White Rice and Type-2 Diabetes Risk
By Dr Rizwana Rahim
TCCI, Chicago, IL
A study published in the British Medical Journal (15 March 2012) must have caused a stir in the rice-eating population of the world. If it did not, it should have because rice is staple food in 17 Asian countries, including China, Japan, India, Pakistan, Indonesia, Bangladesh and others. Other countries in the Americas and Africa also have rice-based diet, but its consumption is highest in China and India (estimated 135 and 86 million metric tons, respectively, 2003-2004); similar pattern in its production (197 and 131 million metric tons, China and India; 2007).
The Harvard researchers, in their March paper, analyzed four published studies, two in Asia (China and Japan) and one each in Australia and the US. They concluded in their Meta-study that when white rice is a major part of the regular diet, the risk of Type-2 diabetes in the consumers increases significantly -- and higher in women than in men. This risk seems to increase with the amount of rice eaten (a 10% increase per every extra serving; 158g / serving). Asians who generally eat more rice seem to be at increased risk. On average, a typical Chinese consumer would take four servings of rice a day, compared to less than one serving per day (i.e., estimated five servings per week) for those in the West.
What causes this risk and why, how to prevent it and what healthy alternatives are there to these traditional and cultural dietary habits? Some of these questions we want to explore here.
First, the white, refined or ‘polished’ rice itself.
Rice plant is hulled to remove the chaff and bran from the seeds or kernel, and the kernel is polished and refined to produce white rice. All through this process, the natural nutrients get gradually removed. Rice sold in the market does not have all the essential amino acids, which make rice not a ‘complete’ protein. White rice kernels lack vitamin A, and if rice is the main staple food for a population, this could lead to gradual vitamin A deficiency in a significant part of this population. One way to compensate is to add the missing nutrients to rice. Rice thus ‘enriched’ in vitamin A is sold in US markets, and carries a label advising the consumer NOT to rinse it off but people used to how the products are sold in India, Pakistan and other Asian countries often do. Another alternative is the genetically modified or bio-engineered rice called ‘golden rice’, which produces beta-carotene that is metabolically converted in the body to vitamin A. Other procedures call for coating the grain with the nutrients in water-insoluble forms, which cannot be washed off.
Most of white rice is carbohydrates (about 80g in 100g rice), protein being less than 10% of that, and fiber less than 20% of the protein. Carbohydrates in food, as digested, release glucose (or sugar) in the blood. We need glucose for energy, but sugar in the blood needs to be controlled, because excess sugar causes health problems. It is critically important in those already suffering from diabetes or at risk of that.
Second, since most food items have carbohydrates, it is also important to know their levels in what we eat and see that we balance high-carbohydrate items. We used to classify food by simple or complex carbohydrates, believing that ‘simple’ carbohydrates would release sugar faster than the ‘complex’ type. In recent decades, however, researchers have come up with a numerical value, Glycemic Index (GI). This is the estimated amount of sugar released in the human body after eating the same amount (50 g) of any food.
If eating simple sugar or glucose gives a GI of 100 after a certain period, then, according to University of Sydney estimates, most fruits and vegetables, some whole grains, pulses, nuts, beans/peas, fructose, e.g., would yield ‘Low’ GI (less than 55). Items among the lowest GI values are hummus (6), peanuts (14), cashews, salted (22). Food items with ‘Medium’ GI (56 to less than 70) include: whole wheat products, basmati rice, baked potatoes and fructose. Some “High’ GI (70 and above) items are white bread, white rice, corn flakes and other cereals, glucose and maltose. And among the highest, in the increasing order, are: instant mashed potatoes (80), short-grain white rice (83), glutinous rice (86), instant rice (87), French baguette (90), and dried dates (103).
One of the anomalies is that although sweet and sugary items predictably have higher GI, starchy foods (potatoes and white bread) rank higher than honey (55) and sucrose (61).
GI is a helpful measure but does not give us a complete picture since it misses such important factors as the amount of food taken , how was it cooked, besides the age, weight, health and genetic differences of the consumers.
