Researchers have identified nearly 200 different lipid molecules in Japanese rice varieties, with pigmented strains – particularly black and green rice – exhibiting a unique composition linked to potential health benefits. The findings, published in January 2026 in the journal Food Research International, could lead to the development of new functional foods aimed at managing blood sugar and reducing the risk of lifestyle-related diseases.
The study, conducted by a team at Hokkaido University, focused on 56 cultivars of japonica rice, a short- to medium-grain variety widely consumed in Japan and accounting for approximately 15% of global rice production. While rice is primarily known for its starch content – comprising over 85% of the grain – researchers are increasingly recognizing the importance of its smaller lipid component, which plays a role in nutrition, flavor, and overall grain quality. “Even though lipids develop up only a small proportion of rice, they are critical in determining its nutritional value,” explained lead author Associate Professor Siddabasave Gowda.
Advances in analytical technologies, including liquid chromatography and mass spectrometry, enabled the team to identify 196 distinct lipid molecules categorized into five major groups. The analysis revealed that black and green rice varieties contain potentially beneficial fats, including fatty acid esters of hydroxy medium-chain fatty acids (FAHMFAs) and N-acyl-lysophosphatidylethanolamines (LNAPEs). This marks the first identification of FAHMFAs in rice, according to the researchers. Previous studies have suggested that these compounds possess anti-inflammatory properties and may contribute to improved metabolic health.
To assess the impact of these pigmented rice varieties on blood sugar levels, the researchers simulated human digestion in a laboratory setting. Cooked rice samples were exposed to digestive enzymes, allowing them to measure the rate at which starches were broken down – a key indicator of how quickly a particular type of rice can raise blood glucose. Results showed that black and green japonica rice resulted in a slower rise in blood sugar compared to typical white rice, suggesting a slower digestion rate and more gradual release of glucose into the bloodstream.
These findings align with broader research into the role of lipids in starch digestibility. Studies have shown that lipid complexation can reduce rice starch digestibility, as demonstrated in research involving rice varieties with differing amylose and lipid contents (Nature, 2023). Further research has explored how removing or adding specific lipid classes to rice flour affects in vitro starch digestibility (Foods, 2022).
Gowda added that his research group has previously identified novel bioactive lipids in other Japanese dietary staples, including fish, herbal teas, and seaweeds, contributing to a growing understanding of the country’s under-explored lipid-rich food resources. “People may be interested in learning about the health benefits of different pigmented rice varieties and, based on this knowledge, choosing the type that best suits their needs,” Gowda stated. The researchers hope their findings will support the development of new “functional” rice products designed to help manage diabetes and other lifestyle-related diseases.