Uptake of ingested pieces of DNA by some host cells occurs naturally. This has been occurring since organisms began relying on each other as food sources. Interestingly, this phenomenon is not restricted to multicellular organisms; uptake and incorporation of DNA in the process of eating appears to have occurred in single-celled eukaryotes, such as protists. Several studies have addressed the fate of ingested DNA in mammalians, including attempts to detect transgenic DNA in chicken or cows fed with glyphosate tolerant soybean and in pork, pigs or dairy cows, beef steers and broiler chicken fed with Bt corn. In none of those studies was transgenic DNA detectable by PCR in various samples.

Experiments conducted by a laboratory at the University of Cologne in Germany found that very small amounts of DNA fragments may be absorbed across the epithelium in the gastrointestinal tract. However, HGT requires not only that the DNA be taken up by cell, but also that the ingested fragments are maintained in the recipient cells by integration into the genome. There is no conclusive evidence that intact genes from foods, whether biotech or non-biotech, integrate into the genome of animal cells.