Most people don't think about either one when making their food choices.
They simply eat what tastes good. With so much confusion around what we should be eating, they figure that they'll just eat what they want---and enjoy it. I was pretty much that way until 2002. That's when I got curious about the optimal diet for humans. I wanted to find out what nature had in mind for us to eat.
After reading 30 or 40 books about diet and health, I read two books over Memorial Day weekend in 2003 that focused primarily on the environmental impact of our food choices. That's when I had my blinding flash of the obvious when I suddenly realized that we humans were eating the wrong food. Those two books were Diet for a New America by John Robbins and Mad Cowboy by Howard Lyman.
Later, in 2005, Dr. Campbell stated in The China Study, "It turns out that if we eat the way that promotes the best health for ourselves, we also promote the best health for the planet." That sounded like a pretty cool win-win proposition to me and I've eaten a mostly whole foods, plant-based diet ever since.
But over the years, I have gradually evolved from eating primarily for my health---to eating primarily for the sustainability of our civilization and, ultimately, the human species.
Why sustainability and "saving the planet?" During the past few years, I have concluded that it's really not about "saving the planet" as we so often hear. It's more about preserving her ability to sustain us. Mother Earth is going to be just fine.
She's been supporting life for four billion years and has seen many species of creatures come and go---and she will survive indefinitely; regardless of how much damage we inflict. It's the future of our species that's in jeopardy.
I specifically remember an article, Endless Summer, by Mark Bittman in the New York Times in July of 2012 (See link below). This is the part that caught my attention:
Climate Central’s projections show that the biggest cities in Florida, and a great deal of the Northeast coastline (including New York City), will be underwater by 2100, when almost everyone now alive will have “managed” to leave the scene. Of course, the calamities won’t be limited to North America, nor is 2100 some magical expiration date; the end isn’t in sight.