If you've agreed with several posts on this blog expressing concern about manipulating science, you'll likely enjoy Michael Fumento's column "Science journals delivering 'political science'" today at townhall.com . Don't miss the comment "The (Political) Science of Salt" at the end.

Today's New England Journal of Medicine reports the second major health outcomes study in a week from the massive Women's Health Initiative, exploding another cherished axiom of nutrition, this one about dietary calcium. Higher intakes of calcium, the study concluded, do not protect against hip fractures, although consuming more calcium does increase bone mineral density slightly (unexamined in the study is the imporant contribution calcium likely plays in blood pressure regulation). No doubt these results, like those last week finding that low-fat diets do not improve health outcomes, will rekindle debates among nutritionists and the medical establishment. Good.

No matter how we have all felt about the wisdom of eating less fat or drinking more milk, a couple other "health outcomes" seem worth mentioning.

• First, these studies offer a great and humbling reminder that our confident embrace of logical explanations for population data demands that population health advisories should be based on randomized trials, not observational studies. They should reinforce our insistence on true evidence-based public health nutrition recommendations.
• Second, randomized health outcomes trials are possible. Many have argued that the importance of the health threat targeted for dietary therapy is so compellingly urgent that waiting for health outcomes trials -- expensive and long-term to be sure -- would be unethical. How ethical is it to tell the population to reconfigure its diet to obtain health benefits that are supported only by population studies whose conclusions are extrapolated into headlines claiming improved health outcomes? Without health outcomes trials examining the validity of the assumptions underlying these extrapolations, the dietary recommendation becomes a house of cards. Let's not gamble with cardsharps.

The salt connection, I hope, is obvious here. Logically, since salt is related to blood pressure and blood pressure is related to the incidence of cardiovascular events, some countries like the U.S. and the U.K. have embraced universal sodium reduction. The theory is clean and neat. But the argument is without evidentiary support. The only health outcomes data today are observational (and those data are only about a decade old, produced long after nutrition know-it-alls confidently concluded that lowering population salt intakes would improve public health). The health outcomes data we do have today shows no improvement in heart attack rate or increased morbidity/mortality for those on lower-sodium diets . In fact, 30% of the studies have identified an increased risk while none have identified a population benefit.

Before 2000, the U.S. Dietary Guideline suggested consuming salt or sodium in moderation. Reasonable advice, if somewhat ambiguous; it matched the ambiguity of the evidence. More recent Guidelines have been more strident even as the observational health outcomes studies accumulated and consistently showed no benefit. We should go back to the pre-2000 Guidelines until we can conduct a controlled trial of the health outcomes of reducing population sodium intake levels.

Today's Food Navigator reports: "Obesity rocketing despite record diet food spending." The headline is for Europe, but describes the U.S. as well. The headline betrays what may prove to be a critical, but erroneous assumption: that people who eat "diet food" have healthier diets, or lower-calorie diets. That linkage has yet to be tested.

For years dietitians have lectured on the fact that there are no "healthy" or "unhealthy" foods, only "healthy" or "unhealthy" diets. But "diet foods" sell, so until we have convincing medical evidence, the public goes on buying them, thinking that they're buying better health. As Peter, Paul and Mary sang in "Where Have All the Flowers Gone?": "When will they ever learn?

I loved this quote from Gina Kolata's news analysis column in today's New York Times entitled "Maybe You're Not What You Eat":

"Whatever is happening to evidence-based treatment?" Dr. Arthur Yeager, a retired dentist in Edison, N.J., wrote in an e-mail message. "When the facts contravene conventional wisdom, go with the anecdotes?"

The furious reaction to last week's JAMA report that low-fat diets don't lead to improved health outcomes reminds me of the current level of civility in Congressional discourse. "Partisan" anti-fat researchers opine in outrage reminiscent of Howard Dean.

The situation reminds me of the hysterical rejection of the 1995 study in the American Heart Association's journal Hypertension showing that hypertensive patients classified as "low-sodium" consumers had vastly higher risk of heart attacks. Critics flayed the methodology, yet all eight subsequent studies of health outcomes in populations with salt intakes typical of those in the U.S. have confirmed either no health benefit or an increased risk of lower salt intakes and the author subsequently was elected president of the American Society of Hypertension and, more recently, elected president of the International Society of Hypertension, a post he currently holds.

Hopefully, our next Dietary Guidelines Advisory Committee will not ignore this powerful new evidence -- our only controlled trial of the health outcomes of low-fat diets -- in favor of mindless regurgitation of politically-correct policy pronouncements, as they greeted the new evidence on salt.

Thank you Dr. Yeager (and Ms. Kolata) for spotlighting our options: follow the evidence or the "experts." We need to insist on evidence-based public health nutrition policies, not the anecdotally-consistent Guidelines being so loudly defended.

The front pages have been crowded with this story, blogged earlier here , and now the editorial writers are beginning to grasp the breadth of impact -- it goes WAY beyond fat.

As USA Today reminds us:

Not long ago, it was generally estimated that 400,000 Americans a year die from obesity. Oops. A new study last year by the Centers for Disease Control and Prevention (CDC) found that obesity accounts for only 26,000 deaths, and that a few extra pounds might add to longevity.

"Similarly, hormone replacement therapy was once thought to protect postmenopausal women against heart attack or stroke. Subsequent studies say it doesn't.

"Yesterday's conventional wisdom is today's myth. No wonder so many are skeptical about whether any study can be believed.

