“This research is fascinating and it’s important,” said Tim Caulfield, who researches health law and policy at the University of Alberta in Canada. Nonetheless, “if history tells us anything, it tells us that it’s unlikely that this is going to revolutionize nutrition.”
For one thing, he said, the basic parameters of a healthy diet are already well known: plenty of whole grains, pulses, dark leafy greens and other vegetables, enough healthy oils and seafood, and very little red meat or refined carbohydrates. The problem is not that the guidelines are wrong or insufficiently personalized, Mr. Caulfield said, but that people are not following them.
Even the focus on a person’s food choices or individual metabolism can distract from other significant contributors to the obesity epidemic, he said: “It is a fantastically complex issue that has to do with our built environment, with socioeconomics, with our food environment, with marketing, and with our activity levels — so many things.”
As a study, Predict is still in its early days; whatever individualized recommendations it might provide, there is no evidence yet that they can improve a person’s health any better than standard dietary guidelines can. Nonetheless, its scope and rigor are novel.
“It will require further validation, and doesn’t equate with preventing heart disease or cancer or other outcomes,” Dr. Topol said. “But it’s still important if we’re ever going to get to the ‘food as medicine’ ideal.”
Participating in the study can be grueling. Subjects are first put through an extensive battery of tests, including hourly blood draws and scans of their body fat and bone mass, in a hospital setting. Then, for two weeks, they must consume a series of set “meals” — a selection of muffins containing different combinations of fat, carbohydrate and protein, along with fiber bars, glucose drinks and protein shakes. Any other food or beverage consumed must be weighed and logged.
Each participant wears a continuous glucose monitor and an accelerometer to measure activity levels and sleep, and provides samples of saliva, urine, feces and blood — everything but tears.