Final report for LNC21-455
Project Information
To improve soil health in the North Central Region, a growing number of beef producers are finishing cattle and other livestock species on plant-species diverse forage and/or cover crops. While meat provides many essential nutrients in the American diet, pilot data from our research team indicated that when livestock are raised and finished on plant-diverse pastures, more omega-3 fatty acids and additional health-promoting phytonutrients such as terpenoids, phenols, carotenoids, and other anti-oxidants concentrate in meat. While linkages among the plant-animal-human health continuum (“healthy plants, healthy animals, healthy humans”) are often touted as the reason why grass-fed beef and other pasture-raised animal-based foods may have additional health benefits, no studies have systematically assessed this.
Using novel metabolomics approaches, the goal of our work was to detail the transfer of hundreds of biochemicals and phytochemicals from the forage/feed consumed by pasture-raised versus feedlot-fed animals, to their food products, and into the body of consumers and determine metabolic health biomarkers in response to consumption.
Phytochemical richness of forage and total mixed ration samples was determined using metabolomics (Objective 1). Second, we compared the presence of phytochemicals and biochemicals in both types of beef (Objective 2). To provide insight into consumer health (plasma metabolomes, inflammation), we conducted a randomized controlled trial and obtain blood samples from participants before and after 16 weeks of weekly consumption of grass-fed beef, pasture-raised pork, chicken and chicken eggs versus conventional grain-fed beef, pork, chicken and chicken eggs (Objective 3). Our central hypothesis: consuming grass-fed beef and other pasture-raised animal-based foods results in metabolic signatures indicative of improved metabolic health.
Cooperating farmers/ranchers assisted with sample collection and provided knowledge on grazed plants. Findings are being shared with producers, consumers, and stakeholders in the North Central region and the US via workshops, tradeshows, articles in traditional and social media, and scientific publications. Up to now, presentations related to this study have been given to over 1000 producers via six presentations in the states of South Dakota, Iowa, Illinois, Missouri, Kentucky and Oklahoma. Outreach partners include the ARS-Northern Great Plains Research Laboratory, grazing coalitions (South Dakota/North Dakota), and stakeholder groups including Understanding Ag, Thousand Hills Lifetime Grazed, Wisconsin Grass-fed beef Coop, and Carbon Cowboys. Project findings have potential for farmers and ranchers in the northcentral region to improve economic viability via more direct sales to consumers while potentially enhancing consumer health.
Ribeye steaks from grass-fed and grain-fed cattle were compared using targeted assays for phytonutrients, B-vitamins, and fat-soluble vitamins. Grain-fed beef showed 15–35% higher vitamin B₁, B₅, B₆, and B₇. Grass-fed beef contained ~88% more α-tocopherol and ~53% more β-carotene. Of 195 phytonutrients detected, 39 differed significantly: 30 elevated in grass-fed (e.g., hippuric acid +78%, p-cresol sulfate +37%, cinnamoylglycine +93%) and 9 in grain-fed (e.g., 4-hydroxyphenylacetic acid +275%, 3-phenyllactic acid +150%). Among 10 classes, carboxylic/hydroxy acids were 160% higher in grain-fed; flavonoids were 123% higher in grass-fed. Multivariate models and pasture survey data, including spatial “terroir” mapping, showed that botanically diverse, well-rested pastures enhanced α-tocopherol and phytonutrient concentrations. Thus, finishing diets and pasture conditions can be strategically managed to enrich beef in vitamins and phytonutrients.
The controlled human feeding trial demonstrated that consumption of pasture-raised beef, pork, chicken, and eggs significantly enhances red blood cell omega-3 fatty acid profiles and reduces the omega-6 to omega-3 ratio in healthy adults compared with conventionally-raised animal-source foods. These changes occurred independently of total energy intake and overall macronutrient distribution and suggest that pasture-raised animal products may represent a viable dietary strategy for improving population-level omega-3 status, particularly among individuals with low seafood consumption. Although no significant effects on traditional cardiometabolic risk markers were observed in this relatively healthy population, the improvements in omega-3 biomarkers—including a transition from high-risk to intermediate-risk omega-3 index values—support the potential for long-term cardiovascular and anti-inflammatory benefits.
The cooperating farmers/ranchers for this project already produce and sell grass-fed beef and pasture-based pork and/or chicken and/or chicken eggs. However, we expect that the results from this project will have an influence on consumer purchases and on the management decisions of existing pasture-based meat and egg producers.
Project Objectives:
(a) Determine if eating grass-fed beef as well as pasture-raised pork, chicken and chicken eggs from animals that ate a plant species-diverse diet elicits more healthful inflammatory and metabolite profiles in adult people than eating conventional grain-fed beef, pork, chicken and chicken eggs.
(b) Translate this information back to producers and consumers by partnering with producer coalitions and stakeholder groups.
Learning Outcomes:
Farmers will learn how finishing cattle on biodiverse forage influences the phytochemical richness of beef.
