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Soybeans are the second-largest US crop after corn, covering about a quarter of American farmland. We grow more soybeans than any other country except Brazil. According to the US Department of Agriculture, more than 90 percent of the soybeans churned out on US farms each year are genetically engineered to withstand herbicides, nearly all of them involving one called Roundup. Organic production, by contrast, is marginal—it accounts for less than 1 percent of total American acreage devoted to soy. (The remaining 9 percent or so of soybeans are conventionally grown, but not genetically modified.)

Americans don’t eat much of these lime-green legumes directly, but that doesn’t mean we’re not exposed to them. After harvest, the great bulk of soybeans are crushed and divided into two parts: meal, which mainly goes into feed for animals that become our meat, and fat, most of which ends up being used as cooking oil or in food products. According to the US Soy Board, soy accounts for 61 percent of American’s vegetable oil consumption.

Given soy’s centrality to our food and agriculture systems, the findings of a new study published in the peer-reviewed journal Food Chemistry are worth pondering. The authors found that Monsanto’s ubiquitous Roundup Ready soybeans, engineered to withstand its own blockbuster herbicide, contain more herbicide residues than their non-GMO counterparts. The team also found that the GM beans are nutritionally inferior.

In the study, the researchers looked at samples of three kinds of soybeans grown in Iowa: (1) those grown from GM herbicide-tolerant seeds; (2) those grown from non-GM seeds but in a conventional, agrichemical-based farming regime; and (3) organic soybeans, i.e., non-GM and grown without agrichemicals.