Q. Your recent documentary The Future of Food is a call to action against GMO agriculture. When did you first get interested in organic food?

A. I became a vegetarian in college. I grew up in the Midwest eating cheeseburgers, Cokes, and ice cream. I stopped eating meat after trying to cook it; I had never really seen it raw and bloody before. As I started eating a healthier diet, I found I no longer had the insomnia or headaches I’d always had. I gave up white flour and white sugar and felt better and better.

Q. Was [your late husband and Grateful Dead guitarist] Jerry into healthy food as well?

A. He went back and forth. On the road, in the ’70s, it was difficult to get good food. But for the last few years, we would have low-fat, vegetarian menus for the whole band.

Q. What do we need to understand about genetic engineering in foods?

A. It was supposed to reduce the amount of herbicides and pesticides used, but in fact more are being used—not less.

Q. What else?

A. What shocks people is how genetic engineering takes place. People think you just put one piece of DNA into another. Actually, it involves many things—what’s called a genetic cassette. The scariest thing to me is the cauliflower mosaic virus, which is used to force the modified gene to express the new trait. Some scientists now have grave concerns, because viruses mutate very easily. They use whatever entity they invade to manufacture more viruses. Plus, antibiotics don’t work against viruses.

Q. What are the potential consequences for humans?

A. There are potential health problems associated with the immune system, organ weight, and stomach lesions—but there have been very few tests, especially for health.

Q. Monsanto and other agricultural manufacturers have essentially begun to patent life itself, in the form of genetically modified DNA. Can you explain the significance of this?

A. It’s really the concept of “claiming the commons.” People aren’t aware of this, but it affects us all. For instance, Monsanto just bought Seminis, a Mexican company that controls most of the world’s vegetable and fruit seeds. So they can withhold seeds and just put out their GM ones. They claim they won’t do this, but I think they bought it because they want to control it.

Q. You interviewed farmers who’ve been sued for growing GM seeds without a license—even when these seeds had blown onto their fields.

A. Yes, the idea that if Monsanto seeds blow onto your land, they own your crop—it’s so shocking! Most farmers end up settling, but a new report estimates Monsanto has 19 active lawsuits against U.S. farmers.

Q. What’s the best solution?

A. If GMOs are labeled, people won’t buy them. That’s what has happened in Europe. Labeling is the way the consumer can really have a say.

Q. What can we do as individuals?

A. Write your senators and congressional representatives. Wherever you shop, let the produce and grocery managers know you don’t want GMOs, or that you want labeling. There are now efforts to get legislation in various states—it’s important to support these grassroots efforts.

Q. And food safety truly is a nonpartisan issue.

A. It’s a cause that can bring people together: We all want the right to choose what’s in our food, and we don’t want anything put there without our knowledge. Food issues are a very positive way to engage politically. It’s a healthy, nondepressing way of doing something for the Earth.

Q. What’s your favorite food?

A. There’s something so thrilling about going to your back yard and picking and eating a peach. It’s sun-warmed, and it seems like a miracle.