In other words: They have a vast and perhaps immeasurable influence.
That's precisely why it's so disappointing that the U.S. Department of Agriculture on Tuesday announced that it would not consider important factors like sustainability and climate change as it reviews these guidelines and issues new recommendations later this year.
In a blog post on Tuesday, Agriculture Secretary Tom Vilsack and Health and Human Services Secretary Sylvia Burwell wrote
that "issues of the environment and sustainability are critically important and they are addressed in a number of initiatives within the Administration."
But, they continued, "We do not believe that the (2015 Dietary Guidelines) are the appropriate vehicle for this important policy conversation about sustainability."
On the second point, they are exactly wrong.
Our diets do affect resource consumption. They contribute to climate change. And those concerns, along with health, should be included in the federal government's dietary guidelines.
Plus, the solutions are so simple: Eat fewer animal products -- especially beef and lamb, which have an outsize contribution to climate change -- and more fruits, vegetable, whole grains and legumes. In February, that's exactly what the government-convened Dietary Guidelines Advisory Committee recommended
to the feds, saying such a diet "is more health promoting and is associated with less environmental impact than is the current U.S. diet."
Better for health.
And better for the planet.
These choices aren't inconsequential. If we're going to avoid catastrophic climate change -- meaning countries drowned by rising seas, more droughts that look like California this year and more floods that look like those in South Carolina over the weekend
-- then research shows we need to drastically cut back on fossil fuel use and also change our diets. Eating beef, in particular, carries a carbon footprint many times the size of other meats, like chicken. And even the most environmentally friendly meats are generally more harmful to the climate than plants.
I'm not arguing the federal government should tell us to be vegetarians. Far from it. But moderating meat consumption in favor of healthier foods would also be good for climate change.
Many researchers that follow this issue closely agree.
"It is very disappointing that this decision went in favor of the industry and not in favor of the science," said Jillian Fry, a PhD in Healthy Policy and Management and a project director at the Johns Hopkins Center for a Livable Future. "Because the science is so clear."
"It is disappointing to see that meat industry influence in Congress and over the administration is trumping science and public opinion in the development of the dietary guidelines," said Kari Hamerschlag, a senior program manager at Friends of the Earth U.S.
Federal officials argue that including sustainability and environmental concerns in the dietary guidelines is outside their scope. Fry, from Johns Hopkins, disagrees.
"The reason we think it's so clearly within the scope of the dietary guidelines is that food security is one of the first concerns you'd have for meeting your nutritional needs," she said. More resource-efficient foods, like plants, also contribute to food security, she said.
Fry told me public pressure to include sustainability in the guidelines may influence policy moving forward, perhaps influencing the 2020 recommendations.
That would be a positive development, although we may not have to wait that long.
"People already are heading in that direction -- of eating less meat," said Peggy Neu, president of the Monday Campaigns, which includes efforts to get people to give up meat on Mondays.
"Meat consumption has gone down 12% from 2007 to 2012
, so it's on the decline" in the United States, she said, "although we're still a nation of meat eaters."
Neu told me she's still hopeful federal diet guidelines will include less meat and more vegetables, even if environmental concerns aren't considered. I hope so, too. In the meantime, however, I also hope awareness about the climate costs of meat (and especially beef) consumption continue to proliferate. The Food Guide Pyramid and MyPlate images influence us.
But they don't have the last word on our diets.