A novel method utilizing DNA barcoding to analyze the plant matter in human feces has emerged, potentially bridging the gap between reported diets and actual consumption. Researchers at the Duke School of Medicine, led by Lawrence David, have devised a genetic marker for plant-based foods that can be identified from fecal samples.
The marker focuses on a specific DNA region found in all plants, known as trnL-P6, which is responsible for powering chloroplasts and converting sunlight into sugars. Although this region differs slightly between plant species, it is universally present. To validate their approach, the scientists examined over 1,000 fecal samples from 324 participants involved in five distinct studies. Approximately twenty individuals had detailed records of their dietary intake.
Published in the Proceedings of the National Academy of Sciences on June 27, the research demonstrates that these DNA markers not only determine the consumed food items but also provide insights into the relative quantities of specific species. Furthermore, the diversity of plant DNA found in feces appears to vary depending on factors such as diet, age, and household income. These findings have significant implications for improving clinical trials, nutrition studies, and related fields.
To identify specific plant sources from the trnL-P6 marker detected in fecal samples, David’s lab utilized a reference database of dietary plants containing markers for 468 species commonly consumed by Americans. With some adjustments, their DNA barcode successfully distinguished 83% of major crop families.
The lab is currently working on expanding the database to include crop families consumed in other regions, such as pearl millet and pili nuts, which are not currently detectable. Although the technology is capable of tracking meat intake, the researchers have not yet incorporated it into their analyses. Understanding the relative ratio of plant to animal intake is considered a crucial nutritional factor.
The scientists initially tested the marker on fecal samples from individuals involved in a weight loss intervention study, where the participants’ diet was precisely known. By searching for markers corresponding to the components of specific meals, they successfully identified the plants consumed and even determined the relative amounts for certain types of plants.
Further experiments involved analyzing samples from adults who had participated in fiber supplementation studies and tracked their diets through surveys. The number of plants detected by the trnL marker correlated well with dietary diversity and quality reported by the participants.
The researchers then applied the DNA barcoding technique to a diverse group of 246 adolescents, both with and without obesity, who had limited dietary records. By analyzing their stool samples, the scientists were able to gain insights into the participants’ diet, which helped understand health and lifestyle patterns among the adolescents. Wheat, chocolate, corn, and the potato family were among the most commonly consumed plant sources in this cohort.
While the barcode couldn’t distinguish between individual members of the cabbage family, such as broccoli and kale, the study revealed that higher-income participants had greater dietary variety. However, as the adolescents grew older, their intake of fruits, vegetables, and whole grain foods decreased, likely due to changes in eating habits as they ate less frequently with their families.
The DNA analysis provided by the barcode offers a proxy for dietary diversity, a known indicator of nutrient adequacy and improved heart health. Additionally, the technique allows for retrospective analysis of dietary data from past studies, providing valuable information for research conducted in the past.
The researchers believe that this new methodology will significantly benefit studies in human nutrition, as it overcomes limitations associated with traditional dietary tracking methods. By utilizing genomics, data on global dietary habits can be gathered regardless of age, literacy, culture, or health status.
The team envisions expanding the application of this technique to studies of diseases worldwide and monitoring food biodiversity in regions facing climate instability or ecological challenges.
Source: Duke University