Writing for the American Council on Science and Health , Kathleen Meister offers sound advice for medical and science writers. Available in PDF , here's the executive summary :

• Scientific studies that show an association between a factor and a health effect do not necessarily imply that the factor causes the health effect. Many such studies are preliminary reports that cannot justify any valid claim of causation without considerable additional research, experimentation, and replication.

• Randomized trials are studies in which human volunteers are randomly assigned to receive either the agent being studied or an inactive placebo, usually under double-blind conditions (where neither the participants nor the investigators know which substance each individual is receiving), and their health is then monitored for a period of time. This type of study can provide strong evidence for a causal effect, especially if its findings are replicated by other studies. Such trials, however, are often impossible for ethical, practical, or financial reasons. When they can be conducted, the use of low doses and brief durations of exposure may limit the applicability of their findings.

• The findings of animal experiments may not be directly applicable to the human situation because of genetic, anatomic, and physiologic differences between species and/or because of the use of unrealistically high doses.

• In vitro experiments are useful for defining and isolating biologic mechanisms but are not directly applicable to humans.

• Observational epidemiologic studies are studies in human populations in which researchers collect data on people's exposures to various agents and relate these data to the occurrence of diseases or other health effects among the study participants. The findings from studies of this type are directly applicable to humans, but the associations detected in such studies are not necessarily causal.

• Useful, time-tested criteria for determining whether an association is causal include:

- Temporality. For an association to be causal, the cause must precede the effect. - Strength. Scientists can be more confident in the causality of strong associations than weak ones. - Dose-response. Responses that increase in frequency as exposure increases are more convincingly supportive of causality than those that do not show this pattern. - Consistency. Relationships that are repeatedly observed by different investigators, in different places, circumstances, and times, are more likely to be causal. - Biological plausbility. Associations that are consistent with the scientific understanding of the biology of the disease or health effect under investigation are more likely to be causal.

• New research results need to be interpreted in the context of related previous research. The quality of new studies should also be assessed. Those that include appropriate statistical analysis and that have been published in peer-reviewed journals carry greater weight than those that lack statistical analysis and/or have been announced in other ways.

• Claims of causation should never be made lightly. Premature or poorly justified claims of causation can mislead people into thinking that something they are exposed to is endangering their health, when this may not be true, or that a useless or even dangerous product may produce desirable health effects.

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Whether it's the health of the planet or of its human inhabitants, it seems we have to learn every generation about the pain and suffering inflicted when we act on improperly-understood "science" -- and, thus, the need to employ a cautionary, evidence-based approach to basing public policy on boldly-asserted scientific truth.

An article in the current American Thinker deals with global warming, but it's not my intent to explore the validity of the scientific clash on that issue, only to "steal" an anecdote to make a further point. Author James Lewis shares this story:

Trofimko Lysenko is not a household name; but it should be, because he was the model for all the Politically Correct "science" in the last hundred years. Lysenko was Stalin's favorite agricultural "scientist," peddling the myth that crops could be just trained into growing bigger and better. You didn't have to breed better plants over generations, as farmers have been doing for ages. It was a fantasy of the all-powerful Soviet State. Lysenko sold Stalin on that fraud in plant genetics, and Stalin told Soviet scientists to fall into line --- in spite of the fact that nobody really believed it. Hundreds of thousands of peasants starved during Stalin's famines, in good part because of fraudulent science.

He then provides context:

When the scientific establishment starts to peddle fraud, we get corrupt science. The Boomer Left came to power in the 1970s harboring a real hatred toward science. They called it "post-modernism," and "deconstructionism" --- and we saw all kinds of damage as a result. Scientific American magazine went so far as to hire a post-modern "journalist" to write for it. John Horgan became famous for writing a book called The End of Science, but never seemed to learn much about real science. It was a shameful episode. ....

Pathological science kills people and ruins lives. Such fake science is still peddled by the PC establishment in Europe and America. ...

Britain is even more vulnerable to politicized science than we are, because medicine is controlled by the Left. That is a huge chunk of all science in the age of biomedicine. But the British Medical Journal and even the venerable Lancet are no longer reliable sources. Their political agenda sticks out like a sore thumb. It was The Lancet that published a plainly fraudulent "survey" of Iraqi civilian casualties a few years ago --- the only "survey" ever taken in the middle of a shooting war. As if you can go around shell-shocked neighborhoods with your little clipboard and expect people to tell the truth about their dead and wounded: Saddam taught Iraqis to lie about such things, just to survive, and the internecine fighting of the last several years did not help. The whole farce was just unbelievable, but the prestigious Lancet put the fake survey into the public domain, just as if it were real science. It was a classic agitprop move, worthy of Stalin and Lysenko. But it was not worthy of one the great scientific journals. Many scientists will never trust it again.

The account continues on global warming, but my point is the broader one: politically-correct science may not be scientifically-correct science and relying on PC science (junk science) risks disasters like that engineered by Stalin. That's true for environmental science. And it's true for nutrition science.