Consumers will learn if consuming such grass-fed beef and other animal-based foods from pasture-raised animals impacts their metabolic health.
Action Outcomes:
Farmers can adopt biodiverse pastures and cover crops to increase healthfulness of their pasture-fed beef, pork, chicken and chicken eggs.
Consumers encouraged to seek out local grass-fed beef, pork, chicken and chicken eggs.
Beef, pork, chicken and chicken eggs are popular foods and provides many essential nutrients in the American diet. Grass-fed beef as well as pasture-raised chicken, pork and chicken eggs are growing in popularity as a type of meat and eggs consumed and pilot data from our research team indicates that when cattle are raised and finished on plant-diverse pastures, additional health-promoting phytonutrients—terpenoids, phenols, carotenoids, and other anti-oxidants—concentrate in beef. While linkages among the plant-animal-human health continuum (“healthy plants, healthy animals, healthy humans”) are often touted as the reason why grass-fed beef may have additional health benefits, no studies have systematically assessed this. Therefore, we will conduct fieldwork and a human feeding trial to study potential connections among plants and compounds in plants, cattle and human health. Then use a variety of educational and outreach efforts to share our findings will all interested people.
Cooperators
Research
Grass-fed beef along with pasture-based pork, chicken and chicken eggs produced on pastures with more diversity of plant species and plant parts available and consumed by the animals will have greater diversity of chemicals in these animal-based foods and will provide health benefits to consumers compared to these conventionally produced foods in pens with a high dietary level of concentrate feeds and less diversity of plant materials consumed.
Objective 1: Plant-species Diversity Characterization and Forage Metabolomics
Forage collection
Pastures on each cooperating farm (Brown’s Ranch, ND; Maier’s Farm, MN; Fox Hills Ranch (ND) will be sampled every 30 days during the last 3 months prior to slaughter. These efforts, led by Dr. Kronberg, will be performed in close collaboration with the farmers as they will know which fields have been grazed and need sampling. Plant samples will be collected in conical tubes, freeze-dried, powdered, and stored at -80°C for metabolomics analysis. Feedlot TMR is provided by Demkota (Aberdeen, SD). All samples (rations and forages) will be submitted for nutritional composition analysis by USDA-ARS, while phytochemical composition will be determined using metabolomics analysis.
Objective 2: Meat Biochemical Richness Characterization
Meat Sampling
Beef and other animal-based foods will be collected from the three cooperating farms/ranches and also from penned animals under the coordination of Dr. Kronberg. Based on previous work it is expected that 46% of probed metabolites are different between grass-fed and grain-fed beef and 10 cattle per farm is sufficient to provide true discovery rates ranging from 96-99 % assuming a fold difference of 1.1-1.25, respectively. The pasture-based and feedlot producers all raise/finish Black Angus cattle.
Meat Analysis
Beef and other meat and egg samples will be analyzed for proximate composition and macronutrient evaluation. They will be evaluated for biochemical richness—vitamin and mineral derivatives, fatty acids, organic acids, antioxidants, phytochemicals, xenobiotics, and other bioactive compounds—via metabolomics. The metabolome data will be overlaid with the plasma metabolome of participants in the human intervention trials to directly establish the impact of biochemical richness of the meat on the human metabolome.
Objective 3: Human Intervention Trials
This 16-wk, randomized, parallel-arm dietary intervention trial was conducted at Center for Human Nutrition Studies (CHNS) at Utah State University in Logan, UT, between March 2025 and August 2025 (see Figures 1 and 2). The study was approved by the Utah State University Institutional Review Board (IRB protocol 14156) and conducted in accordance with the principles of the Declaration of Helsinki. All participants provided written informed consent before enrollment. The trial was registered at ClinicalTrials.gov (NCT06768775) prior to completion of the study
Participants
Participants were recruited from the local community in Cache Valley, UT, through flyers, email announcements, and social media postings. Interested individuals completed a prescreening survey via REDCap (Research Electronic Data Capture) or contacted the study team by phone or email. Eligibility criteria included men and women aged 30–65 y with a BMI between 25 and 35 kg/m², weight stability (±4% body weight over the previous 3 mo), hemoglobin A1c (HbA1c) ≤6.4%, and fasting plasma glucose <126 mg/dL. Exclusion criteria included heavy alcohol consumption >14 drinks/wk, use of lipid-lowering or anti-inflammatory medications, omega-3 supplements or autoimmune or inflammatory disease, chronic metabolic or cardiovascular disease, pregnancy or lactation, or inability or unwillingness to consume the study-provided animal-source foods.
Randomization and Blinding
Eligible participants were randomized in a 1:1 ratio to 1 of 2 treatment groups using a computer-generated randomization sequence: 1) pasture-raised animal-source foods or 2) conventionally-raised animal-source foods. Participants and laboratory personnel conducting biochemical analyses were blinded to treatment allocation.
