WASHINGTON, Oct. 12, 2007 — For the first time, scientists have linked the all-too-human preference for a food — chocolate — to a specific, chemical signature that may be programmed into the metabolic system and is detectable by laboratory tests. The signature reads ‘chocolate lover’ in some people and indifference to the popular sweet in others, the researchers say.
The study by Swiss and British scientists breaks new ground in a rapidly emerging field that may eventually classify individuals on the basis of their metabolic type, or metabotype, which can ultimately be used to design healthier diets that are customized to an individual’s needs. The study is scheduled for publication in the Nov. 2 issue of American Chemical Society’s Journal of Proteome Research, a monthly publication.
Sunil Kochhar and colleagues studied 11 volunteers who classified themselves as ‘chocolate desiring’ and 11 volunteers who were ‘chocolate indifferent.’ In a controlled clinical study, each subject — all men — ate chocolate or placebo over a five day period while their blood and urine samples were analyzed. The ‘chocolate lovers’ had a hallmark metabolic profile that involved low levels of LDL-cholesterol (so-called ‘bad’ cholesterol) and marginally elevated levels of albumin, a beneficial protein, the scientists say.
The chocolate lovers expressed this profile even when they ate no chocolate, the researchers note. The activity of the gut microbes in the chocolate lovers was also distinctively different from the other subjects, they add.
If people who dislike chocolate take cholesterol-lowering statins then will that increase their desire for chocolate? Or does the chain of cause and effect flow in some different direction?
Does this difference have a genetic cause? Just how many of our preferences and desires have genetic causes?
If we turned on a gene that increases longevity and causes cholesterol to get expelled would we crave more chocolate as a result? At least we'd live longer and therefore would gain more time to each chocolate.
The study focused on a gene called SIRT1, which the researchers found prevents cholesterol buildup by activating a cellular pathway that expels cholesterol from the body via HDL (high density lipoprotein or “good cholesterol”).
“SIRT1 is an important mediator of cholesterol efflux, and as such it's predicted to play a role in the development of age-associated diseases where cholesterol is a contributing factor,” said Leonard Guarente, MIT professor of biology and senior author of a paper on the work to be published in the Oct. 12 issue of Molecular Cell.
Drugs that enhance the effects of SIRT1 could lower the risk of cholesterol-related diseases, Guarente said. Potential drugs could be based on polyphenols, which are found in red wine and have been shown to enhance SIRT1. However, the quantities naturally found in red wine are not large enough to have a significant impact on cholesterol levels.
In earlier studies, Guarente has shown that high levels of SIRT1 can be achieved with extreme calorie restriction, but that is unappealing for most people.
Would taking resveratrol increase one's desire for chocolate?
But there is a downside to tuning your metabolism to crave chocolate. Chocolate lovers can be bribed with chocolate.
"Student evaluations of a professor have major influence on what happens to the professor's career - whether a university or college chooses to retain him, give him tenure and even teaching assignments," Youmans said. "We began wondering if outside influences could affect how students rated a professor. People pride themselves in being fair and objective when they are asked to give an assessment of someone else's performance, such as evaluating a professor. But what if they really aren't being objective? What if something else could influence their judgments?"
To test their theory, Youmans visited undergraduate classes with laboratory sections, study sections led by a teaching assistant that drew students from a larger lecture into two smaller groups. In one group, Youmans passed out the evaluations and collected them when the students were finished. In the second group, when it was time for the students to assess their professor's performance, Youmans repeated what was done in the first class, except he offered the students chocolate, saying it was leftover from a prior event, while passing out the evaluations.
Youmans and Jee repeated the experiment in three different classes, and each time the result was the same: The groups that received the offer of chocolate gave their professors higher ratings than the groups that were not offered candy, even though students from either group were rating a class and instructor that they had experienced together.
"I should point out that not everyone in the classes offered chocolate took the candy. Also, we made it clear in all the classes that we were not affiliated with the professor, just 'strangers' asked to pass out and retrieve the evaluations," Youmans said. "But we found that the good feelings brought on by the offer of chocolate from a complete stranger, even in those students who didn't accept the candy, affected the professors' evaluations in a positive way."
So if you need someone to maintain their objectivity be aware of the danger chocolate poses to the human capacity to render objective judgments.
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