How rice is milled, and why people dieting choose brown rice

Rice names split on milling more than on color. Remove only the husk and the bran and germ remain: that is brown rice. Mill those layers away and it is white rice. Pre-germinated brown rice is brown rice soaked until it sprouts. Black rice is a grain whose bran carries pigment. Glutinous rice is a starch with almost no amylose, which is a different cut from milling. People who are dieting reach for brown rice because of that bran. One trial measured the difference on a single batch of grain.

What the studies looked at

Geng Zhang and colleagues, in 2011, fed one batch of brown rice and the white rice milled from it for 16 weeks. The participants were 202 middle-aged adults in China with metabolic syndrome or a high risk of diabetes. Each group had 101 people, randomized in strata of sex and 5-year age band. Mean age was 49.8 years in the white-rice group (SD 7.1) and 49.6 in the brown-rice group (SD 6.7). Mean BMI was 25.4 and 25.9.

Rice was served at a campus cafeteria for lunch, Monday through Friday. Dinner and Saturday portions were taken home. Other staple foods were allowed only on Sunday. A 225 g portion of cooked rice was 100 g of dry rice. The rice-to-water ratio was 1:1 for white rice and 1:1.25 for brown rice, and the brown rice was soaked for at least 1 hour. People ate as much as they wanted. The meals were not a prescribed calorie cut. Adherence was 90.9% for white rice (SD 17.1) and 88.7% for brown rice (SD 23.2). Of the 202 people, 193 (95.5%) finished the 16 weeks.

The same paper measured the glycemic index of this rice in 10 healthy adults. Ages were 20–23 years, and BMI was 19.1–22.6. With glucose as 100, white rice was 63 and brown rice was 59.

Yukihiko Ito and colleagues, in 2005, fed white rice, brown rice, and pre-germinated brown rice from the same short-grain japonica grown in Hokkaido. There were 19 healthy adults, mean age 29 years (SE 1, range 23–41), mean BMI 21.4 (SE 0.8). Each meal provided about 50 g of available carbohydrate. Insulin was measured in the 15 people who agreed.

Results

In Zhang’s table, energy per 100 g of dry rice was 1750 kJ for brown rice and 1720 kJ for white rice. That is about 418 kcal and 411 kcal. Protein was 9.48 g and 9.13 g. The split was the bran. Fiber was 5.75 g and 2.84 g, magnesium 111 mg and 18 mg, thiamin 0.40 mg and 0.08 mg, and vitamin B6 1.06 mg and 0.16 mg. Fat was 3.45 g and 1.22 g, and iron was 1.18 mg and 0.53 mg. This white rice was the same brown rice milled further. Iron was not added afterward.

After 16 weeks, fasting glucose, insulin, HOMA-IR, glycated hemoglobin, BMI, waist circumference, and blood pressure showed no confirmed difference between groups. BMI in the brown-rice group fell 0.17 from baseline (p = 0.002). The difference from white rice was −0.09 (p = 0.23). LDL cholesterol fell further in the white-rice group. The brown-rice change minus the white-rice change was 0.30 mmol/L (95% CI 0.04 to 0.55, p = 0.02). That difference was 0.82 mmol/L among people who had diabetes at baseline (p = 0.03) and 0.06 mmol/L among those who did not (p = 0.67). Among people with diabetes, diastolic blood pressure fell 8.65 mm Hg on brown rice and 2.90 mm Hg on white rice. The between-group difference was −5.75 mm Hg (95% CI −10.3 to −1.18, p = 0.02). The paper marks that blood-pressure comparison as a post hoc analysis and says to read it with caution.

Ito’s glycemic index, with glucose set at 100, was 75.9 for white rice (SE 6.6), 61.5 for brown rice (SE 4.7), and 56.9 for pre-germinated brown rice (SE 2.9). Brown rice and pre-germinated brown rice were lower than white rice (p < 0.05, n = 19). The 30-minute glucose peak was 131.6 mg/dL for white rice (SE 4.1) and 130.9 mg/dL for brown rice (SE 4.1). The insulin area over 120 minutes did not differ significantly between the meals (n = 15). The glucose area for pre-germinated brown rice did not differ from brown rice.

Why people who are dieting pick it

The number these papers leave for someone who is dieting is the bran, measured as composition. Per 100 g of the same dry rice, energy is about 418 kcal and 411 kcal, and fiber is 5.75 g and 2.84 g. On the same dry weight the calorie gap is small and the fiber gap is large. Neither trial scored hunger or fullness.

In Ito’s japonica, after available carbohydrate was matched at about 50 g, the two-hour glycemic index split into 61.5 and 75.9. The 30-minute peaks were 131.6 mg/dL and 130.9 mg/dL. The glucose split sits in the two-hour index. The rice Zhang served had indexes of 63 and 59, so milling alone did not always open a gap of that size.

These 16 weeks were not a diet with a set calorie cut. People ate the rice freely. BMI in the brown-rice group fell 0.17 from baseline, and the difference from the white-rice group was −0.09 (p = 0.23). Fasting glucose did not separate between the groups either.

Limits

Zhang’s participants were middle-aged adults with metabolic risk. The trial did not cut calories toward a weight target, and it has no hunger score. The look of the rice showed who was eating brown rice. At baseline, diabetes was 29.7% in the white-rice group and 16.8% in the brown-rice group (p = 0.03). Blood-pressure medication was 44.6% and 29.7% (p = 0.03). Blood pressure and LDL in the diabetes subgroup are post hoc.

Ito is one meal in 19 people, after nothing but water since the night before. What body weight does over days of eating sits outside this curve. The 30-minute peaks matched, so the brown-rice glucose difference sits in the two-hour index.

What this means for a log

A photo shows brown rice or white rice by whether the bran is still visible. In this table, energy per 100 g of dry rice is nearly the same, and the split is fiber at 5.75 g and 2.84 g and magnesium at 111 mg and 18 mg. The study set 225 g cooked equal to 100 g dry for both, and brown rice was cooked with more water. A bowl matched by volume alone drops that fiber and magnesium gap out of the record. Lowering the calories because the name says brown rice also misses the 1750 kJ and 1720 kJ in the table.