Regular amazake intake has been shown to support digestive health by improving bowel regularity, stool quality, and overall intestinal function. It can significantly reduce constipation symptom burden.

One contributor to these effects is Aspergillus oryzae koji cells generated during fermentation. These microbial cell components support the mechanical aspects of digestion and promote intestinal transit. Additionally, fermentation derived proteins and oligosaccharides contribute to stool bulk and support waste movement through the intestines. These help normalize bowel habits, and clinical trials consistently show improvement in bowel movement frequency.

Preclinical studies also show that amazake consumption enhances the expression of occludin, a protein critical for maintaining gut barrier function.

Digestive benefits observed in clinical studies were associated with favorable changes in the gut microbiota. Regular amazake intake has been shown to increase beneficial bacterial groups (Bifidobacterium and Lactobacillales) while decreasing potentially inflammatory taxa (Escherichia-Shigella.) These microbiome shifts were observed alongside improvements in constipation assessment scores and stool form, suggesting that modulation of the intestinal ecosystem contributed to enhanced digestive function.

Therefore, clinical research suggests that amazake supports digestive health through a multifaceted mechanism: improving bowel regularity and stool characteristics, supporting intestinal transit, reinforcing gut barrier integrity, and fostering a microbiome environment associated with healthy digestion.

Clinical Research Studies  

“Ingredients, Functionality, and Safety of the Japanese Traditional Sweet Drink Amazake“, DOI: 10.3390/jof7060469, June 2021 

“Effects of Amazake Made from Sake Lees and Rice Koji on Bowel Movements: A Randomized, Placebo-Controlled, Parallel-Group Comparative Study”, PIER: 47050/759, 2019 

“Effect of malted-rice amazake on intestinal environment”, DOI: 10.1254/jpssuppl.92.0_2-P-134, March 2019 

“Effects of amazake consumption on constipation”, DOI: 10.18892/jsnas.16.0_36, 2017 

“The effects of oral intake of amazake on lipid metabolism”, J-GLOBAL ID: 202302290877897346, March 2023 

“Changes in the fecal gut microbiome of home healthcare patients with disabilities through consumption of malted rice amazake”, DOI: 10.1152/physiolgenomics.00062.2023, December 2023 

“Effects of Malted Rice Amazake on Constipation Symptoms and Gut Microbiota in Children and Adults with Severe Motor and Intellectual Disabilities: A Pilot Study”, DOI: 10.3390/nu13124466, December 2021 

“Effects of Koji amazake and Its Lactic Acid Fermentation Product by Lactobacillus sakei UONUMA on Defecation Status in Healthy Volunteers with Relatively Low Stool Frequency”, DOI: 10.3136/fstr.25.853, August 2019 

“Intake of Koji Amazake Improves Defecation Frequency in Healthy Adults”, DOI: 10.3390/jof7090782, September 2021 

Clinical research has shown that regular amazake consumption can improve skin health across multiple dimensions, including hydration, elasticity, skin barrier function, texture  and oil balance.

One of the most consistently observed benefits is improved skin hydration and moisture retention. Glucosylceramide, a bioactive lipid naturally present in amazake as a result of fermentation supports epidermal hydration and barrier integrity.

Research has also shown improved skin elasticity and firmness, and reduction in pore sagging. These clinical outcomes are supported by complementary cell-based studies showing extracts derived from rice koji can stimulate fibroblast-mediated collagen gel contraction and suppress matrix metalloproteinases, providing a possible biological basis for the elasticity and firmness improvements observed in humans.  

Amazake also positively influences skin texture and appearance. Clinical studies show reduced facial sebum content, suggesting improved oil balance and regulation of lipid accumulation. As well as improved under-eye brightness, reduced skin redness and reduced brown spots.

Ingesting amazake regularly was therefore shown to support skin hydration, barrier integrity, elasticity, texture and oil balance, contributing to overall skin health and appearance.

Clinical Research Studies 

“Investigation of the Effects of Amazake Intake on Skin: A Randomized, Double-Blind, Placebo-Controlled, Parallel-Group Comparative Study", PIER: 46110/1841, 2018 

“Effect of intake of amazake on skin barrier functions in healthy adult women subjects -A randomized, double-blind, placebo-controlled study”, JP PHARMACOLOGY: 45(11):1811-1820, January 2017 

"Effects of Rice Koji Amazake Intake on Skin: A Randomized, Double-Blind, Placebo-Controlled, Parallel-Group Comparative Study", PIER: 47080/1269, 2019 

“Koji amazake Maintains Water Content in the Left Cheek Skin of Healthy Adults: A Randomized, Double-Blind, Placebo-Controlled, Parallel-Group, Comparative Trial“, DOI:10.2147/CCID.S366979, July 2022 

“Amazake made from sake cake and rice koji suppresses sebum content in differentiated hamster sebocytes and improves skin properties in humans”, DOI: 10.1080/09168451.2020.1756734, August 2020 

"Effects of Hot Water Extracts of Sake Lees and Rice Koji on Collagen Gel Contraction by Cultured Fibroblasts, and on MMPs and Lipid Production in Sebaceous Gland Cells", PIER:46120/1985, 2018 

“Ingredients, Functionality, and Safety of the Japanese Traditional Sweet Drink Amazake”, DOI: 10.3390/jof7060469, June 2021 

Clinical research demonstrates that regular amazake consumption can positively modulate the gut microbiome, contributing to improvements in intestinal balance and digestive function.

