Biomarkers of food intake

Most of the existing evidence on relationships between diet and health is based on epidemiological studies. Though widely used, these data have several limitations. For example, dietary assessment is often conducted through self-reported dietary recalls, food frequency questionnaires or diet diaries – each of which can be a considerable source of error. Dietary biomarkers of food intake are a more objective method of dietary exposure. Date of preparation: February 2019.

Contribution:

• Dr Ana Rodriguez Mateos PhD Lecturer, Department of Nutritional Sciences, Faculty of Life Sciences and Medicine, King’s College London, UK. OpeN-Global Expert Partner.

Relevance of biomarkers of food intake for health

Most of the existing evidence on relationships between diet and health is based on epidemiological studies, which have a number of limitations.

Traditionally, dietary assessment has been measured with self-reported dietary recalls, food frequency questionnaires or diet diaries, which have a considerable source of error (1). For example, detailed information on the food or beverage consumed (brand, variety, etc.) and the way it was cooked or processed is not usually documented in dietary records.

It is also common for subjects participating in observational studies to under-report their true habitual food intake, or change their diet, during the period of the survey (2).

In addition, food composition databases are limited and often inaccurate,  in particular in low and middle income countries (3).

The 24-h food recall is the most widely used dietary assessment method in low-income countries, but very few studies have assessed its validity in their study settings (4). A systematic review of 16 studies investigating the accuracy of self-reported dietary intake (using doubly labelled water or basal metabolic rate) in low and middle-income countries found that almost half of the studies found underreporting in over 50% of the sample size, while 7 out of the 16 studies found evidence of overreporting (5).

In recent years, extensive efforts have been made to develop more reliable dietary assessment techniques, in particular on the discovery and validation of dietary biomarkers of food intake as a more objective method of dietary exposure (6).

A small number of biomarkers of intake of food or food components have been identified through the analysis of correlations of the biomarkers with dietary intake in epidemiological studies (6). Such biomarkers are usually plasma, serum or urinary food-derived metabolites or catabolites identified by analytical techniques such as GC–MS or HPLC–MS. The reliability of such biomarkers over time needs to be assessed carefully, to ensure that they reflect habitual exposure, especially when samples are collected at a single point, which is usual in epidemiological studies.

Currently, very few biomarkers of dietary intake have been fully validated, and to our knowledge, no study has been conducted in low income countries using validated biomarkers of food intake. This represents an innovative research opportunity.

Methods for measurement of biomarkers of food intake

Biomarkers of food intake are typically measured in human urine, plasma or serum.

The most used methods are untargeted and targeted metabolomics using liquid chromatography-mass spectrometry or/and NMR (7,8). Few studies have used stable isotope ratios as nutritional biomarkers (9).

Several factors influence the use of these techniques:

• Blood and urine samples need to be collected and immediately stored at -20°C – or ideally -80°C.
• Metabolomic analysis using LC-MS is generally expensive and in many cases such technology is not available onsite.

Development of more cost effective and practical techniques for samples collection and storage such as dried blood spots in the context of metabolomics and dietary biomarkers are needed, and is a research priority in order to further develop the potential of this innovative method to improve outcomes in global health.