Report biomarkers of
protein intake
BGZ2024: Food for life
, What is the aim of the practical training?
The objective of this practical was to measure different biomarker methods on
individuals which excreted 24-hour urea to track down their protein intake. To
determine protein intake two methods can be used: keeping up a food diary three days
before urea excretion and the measurement of the biomarker nitrogen (N) in the
excreted urea. Because of this practical we were able to keep an accurate food diary
lasting for three days and learned how to properly measure nitrogen substances in the
excreted urea through the UV-method on the spectrophotometer and how well
grounded this biomarker is to estimate protein intake. Throughout the lab the practical
leader also mentioned which sources were important in biomarker studies, the validity
of the different biomarkers and how to identify measurement error which we learned
what to pay attention to during a practical using these biomarkers.
Briefly describe the used methodologies.
Food diary
Three consecutive days before the practical (15 th, 16th, and 17th) the habitual food
intake had to registered in the food diary. Before the meal I weighed the food and
wrote it down immediately to minimize memory bias. Sometimes the weight of the food
was on the package, so this wasn’t necessary. Besides the weight I also noted the
method of cooking, the brand, and the processing of the food. I used the
‘voedingsmiddelentabel’ to calculate the energy and macronutrient intake of all the
registered food.
Biochemical measurement of urinary urea
Urine collection
On the last day of the food diary (17th), one day before the practical, 24 h urine had to
be collected in an empty jar which I picked up on Monday (8 th) after the practical
instruction lecture in UNS 40 at the lab where I also weighed the empty jar (182.4g). In
the morning of the urine day collection the first void had to be discarded in the toilet,
after that void all the urine excretion of that day and night had to be collected in the
jar. The morning after (18th) the first void also had to be collected in the jar, this was
the same time as the day before. Strenuous exercise during had to be avoided during
the urine collection period.
Urine analysis
At the start of the practical on Friday (18th) the urine bottle was weighed again and
had to be gently shaken to homogenize the urine and one vial had to be filled with
2
protein intake
BGZ2024: Food for life
, What is the aim of the practical training?
The objective of this practical was to measure different biomarker methods on
individuals which excreted 24-hour urea to track down their protein intake. To
determine protein intake two methods can be used: keeping up a food diary three days
before urea excretion and the measurement of the biomarker nitrogen (N) in the
excreted urea. Because of this practical we were able to keep an accurate food diary
lasting for three days and learned how to properly measure nitrogen substances in the
excreted urea through the UV-method on the spectrophotometer and how well
grounded this biomarker is to estimate protein intake. Throughout the lab the practical
leader also mentioned which sources were important in biomarker studies, the validity
of the different biomarkers and how to identify measurement error which we learned
what to pay attention to during a practical using these biomarkers.
Briefly describe the used methodologies.
Food diary
Three consecutive days before the practical (15 th, 16th, and 17th) the habitual food
intake had to registered in the food diary. Before the meal I weighed the food and
wrote it down immediately to minimize memory bias. Sometimes the weight of the food
was on the package, so this wasn’t necessary. Besides the weight I also noted the
method of cooking, the brand, and the processing of the food. I used the
‘voedingsmiddelentabel’ to calculate the energy and macronutrient intake of all the
registered food.
Biochemical measurement of urinary urea
Urine collection
On the last day of the food diary (17th), one day before the practical, 24 h urine had to
be collected in an empty jar which I picked up on Monday (8 th) after the practical
instruction lecture in UNS 40 at the lab where I also weighed the empty jar (182.4g). In
the morning of the urine day collection the first void had to be discarded in the toilet,
after that void all the urine excretion of that day and night had to be collected in the
jar. The morning after (18th) the first void also had to be collected in the jar, this was
the same time as the day before. Strenuous exercise during had to be avoided during
the urine collection period.
Urine analysis
At the start of the practical on Friday (18th) the urine bottle was weighed again and
had to be gently shaken to homogenize the urine and one vial had to be filled with
2
