It's as inevitable as rain the day after you wash and wax your car. Sometime after a significant health breakthrough, there's a second study that challenges first one.

Call it research ricochet.It's why so many published studies end with a "More Research Is Needed" subhead. It's why last week's column explained the benefits of you developing "a dieting identity."In the early 1980s, for instance, Dirk Pearson and Sandy Shaw's treatise titled Life Extension advocated antioxidant supplementation as a way to look and feel younger, and the book created quite a buzz.By the early 1990s, taking antioxidants like vitamin B-1, B-5, B-6, C, E, beta carotene, and selenium in pill form with meals, while not quite run-of-the-mill, was clearly no longer radical. Many in search of optimal health were doing so.But in April of 1994, research ricochet created a bigger buzz. The New England Journal of Medicine published the results of eight-year study of nearly 30,000 Finnish men aged 50 to 69 that found a higher rate of lung cancer in those who took 20 milligrams of beta carotene daily than those who did not. Subjects who took 50 milligrams of vitamin E or both beta carotene and vitamin E daily developed lung cancer at the same rate as the subjects taking a placebo.While these results certainly stunned me, they did not stop me from taking my standard dozen-or-so antioxidants, for I value something more than any single study: personal experience. And personal experience had demonstrated without a doubt that I recovered quicker from intense bouts of exercise when I supplemented my diet with dozen or so antioxidants daily.It also seemed to help me stave off those seasonal sicknesses that often plague public schools.Another reason I never wavered: all of the nearly 30,000 subjects were cigarette smokers. Since it can take several years for a typical lung cancer to reach a size that is detectable on an x-ray, some, many, or even all of the stricken subjects could have had the disease before the supplementing began.Moreover, other lifestyle factors affected the study results. The subjects who drank large amounts of alcohol and took beta-carotene, for example, had higher rates of lung cancer than the subjects who took the supplement and drank little alcohol.Less than four years later, research ricochet occurred again - from a deeper investigation of the same study ironically. The Journal of the National Cancer Institute published follow-up work that found vitamin E supplementation greatly reduced the incidence of prostate cancer and prostate cancer death in the nearly 30,000 older, male smokers.The diagnosis of prostate cancer in those supplementing with vitamin E was 32 percent lower than in subjects who didn't. Those subjects who did take vitamin E yet still developed prostate cancer were 41 percent less likely to die from it than those who didn't.The aforementioned study was performed to the highest standards. It was randomized, double-blind, and placebo-controlled, and the two journals that published the results are beyond reproach. All that suggests something that's potentially unsettling - yet probably common sense.What may be a beneficial supplement for others may be harmful to you.That means you need to rely on personal experimentation more so than published studies. But what sorts of personal experiments?Those that help establish your dietary identity.I shared provided a portion of mine in lieu of a definition in last week's article simply because abstract concepts are difficult to conceptualize. This week, I'll try to further clarify how to develop a dieting identity by using a hypothetical situation.Let's say you really want to be as healthy as can be, but you love any type of meat and any type of sweet. What can you do to possibly achieve the former without sacrificing the latter?Experiment with a form of the Paleo diet.Paleo diets allow you to eat meat to your heart's content. And you might just discover that if you indulge in that craving, the other dissipates to some degree. Or you may find, as a few friends of mine have, that fruits taste much sweeter after you wean yourself off of the added sugars found in sweetened beverages, cereals, cakes, cookies, and donuts that Paleo diets forbid.You might also find that you lose some weight, but maybe not as much as you expect based on the reduction of your waistline. This discovery would mean that you probably have some sort of an averse reaction to wheat and/or other grains and that by eliminating them from your diet you've lost what some call "wheat belly."It's also as possible that none of this will happen because, after all, our metabolic processes could very well be as unique as our fingerprints.In that case, you alter what you've been attempting a bit and experiment again and again until you find a way of eating that feels right and that you believe in.