Dietary Intervention
Participants in the pasture-raised group received beef, pork, chicken, and eggs that were sourced from suppliers that used pasture-based production systems, which were visited and verified by the research team. Pasture-raised beef came from cattle raised exclusively on pasture without grain finishing. Pasture-raised chicken and eggs were sourced from poultry with pasture access and diets supplemented with omega-3-rich feedstuffs such as fishmeal and flaxseed. Pasture-raised pork came from heritage breed pigs with forage access and grain supplementation. Participants in the conventionally-raised group received beef, pork, chicken, and eggs purchased from a nationwide grocery retailer, representing typical grain-finished beef, confined animal feeding operation (CAFO) pork and chicken, and conventional eggs from caged laying hens.
All participants were instructed to substitute the study-provided meat and eggs for their habitual consumption of these foods (targeting approximately 6–8 oz of meat per day and ~10-12 eggs per week) and to otherwise maintain their usual dietary and physical activity habits. Participants were explicitly instructed not to consume seafood or omega-3 supplements for the duration of the trial and not to share study foods with family members. Compliance was monitored through weekly study food pickups at the Center for Human Nutrition Studies (CHNS), participant check-ins, and dietary assessment.
Clinical Assessments
Participants attended 3 clinic visits at the CHNS: a baseline visit (week 0), an interim screening visit (before randomization), and an endpoint visit (week 16). At baseline and endpoint visits, participants arrived after a 12-h overnight fast. Anthropometric measurements (height, body weight, and resting blood pressure [systolic blood pressure (SBP) and diastolic blood pressure (DBP)]) were recorded according to standardized protocols. Height was measured to the nearest 0.1 cm using a wall-mounted stadiometer, and body weight was measured to the nearest 0.1 kg using a calibrated electronic scale. Resting blood pressure was measured in triplicate after a 15-min seated rest using an automated oscillometric blood pressure monitor (Omron HEM-907XL, Omron Healthcare, Lake Forest, IL, USA), with the average of the three measurements used for analysis.
Blood Collection and Processing
Fasting venous blood was collected into three 6-mL EDTA tubes for plasma and RBC separation and one 6-mL serum tube for clinical chemistry. Samples were stored at 4°C and processed within 40 min of collection. Tubes were centrifuged at 3000 × g for 15 min at 4°C. Plasma was aliquoted into cryovials and stored at −80°C. RBC pellets were washed 3 times with phosphate-buffered saline (PBS), aliquoted, and stored at −80°C for subsequent fatty acid analysis. Serum samples were stored at −80°C for future analysis. Clinical chemistry panels, including total cholesterol, high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, triglycerides, very-low-density lipoprotein (VLDL) cholesterol, fasting glucose, and HbA1c, were analyzed by a certified clinical laboratory (LabCorp Laboratories).
Fatty Acid Analysis
Fatty acids were extracted from RBC membranes and transesterified into fatty acid methyl esters (FAMEs) following the method of O'Fallon et al. (19). Briefly, samples were saponified in 10 N KOH in methanol with the addition of an internal standard (heneicosanoic acid, C21:0) and incubated at 55°C for 1.5 h. Methylation was subsequently performed using H₂SO₄ in methanol. The resulting FAMEs were extracted into hexane containing 0.01% butylated hydroxytoluene (BHT) to prevent oxidation. FAMEs were analyzed using gas chromatography equipped with flame ionization detection (GC-FID; Shimadzu Scientific Instruments, Columbia, MD) on a fused silica capillary column (SP-2560, 100 m × 0.25 mm internal diameter × 0.20 μm film thickness; Supelco) The oven temperature program was as follows: 140°C with a 5-min hold, ramped at 4°C/min to 240°C, and held for 15 min (total run time approximately 40 min). Injector and detector temperatures were maintained at 250°C. Helium was used as carrier gas at a constant flow of 1.5 mL/min, with a split ratio of 100:1. Individual fatty acids were identified by comparison with authentic reference standards (Nu-Chek Prep), including a GLC-37 FAME mixture and additional long-chain omega-3 PUFA standards (EPA, docosapentaenoic acid [DPA; 22:5n-3], and DHA). Quantification was achieved using a 4-point calibration curve for each fatty acid relative to the internal standard (C21:0). Fatty acid concentrations are expressed as a percentage of total identified fatty acids. Pooled quality control samples were included in each analytical run to verify precision and reproducibility across batches. Intra-assay and interassay CVs were <5% and <8%, respectively, for all major fatty acids. The omega-3 index was calculated as the sum of EPA and DHA expressed as a percentage of total RBC fatty acids (20). The omega-6 to omega-3 ratio was calculated as the sum of all omega-6 fatty acids divided by the sum of all omega-3 fatty acids.
