Biomarkers of food intake for nuts and vegetable oils: an extensive literature search

Abstract

Nuts and vegetable oils are important sources of fat and of a wide variety of micronutrients and phytochemicals. Following their intake, several of their constituents, as well as their derived metabolites, are found in blood circulation and in urine. As a consequence, these could be used to assess the compliance to a dietary intervention or to determine habitual intake of nuts and vegetable oils. However, before these metabolites can be widely used as biomarkers of food intake (BFIs), several characteristics have to be considered, including specificity, dose response, time response, stability, and analytical performance. We have, therefore, conducted an extensive literature search to evaluate current knowledge about potential BFIs of nuts and vegetable oils. Once identified, the strengths and weaknesses of the most promising candidate BFIs have been summarized. Results from selected studies have provided a variety of compounds mainly derived from the fatty fraction of these foods, but also other components and derived metabolites related to their nutritional composition. In particular, α-linolenic acid, urolithins, and 5-hydroxyindole-3-acetic acid seem to be the most plausible candidate BFIs for walnuts, whereas for almonds they could be α-tocopherol and some catechin-derived metabolites. Similarly, several studies have reported a strong association between selenium levels and consumption of Brazil nuts. Intake of vegetable oils has been mainly assessed through the measurement of specific fatty acids in different blood fractions, such as oleic acid for olive oil, α-linolenic acid for flaxseed (linseed) and rapeseed (canola) oils, and linoleic acid for sunflower oil. Additionally, hydroxytyrosol and its metabolites were the most promising distinctive BFIs for (extra) virgin olive oil. However, most of these components lack sufficient specificity to serve as BFIs. Therefore, additional studies are necessary to discover new candidate BFIs, as well as to further evaluate the specificity, sensitivity, dose-response relationships, and reproducibility of these candidate biomarkers and to eventually validate them in other populations. For the discovery of new candidate BFIs, an untargeted metabolomics approach may be the most effective strategy, whereas for increasing the specificity of the evaluation of food consumption, this could be a combination of different metabolites.Electronic supplementary materialThe online version of this article (10.1186/s12263-019-0628-8) contains supplementary material, which is available to authorized users.

Mediterranean diet intervention in overweight and obese subjects lowers plasma cholesterol and causes changes in the gut microbiome and metabolome independently of energy intake

“…However, our data indicated that only nut consumption significantly increased over the intervention with MD. Therefore, increase in urinary urolithin glucuronides was most likely attributed to the intake of walnuts in our study as previously reported by others 50. Recently, urolithin A has been shown to improve intestinal barrier function in a preclinical model51 and has also been associated with lower cardiometabolic risk 52.…”

Adipokines and Adipose Tissue-Related Metabolites, Nuts and Cardiovascular Disease

“…Since nuts are sources of fats and a wide variety of micronutrients and phytochemicals, after ingestion, several of their constituents, as well as their derived metabolites, are found in the bloodstream and urine. These molecules appear to serve as markers of nut intake, where α-linolenic acid, urolithins, and 5-hydroxyindole-3-acetic acid appear to be markers of walnut intake, α-tocopherol and catechin-derived metabolites appear to be markers of almond intake, and selenium marks Brazil nut consumption [22].…”

“…In addition to their high content of polyunsaturated fatty acids (PUFA) and monounsaturated fatty acids (MUFA), phytochemicals, dietary fibers, magnesium, L-arginine, and antioxidants compose these foods. Together, these nutrients act by modulating the intestinal microbiota [20,21] and are precursors of a series of metabolites [22,23]. In addition, nut consumption is inversely associated with the incidence of CVD, coronary artery disease (CAD), atrial fibrillation, as also with CVD mortality, CAD mortality, and stroke mortality [24].…”

Food intake biomarkers for berries and grapes

“…Another important issue to consider is the presence of confounding factors such as consumption of other foods rich in ellagitanins and anthocyanins. Special attention should be put on nut intake, as these are a well-known source of ellagitannins [ 58 ]. Regarding anthocyanin intake, among vegetables and fruits, red radish, red cabbage, black beans, eggplants, grapes, pomegranate, and cherries represent likely confounding factors [ 104 ].…”