Summary

A Hokkaido University study of 56 japonica rice varieties identified 196 lipid molecules and found distinctive lipid profiles in black and green rice. These varieties also showed slower starch breakdown than typical white rice in a laboratory digestion model.

A Hokkaido University study of 56 japonica rice cultivars collected across Japan found that black and green rice had distinctive lipid profiles and slower starch breakdown than typical white rice in a laboratory digestion test. The researchers identified 196 lipid molecules, including a class called FAHMFAs that had not previously been identified in rice.

The findings were published in Food Research International in January 2026. They add detail to the nutritional differences between rice varieties, while the health-related results remain based on chemical analysis and simulated digestion rather than a human feeding study.

Contents

What the researchers measured

Rice is composed mostly of starch: more than 85% by weight, according to the university, with about 10% protein and roughly 2% fat. Although lipids make up a small fraction of the grain, they contribute to cell structure, energy storage, signalling, flavour and grain quality.

The research team examined 56 japonica varieties, including brown, red, green and black rice. Japonica rice is generally short- to medium-grain, soft and slightly sticky when cooked, and represents roughly 15% of global rice consumption.

The researchers used liquid chromatography and mass spectrometry to separate and identify lipid molecules in the samples. The analysis found 196 lipid types belonging to five major groups, providing a detailed chemical profile of the varieties.

Distinctive lipids in pigmented rice

The colourful varieties, particularly black and green rice, were reported to have a higher health-promotion index based on their lipid composition. They contained FAHMFAs, or fatty acid esters of hydroxy medium-chain fatty acids, as well as LNAPEs, a group known as N-acyl-lysophosphatidylethanolamines.

FAHMFAs are the most distinctive finding in the study because this is the first reported identification of the lipid class in rice. Earlier research in other biological systems has linked FAHMFAs and LNAPEs with anti-inflammatory effects and aspects of metabolic health. In this study, they are best understood as candidate bioactive compounds identified in particular rice varieties, rather than as demonstrated human health treatments.

A laboratory signal for slower starch digestion

The team also tested how the rice samples behaved during simulated human digestion. After cooking, selected samples were exposed to digestive enzymes, and the researchers measured how quickly their starch broke down.

Black and green japonica rice showed slower starch breakdown than typical white rice in this assay. Slower breakdown is used as a laboratory indicator that starch may become available for absorption more gradually, potentially producing a less rapid rise in blood glucose after a meal.

Because this part of the work used an in-vitro digestion model, it provides evidence about the samples' composition and behaviour under controlled laboratory conditions. Actual glucose responses in people can also vary with serving size, cooking and processing, the rest of a meal, and individual physiology.

Why the finding matters

The results show that rice varieties can differ not only in colour and taste but also in their detailed lipid composition and starch-digestion behaviour. That gives food scientists and plant breeders additional characteristics to investigate when developing rice with specific nutritional properties.

Hokkaido University says the findings could support the development of functional rice products intended to help manage blood sugar and other lifestyle-related conditions. The immediate evidence supports further research and product development: the study itself did not include human participants or clinical health outcomes.

The work also illustrates why rice lipids are receiving more attention. Even though they represent only a small part of the grain, modern lipidomic methods can reveal compounds that conventional nutritional measurements would group together or overlook.

Sources