Researchers wanted to find out if special tests on blood and urine could accurately show what foods people eat, instead of just asking them what they ate. They fed 21 young adults specific meals for three different days and then tested their blood and urine to see if certain chemicals matched the foods they ate. They found that some foods do leave detectable traces—like fish, whole grains, and fruits—but other foods didn’t show up as clearly as expected. This research suggests that biological markers could someday help doctors and nutritionists better understand people’s eating habits, though more work is needed to make these tests reliable.

The Quick Take

  • What they studied: Can scientists use blood and urine tests to figure out what foods people ate, instead of relying on people to remember and report their meals?
  • Who participated: 21 healthy young adults (average age 25 years old) with normal body weights participated in the study
  • Key finding: Certain foods left measurable traces in blood and urine—fish, whole grains, and fruits showed the clearest signals—but not all foods produced detectable markers, and some expected markers didn’t appear as predicted
  • What it means for you: In the future, blood and urine tests might help track what you eat more objectively, but scientists still need to refine these tests before they can be used in real-world settings

The Research Details

This was a carefully controlled feeding study where 21 young adults ate specific meals on three separate days while researchers watched. Each day, participants ate foods from certain groups (like whole grains, dairy, and fish on one day) while avoiding other food groups. The researchers collected blood samples and 24-hour urine samples after each feeding day and used advanced laboratory equipment to search for chemical markers that matched the foods eaten. They compared what the tests showed against what people actually ate and what people remembered eating.

The study used a crossover design, meaning each person participated in all three different feeding days. This approach helps researchers see how the same person’s body responds to different foods, which makes the results more reliable. The researchers used a technique called liquid chromatography mass spectrometry, which is like a sophisticated fingerprint reader for chemicals in the body.

Traditional dietary assessment relies on people remembering and accurately reporting what they eat, which is often inaccurate. Biological markers—chemical traces left by foods in the body—could provide objective evidence of what someone actually consumed. This study is important because it tests whether these markers actually work in real conditions with real foods, not just in laboratory settings.

This study has several strengths: it was carefully controlled with known food amounts, it used advanced laboratory methods, and it compared multiple assessment methods. However, the sample size was small (only 21 people), all participants were young and healthy, and the feeding periods were short (48 hours). These factors mean the results may not apply to older people, those with health conditions, or long-term eating patterns.

What the Results Show

The researchers identified several food-specific chemical markers that worked well. Fish consumption was clearly marked by a compound called 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid. Whole grain intake showed up as 3,5-dihydroxybenzoic acid. Fruit consumption left traces of fructose and another compound called s-methylcysteine. Chicken meat produced three specific markers: 3-methylhistidine, anserine, and carnosine. Vegetables showed five different markers, with sulforaphane and β-carotene being the strongest signals. Legumes produced a marker called glycine betaine.

Interestingly, not all expected markers appeared. For example, sodium in urine didn’t match the amount of salt people actually ate, suggesting that sodium isn’t a reliable marker for salt intake. The researchers also found that when people reported what they ate, their reports were reasonably accurate (matching actual intake more than 40% of the time), which was better than some expected.

The study showed that different foods leave different chemical fingerprints in the body, but the strength of these signals varies. Some foods are ’loud and clear’ markers, while others are ‘quiet and hard to hear.’ This variation is important because it means scientists can’t use a one-size-fits-all approach to dietary biomarkers.

The research revealed that blood and urine samples captured different information. Some markers showed up better in urine, while others appeared in blood. This suggests that future dietary assessment tools might need to use both types of samples to get a complete picture. The study also showed that the relationship between food intake and biomarkers isn’t always straightforward—sometimes more food doesn’t produce proportionally more marker, which complicates interpretation.

This study confirmed some previously reported connections between foods and chemical markers but failed to confirm others. This suggests that earlier research may have been done under different conditions or with different food amounts. The findings highlight that biomarkers need to be tested across various real-world scenarios, not just in controlled laboratory settings, before they can be trusted for practical use.

The study had several important limitations. Only 21 young, healthy adults participated, so results may not apply to older people, children, or those with diseases. The feeding periods lasted only 48 hours, so we don’t know if these markers work for longer-term dietary patterns. Participants ate meals under observation, which isn’t how people normally eat. The study also didn’t test realistic food amounts—people typically eat more varied diets with different portion sizes. Finally, some previously identified biomarkers didn’t show up at all, suggesting that our current understanding of dietary markers is incomplete.

The Bottom Line

At this stage, blood and urine biomarkers should not replace traditional dietary assessment methods. However, they show promise as a complementary tool for research purposes. If you’re participating in nutrition research, be aware that scientists may use these tests alongside your food reports. For personal health tracking, continue relying on food diaries and discussions with healthcare providers, as biomarker testing isn’t yet ready for individual use.

Nutrition researchers and scientists should pay attention to this work, as it advances the field of dietary assessment. Healthcare providers may eventually use these tests to verify patient reports about eating habits. People with chronic diseases who need careful dietary monitoring might benefit once these tests are refined. However, the general public doesn’t need to seek out biomarker testing yet.

This research is foundational work. It will likely take 5-10 years of additional studies before biomarker panels could be used in clinical settings. Scientists need to test these markers in larger groups, diverse populations, and with realistic eating patterns before they become practical tools.

Want to Apply This Research?

  • Track the specific foods identified as having clear biomarkers: fish, whole grains, fruits, chicken, legumes, and vegetables. Log daily servings of each category and note any patterns in energy levels or digestion.
  • Focus on increasing intake of the foods with the strongest biomarkers (fish, whole grains, vegetables, and fruits) since these are easiest to objectively measure. Set weekly goals like ’eat fish twice’ or ’eat vegetables with every meal’ and track completion.
  • Create a simple food diary within the app that tracks the six food categories with strong biomarkers. Use a weekly summary view to see patterns and trends. Compare your reported intake against your consistency—if you report eating fish but rarely log it, this reveals reporting gaps that biomarker testing could eventually catch.

This research is preliminary and not yet ready for clinical use. Biomarker testing for dietary assessment is not currently recommended for personal health decisions. If you have concerns about your diet or nutrition, consult with a registered dietitian or healthcare provider who can use established assessment methods. This study involved only young, healthy adults and may not apply to other populations. Do not use biomarker testing to replace medical advice or established dietary guidance.