關於大米的知識

Nutrition

Brown rice offers more health benefits than white rice.

Both white and brown rice contain mostly carbohydrates and some protein, with little to no fat or sugar. Cooked rice contains a lot of water, which makes up 70% of its total weight. White rice and brown rice have similar calorie, carbohydrate, protein and fat content. One 100g serving of white, short-grain rice contains the following nutrients:

Nutrition Quantity % Daily Value (DV)
Calories 130
Carbohydrates 28.7 grams (g) 10%
Protein 2.36 grams 5%
Fat 0.19 grams 0%

Carbohydrates

Rice is primarily composed of carbohydrates and makes up nearly 80%Trusted Source of total dry weight. Most of the carbohydrates in rice are starches. Starch is the most common form of carbohydrate in food. Starch is composed of long chains of glucose called amylose and amylopectin. Different types of rice contain different amounts of these compounds, which can affect the texture:

  • Basmati rice is rich in amylose, which means it does not stick together after cooking.
  • Glutinous rice or glutinous rice has low amylose content and high amylopectin content and becomes sticky after cooking. This makes it ideal for risotto, rice pudding and eating with chopsticks.

These compounds also affect how easily the body digests rice. The body takes longer to digest high-amylose rice because amylose slows down starch digestion. In comparison, glutinous rice is easily digested by the body. While many people find sticky rice more palatable, rapid digestion can cause blood sugar levels to rise, especially in people with diabetes.

Fiber

Brown rice contains more dietary fiber than white rice - 1.6g per 100g. During the processing of white rice, the grain loses its bran, or seed coat, and most of its fiber. Bran contains mostly insoluble fiber, such as hemicellulose, and almost no soluble fiber. White rice and brown rice contain different amounts of soluble fiber, called resistant starch.

Resistant starch increases butyrate in the gut. Butyrate promotes intestinal health by reducing inflammation, improving intestinal barrier function, and reducing the risk of colon cancer.

White rice and brown rice

White rice is refined, polished and has the bran and germ removed. This will improve its cooking quality, shelf life and taste, but will significantly reduce its nutritional value. That said, manufacturers often concentrate white rice or replace some vitamins after processing. Brown rice is a complete whole grain that contains the bran and germ, which are the most nutritious parts of the grain. They contain fiber, vitamins, minerals and antioxidants. Therefore, brown rice may contain more fiber and nutrients than white rice. Always compare labels when shopping. Brown rice is more suitable for diabetics. White rice can raise blood sugar, while brown rice has a lower glycemic index and helps control blood sugar.

Health Benefits of Brown Rice

Other than providing energy and essential nutrients, refined white rice offers no health benefits. Fortified white rice does contain B vitamins that are important for health. On the other hand, regular consumption of brown or whole grain rice has many health benefits. Always compare labels when shopping.

Heart Health

Brown rice is a whole grain. Whole grains have a wide range of health benefits. According to the American Heart Association, whole grains improve blood cholesterol levels and reduce the risk of heart disease, stroke, type 2 diabetes and obesity. Brown rice contains several heart-healthy ingredients such as minerals, antioxidants, lignans, and dietary fiber. Eating high-fiber rice instead of white rice may help with weight loss while lowering cholesterol.

Healthy plant compounds

Brown rice contains several other plant compounds that research shows may have health benefits. White rice is a poor source of antioxidants and other plant compounds. Pigmented rice, including red-grained varieties such as purple rice, is especially rich in antioxidants.

The bran of brown rice may be a good source of lignans and ferulic acid:

  • Lignans are antioxidants that have been linked to reduced risk of heart disease, menopausal symptoms, osteoporosis and breast cancer.
  • Ferrulic acid is a potent antioxidant found in rice bran. Studies show that it has anti-inflammatory and antibacterial properties and may help prevent cancer and diabetes.

Vitamins and Minerals

The nutritional value of rice depends on the variety and cooking method. The bran and germ contain high concentrations of vitamins and minerals. White rice does not contain bran or germ and lacks these essential dietary nutrients. Concentration may add some vitamins to white rice. Be sure to read labels when shopping as different brands may have different added vitamins.

The following table shows the content of different nutrients in 100 grams of brown rice, white rice, and concentrated white rice compared:

Brown rice White rice Fortified white rice
Manganese 42% DV 16% DV 16% DV
Niacin 16% DV 3% DV 9% DV
Thiamine 15% DV 2% DV 14% DV
Selenium 11% DV 14% DV
Magnesium 9% DV 2% DV 2% DV
  • Manganese: Many foods, especially whole grains, contain this trace mineral. It is essential for metabolism, growth, development and the body’s antioxidant system.
  • Niacin: Also known as vitamin B-3, the niacin in rice mainly exists in the form of niacin. Soaking rice in water before cooking may increase its absorption.
  • Thiamine: Also known as vitamin B-1, thiamine is essential for metabolism and the function of the heart, muscles, and nervous system.
  • Selenium: A mineral with multiple important functions in DNA, oxidative damage, and hormones.
  • Magnesium: This mineral is critical for blood pressure, protein synthesis, energy, and more.

Rice also contains some pantothenic acid, phosphorus, riboflavin, vitamin B-6, copper and folate.

Risk

Rice is a safe staple food. However, eating rice regularly can be risky, especially when it makes up a large portion of a person's daily food intake.

Type 2 diabetes

Type 2 diabetes is a common disease characterized by high blood sugar. White rice may increase the risk of type 2 diabetes, according to a 2019 review. This is because it has a high glycemic index score, which means it can cause a big spike in blood sugar after a meal. Foods with a high glycemic index may increase the risk of diabetes.

That said, the review concluded that the differences between brown and white rice are inconclusive and further research into dietary patterns that characterize rice is needed.

On the other hand, brown rice—like other whole grains that contain fiber—may help reduce the risk of type 2 diabetes.

This difference between white and brown rice may be due to differences in the type and amount of fiber and their glycemic index scores. It's important to note that eating too many carbohydrates from any source can raise blood sugar levels, so portion control is important whether the rice is whole grain or refined.

Eating fiber-rich whole grains instead of refined grains may have significant health benefits, including a lower risk of diabetes.

Heavy metals

Over time, heavy metals can accumulate in the body, causing adverse health effects. These include cadmium, chromium, lead, nickel and arsenic. Many studies have reported that rice from many countries contains excessive levels of heavy metals. This is a particular concern because rice forms a large part of a person's diet. Bran contains high concentrations of heavy metals, which is why brown rice contains more heavy metals than white rice. Rice accumulates more mercury and arsenic than other common food crops grown in contaminated areas. All grains readily absorb arsenic, but more appears to be collected in rice compared with wheat and barley. If possible, people should avoid eating rice grown near heavily polluted industrial and mining areas. This also applies to other food crops such as vegetables.

Antinutrients

Brown rice also contains an antioxidant called phytic acid or phytate. This is called an antinutrient because it prevents the body from absorbing essential minerals such as iron and zinc. Producers can reduce phytic acid levels by soaking and sprouting seeds and fermenting rice before cooking.

Summary

Rice is a staple food around the world. White rice is the most common, but brown rice may have more health benefits. As a good source of many healthy minerals and antioxidants, brown rice may help prevent heart disease. On the other hand, white rice—especially glutinous rice—provides fewer nutrients and may increase the risk of type 2 diabetes. Be sure to read the Nutrition Facts list and compare nutritional content, and buy fortified rice when available.

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