Third, since GI fails to include these factors, a Harvard research team in 1997 developed a more realistic measure, Glycemic Load (GL): GL = GI/100 x net carbohydrates (total minus fiber) consumed. It is an increase in the area of a two-hour blood glucose response curve of a blood sample from people, after eating food with 50 g of available carbohydrate, after a 12-hour fast.
GLs up to 10 are considered ‘low’, and above 20, ‘high’. A low GL indicates low rates of digestion and absorption of carbohydrates in food, which in turn means (not always) low demand for insulin, and improved control of sugar and lipids in the blood. [A direct measure of insulin in response to food is also very helpful.]
For comparison, here are GLs of some of common food, with the serving size, and net carbohydrates (NC).
Bean sprouts, 104 g/1 cup, 4 NC (GL 1), GL 2 : peanuts, 113 g, 15 NC (GL 2); grapefruit, 166 g, ½ large, 11 NC (GL 3); sugar/sucrose, 1tbsp/12 g, 12 NC (GL 8); honey, 1 tbsp/21 g, 17 NC (GL 9); ice cream, 1 cup/72 g, 16 NC (GL 10); white bread, 1 slice/30 g, 14 NC (GL 10).
Pizza, 2 slices/260 g, 42 NC (GL 13); low-fat yogurt, 1 cup/ 245 g, 47 NC (GL 16); Raisins, 1 small bag/43 g, 32 NC (GL 20); Brown rice, 1cup/195 g, 42 NC (GL 23); Baked potato, 1 medium/ 173 g, 33 NC (GL 28); Potato chips, 4 oz/114 g, 55 NC (GL 30); Macaroni-cheese, 1 serving/166 g, 47 NC (GL 30); white rice, 1 cup/ 186g, 52 NC (GL 33); Snicker bar, 1bar/113 g, 64 NC (GL 35); Glucose, 50 g, 50 NC (GL 50).
GLs may be more realistic, but they still present some problems: For instance, a four-oz bag of peanuts (GL 2) and a medium-sized apple (GL 6), both considered low GLs, may seem good for a snack, but that serving of peanuts has more than 500 calories, as opposed to 72 calories in apple. This huge difference between 2 low-GL items makes a big dent into a calorie-conscious regimen. In food, carbohydrates (low or high) are not free to be rapidly digested and released into the blood stream, but are often physically incorporated/mixed/trapped in fat, protein and fiber, which may slow down digestion/absorption (and thus slow release of sugar). Another factor that the GI-GL ignores is the effect of salt added to the food, and its ability to increase blood sugar levels.
Sugar (glucose) increases in blood, under normal conditions, trigger the beta cells in the pancreas to release insulin, the hormone that reduces high levels of glucose in blood, and converts glucose to glycogen to be stored in liver. Insulin also helps glucose enter into muscles, adipose and other tissues.
In patients with Type 1 diabetes, there is loss of insulin-producing beta cells in the pancreas, resulting in insulin deficiency (insulin-dependent diabetes mellitus, IDDM, or juvenile diabetes), and the patients have to take insulin injections to help regulate blood sugar, or else sugar levels increase and harm other organs. The symptoms develop over a short time, and the patients are already sick before diagnosis. In the US, about 1.3 million people suffer from Type 1 (5% of the population).
Over 90% of the diabetics in US (20 million) suffer from Type 2 diabetes: their pancreas does produce insulin but either at insufficient levels or there is insulin-resistance or problems with insulin-receptors (or a combination of these conditions), resulting in the lack of needed response, and the patients have to regulate the blood sugar through prescribed drugs or insulin injections. Type 2 develops slowly and some who may have high blood pressure may not show any symptoms. In addition, over 40 million in the US also have early Type 2 diabetes. The 2010 statistics show that about 285 million in the world have Type 2 diabetes, which make up 90% of the cases.
Regardless, for a healthy balanced diet, we have to consider not just GI and GL but many other factors. Nutritionists often advise us to use whole grains, instead of refined carbohydrates as white rice, and include in our diet sufficient protein, such as meat, fish, beans, or nuts in proper quantity, and to make sure the diet is low-fat, high-fiber, and the caloric-intake is controlled well.
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