Study Food Fatty Acid Analysis
Representative samples of all study foods (ground beef, pork loin, chicken breast, and eggs from both pasture-raised and conventional sources) were analyzed for fatty acid composition using the same GC-FID method described previously. Three independent samples of each food type were analyzed to ensure reproducibility.
Dietary Assessment
Dietary intake was assessed throughout the 16-wk intervention using the Automated Self-Administered 24-Hour Dietary Assessment Tool (ASA24) developed by the National Cancer Institute (https://asa24.nci.nih.gov/). Participants completed ≥3 dietary recalls per month, including 2 weekdays and 1 weekend day, to capture habitual eating patterns. These data were used to monitor compliance with the study protocol and to quantify background intakes of macronutrients and fatty acids. In addition, participants completed food logs at the time of weekly study food pickups, documenting the amount of beef, pork, chicken, and eggs consumed and the method of preparation. All dietary intake data were processed and analyzed by trained research staff using R and Python, with nutrient composition estimates obtained from ASA24 dietary recall exports, including total energy, macronutrient intake (protein, fat, and carbohydrate), dietary fiber, and fatty acid composition.
Sample Size Calculation
Sample size was determined based on expected changes in RBC omega-3 PUFA composition, informed by prior intervention studies of grass-fed and conventional red meat consumption (16, 17). Assuming an effect size of 0.8 percentage points in RBC omega-3 fatty acids, a standard deviation of 1.0 percentage points, α = 0.05 (2-tailed), and 80% statistical power, a minimum of 64 participants (n = 32 per group) was required. To account for an anticipated 15–20% dropout rate, the recruitment target was set at 80 participants (n = 40 per group).
Statistical Analysis
All data were analyzed using GraphPad Prism version 10.0 (GraphPad Software) and R version 4.3.0 (R Foundation for Statistical Computing). Descriptive statistics were used to summarize baseline participant characteristics, with continuous variables presented as means ± SDs and categorical variables as frequencies and percentages. Between-group differences at baseline were assessed using unpaired t tests (Welch's correction applied when variances were unequal) for continuous variables and chi-square tests for categorical variables.
The primary analysis evaluated differences in RBC fatty acid composition at the postintervention time point (week 16) using analysis of covariance (ANCOVA), with baseline values included as covariates and treatment group as the independent variable. Similar models were applied for plasma fatty acids, clinical chemistry outcomes, and dietary intake variables. Sex-stratified analyses were performed given known sex differences in fatty acid metabolism (21, 22). For the primary outcome (RBC fatty acids), results are presented separately for males and females using unpaired t-tests (Welch's correction where appropriate) to compare treatment groups within each sex.
For outcomes with multiple groups (treatment × sex), 2-way ANOVA was performed to assess main effects of treatment, sex, and treatment × sex interaction. When significant interactions were detected (P < 0.05), post hoc pairwise comparisons were conducted using Tukey's multiple comparisons test to control for type I error. Effect sizes for between-group comparisons are reported as Hedges' g, calculated as the standardized mean difference with correction for small sample sizes. Hierarchical clustering analysis was performed on RBC fatty acid data using Euclidean distance and complete linkage methods to visualize clustering patterns by treatment group and sex. Data were row-scaled (z-scores) before clustering. Heatmaps were generated using the heatmap package in R.
All statistical tests were 2-tailed, and statistical significance was set at P < 0.05. Given the exploratory nature of secondary outcomes, no adjustment for multiple comparisons was applied. Assumptions of normality were assessed using the Shapiro-Wilk test and visual inspection of Q-Q plots. When normality assumptions were violated, nonparametric alternatives (Mann-Whitney U test) were used. Homogeneity of variance was assessed using Levene's test, and Welch's correction was applied to t tests when variances were significantly different between groups. All randomized participants (n = 80) completed the study and were included in the final intention-to-treat analysis.
Objective 4: Outreach
Our proposed efforts to disseminate the findings to producers, consumers, and the scientific community are described in detail in the Outreach subsection. All farmers provided key input to the design and rationale of this study, and farmer cooperators will have important roles in disseminating the findings to peers.
2023 Update
All soil samples, which were collected from the three regenerative agriculture style farms and adjacent conventional style farmland, were analyzed for many conventional and soil health-related attributes and all forage samples have been freeze dried and will be analyzed soon. All grass-fed beef was procured from the three cooperating farms and is now in storage in a freezer at Utah State University. Preparations are underway to start the human feeding trial including obtaining approval from the Institutional Review Board at Utah State University to conduct the trial.
2024 Update
Soil health of study pastures versus adjacent cropland growing annual cash crops
Total soil microbial biomass and functional microbial group diversity were generally better on the three pasture-based grass-fed beef operations than on nearby cropland growing annual cash crops. Microbial respiration (measured as carbon dioxide production) was higher to considerably higher (a good sign) on some of the study pastures compared to nearby cropland, but was not higher in all cases perhaps because one of the cropland soils had lots of corn residue tilled into it where soil microbes could digest it and produce carbon dioxide.
