Peter Lehner is executive director of the Natural Resources Defense Council (NRDC). This Op-Ed is adapted from one that appeared on the NRDC blog Switchboard. Lehner contributed this article to Live Science's Expert Voices: Op-Ed & Insights.

Americans consume more processed and packaged food than just about anyone else in the world. Processed foods, many of which contain added sugar , preservatives and chemical additives, are hard-wired into our food system, and make up the majority of the American diet. In her upcoming documentary Fed Up, headed to theatrical release on May 9, co-producer Laurie David explores the roots and consequences of this diet, and how the U.S.industrialized food system could be a major contributor to the national obesity epidemic .

How did the way we eat become so unhealthy? Our food system is dysfunctional, all along the chain from farm to fork. The way we eat now is not good for our bodies — and it's not good for our planet. Eating processed and packaged food might be even more risky than most of us realize. In a recent report, NRDC focused on a single legal loophole that allows hundreds, if not more than a thousand, chemical additives into the U.S. food supply — those unpronounceable ingredients on the back of the box — bypassing safety review by the U.S. Food and Drug Administration (FDA).

When we pick up a package of food at the store — cereal, frozen pizza, chips, an energy drink, a nutrition bar, cake — we assume that everything in it is OK to eat. Companies wouldn't be allowed sell those foods otherwise, right? But because of a giant loophole in food safety law — the "generally recognized as safe," or GRAS, loophole — chemical manufacturers can decide for themselves if the product they've created is safe to consume.

Their safety assessments don't have to be reviewed or approved by anyone else, and often manufacturers don't even have to disclose the name of the additive, or how it's used, to the FDA or to the public. Often, the agency isn't even notified when chemical additives enter our food supply.

All this adds up to a serious lack of oversight intowhat goes into Americans' food. And that oversight is sorely needed to protect our health. Some additives which manufacturers claim to be generally recognized as safe have been linkedto fetal leukemia in human cell tests, or testicular degeneration in animal tests, or according to FDA scientists, may trigger an allergic reaction in people with peanut allergies.

Despite these potential risks, these additives are already in our food supply. NRDC found these additives listed as ingredients in at least 20 food products.

The FDA can't do its job and protect public health if it doesn't know the identity of these chemicals in the first place, or if it can't review the evidence demonstrating that their use in food is safe.

Ultimately, the U.S. Congress needs to close the GRAS loophole that allows manufacturers to leave the FDA and the public in the dark about the safety of chemical additives in food. But the FDA can, and should, move now to end the inherent conflict of interest in the current system for reviewing the safety of chemical additives in food — and when the agency does review a manufacturer's safety claims, the concerns noted by FDA scientists should be made available to the public.

The widespread use of chemical additives is just one of several deep-rooted problems in our industrialized food system. Our food system encourages the consumption of processed and packaged foods over fresh, healthier, locally grown foods. We end up craving the sugar that sneaks into processed foods, and so we keep buying more of it — and we assume that it's safe to eat.

The impacts of our food system are chronic, not just in our bodies, but throughout the natural systems that sustain our health and the planet. Our food system encourages food waste on a massive scale — about 40 percent of the food in this country never gets eaten. It gets thrown away, wasting not only the food itself but all the resources that went into producing it, including 25 percent of our fresh water and 4 percent of our oil. Food waste also produces about one-quarter of U.S. methane emissions, making it a source of climate pollution that needs to be addressed. [Sell-By Labels Send Edible U.S. Food to the Dump (Op-Ed)]

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The industrial livestock operations that produce the vast quantities of meat consumed in this country pollute the air, the water and atmosphere. The abuse of antibiotics in the livestock industry — where animals that aren't sick are fed low doses of antibiotics day after day to try to compensate for unsanitary conditions — risks impairing the effectiveness of those essential medicines when we really need them.

Our industrialized agricultural system relies heavily on the intensive use of chemical fertilizers, herbicides and pesticides, which pose serious threats to human health and wildlife, pollute water, and deplete nutrients in the soil. Excess fertilizer from agriculture is a significant source of global-warming pollution. So industrial agriculture adds to climate pollution while also bearing the brunt of its effects, such as extended droughts and heat waves that wither crops in the field, and heavy rains that drown out spring plantings.

We are paying dearly for the way we eat. But while our food system may be unsustainable, it's not unfixable. By raising awareness of these issues, ensuring that strong, health-protective standards are being enforced by the agencies responsible for protecting the public, not profits, and encouraging business and industry to shift toward more sustainable practices, our nation can begin to create a healthier, more sustainable food system for all.

Lehner's most recent Op-Ed was "Closing Clean Water Act Loophole Will Protect Drinking Water and Benefit Bathers and Breweries Alike." This Op-Ed is adapted from "Fed Up with Our Dysfunctional Food System," which appeared on the NRDC blog Switchboard. The views expressed are those of the author and do not necessarily reflect the views of the publisher. This version of the article was originally published on Live Science.