Increased Whole-Food Flaxseed Supplementation Linked to Improved Liver Fat, Metabolic Health and Gut Microbiota in NAFLD

Written by Keely Puchalski, ND. Results from a 12-week randomized controlled trial suggest that daily supplementation with 30 g of whole-food flaxseed powder may significantly reduce intrahepatic lipid content, improve body composition, liver function and lipid profiles, while beneficially modulating gut microbiota in obese adults with Non‑alcoholic fatty liver disease (NAFLD).

bowl of flaxseedNon-alcoholic fatty liver disease (NAFLD) — also referred to as metabolic dysfunction-associated steatotic liver disease (MASLD) — is a leading and growing global public-health problem characterized by excess hepatic fat accumulation in people who consume little or no alcohol1. A large body of epidemiologic work shows the prevalence of NAFLD has risen sharply worldwide over recent decades, with pooled estimates commonly reported in the ~30-38% range depending on diagnostic method, and higher rates observed in men and in regions with rising obesity and type 2 diabetes2-4. In the United States, national estimates put adult NAFLD prevalence at roughly 24% (with NASH present in a smaller proportion), and NASH is among the fastest-increasing indications for liver transplantation5,6. The rising burden parallels global increases in obesity, type 2 diabetes, and sedentary lifestyles, and because NAFLD can progress to NASH, fibrosis, cirrhosis and hepatocellular carcinoma, early dietary and metabolic interventions are a priority for reducing long-term liver morbidity and related cardiometabolic risks7-9. Emerging nutritional research suggests that flaxseed supplementation or flaxseed oil may help reduce liver fat accumulation, visceral adiposity, and related metabolic risk markers in adults with fatty liver and/or overweight/obesity10,11.

To evaluate the relationships between flaxseed supplementation, hepatic fat, metabolic parameters and gut microbiota, Tian, et al. (2025) conducted a randomized controlled clinical trial in China. Participants (n = 50 completers: flaxseed group n = 25; control group n = 25) with diagnosed NAFLD (via MRI-PDFF ≥ 5 %) were enrolled. The flaxseed group received 30 g per day of flaxseed powder in water consumed before lunch or dinner for 12 weeks along with health education, while the control group received health education alone. Flaxseed participants were not blinded – the study authors reported difficulty finding a comparable placebo. The primary outcome was intra‐hepatic lipid content measured by magnetic resonance imaging proton density fat fraction (MRI-PDFF). All MRIs were conducted by the same examiner. Key secondary outcomes included body composition (body fat %, visceral fat area), liver function (TBIL, DBIL, IBIL, AST), and lipid metabolism (TC, TG, HDL-C, ApoA1). Gut microbiota changes were also assessed via 16S rRNA sequencing of fecal samples.

Key Findings:

  • Liver fat content: The flaxseed group had a significant reduction in liver fat (MRI-PDFF −5.28% from baseline; p = 0.006) and compared with the control group (−1.23%; p = 0.225). Between-group difference: p = 0.001.
  • Subgroup effect (moderate NAFLD): Among participants with moderate NAFLD (MRI-PDFF 10–25%), liver fat in the flaxseed group decreased by −8.87% (p = 0.006) from baseline.
  • Body composition: In the flaxseed group, body fat percentage decreased (−6.40% ± 2.16; p = 0.001) and visceral fat area decreased from baseline (−28.90 cm²; p = 0.017).
  • Liver function biomarkers improved: In the flaxseed group, TBIL, DBIL, IBIL, and AST decreased significantly (all p < 0.05) from baseline. Changes in the control group were minimal and not statistically significant.
  • Lipid profile improved: Triglycerides (TG) decreased by 0.40 mmol/L, HDL-C increased by 0.10 mmol/L, and ApoA1 increased by 0.12 mmol/L in the flaxseed group (all p < 0.05). Control group changes were negligible.
  • Gut microbiota shifts: Flaxseed supplementation increased Bacteroidetes and Actinobacteria, decreased Firmicutes (a phylum often elevated in obesity), and at the genus level increased Clostridium_sensu_stricto_1, Parasutterella, Lachnospiraceae_NK4A136_group, Eubacterium_xylanophilum_group, and Bifidobacterium, while decreasing Coriobacteriaceae_UCG-002 from baseline (all p < 0.05).
  • Correlation analyses: Increased Bifidobacterium was positively correlated with ApoA1 and HDL-C and negatively correlated with AST, TBIL, DB IL, IBIL, LDL-C, LP(a), TC, and TG (p < 0.05). Clostridium_sensu_stricto_1 was negatively correlated with glucose (p < 0.05), and Coriobacteriaceae_UCG-002 was positively correlated with ALT, AST, DBIL, and TG (p < 0.05).

The study demonstrated that daily intake of flaxseed powder over 12 weeks led to statistically significant reductions in liver fat content among obese adults with NAFLD, as measured by MRI-PDFF, compared with placebo. Improvements were also seen in lipid profiles and body composition, alongside favorable shifts in gut microbiota diversity and composition.

Using MRI-PDFF, a non-invasive and highly reliable imaging technique, strengthened the quality of these findings. The randomized controlled design and inclusion of microbiota analysis added further depth by exploring potential mechanisms behind the observed benefits. However, the modest sample size (n = 50) and relatively short intervention period limit generalizability, and only one dosage (30 g/day) was tested. Liver biopsy data were not collected, leaving histologic effects – such as inflammation or fibrosis – unclear.

The authors suggest that flaxseed’s α-linolenic acid (ALA), lignans, and soluble dietary fiber may reduce hepatic lipid synthesis, enhance insulin sensitivity, modulate inflammatory responses, and beneficially alter gut microbiota, collectively improving hepatic fat metabolism.

Overall, the authors concluded that flaxseed powder supplementation may represent a promising nutritional approach for individuals with NAFLD, given the measurable improvements in liver fat, lipid metabolism, and gut microbial composition. They emphasized that these findings are preliminary, supportive of previous similar trials, and warrant larger and longer-term trials in broader populations to confirm efficacy, determine optimal dosing, and clarify mechanisms.

Source: Tian, Yanyan, Yuhao Zhou, Wang Liao, Jiayue Xia, Qiaosheng Hu, Qing Zhao, Rui Zhang, Guiju Sun, Ligang Yang, and Lihua Li. “Flaxseed powder supplementation in non-alcoholic fatty liver disease: A randomized controlled clinical trial.” Food & Function 16, no. 4 (2025): 1389-1406.

Open Access Article

Click here to read the full text study.

Posted March 19, 2026.

Keely Puchalski, ND, is a licensed naturopathic physician and natural products expert with a clinical focus on mental health. She earned her ND from Sonoran University of Health Sciences (formerly Southwest College of Naturopathic Medicine) in 2020. Dr. Puchalski has conducted original research in botanical medicine, with discoveries leading to multiple patents and high-impact journal publications. She has authored eight peer-reviewed papers and presented her work at national conferences, webinars, and educational events.

She is the co-founder of Restored Counseling & Wellness Center in Gilbert, AZ, where she leads a collaborative team of therapists and naturopathic doctors dedicated to integrative mental health care:  https://restoredcw.com.

References:

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