Dietary Studies Using Biomarkers Are a Better Proposition, But Still Require Care in Interpretation

Most human dietary studies gather data via participant self-reporting, which has its limitations. Using biomarkers to examine levels of specific dietary components is a step up from that, but it doesn't remove the core issues inherent in looking at specific dietary components in isolation. For example, we know that overall calorie intake level is enormously important in determining health and longevity, and that correlates with levels of different dietary components. Also, people who make better efforts to take care of their health tend to have better diets, but that effort extends beyond just diet. So levels of specific dietary components in human studies are going to correlate with all sorts of other line items that can impact health and longevity, such as exercise, calorie intake, amount of visceral fat tissue, conscientiousness in use of medical resources, and so on.

Correlation is not causation, but invariably when it comes to diet there are all sorts of vested interests willing to sell you the idea that you should believe otherwise. This study reports a large enough result to awake that contingent:

Polyphenols are naturally occurring compounds found largely in fruits, vegetables, coffee, tea, nuts, legumes and cereals. More than 8,000 different phenolic compounds have been identified in plants. Polyphenols have antioxidant, antiinflammatory, anticarcinogenic, etc. effects.

Polyphenols might have a role in the prevention of several chronic diseases, but evaluating total dietary polyphenol (TDP) intake from self-reported questionnaires is inaccurate and unreliable. A promising alternative is to use total urinary polyphenol (TUP) concentration as a proxy measure of intake. The current study evaluated the relationship between TUPs and TDPs and all-cause mortality during a 12-y period among older adult participants. The study population included 807 men and women aged 65 y and older from the Invecchiare in Chianti study, a population-based cohort study of older adults living in the Chianti region of Tuscany, Italy.

In conclusion, the research proves that overall mortality was reduced by 30% in participants who had rich-polyphenol diets (greater than 650 mg/day) in comparison with the participants who had low-polyphenol intakes (less than 500 mg/day). "[The] results corroborate scientific evidence suggesting that people consuming diets rich in fruit and vegetables are at lower risk of several chronic diseases and overall mortality." Moreover, the research stresses the importance of evaluating - if possible - food intake by using nutritional biomarkers, not only food frequency questionnaires.

Link: http://dx.doi.org/10.3945/jn.113.177121

Comments

Coffee and tea may contain polyphenols... but it's not the polyphenols that slow aging... it's the caffeine! Caffeine is an excellent anti-aging drug, especially for your brain, but you should probably balance it out with taurine, and B vitamins to lower the homocysteine produced by caffeine, prevent the anxiety caused by caffeine, and protect your brain some more.

Posted by: Carl at October 11th, 2013 9:31 AM

A few questions come to mind-

Could higher urinary excretion be a marker of poorer absorption?

Are high polyphenol diets low in meat, fat, and processed foods?

Perhaps, the study controls for these and other confounders.

Posted by: Lou Pagnucco at October 11th, 2013 11:48 AM

A question that comes to mind is, why doesn't my toilet automatically check this stuff and give me daily/weekly reports and graphs? (I know the answer, but still.)

Posted by: Dennis Towne at October 12th, 2013 12:15 AM

Carl, there's not nearly enough evidence for end-users to be taking your claim seriously, and the jury is still very much out on the ultimate effects of caffiene.

That's not to say that I think caffiene is bad. Rather, we just don't know enough about the biochem for you to be making those kinds of claims.

Posted by: Dennis Towne at October 12th, 2013 12:18 AM

Don't be an idiot Dennis. People have been drinking coffee for hundreds of years. And they did so in very high doses. We know what it does to them. And at 3 cups per day, what it does is significantly reduce all cause mortality, and dramatically reduce dementia. Unless it's decaffeinated.
You don't need to know anything about biochem to recognize that. But actually, people do have a good idea of the biochemistry of caffeine.

Posted by: Carl at October 12th, 2013 9:48 AM

Carl, I don't think it does anyone good, including yourself, to call someone an "idiot". Caffeine isn't personal.

With that being said, Dennis is right in the sense that you should back up what you claim with actual data of some sort. If you got it then share it. Link away.

Posted by: Jonathan at October 12th, 2013 4:39 PM

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