Human feeding trial
Our recent evaluations of grass-fed beef using gas chromatography to evaluate fatty acid composition of meat samples and using ultra-high performance liquid chromatography tandem mass spectrometry (for targeted metabolomics) to identify many phytochemical metabolites have indicated that this type of beef generally has higher levels of many healthful compounds (phytochemical antioxidants, co-factors/vitamins and lipid metabolites) compared to grain-fed beef. The phytochemicals were directly traceable to the greater presence of phytochemicals in the forages they grazed compared to total mixed rations fed to feedlot cattle. Higher concentrations of Vitamins A (carotenes) and E (alpha-tocopherol) were also found in grass-fed beef. However, our recent four- or six-week human feeding trials, which were conducted by Dr. Stephan van Vliet and his team, have indicated that it is very challenging to find indications of improved health in the blood of people consuming grass-fed beef when they are also consuming a lot of ultra-processed foods. These studies indicate that simply switching from a diet high in ultra-processed foods to consuming a whole foods-based diet improves healthful biomarkers irrespective of whether the foods are conventionally or regenerative-organically produced. However, we don’t yet know what changes can occur in blood biomarkers with a longer human feeding trial of several months duration, with more people in the study, and with more pasture-based animal foods fed. So, the Institutional Review Board-approved human feeding trial we recently started is described below.
Study Design: A randomized controlled trial (parallel-arm design) with 80 adult participants (age 30–65, roughly equal men and women) divided into two diet groups. Over a 4-month intervention period, one group will consume pasture-raised meat and eggs while the other group will consume conventionally produced meat and eggs. All meats and eggs are provided to participants to ensure compliance and consistent intake. Participants are instructed to prepare these foods at home as part of their normal diet, but to avoid other sources of long-chain omega-3s, such as fish or omega-3 supplements, during the study. This dietary control helps isolate the effect of the differing food combinations on health outcomes.
Objectives: The primary objective is to determine the long-term effect of consuming pasture-raised animal products on red blood cell (RBC) omega-3 levels. In other words, the study will measure whether people who eat grass-fed meat and eggs for 4 months show an increase in the omega-3 content of their blood (specifically, the membranes of their red blood cells) compared to those eating grain-fed products. The RBC omega-3 level, often termed the “Omega-3 Index,” is an emerging indicator of cardiovascular health (higher values are associated with lower risk of heart disease). We hypothesize that the pasture-based diet, being richer in omega-3, will raise participants’ Omega-3 Index over the course of the trial, whereas the conventional diet may not.
Secondary Outcomes: The trial also monitors a broad panel of other health biomarkers to provide a comprehensive comparison of the two diets. This includes blood lipid profiles (cholesterol panel including LDL, HDL, triglycerides), and metabolomic markers. By measuring these at baseline and at the end of the study, we aim to see if the pasture-raised diet leads to improved metabolic health relative to the conventional diet. Notably, prior studies have suggested that diets richer in omega-3 and certain antioxidants (like those found in pasture-based animal food products) may reduce inflammation. Our trial will directly test this in a controlled setting.
Methodology and Protocol: Participants undergo health screenings and baseline measurements before starting the diet intervention. They then receive weekly portions of either pasture-raised or conventional meat and eggs to consume at home, with adherence monitored via food logs and regular check-ins. The trial is parallel-arm to maintain clear separation between diet types. At the end of 4 months, participants will have end-of-study measurements made, which are identical to those done at the beginning to determine their baseline (pre-trial) state. The research team will then analyze changes in RBC omega-3 levels and other markers between the two groups. Statistical analyses (linear models controlling for factors like age, sex, BMI) will determine if any observed differences are significant. This careful design ensures that any improvements in omega-3 status in the pasture-fed group can be confidently attributed to the diet differences.
Human Trial Outlook: The ongoing human feeding trial will provide critical evidence on whether these nutritional differences translate into health differences. We anticipate that participants eating the pasture-raised diet will show higher RBC omega-3 levels and possibly more favorable lipid markers and levels of antioxidants than those associated with the conventional diet. If our hypothesis is confirmed, it will substantiate the idea that grass-fed animal-based foods are not just a boutique preference but have real, quantifiable benefits for human health. Such findings could inform dietary recommendations and agricultural practices, highlighting the value of regenerative, grass-based farming not only for the environment, but also for consumer well-being. On the other hand, if no significant differences are observed, that too is valuable information, indicating that factors beyond fatty acid content (such as overall diet context or genetics) play a larger role in these health outcomes.
Additionally, as we proceed, we will continue to balance technical analysis with accessible explanations, ensuring that the significance of our findings is understood by scientists, funding partners, and the general public. The next steps will be to complete the human trial, analyze the results, and report on whether consuming pasture-raised foods indeed leads to the anticipated improvements in human health markers.
