An interventional study of High Palmitic Acid Diet and High Stearic Acid Diet in CVD Risk, sponsored by Tufts University. Not yet recruiting at 1 site in United States. Open to female participants aged 50 Years and older. Per ClinicalTrials.gov, last updated 2026-08-17.
Sponsored by Tufts University · Not applicable, Interventional, and Basic science
Stearic acid and palmitic acid are two common consumed saturated fatty acids found in foods. Palmitic acid is associated with increases in blood cholesterol, whereas stearic acid is generally considered neutral with respect to blood cholesterol. However, the mechanisms underlying these different effects are not fully understood. The goal of this clinical trial is to determine how replacing dietary palmitic acid with stearic acid affects microorganisms living in the gastrointestinal tract (gut microbiome) and the metabolites they produce, including secondary bile acids, and whether these changes influence heart and metabolic health in postmenopausal women. The main question it aims to answer is whether the cholesterol lowering effect of dietary stearic acid, compared to dietary palmitic acid is due to changes in the composition and function of the gut microbiome and bile acid metabolism. Participants will consume a controlled diet high in palmitic acid for a 10-day run-in period, followed by a controlled diet high in stearic acid for 28 days. During the study, participants will provide biological samples, including blood samples collected in both fasting and non-fasting states, for assessment of cardiometabolic outcomes. Participants will also swallow mini-pills designed to collect samples from different regions of the gastrointestinal tract to assess the gut microbiome and related metabolites. Results will contribute to understanding the relationship between stearic acid mediated microbiota effects on cardiometabolic heath.
Stearic acid (18:0) is unique among saturated fatty acids (SFAs) as it does not increase cardiovascular disease (CVD) risk. Prior work by the study investigators suggests that gut microbiome-mediated alterations in secondary bile acid (BA) metabolism as a potential mechanism for the cholesterol-lowering effects of 18:0. However, to test this hypothesis the investigators were limited to traditional fecal sampling methods, which primarily reflect colonic microbes and do not capture regional heterogeneity in microbial communities or BA transformations which occur mainly in the small intestine. Using a novel ingestible device (mini-pill) which provides real-time sampling of the gastrointestinal environment, this study aims to comprehensively investigate the impact of dietary 18:0 on gut microbial BA transformations in modulating cardiometabolic risk. The study design includes a controlled 38-day dietary intervention trial in post-menopausal females using whole-foods enriched in commercially available sources of 18:0. The objectives are to determine the effect of dietary 18:0 on (i) microbiome composition and BA related functional pathways along the GI tract relative to stool; (ii) BA profiles along the GI tract, in stool and plasma; and (iii) FXR activation (reflected by FGF19 levels) and endogenous cholesterol synthesis in mediating the association between BA metabolizing microbes and BA profiles on CVD risk factors. Fecal whole-genome shotgun sequencing, targeted BA profiling, and bioinformatics will be used to address these objectives. Results will contribute to optimizing dietary/nutrient-labeling guidance to reduce CVD risk by expanding the evidence-base for classifying 18:0 and may offer novel strategies for preventing heart disease by targeting specific gut microbes or BA pathways.
Tufts University is the lead sponsor of 228 studies on the registry; 23 are open to participants now.
Of its 11 completed or terminated interventional studies of FDA-regulated products, 8 (73%) have results posted.
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Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Periods have stopped for good: usually no period for 12 months in a row without another medical reason, sometimes confirmed by a blood test (FSH).
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Postmenopausal
Periods have stopped for good: usually no period for 12 months in a row without another medical reason, sometimes confirmed by a blood test (FSH).
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
BMI (body mass index)
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
A controlled 38-day intervention with a10 day run-in phase with a diet high in palmitic acid to stabilize baseline variables, followed by a 28 diet phase with a diet high in stearic acid
Other: High Palmitic Acid Diet · Other: High Stearic Acid Diet
The main source of palmitic acid that will be used to prepare the meals will include blends of palm oil and safflower oil, which are commercially available. These blends will be incorporated into foods such as muffins, cookies, sauces, and mixed dishes (e.g., casseroles).
The main source of stearic acid that will be used to prepare the meals will include blends of cocoa butter, fully hydrogenated soybean and safflower oil, all of which are commercially available. These blends will be incorporated into foods such as muffins, cookies, sauces, and mixed dishes (e.g., casseroles).
Relative Abundance of Gut Microbial Taxa (%)
Gut microbial composition in gastrointestinal luminal and stool samples will be assessed using whole-genome shotgun metagenomic sequencing and reported as relative abundance (%). Alpha and beta diversity will also be evaluated as part of the microbiome analyses.
Time frame: End of the 10-day palmitic acid run-in period and end of the 28-day stearic acid intervention period.
Relative Abundance of Gut Microbial Functional Pathways (%)
Gut microbial functional pathways in gastrointestinal luminal and stool samples will be assessed from whole-genome shotgun metagenomic sequencing data using bioinformatic pathway analysis and reported as relative abundance (%). Analyses will include pathways related to bile acid metabolism as well as other microbial metabolic pathways.
