The health benefits of multigrain rice depend less on how many grains are mixed in than on maintaining the right ratio. Around five grain varieties, with a rice-to-multigrain ratio of about 4 to 1, is the generally recommended standard. Exceeding this level can reduce antioxidant content or cause side effects from excessive dietary fiber intake.
Multigrains are recommended over white rice because of the milling process. Less-milled grains are rich in micronutrients such as vitamins and minerals, as well as dietary fiber, which helps blood sugar rise gradually after meals. Although levels vary by grain type, multigrains generally contain about 5 to 8 grams of dietary fiber per 100 grams. In a study published in the Journal of the Academy of Nutrition and Dietetics, 20 adults consumed multigrain rice and white rice, and the glycemic index (GI) was measured at about 69 for multigrain rice and about 86 for white rice. The glycemic index indicates how quickly carbohydrates raise blood sugar as they are digested and absorbed. A domestic study also found that multigrain rice containing 40% barley showed gentler rises and falls in blood sugar than white rice. However, GI values vary widely depending on milling, cooking methods, and measurement conditions, so they are generally interpreted as relative differences rather than absolute values.
A domestic study has also examined the link to breast cancer. According to an analysis by a research team at Seoul National University College of Medicine, women who ate more white rice than multigrain rice had a 35% higher risk of developing breast cancer compared with the control group. Meanwhile, among women under 50, those who ate multigrain rice three or more times a day had a 33% lower risk than those who ate it once or less. The researchers suggested that dietary fiber in multigrains helps eliminate carcinogens and waste, while vitamin E inhibits the formation of carcinogens. However, as this is an epidemiological study examining correlation, it is difficult to conclude that consuming multigrains directly prevents breast cancer.
Indiscriminately increasing the variety of grains can actually reduce the benefits. A domestic study comparing the nutritional content of 5-, 8-, 16-, 17-, 20-, and 25-grain multigrain rice products on the market found that mixing five varieties produced the highest antioxidant content, according to a report in the Korean Journal of Food and Nutrition. Increasing the number of grain varieties beyond that actually reduced the content.
The ratio is another variable. When the proportion of multigrains becomes excessively high, dietary fiber intake per meal (300 grams) can rise to 15 to 20 grams. The adequate daily intake of dietary fiber for adults set by the Korean Nutrition Society and the Ministry of Health and Welfare is 25 grams for men and 20 grams for women, meaning that a single meal can come close to a full day's worth. Excessive dietary fiber intake can cause abdominal bloating, gas, or constipation. Some analyses suggest that exceeding 60 grams a day can impair the absorption of minerals such as iron, calcium, magnesium, and zinc, as well as vitamins. People with weak digestion may find multigrain rice burdensome on the stomach, so intake should be adjusted. For young children, it is recommended to begin mixing in one type of grain at a time starting at age 4, gradually increasing the amount and variety. Starting with softer-textured grains such as foxtail millet or proso millet, and adjusting the proportion of white rice accordingly, can help reduce resistance.