2025 Update
Metabolomic Analysis
Grain-fed beef showed 15–35% higher vitamin B₁, B₅, B₆, and B₇. Grass-fed beef contained ~88% more α-tocopherol and ~53% more β-carotene. Of 195 phytonutrients detected, 39 differed significantly: 30 elevated in grass-fed (e.g., hippuric acid +78%, p-cresol sulfate +37%, cinnamoylglycine +93%) and 9 in grain-fed (e.g., 4-hydroxyphenylacetic acid +275%, 3-phenyllactic acid +150%). Among 10 classes, carboxylic/hydroxy acids were 160% higher in grain-fed; flavonoids were 123% higher in grass-fed. Multivariate models and pasture survey data, including spatial “terroir” mapping, showed that botanically diverse, well-rested pastures enhanced α-tocopherol and phytonutrient concentrations. Thus, finishing diets and pasture conditions can be strategically managed to enrich beef (and likely other meat) in vitamins and phytonutrients.
Human Participant Characteristics and Interventional Feeding Study
A total of 145 individuals were screened for eligibility, 80 of whom met inclusion criteria and were randomized. Forty participants were allocated to the pasture-raised ASFS treatment group and 40 to the conventionally-raised ASFS treatment group. The study achieved complete retention, with all 80 participants (100%) completing the full 16-week intervention period and attending both baseline and endpoint clinic visits.
The two treatment groups were well balanced at baseline, with no significant differences observed in demographic or clinical variables. The pasture-raised ASFS group included 19 females (47.5%) and 21 males (52.5%), whereas the conventionally-raised ASFS group had an identical sex distribution. Mean age was 41.0 ± 8.9 y in the pasture-raised ASFS group and 37.8 ± 8.5 y in the conventionally-raised ASFS group. Anthropometric measures were comparable between groups, with mean BMI values of 27.1 ± 4.0 kg/m² and 27.8 ± 4.6 kg/m² for pasture-raised and conventionally-raised ASFS groups, respectively.
Baseline cardiometabolic markers—including systolic blood pressure (SBP), diastolic blood pressure (DBP), total cholesterol, triglycerides, HDL cholesterol, LDL cholesterol, plasma glucose, and HbA1c—did not differ between treatment arms, confirming successful randomization. Mean values for all clinical parameters were within normal ranges, consistent with the enrollment of a generally healthy population.
Fatty Acid Composition of Study Foods
Pasture-raised and conventionally raised products differed in several fatty acid classes, with the most pronounced differences observed in beef. In ground beef, pasture-raised samples contained significantly higher concentrations of alpha-linolenic acid (ALA; 1.34 ± 0.05% vs. 0.28 ± 0.07%), docosapentaenoic acid (DPA; 0.35 ± 0.06% vs. 0.10 ± 0.02%), docosahexaenoic acid (DHA; 0.02 ± 0.00% vs. 0.00 ± 0.00%), and total omega-3 fatty acids (1.74 ± 0.07% vs. 0.46 ± 0.10%) compared with conventionally raised beef. The omega-6 to omega-3 ratio was markedly lower in pasture-raised beef (1.35 ± 0.06) than in conventional beef (7.42 ± 1.44). Eicosapentaenoic acid (EPA)was the only omega-3 fatty acid that was slightly higher in conventional beef (0.07 ± 0.02% vs. 0.03 ± 0.01%), consistent with low dietary availability and limited endogenous synthesis of EPA in ruminants.
Similar directional patterns were observed in chicken. Pasture-raised chicken breast contained higher EPA, DPA, DHA, and total omega-3 fatty acids (e.g., total n-3: 4.41% vs. 1.29%) and a correspondingly lower omega-6 to omega-3 ratio (6.6 vs. 14.8) compared with conventionally raised chicken. Because only two independent packages per production system were available, these values are presented descriptively rather than with inferential statistics. Pasture-raised pork also demonstrated modest increases in omega-3 fatty acids (0.62% vs. 0.50% total omega-3), though differences were less pronounced than in beef or chicken.
Both pasture-raised and conventionally raised products contained substantial amounts of saturated fatty acids, with palmitic acid (C16:0) and stearic acid (C18:0) being the predominant saturated species in all meats. Oleic acid (C18:1n-9) was the major monounsaturated fatty acid across all samples. Linoleic acid (C18:2n-6), the primary dietary omega-6 fatty acid, was present in considerable quantities in all products, with pasture-raised chicken exhibiting the highest concentrations (23.22% vs. 17.66% in conventionally-raised chicken).
Dietary Intake and Macronutrient Composition
Macronutrient intake assessed via ASA24 dietary recalls was largely comparable between treatment groups overall and when stratified by sex. Participants consuming conventionally raised foods reported a mean protein intake of 22.1 ± 4.5% of total energy, fat intake of 40.9 ± 5.6%, carbohydrate intake of 37.1 ± 8.0%, and fiber intake of 16.1 ± 5.5 grams/day. Participants consuming pasture-raised foods reported similar macronutrient distribution, with protein intake of 23.0 ± 4.6% of total energy, fat intake of 41.6 ± 5.3%, carbohydrate intake of 35.4 ± 9.7%, and fiber intake of 16.2 ± 4.4 grams/day.
