Abstract
The questioned reliability of 15:0, 17:0, and trans9-16:1 acids as biomarkers of dairy fat intake also questions the relationship between the intake of these products and their health effects. Two studies were conducted in the same geographical region. In an intervention study, volunteers followed a diet rich in dairy products followed by a diet without dairy products. Plasma and erythrocyte fatty acids (FA) were analyzed, and their correlations with dairy product intakes were tested. The FA biomarkers selected were validated in the Gipuzkoa cohort of the European Prospective Investigation into Cancer and Nutrition (EPIC) observational study. The correlation coefficients between plasma concentrations of iso16:0, iso17:0, trans11-18:1, cis9, trans11-18:2, and cis6-18:1 and the dairy fat ingested are similar in both studies, indicating that their concentration increases by 0.8 µmol/L per gram of dairy fat ingested. The biomarkers are positively related to plasma triglycerides (r = 0.324 and 0.204 in the intervention and observational studies, respectively) and total cholesterol (r = 0.459 and 0.382), but no correlation was found between the biomarkers and atherogenicity indexes. In conclusion, the sum of the plasma concentration of the selected FAs can be used as biomarkers of dairy product consumption. A linear relationship exists between their plasma concentrations and ruminant product intake. These biomarkers allow for obtaining consistent relationships between dairy intake and plasma biochemical parameters.
Highlights
Dairy products comprise a group of heterogeneous food products consisting primarily of milk, cheese, and yogurts from ruminants, mostly cows, sheep, and goats
Small differences in diet are reflected in plasma concentrations of fatty acids (FA), this study demonstrates that the concentration of the proposed biomarkers is mainly due to the sum of the contributions of dairy products and red meat and that the contribution of both types of food is similar in both studies
The use of plasma concentrations of selected FAs as biomarkers of dairy intake in an intervention study was validated in an observational study
Summary
Dairy products comprise a group of heterogeneous food products consisting primarily of milk, cheese, and yogurts from ruminants, mostly cows, sheep, and goats They provide a large number of essential nutrients that could be of benefit for most people. The contradictory results of published research could be due to any or several of the following reasons: the great variability of the nutritional composition of dairy products, different dietary patterns and intake of these products in various regions and countries, and the use of dietary questionnaires to obtain data on intake of dairy products These methods are inherently imprecise in calculating the intake of dairy products and the nutrients provided by the diet. Coefficients of variation obtained in epidemiological studies are quite high and the conclusions are not consistent For these reasons, it is necessary to define reliable biomarkers to determine as objectively as possible the intake of dairy products. It was hypothesized that suitable fatty acid biomarkers, present almost exclusively in ruminant fat and showing a proportional relationship with ingested dairy fat, will allow for obtaining consistent relationships between dairy intake and plasma biochemical parameters
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