One of the most consistently reported findings is an increase in beneficial bacterial groups, including Bifidobacterium. This genus is widely associated with gut health due to its role in supporting the intestinal barrier, promoting normal bowel function, and contributing to the synthesis of certain B vitamins. In amazake studies, increases in Bifidobacterium were observed alongside significant improvements in constipation assessment scores.

Amazake has been shown to increase the relative abundance of Lactobacillales and Bacteroides, while reducing potentially unfavorable or inflammatory taxa such as Escherichia-Shigella. These microbial shifts occurred concurrently with improvements in overall bowel comfort, stool consistency and stool frequency.

In some studies, amazake intake was associated with a more balanced Firmicutes to Bacteroidetes ratio, often associated with improved intestinal function and metabolic efficiency.

Amazake is prebiotic by providing a combination of fermentation-derived components including Aspergillus oryzae koji cells, oligosaccharides and resistant proteins. These support the growth and activity of beneficial bacterial populations.

Amazake’s clinical and preclinical evidence suggests that it supports microbiome health by increasing beneficial bacteria, reducing potentially inflammatory taxa, and promoting a more balanced microbial ecosystem.

Clinical Research Studies 

“Effect of malted-rice amazake on intestinal environment”, DOI: 10.1254/jpssuppl.92.0_2-P-134, March 2019 

“Changes in the fecal gut microbiome of home healthcare patients with disabilities through consumption of malted rice amazake”, DOI: 10.1152/physiolgenomics.00062.2023, December 2023 

“Intake of Koji Amazake Improves Defecation Frequency in Healthy Adults”, DOI: 10.3390/jof7090782, September 2021 

Research on long-distance runners has shown that regular amazake consumption can reduce endurance training fatigue. Amazake’s fermentation with Aspergillus oryzae increases the availability of free amino acids, including all essential amino acids required for muscle tissue maintenance. In addition, amazake provides glucose, supporting glycogen store replenishment after prolonged exercise. Together, these nutrients help support energy recovery, muscle tissue maintenance, and overall physical resilience in endurance athletes. 

Clinical Research Studies 

"Effects of Rice Koji Amazake Intake on Localized Physical Fatigue and Subjective Symptoms During Training in Track and Field Athletes", NDL BIB ID: 030077717, October 2019 

“Ingredients, Functionality, and Safety of the Japanese Traditional Sweet Drink Amazake“, DOI: 10.3390/jof7060469, June 2021 

Studies show that amazake provides antioxidant support through the fermentation-driven enhancement of antioxidant activity. Food chemistry analyses have demonstrated that amazake exhibits measurable free-radical–scavenging activity, including DPPH radical-scavenging and lipid-peroxidation–inhibitory activity. 

This antioxidant activity develops during the koji production and saccharification process, as enzymes produced by Aspergillus oryzae cultures act on rice components to generate antioxidant-active compounds. Fermentation increases the availability of free ferulic acid and other phenolic compounds. Ferulic acid is a well characterized antioxidant known for its stability and protective properties. Ergothioneine, a rare antioxidant amino acid associated with cellular protection against oxidative stress, has also been reported as a component of amazake.

Clinical Research Studies  

“Effects of koji Production and Saccharification Time on the Antioxidant Activity of amazake”, DOI: 10.3136/fstr.13.162, 2007 

“Radical Scavenging Activity of the Japanese Traditional Food, Amazake”, DOI: 10.3136/fstr.17.209, 2011 

“Liposoluble Antioxidative Components in Japanese Traditional Fermented Food "Amazake’ Made from Brown Rice”, DOI:10.4172/2155-9821.1000317, January 2018 

“Changes in Polyphenol Content during the manufacturing process of Amazake”, ISSN: 2186-5574, 2022 

“Ingredients, Functionality, and Safety of the Japanese Traditional Sweet Drink Amazake“, DOI: 10.3390/jof7060469, June 2021 

"Development and Functional Evaluation of Amazake Ice Cream Made with Gifu Prefecture Rice (Hatsushimo), Black Glutinous Rice, and GABA-Enriched Rice", DOI: 10.11274/bimi.17.2_55, 2018   

Clinical studies indicate that regular amazake consumption can reduce perceived fatigue and support recovery from daily mental and physical load. Benefits have been observed in contexts involving sustained activity, cumulative stress, and metabolic demand. Amazake intake has been shown to significantly increase the sense of relief from fatigue and improve mood-related measures. These findings suggest that amazake can attenuate fatigue perception after exertion, supporting faster subjective recovery. 

Clinical Research Studies  

"Effects of Amazake Made from Sake Lees and Rice Koji on Daily Fatigue: A Randomized, Double-Blind, Placebo-Controlled Crossover Trial", PIER: 48110/1925, 2020 

"Effects of Rice Koji Amazake Intake on Localized Physical Fatigue and Subjective Symptoms During Training in Track and Field Athletes", NDL BIB ID: 030077717, October 2019 

“Ingredients, Functionality, and Safety of the Japanese Traditional Sweet Drink Amazake”, DOI: 10.3390/jof7060469, June 2021