Total energy intake did not differ significantly between groups. Absolute protein intake (grams/day) was modestly higher in the conventionally raised group; however, this difference did not translate to differences in macronutrient distribution or total energy intake. When stratified by sex, no significant differences in macronutrient distribution were observed between treatment groups among males or females. Collectively, these findings indicate that participants in both groups maintained similar overall dietary patterns throughout the intervention, supporting the interpretation that observed differences in fatty acid biomarkers were attributable to differences in the fatty acid composition of the study foods rather than differences in total energy or macronutrient intake.
Red Blood Cell Fatty Acid Composition
In male participants, consumption of pasture-raised ASFs resulted in dramatically higher concentrations of long-chain omega-3 fatty acids compared with conventionally-raised ASFs. Specifically, EPA was 1.72 ± 0.92% in the pasture-raised ASFS group compared with 0.16 ± 0.09% in the conventionally-raised ASFS group, representing a >10-fold increase. DPA was 0.45 ± 0.29% in pasture-raised ASFS consuming males compared with 0.78 ± 0.34% in conventionally-raised ASFS consuming males, and DHA showed a strong trend toward higher concentrations (1.71 ± 1.69% compared with 0.93 ± 0.35%). ALA was also elevated in the pasture-raised group 0.17 ± 0.10% compared with 0.06 ± 0.05%.
Total omega-3 fatty acids were nearly 4-fold higher in males consuming the pasture-raised diet (7.93 ± 1.76%) compared with males consuming the conventional diet (2.00 ± 0.56%). The omega-6 to omega-3 ratio was markedly reduced in the pasture-raised ASFS group (1.37 ± 0.72 compared with 6.16 ± 2.13). The omega-3 index—defined as the sum of EPA and DHA as a percentage of total RBC fatty acids—was elevated in pasture-raised ASFS consuming males (5.66 ± 1.79%) compared with conventionally-raised ASFS consuming males (1.09 ± 0.36%).
Similar patterns were observed in female participants. EPA was 1.40 ± 0.48% in the pasture-raised ASFS consuming group compared with 0.27 ± 0.22% in the conventionally-raised ASFS consuming group, DPA was 1.82 ± 0.59% compared with 0.89 ± 0.35%, and DHA was 3.83 ± 1.44% compared with 1.21 ± 0.73%. ALA was also significantly higher in pasture-raised ASFS consuming females (0.38 ± 0.31% compared with 0.07 ± 0.04%. Total omega-3 fatty acids were 8.01 ± 1.60% in pasture-raised ASFS consuming females compared with 2.49 ± 0.96% in conventionally-raised ASFS consuming females.
The omega-6 to omega-3 ratio was significantly reduced in pasture-raised ASFS consuming females (1.92 ± 0.70 compared with 5.36 ± 1.24). The omega-3 index was significantly elevated in pasture-raised ASFS consuming females (5.23 ± 1.38%) compared with conventionally-raised ASFS consuming females (1.48 ± 0.72%).
Statistical analysis with treatment and sex as factors revealed important effects of food type group, sex, but also an important interaction between food type eaten and sex of consumer for total omega-3 fatty acids. Similar patterns were observed for individual omega-3 fatty acids (EPA, DPA, DHA). A multiple comparisons statistical test indicated that pasture-raised ASFS consuming males and females exhibited higher EPA, DPA, and DHA concentrations than their conventionally-raised ASFS consuming counterparts.
Analysis of RBC fatty acid profiles revealed clear separation between pasture-raised and conventionally-raised ASFS consuming groups, with participants clustering primarily by treatment assignment rather than by sex. The heatmap demonstrated that pasture-raised ASFS consuming groups exhibited elevated concentrations of omega-3 fatty acids—including EPA, DPA, and DHA—and reduced concentrations of certain omega-6 fatty acids compared with conventionally-raised ASFS consuming groups.
Major saturated fatty acids (C16:0, C18:0) and monounsaturated fatty acids (C18:1n-9) in RBCs did not differ between treatment groups in either sex, indicating that the intervention specifically affected PUFA composition without altering saturated or monounsaturated fatty acid profiles.
Plasma Fatty Acid Composition
Plasma fatty acid composition was analyzed in a subset of participants (n = 5 per treatment group per sex; total n = 20) at the postintervention time point. Among male participants, total omega-3 fatty acids were higher in the pasture-raised ASFS consuming group (3.87 ± 0.95%) compared with the conventionally-raised ASFS consuming group (3.11 ± 1.31%). The plasma omega-6 to omega-3 ratio was significantly lower in pasture-raised ASFS consuming males (8.90 ± 1.36) compared with conventionally-raised ASFS consuming males (12.08 ± 2.88). Individual omega-3 fatty acids—including ALA, EPA, DPA, and DHA—showed trends toward higher concentrations in pasture-raised ASFS consuming males, though these differences did not reach statistical-supported differences for individual fatty acids.
