First it was slow. Then local, then organic. Now it is firmly grass-fed.

As a rare geophysicist studying diet’s environmental consequences, I am asked daily by my colleagues – a bit bemused by my new field yet quantitatively astute and environmentally concerned – about the latest claim made about impacts of food production on the physical environment.

In this role, I get to keep a sensitive finger on the envirofood pulse. Unambiguously, grass-fed beef is all the rage now. Even the New York Times Op-Ed page featured a recent piece extolling the virtues of grazing cattle.

Depending on your guiding environmental objectives, grass-fed beef may indeed be the greatest thing since Guns n’ Roses or the environmental equivalent of entrusting former Secretary of Defense Donald Rumsfeld with military preparedness.

Yet on reasonably balancing the main geophysical dimensions of dietary choices, grass-feeding loses most of its touted allure, relegating its role in a rational food production system to the margins.

To be sure, the flesh of a healthy, thriving animal is clearly nutritionally superior to the biochemically compromised, microbiologically teeming ecosystem that is the bulk of the nation’s meat supply.