Rice feeds more than half the world’s population. Most of us think of it as almost entirely starch, and for the most part, that is accurate. More than 85% of rice is carbohydrate. But scientists are learning that even the small fraction made up of fats may influence how rice behaves in the body.
In a study published in Food Research International, researchers at Hokkaido University analyzed 56 japonica rice varieties grown across Japan. Japonica rice is the short- to medium-grain rice commonly eaten in Japan and used in dishes like sushi. The team examined white, brown, red, green and black cultivars to better understand their lipid composition.
Although fats account for only about 2% of rice by weight, lead author Associate Professor Siddabasave Gowda said they may play an outsized role.
“Although lipids make up only a small proportion of rice, they are critical in determining its nutritional value,” he explained.
Using advanced laboratory techniques, the researchers identified 196 different lipid molecules across the rice samples. Pigmented varieties, especially black and green rice, stood out. They contained higher levels of certain lipid compounds, including FAHMFAs and LNAPEs. These compounds have previously been linked in cell and animal studies to anti-inflammatory activity and metabolic effects. The authors report this is the first time FAHMFAs have been identified in rice.
The team also examined how quickly starch from different rice types broke down using a simulated digestion model. In this lab system, cooked black and green rice released glucose more slowly than typical white rice. Slower breakdown during digestion generally suggests a more gradual rise in blood sugar after a meal.
However, these findings come from laboratory simulations, not human feeding trials. The study did not test how people’s blood sugar actually responds after eating these rice varieties. That distinction matters. While the results are promising, they do not prove that switching to black or green rice will improve blood sugar control in real-world settings.
For everyday eaters, the takeaway is not that white rice is harmful. Instead, the research adds to a growing body of evidence that whole and pigmented grains may contain additional bioactive compounds beyond starch. As always, overall dietary patterns matter more than any single food choice.
The study was supported by Japanese government research grants aimed at advancing food and agricultural science.