As a nerd, I like the idea of reading science news.  Unfortunately, science coverage in the general interest press is almost uniformly awful.  There are a lot of reasons for this: reporters can’t possibly be current in every area of science (and in fact are probably not current in any of them), editors don’t seem to think the general public is interested in science except as it immediately applies to their lives (and they’re probably right), and the process of writing a science news article is like a giant game of password.  When you read a story in a newspaper, what you’re reading is an article summarizing a press release summarizing a journal article summarizing a study.  Clearly, information is lost, distorted, and spontaneously generated at every step of that process, so what you see in the newspaper often bears little resemblance to what was actually done.  Some amount of that distortion is deliberate:  Scientists try to make the data tell a story, the journal’s marketers try to write a press release that will get the journal’s name in papers around the country, the journalist tries to write a story that will get printed, and the editor tries to shape it into something he thinks will sell papers (or magazines, or page views, or whatever).

This rant was brought on by a story in today’s L.A. Times called “Permanent diet may equal longer life“.  It’s about a 20-year longtudinal study of reduced calorie (RC) diets in Rhesus macaques (n=76).  As you can guess from the title, the angle is that reduced calorie diets can help humans live longer.  They don’t take any time getting there, here’s the first graph (thanks to The Wire, I can throw newsroom slang around like a seasoned pro):

For a country in which roughly 200 million people are overweight or obese, scientists today have discouraging news: Even those who maintain a healthy weight probably should be eating less.

In the second we get “It has been shown to significantly extend the lives of yeast, worms, flies, spiders, fish, mice and rats” followed by

“It adds to the evidence piling up that caloric restriction, independent of thinness, is a healthy way to stay alive and healthy longer,” said Susan Roberts of the Human Nutrition Research Center on Aging at Tufts University, who wasn’t involved in the study. “Less diseases in old age has to be something most everyone wants.”

and then “Mild caloric restriction is beneficial to everybody,” said Dr. Luigi Fontana, a medical professor at Washington University in St. Louis.” Oh man, I want to live longer, how do I cut my own calories!?!  That question is answered, and the answer is followed by a competent summary of the study’s methodology.  But wait a minute… for those who are still reading, the fifth graph from the end, after the jump, finally comes clean with

It also isn’t clear whether caloric restriction would extend human lives by very much, Phelan said. … He calculated that reducing intake by 35% would extend the human life span by just two years.

Huh, but I don’t understand, calorie restriction is going to make me live longer, and prevent heart disease, cancer, and diabetes!  It’s going to improve my brain health!  Except it’s not.  The study doesn’t support any such conclusions about human health.  I became convinced of that when I checked out the lovely inset graphic.  If I count those dots correctly, 16 of the control group monkeys got diabetes during the study period.  That’s almost half of the group (the text of the journal article reveals that most of those actually have pre-diabetes, for which they received medical treatment).  Maybe what’s actually happening here is that the diet they feed the monkeys, referred to in the story as “lab chow”, is actually really bad for them.  The comparison to human nutrition that the Times story wants to imply rests on the assumption that the control regime is somehow equivalent to a typical human diet.  Instead monkey chow*, like most pet food, is a cereal made from the castoffs of human food processing, designed to have low cost and a long shelf life.  All the stuff you can read about it being “scientifically formulated” and “nutritionally balanced” really just means that it has enough micronutrients (vitamins, minerals, etc.) so that the monkeys won’t get any of the deficiency diseases (that we know about), and that it’s balance of macronutrients (fat, protein, carbohydrates) falls within the nutritional consensus.  Of course, we’ve known for a long time that nutrition is much more complicated that keeping fat low and getting enough B12.

I should note here that this story is also a summing-up of a lot of prior research on reduced calorie diets, which has been an ongoing area of research since about 1935.  This study is far from the only one on which to base claims that such a diet would benefit from humans, but it doesn’t seem to make nearly as strong a contribution to that argument as the story wants to claim.

*The study does not indicate what food was fed to the monkeys, presumably they made at least the reduced calorie formulation themselves.  All they say is “Animals in this study are fed a semipurified, nutritionally fortified, low fat diet containing 15% protein and 10% fat.”