Identifying and annotating the molecular composition of individual foods will improve scientific understanding of how foods impact human health and how much variation exists in the molecular composition of foods of the same species. The complexity of this task includes distinct varieties and variations in natural occurring pigments of foods. Lipidomics, a sub-field of metabolomics, has emerged as an effective tool to help decipher the molecular composition of foods. For this proof-of-principle research, we determined the lipidomic profiles of green, yellow and red bell peppers (Capsicum annuum) using liquid chromatography mass spectrometry and a novel tool for automated annotation of compounds following database searches. Among 23 samples analyzed from 6 peppers (2 green, 1 yellow, and 3 red), over 8000 lipid compounds were detected with 315 compounds (106 annotated) found in all three colors. Assessments of relationships between these compounds and pepper color, using linear mixed effects regression and false discovery rate (<0.05) statistical adjustment, revealed 11 compounds differing by color. The compound most strongly associated with color was the carotenoid, β-cryptoxanthin (p-value = 7.4 × 10−5; FDR adjusted p-value = 0.0080). These results support lipidomics as a viable analytical technique to identify molecular compounds that can be used for unique characterization of foods.

Objectives Astaxanthin, a predominately marine-source carotenoid, is the subject of a large number of studies for its antioxidant and anti-inflammatory properties. Astaxanthin is not generally a primary carotenoid in human plasma due to relatively low dietary intake. Salmon is the one of the few dietary sources of astaxanthin in typical American diets and the concentration may vary by the source of salmon foods. A study was performed to 1) Compare astaxanthin concentration in various sources of salmon; 2) Compare astaxanthin plasma concentrations before and after salmon consumption. Methods An assortment of salmon types and forms was purchased in the greater Denver, CO region: wild Pacific, farmed Atlantic, canned and pouch. Plasma samples were collected from five participants prior to and after a five week Mediterranean diet intervention study, which included two servings of salmon per week. Salmon samples were freeze-dried, then both salmon (in triplicate) and plasma samples were prepared by liquid-liquid extraction for untargeted liquid chromatography-mass spectrometry analysis. An accurate mass and retention time database was used to identify and quantify astaxanthin. ANOVA with Tukey multiple testing corrections was used to assess the relationship between astaxanthin and the different salmon products, and paired t-tests for astaxanthin in plasma. Results Astaxanthin concentration was significantly higher in fresh salmon compared to pouch packaged (23.0-fold; P = 1.70e-04) and canned (34.9-fold; P = 1.23e-08). Interestingly, astaxanthin levels were similar between fresh wild Pacific and fresh farmed Atlantic salmon (0.91-fold, P = 0.82) and by mode of cooking (i.e., fresh, cooked, frozen; P = 0.81). Astaxanthin concentration in plasma was significantly increased after farmed Atlantic salmon consumption (1.98-fold, P = 6.16e-09). Conclusions Our data suggest that astaxanthin concentration varies among different processed salmon products compared to wild and farmed salmon. After salmon consumption, plasma astaxanthin concentration increased and may have potential as a biomarker of salmon consumption. Funding Sources National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).

Objectives Foods are comprised of thousands of compounds that may be absorbed upon ingestion. Metabolomics offers the unprecedented capability of measuring these small molecules to discover biomarkers of intake and examine how dietary patterns may exert their effects on health. The objectives of this study were to: 1) perform metabolomics analyses of 100 foods provided as part of a controlled feeding Mediterranean-style eating pattern (MED) intervention to identify food-specific compounds (FSC); and 2) determine which FSC were observed in participants’ plasma samples. Methods Individuals (n = 41) completed a randomized, crossover, controlled feeding study with two five-week MED interventions separated by a four-week washout. Following extraction into lipid-rich and hydrophilic fractions, samples of 100 foods were analyzed in triplicate using liquid chromatography-mass spectrometry (LCMS). Participant plasma was collected pre- and post- each intervention period and similarly analyzed by LCMS. Food compounds were determined to be FSC if they were present in all replicates of a food but no other foods. Plasma data were assessed to determine presence of FSC. Analyses were completed using Mass Profiler Professional (MPP), and descriptive statistics were generated. Results A total of 1390 ± 1044 (mean ± SD, range 14–4908) compounds per food were detected. Ninety-nine foods contained FSC (mean 296 ± 393, range 1–2472) with 17% of all compounds unique to a given food. Feta cheese had the greatest number of FSC; pure maple syrup had the lowest. Ninety-six foods had at least one FSC detected in plasma (mean 28 ± 32, range 1–143) with 16% of all FSC found in plasma. Grape juice, apple juice, romaine lettuce, and peanuts each had one FSC in plasma, while salmon and beef had 143 and 76 FSC in plasma, respectively. Conclusions Metabolomics analyses of both foods and plasma confirmed that foods have compounds that are unique and that these unmetabolized compounds can be detected in plasma following consumption. This information can be used to identify food intake biomarkers and link specific components of eating patterns to health outcomes. Additional studies to examine reproducibility and determine dose-response will be vital to elucidating the relationship between food compounds within MED and health. Funding Sources NIH/NIDDK; Beef Checkoff (MED feeding study).

Objectives Salmon consumption may promote cardiovascular (CV) health through nutrients such as omega-3 fatty acids (n-3 FAs) or other yet unidentified compounds. Metabolomics allows for the comprehensive analysis of small molecules in foods and human samples. The objectives of this study were to: 1) identify compounds present in salmon that were increased in plasma after consumption of a salmon-containing Mediterranean-style eating pattern (MED); and 2) evaluate associations between salmon compounds detected in plasma and CV biomarkers. Methods Individuals (n = 41) completed a 16-week randomized, crossover, controlled feeding study of a MED containing 2 servings salmon/week. Assessments were completed pre- and post-intervention, where CV biomarkers (e.g., blood pressure, lipid profile) were measured and fasting plasma collected. Samples of participants’ plasma, salmon, and 99 other foods in the trial were analyzed in triplicate via liquid chromatography-mass spectrometry (LCMS). Compounds were determined to be unique-to-salmon (UTS) if detected in all replicates of salmon but none of the other 99 foods. For UTS compounds that were found in plasma, linear mixed effects models were used to assess change from pre- to post-intervention and the association between this change and changes in CV biomarkers. Significance was assessed after adjustment for false discovery rate. Results Relative to the other 99 foods, 508 compounds were determined to be UTS, and 143 of these UTS compounds were detected in plasma. Forty-eight UTS compounds significantly increased in plasma from pre- to post-intervention. Two compounds, a phosphatidylglycerolphosphate (40:4) and a triglyceride (58:11), were associated with improvement in ≥1 CV biomarker. The former, a cardiolipin precursor, was associated with improvements in total cholesterol, LDL cholesterol, and Apolipoprotein B. Conclusions Salmon compounds are detectable in human plasma after consumption within a complex diet and increase after intervention, suggesting potential as intake biomarkers. Further, bioactive compounds beyond nutrients such as n-3 FAs may be associated with CV benefits. Future studies should be conducted to quantify concentrations and define dose-response. Funding Sources NIH/NIDDK; Beef Checkoff (MED feeding study).