“Of course, this is just the first step,” Cifuentes says. Just because a compound is shown to be bioactive in culture doesn't mean it will work in vivo. When we eat, food is broken down; some components are not absorbed, and others are degraded. “One thing is how you eat these polyphenols, and another is what is happening to them in your stomach, in your intestine, [and] in your liver.”A SYMPHONY OF FOOD
That question–what happens to food once it is eaten–is one of bioavailability. And it is a question being tackled by Francesco Capozzi and Alessandra Bordoni, both of the University of Bologna, who are organizing this month's third International Conference on Foodomics (May 22-24) in Cesena, Italy.
The chemical composition and nutritional value of food are governed by everything from the genome of the organism from which its made and the environment in which it grows, to interaction with digestive enzymes in the human gut and metabolism in the liver, says Capozzi.
“This is probably why metabolomics is gaining more success now,” suspects Capozzi, “because it is the last step, and it's just summarizing all the cascade effects … [that] in the end produced that ensemble of molecules.”
Still, just as a symphony loses its magic when described simply as notes and frequencies, so too does food, says Capozzi. “We can't depict any food by means of a group of molecules.” Yet, Bordoni adds that foodomics is a field that can harmonize different technologies.
A physician and nutritionist, Bordoni is coordinating a EU-funded project called PATHWAY-27, which aims to evaluate the effectiveness of three specific bioactive components—docosahexaenoic acid, 2-glucan, and anthocyanins—in preventing metabolic syndrome. The project will consider these bioactives not as discrete molecules, but as ingredients of bioactive enriched foods. As such, it will consider the effect of the food matrices, as well as the metabolic profile of urine in people eating these enriched foods. Bordoni is also co-administering (with Capozzi) a second EU-funded project called CHANCE, which Capozzi describes as an observational study looking at how and what people eat, and their resulting metabolic profiles.
To unravel these profiles, Capozzi, a chemist, uses nuclear magnetic resonance (NMR). According to Capozzi, MS is a far more sensitive and higher-resolution tool, and is especially useful for profiling studies. But NMR is more robust and absolutely quantitative. As MS practitioners know well, the technique suffers from issues of ion suppression, competition, and other confounding effects that make quantification difficult—a situation especially problematic in areas like metabolomics.
“NMR is not depending on any condition, because you just put the urine in the tube and you measure it. And you will get the same NMR spectrum in all laboratories having a similar spectrometer,” says Capozzi. NMR's other advantage is its wide dynamic range, meaning that both low and high abundance molecules can be detected in the same spectrum.
Bordoni and Capozzi recently turned their NMR towards Parmigiano Reggiano cheese. According to Bordoni, many Italians believe that older, harder Parmesan cheese is more easily digested than younger, softer ones, and are willing to pay more for the privilege. But when it comes to nutrition, what really matters the most is what the body takes up. So, is there any measurable difference between the two cheeses when it comes to nutrient bioavailability?
To find out, the team set up a system to recapitulate the digestion of 15- and 30-month-old cheese samples in vitro. They then took aliquots at various time points and analyzed digested protein content by proton-NMR. The resulting signatures suggest that the older cheese is indeed digested somewhat more rapidly, but the end product for the body is (unsurprisingly) the same.
“At the end, the two cheeses arrive to the same amount of bioavailable amino acids,” confirms Capozzi.
Capozzi and Bordoni have since applied this same type of analysis to a kind of Italian ham called bresaola (comparing old and new production processes), as well to fish. The results of these latter analyses are not yet published, but the cheese study was included in a special food chemistry issue of Magnetic Resonance in Chemistry.THE METABOLITES OF SIN
At Leiden University in the Netherlands, Robert Verpoorte, Professor of Pharmacognosy and Plant Biotechnology, along with with Young Hae Choi, apply proton NMR to the study of Palatinate wines.