Among female participants, no differences were observed in total omega-3 fatty acids, the omega-6 to omega-3 ratio, or individual fatty acid species between pasture-raised and conventionally-raised ASFS consuming groups. Major saturated and monounsaturated fatty acids did not differ between treatment groups in either sex.
Cardiometabolic Biomarkers
Changes in cardiometabolic biomarkers from baseline to week 16 were compared between treatment groups using appropriate statistical procedures. No differences were observed between pasture-raised and conventionally-raised ASFS consuming groups for any cardiometabolic outcome in either sex.
In females, the between-group difference in DBP change was not different. Similarly, changes in HDL cholesterol, LDL cholesterol, plasma glucose, SBP, total cholesterol, and triglycerides did not differ between groups.
In males, similar results were observed for all cardiometabolic markers: DBP, HDL cholesterol, LDL cholesterol, plasma glucose, SBP, total cholesterol, and triglycerides.
Overall, cardiometabolic markers remained stable throughout the intervention in both treatment groups, with no evidence of adverse effects or clinically meaningful changes attributable to the dietary intervention. Body weight and BMI also remained stable in both groups throughout the 16-wk intervention period.
We sought to chemical describe how plant materials that livestock consume influence the chemistry of meat and eggs and then how these foods influence that health of human consumers. We mostly met our objectives. Our results further attest that phytonutrients are a dominant class of nutrients responsible for separation of grass-fed and grain-fed beef, in addition to previous reports on omega-3 fatty acids, and these profiles can reliably indicate the diet of cattle.
Given that the dietary intervention could not be conducted for six or more months, consumption of only grass-fed beef may not have provided the health benefits of combining grass-fed beef with pasture-raised pork, chicken and chicken eggs. Therefore, the decision was made to combine other pasture-raised foods with grass-fed beef for the human feeding study. The randomized dietary intervention demonstrated that consumption of pasture-raised beef, pork, chicken, and eggs significantly enhanced RBC omega-3 fatty acid profiles and reduced the omega-6 to omega-3 ratio in healthy adults compared with conventionally-raised animal-source foods. These changes occurred independently of total energy intake and overall macronutrient distribution and suggest that pasture-raised animal products may represent a viable dietary strategy for improving population-level omega-3 status, particularly among individuals with low seafood consumption. Although no significant effects on traditional cardiometabolic risk markers were observed in this relatively healthy population, the improvements in omega-3 biomarkers—including a transition from high-risk to intermediate-risk omega-3 index values—support the potential for long-term cardiovascular and anti-inflammatory benefits.
Future research should explore the effects of pasture-raised animal-source foods in populations with elevated cardiometabolic risk, assess longer-term clinical outcomes (including cardiovascular events), and investigate the broader metabolic and inflammatory pathways through which these foods may influence human health. Additionally, comprehensive environmental life cycle assessments are needed to evaluate the sustainability implications of scaling pasture-based production systems. From a public health perspective, enhancing the omega-3 content of commonly consumed animal-source foods through pasture-based management and targeted feed supplementation represents a promising complementary strategy to seafood consumption for addressing the persistent omega-3 intake gap in the United States.
Lastly, the producers cooperating in this study were already producing pasture-based animal-sourced foods and plan to continue doing this. However, the findings of this research project may lead to greater demand for pasture-based animal-sourced foods and therefore more production of this type of animal-based foods.
Education
To date, oral presentations of our new information on the healthfulness of grass-fed beef and other pasture-based animal foods has been provided to farmers, ranchers and general consumers at a variety of conferences and meetings in the northcentral region of the US as well as in other areas of the US (in South Dakota, Iowa, Illinois, Missouri, Kansas, Kentucky and Oklahoma) and this information will be provided via oral presentations at more conferences and meetings in 2026.
Project Activities
Educational & Outreach Activities
Participation summary:
An update on our research project was given by Scott Kronberg at the 2025 Northern Plains Sustainable Agriculture Society Conference in Aberdeen, SD and a more advanced update of the research project will be given at the 2026 Northern Plains Sustainable Agriculture Society Conference will be given by Scott in January of 2026.
Learning Outcomes
- How the healthfulness of beef and other pasture-raised animal-based foods can be improved by raising them on pasture where they can eat a variety of plant species and obtain a great variety of healthful compounds from the plants.
Project Outcomes
Improving the forage species diversity of pastures and increase production of beef, pork, chicken and chicken eggs raised on forage-based diets.
A research project evaluating the effect on different types of supplements fed to pasture-raised pigs and chickens on the nutrition content of pork, chicken meat and eggs would provide very useful information to farmers raising pasture-based pork, chickens and chicken eggs.