterol levels, hence were more likely to succumb to cancer.  I would concur.

The other NHLBI study was the Lipid Research Clinics (LRC) Coronary Primary Prevention Trial.  This trial collected 3,800 men who had cholesterol levels over 265 mg/dl, considered imminently likely to suffer a heart attack.  All of the participants were counseled to eat a cholesterol-lowering diet, but half of them took a cholesterol-lowering drug called cholestyramine, while the control group took a placebo.  So, to clarify, the only difference between the two groups was the presence or absence of the cholesterol-lowering drug.  This means that the only variable being tested was the effectiveness of the drug, nothing else.  Here are the results:  In the control group, cholesterol levels dropped 4%, 158 men suffered non-fatal heart attacks, 38 died from heart attacks, and overall 71 men died.  In the group receiving cholestyramine, cholesterol levels dropped by 13%, 130 men suffered non-fatal heart attacks, 30 died from heart attacks, and overall 68 men died.  Putting the heart disease numbers aside, 71 deaths versus 68 deaths.  This means that the cholesterol-lowering drug had improved by less than 0.2% the chance that any one of the men who took it would live through the next decade.  Very insignificant.  Any right-minded person would wonder, then, how such an unimpressive cholesterol-lowering drug trial was featured in Time magazine as proof that cholesterol was a plague to us all, and that we need to lower our cholesterol by eating low-fat, low-cholesterol diets.  The heading of the article read "Sorry, It's True. Cholesterol Really Is a Killer."  Basil Rifkind, who headed the study, was quoted in the article as saying, "It is now indisputable that lowering cholesterol with diet and drugs can actually cut the risk of developing heart disease and having a heart attack."  That may be true, but it doesn't appear to save any lives, and that's the ultimate goal. 

I hope it is clear at this point that the research backing the diet-heart hypothesis is surprisingly thin.  You would think that for an entire nation to adopt these low-fat diets as the gold-standard in healthy eating, and most of the civilized world for that matter, there would need to be a wealth of research supporting it.   As I've shown here, the science is ambiguous at best, but by this point, the media had grabbed a hold of the low-fat diet so hard that it would never let go.  The USDA Dietary Guidelines for Americans are republished every 5 years and they're considered to be the most comprehensive, unbiased assessment of the science by many in the field of nutrition, even though they've barely changed since 1980.  Dietitians blindly take it as truth and implement it in their work often without questioning it.  To them I say, get some historical context.

Next time, in what will definitely be the last part of this Historical Context series, I'll wrap up all of this information in a nice, neat little package and attempt to bring it all together.

1 comment:

  1. Awesome post man. I'm printing this one out and having poppa read it.
    It's too bad our parents generation have this "low-fat" lifestyle engrained so strongly in their minds. It's a classic example of "follow the leader." Only problem is that the leader is based on shitty science