"The latest surprising finding is that low-fat diets don't reduce the rate of heart disease, stroke, breast cancer or colorectal cancer, or even result in greater weight loss. That's the conclusion of a government-sponsored study published Wednesday in the Journal of the American Medical Association. It followed nearly 50,000 overweight, postmenopausal women for an average of eight years.

...

"The low-fat study only means that there's no magic bullet, which leaves an obvious if unpleasant fact: Good health comes from a balanced diet, frequent exercise and avoiding obvious risks. Family history and genes count for a lot also, regardless of diet."

It's not that all of "yesterday's conventional wisdom is today's myth." Only when the conventional wisdom isn't based on sufficiently-rigorous thinking or evidence. Here, as in the salt case, we have a very plausible theory (hypothesis) and a bunch of obvservational studies, though far from consensus the fat studies seemed less controversial than those for salt. What we lacked was a randomized trial. Now we have it. NOW we're prepared to act on the evidence or, in the case of fat, perhaps not act.

This study may have cost $415 million, but if we learn the harsh lesson about prejudging before we conduct a controlled trial of the health outcomes of the proposed intervention, it will be money very well spent.

Until yesterday, everyone "knew" that low-fat diets were the cornerstone of a healthy diet. Publication in the Journal of the American Medical Association of results of an 8-year, $415 million study of nearly 50,000 American women found that what everyone "knew" was dead wrong. There was no health benefit among the almost 20,000 women on low-fat diets. They had the same incidence of breast cancer, colorectal cancer, heart disease and stroke as the 29,000 women who ate regular diets. Experts on every side of the issue agree the study is conclusive due to its size and quality ... and $400+ million pricetag.

Expensive study? You bet. Worthwhile investment? Priceless.

Not only have we spent billions of dollars researching low-fat diets, but food manufacturers have invested additional billions re-engineering the foods we eat. Americans have not only paid premium prices for specially-concocted low-fat foods and kept low-fat cookbook publishers in business for the past quarter-century, but consumers anguished over their inability to strip even more fat out of their daily diets. No more.

This was a front-page, above-the-fold story in every newspaper in the country (e.g. The Washington Post - "Low-fat diet's benefits rejected" - and NY Times - "Low-fat diet does not cut health risks, study finds"). The New York Times editorialized: "The results clearly surprised the investigators and may sound the death knell for the belief that reducing the percentage of total fat in the diet is important for health."

While this is clearly the diet-related news story of our new millennium, most discussions have omitted mention of three additional key lessons we should be learning:

• First, medical science is evolutionary. What we "know" today is subject to further investigation and revision as we learn more. It is a process of creative destruction. We need to be prepared to "move on" when the evidence demonstrates the error of our ways.
• Second, we can save time, expense, anguish -- and people's health -- if we are a bit more patient and humble about the confidence we place in the results of medical studies. All studies are not of the same quality. This was a high quality randomized controlled trial -- the "gold standard." A well-done randomized trial of health outcomes should be required before our officials begin the drumbeat -- and trigger billions of dollars of expenditures -- for a massive dietary change. To re-state an earlier post on this blog : this is why we should insist on true evidence-based public health decision-making. Evidence-based decisions follow a rigorous process defined by the world-renowned Cochrane Collaboration.
• Third, we should require the same kind of controlled trial of the health outcomes of advice to restrict dietary salt as we now have to restrict dietary fat. There are only ten observational studies of the health outcomes of reducing salt in a U.S.-like population. We need to ask the outcomes question: does eating less salt reduce heart attacks or extend life? We need a controlled trial of this question even though it may cost $100 million or more. As in the case of low-fat diet advocacy, the government is spending multi-fold that amount and compliant food manufacturers are investing huge amounts trying to reduce salt intakes when, in truth, we have no evidence that it will make a difference. In fact, the observational studies show that in populations with salt intakes like the U.S., there is no health benefit and may even be a risk in low-salt diets (see our website discussion ).

It is hard to exaggerate the importance of this JAMA study. And it's impossible to ignore the validity of the Salt Institute's observation that pursuing a policy of universal sodium reduction without a randomized health outcomes study is sheer folly.

The UK's Advertising Standards Authority has chastised the government's Food Standards agency for misleading anti-salt statements breaching standards of social responsibility, substantiation and truthfulness. FSA was also forced to recant its statement that snacks were unhealthy.

It is refreshing to see recognition of the obvious fact that government bureaucrats can have every bit as much bias as "private" interests. All parties to public health strategic discussions should insist on fair statement of the evidence. There is room for disagreement whether, for example, messages should be directed to the entire public or to sensitive individuals or sub-groups, but there is no place for abusing the data -- or the public trust.

So says Dr. Donald Kennedy, the editor of America's foremost scientific journal, Science, in an article in yesterday's New York Times about a Congressional briefing on the intersection of science and public policy.

Right on!

Replication is the key. If scientists cannot replicate a study because its design is not divulged or if their replicated protocol does not produce the same results, then science has failed.

That's why the federal Data Quality Act establishes replication as one of the key criteria for determining whether a study meets the high standards that we should require in using science to support public policy.

That is a key issue before the 4th U.S. Circuit Court of Appeals when it convenes in Richmond tomorrow to receive oral argument in Salt Institute v. Leavitt, the first challenge reaching a federal appeals court seeking to define how the Data Quality Act will be interpreted.

The issue here is that the National Heart, Lung and Blood Institute has been characterizing results of studies it pays for without allowing qualified experts access to enough data to be able to judge whether the statements are true or not.

Kennedy is quoted saying "Peer review isnot a process that guarantees truth. If it were, no one would ever repeat experiments. Replication is the ultimate test of truth in science."