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Updated 14 November 2019

Urine and blood tests can reveal what you've been eating, new study finds

Tests can now measure dietary intake accurately, which has long been a challenge for dietitians, physicians and researchers who used to rely on people to record their food intake themselves.

There’s a major challenge in assessing diets – whether it’s for nutritional studies or for the purposes of a physician or dietitian looking at a patient’s eating habits – in that it relies on participants to record their food intake themselves. This is, however, subject to human error, forgetfulness, and in some cases, even omission.

But, in a new development, researchers at McMaster University have identified several chemical signatures that are detectable in blood and urine, and can accurately reflect dietary intake. This positive news potentially offers a new tool for researchers, physicians and dietitians to measure the value of fad diets and develop health policies. 

Read: Here’s how going on fad diets can mess with your brain

According to Philip Britz-McKibbin, a professor in the Department of Chemistry and Chemical Biology at McMaster University and lead author of the study, this challenge may be one of the main reasons for the “lack of real progress in nutritional sciences and chronic disease prevention”.

The study

The research, published in the journal Nutrients, notes that a large body of evidence has linked unhealthy eating patterns with a concerning increase in obesity and chronic disease worldwide, but that existing methods of assessing dietary intake in nutritional epidemiology relies on food frequency questionnaires or dietary records, which are prone to bias and selective reporting.

Previous research published in the NCBI also mentions that the goal of any dietary survey is to measure what people eat – more precisely, to measure what foods and supplements people habitually eat or usually ingest, but these survey methods are largely based on memory (recall), resulting in errors in the measurement of nutrient intake.

This study therefore had scientists study participants on two contrasting diets over a two-week period. The two diets included the Prudent diet (rich in fruits, vegetables, lean meats and whole grains), and a contemporary Western diet (rich in processed foods, red meat, trans fats and sweetened beverages).

The scientists then set out to determine if they could identify chemical signatures, or metabolites, that reflected any changes in participants’ dietary intake, and measure those markers. They then compared the data with the food study participants were provided with and reported that they had eaten. 

The specimens analysed were from healthy individuals who participated in the Diet and Gene Intervention Study (DIGEST).

Hopeful results

Researchers were able to validate a panel of metabolites in urine and plasma that matched  participants' reporting on their consumption of fruits, vegetables, protein and/or fibre.

"We were able to detect short-term changes in dietary patterns which could be measured objectively," says Britz-McKibbin. "And it didn't take long for these significant changes to become apparent.”

However, Britz-McKibbin says that our diets are composed of thousands of different kinds of chemicals, making food chemistry highly complex. For this reason, researchers don't know what role all of them may play in overall health.

In the future he hopes to broaden this study by examining a larger cohort of participants over a longer period of time. 

Image: iStock

 
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