Time frame: End of the 10-day palmitic acid run-in period and end of the 28-day stearic acid intervention period.
Concentrations of Bile Acids in Gastrointestinal Luminal Samples (nmol/mL)
Primary and secondary bile acids, including conjugated and unconjugated bile acids, will be quantified in gastrointestinal luminal samples using targeted mass spectrometry and reported as nmol/mL.
Time frame: End of the 10-day palmitic acid run-in period and end of the 28-day stearic acid intervention period.
Concentrations of Bile Acids in Plasma (nmol/mL)
Primary and secondary bile acids, including conjugated and unconjugated bile acids, will be quantified in fasting and postprandial plasma using targeted mass spectrometry and reported as nmol/mL.
Time frame: End of the 10-day palmitic acid run-in period and end of the 28-day stearic acid intervention period.
Concentrations of Bile Acids in Stool (nmol/mg dry weight)
Primary and secondary bile acids, including conjugated and unconjugated bile acids, will be quantified in stool using targeted mass spectrometry, normalized to fecal dry weight, and reported as nmol/mg dry weight.
Time frame: End of the 10-day palmitic acid run-in period and end of the 28-day stearic acid intervention period.
Plasma Metabolite Concentrations (µmol/L)
Plasma metabolites will be measured using targeted metabolomic profiling and reported as concentrations in µmol/L.
Time frame: End of the 10-day palmitic acid run-in period and end of the 28-day stearic acid intervention period.
Fecal Metabolite Concentrations (nmol/mg dry weight)
Fecal metabolites will be measured using targeted metabolomic profiling, normalized to fecal dry weight, and reported as nmol/mg dry weight.
Time frame: End of the 10-day palmitic acid run-in period and end of the 28-day stearic acid intervention period.
Serum Cholesterol metabolism markers
Cholesterol synthesis markers (squalene, desmosterol, lathosterol) and cholesterol absorption markers (phytosterols) will be measured using gas-liquid chromatography, normalized to total cholesterol, and reported as 10² mmol/mol total cholesterol.
Time frame: End of the 10-day palmitic acid run-in period and end of the 28-day stearic acid intervention period.
Fibroblast growth factor 19 (FGF19) Concentration (ng/mL)
Fibroblast growth factor 19 (FGF19) concentrations in distal ileum contents and plasma will be measured using a human FGF19 ELISA and reported as ng/mL.
Time frame: End of the 10-day palmitic acid run-in period and end of the 28-day stearic acid intervention period.
Plasma Lipid Concentrations (mg/dL)
Plasma HDL cholesterol and triglyceride concentrations will be measured using enzymatic assays. LDL cholesterol will be calculated using the Friedewald formula. Individual lipid measures will be reported in mg/dL.
Time frame: End of the 10-day palmitic acid run-in period and end of the 28-day stearic acid intervention period.
Serum Glucose Concentration (mg/dL)
Serum glucose concentration will be measured using an enzymatic assay and reported in mg/dL.
Time frame: End of the 10-day palmitic acid run-in period and end of the 28-day stearic acid intervention period.
Serum Insulin Concentration (µIU/mL)
Serum insulin concentration will be measured using radioimmunoassay (RIA) and reported in µIU/mL.
Time frame: End of the 10-day palmitic acid run-in period and end of the 28-day stearic acid intervention period.
Serum High-Sensitivity C-Reactive Protein Concentration (mg/L)
Serum high-sensitivity C-reactive protein (hsCRP) concentration will be measured using a chemiluminescent immunoassay and reported in mg/L.
Time frame: End of the 10-day palmitic acid run-in period and end of the 28-day stearic acid intervention period.
Serum IL-6 and TNF-α Concentrations (pg/mL)
Serum interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) concentrations will be measured using a multiplex immunoassay and reported in pg/mL.
Time frame: End of the 10-day palmitic acid run-in period and end of the 28-day stearic acid intervention period.
Plan to share: Yes — De-identified individual participant data underlying the results reported in publications arising from this study will be shared. This includes demographic characteristics, baseline measures, intervention exposure data, outcome measures, and other variables necessary to reproduce the primary and secondary analyses reported in study publications. All direct identifiers will be removed prior to data sharing.
Supporting information: Analytic code
Time frame: Data will be available beginning 6 months after publication of the primary study results and up to 7 years, thereafter.
Access criteria: De-identified individual participant data and supporting study documentation will be made available to researchers and the public through established data repositories, as appropriate. Data generated from this study may be deposited in repositories such as the Ag Data Commons, the National Agricultural Library, the Human Metabolome Database (HMDB), and the National Center for Biotechnology Information (NCBI) Sequence Read Archive (SRA), consistent with repository requirements and applicable regulations. Supporting information, including study protocols, data dictionaries, metadata, and analytic documentation, will be provided as appropriate to facilitate data reuse. Data will be accessible through the respective repository access procedures and policies.
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