CLE Diet Project!

What Have We Learned So Far?

The Cleveland Diet Project is an ongoing research project led by the Museum’s Curator of Human Health & Evolutionary Medicine, Dr. Nicole Burt. The purpose of this research is to understand what people are eating in Cleveland by using both biomarkers (cut hair samples) of diet and data collected from diet surveys. Analysis and interpretation of the data are ongoing. Updates on the project can be found on this page, so check back for more information. Results will also be published in scientific journals, and citations will be posted here. Thank you for your participation, interest, or both!

Stable Isotope Analysis

Preliminary Results
Isotope ratio mass spectrometry can be used to reconstruct diet from organic samples such as hair. Stable isotope analysis measures the ratio of heavy to light stable isotopes—forms of elements (e.g., carbon or nitrogen) that have the same atomic number but a different number of neutrons—in a sample. We report these ratios as delta (δ) values written as δ13C for carbon and δ15N for nitrogen. These ratios reflect an individual’s dietary pattern for a set period of time. They allow us to understand what foods a person is eating, but they cannot be used to identify that person as an individual.

Nitrogen values indicate trophic level, which is a measure of diet composition. The more enriched (or larger) numbers indicate a diet containing more meat and fish, while less enrichment indicates the plant-based diet of a vegan/vegetarian. Carbon values are most dependent on the photosynthetic pathways of the plants an individual is eating. Most of the domesticated foods we eat are what we call C3 plants, while tropical grasses like corn and sugarcane are categorized as C4 plants. Processed foods that incorporate processed sugars (such as corn syrup) are also enriched in C4.

In their dietary surveys, most participants identified themselves as omnivores with a low or average consumption of fish. A few indicated that they were vegetarians or vegans. A few people indicated that they mainly ate processed food and drank a lot of sugary beverages. We compared these reports of diet with reconstructed diets from hair samples. It is important to use both, as food-survey questionnaires have been proven inaccurate in many populations.

We are still processing samples, but in the small sample we have, we do see dietary differences among the Clevelanders who participated. A few individuals are clearly vegetarians or vegans, while some people have isotopic signals that suggest they are eating more processed foods than they reported.

Figure 1: Graph showing IRMS results from the first 30 samples. If a data point appears below the dotted yellow line, the individual represented is likely a vegan or a strict vegetarian. The dotted green line indicates the cutoff between C3 and C4. Data points near this cutoff represent individuals who likely have more added sugar or processed foods in their diets.

Cle diet project graph 1

What Do People Think About Diet?

To better understand diet, we want to know more about what people eat, why they eat it, and what they wish they were eating. To gain this understanding, we are analyzing survey data collected with our biosamples and also incorporating analysis of food images contributed to the project by participants. Diet has important effects on our health, but it also plays a significant role in our social well-being. It helps us express our culture and who we are as individuals, it is shared with friends and loved ones, and of course it is used to build the tissues that make up our body. When we study diet, we are studying more than just what people are eating.

Figure 2: Graphs showing relationships among survey responses from individuals represented by current samples (n=90). 2a: Self-ascribed diet quality (excellent, good, fair, poor) shown broken down by self-ascribed gender; 54% of males view their diet as excellent/good and 70% of females view their diet as excellent/good. 2b: Self-ascribed diet quality (excellent, good, fair, poor) shown broken down by self-ascribed BMI. 2c: Self-ascribed diet quality (excellent, good, fair, poor) shown broken down by whether participants are on their preferred diet; about 50% of respondents were happy with their diet, with 62% of those not happy with their diet indicating they had a fair or poor diet.

Clearly, many factors influence what our community is eating and why. To better understand how people view meals in terms of their healthiness or unhealthiness, we are also collecting photos of individuals’ meals. Eventually, we will be researching how different people view the healthiness of the same meals.

Figure 3: Below is a selection of meal photos submitted by participants. Some choose to show food from an average day, while others share photos of meals from special occasions.

Cle diet project photos of meals