Written by Tatjana Djakovic, Staff Writer. Randomized double-blind placebo controlled study demonstrated that rice containing resistant starches improved endothelial function, blood glucose and oxidative stress in 90 patients with pre-diabetes or newly diagnosed type 2 diabetes
Cardiovascular disease remains one of the main health problems in the United States claiming many lives annually. In 2009, heart disease caused about 1 out of every 6 deaths in the United States. The total direct and indirect cost of heart disease and stroke in the United States for 2009 is estimated to be $312.6 billion. There are multiple preceding conditions associated with the formation of cardiovascular disease. Adults with diabetes are two to four times more likely to have heart disease or a stroke than adults without diabetes. (1) The symptoms of cardiovascular disease are endothelial dysfunction (damage to the inner lining of blood vessels) impaired glucose tolerance (blood sugar levels that are higher than normal). (2) A high carbohydrate meal is thought to suppress the dilation of blood vessels which might increase cardiovascular risk. (3).
Resistant starch is a type of carbohydrate found in navy beans, raw bananas, fruits, vegetables, grains, legumes, and some dairy foods and isn’t entirely broken down by the body. It is known to have an effect similar to some dietary fibers and foods with low glycemic index in the small and large intestines, by increasing the indigestible portion. Human and animal studies have reported a decrease in blood glucose and insulin by a single dose administration of resistant starch. (4)
In the present randomized double-blind placebo controlled study, 90 subjects were randomly assigned to consume either their usual diet with cooked refined rice (control) or the rice containing resistant starch (6.51g) for one of any of three main meals (mostly dinner) during the 4-week intervention. (5) The control meal was indistinguishable from the test food in taste, smell, and appearance. The researchers evaluated whether dietary treatment with rice containing resistant starch reduces blood glucose and oxidative stress as well as improves endothelial function (control of inflammation and constriction or dilation of blood vessels) compared with control subjects with newly diagnosed type 2 diabetes.
There was an improvement in glucose and insulin metabolism as well as reduction in oxidative stress (over production of free radicals) The insulin levels decreased significantly at 30 minutes after meal consumption by 13.9% compared to a 6.24% decrease in the placebo group (p=0.044). There was a 12.1% decrease in insulin resistance (a condition in which cells do not respond normally to insulin) compared to 5.23% increase in the placebo group (p=0.045). (5)
The markers of oxidative stress were reduced after consumption of a rice meal containing resistant starch. One of those markers, 8-epi-PGF2∞, which has been to shown to constrict blood vessels (6), decreased by 12.5% compared to 4.4% decrease in the placebo group (p=0.001). A non-invasive measure of endothelial function, (RH-PAT, a probe that measures how blood vessels in finger tip respond to initial rush of blood after blood pressure band around the arm is released) showed improvement in the group that used rice containing resistant starch (p<0.001) Also total concentration of a compound nitric oxide (dilates blood vessels) was increased in group taking resistant starch (p=0.002).
The researchers suggest that the improvement of endothelial function might be explained in the following way: the decreasing effect of low-glycemic index carbohydrate on blood glucose decreases oxidative stress, which increases the levels of nitric oxide which dilates the blood vessels, and thereby improve endothelial function. Since rice is one of the principal foods, rice containing resistant starch could be useful for a supplementary means of therapy to reduce risk of cardiovascular disease. (5)
Source: Kwak, Jung Hyun, et al. “Dietary treatment with rice containing resistant starch improves markers of endothelial function with reduction of postprandial blood glucose and oxidative stress in patients with prediabetes or newly diagnosed type 2 diabetes.” Atherosclerosis 224.2 (2012): 457-464.
© 2012 Elsevier Ireland Ltd. All rights reserved.
Posted April 18, 2013.
References:
- Lloyd-Jones, Donald, et al. “Heart Disease and Stroke Statistics—2009 Update A Report From the American Heart Association Statistics Committee and Stroke Statistics Subcommittee.” Circulation 119.3 (2009): 480-486.
- Su Y. Liu XM, et al. The relationship between endotelial dysfunction and oxidative stress in diabetes and prediabetes. Int J Clin Pract 2008;62:877-82.
- Kowano H, et al., “Hyperglycemia rapidly suppresses flow-mediated endothelium-depended vasodilation of brachial artery. J Am Coll Cardiol 1999;34: 146-54.
- Byrnes SE, et al., Amylopectin starch promotes the development of insulin resistance in rats. J Nutr 1995; 125: 1430-7.
- Kwak, Jung Hyun, et al. “Dietary treatment with rice containing resistant starch improves markers of endothelial function with reduction of postprandial blood glucose and oxidative stress in patients with prediabetes or newly diagnosed type 2 diabetes.” Atherosclerosis (2012).
- Fukunaga, et al. “Stimulatory Effect of 8-Epi-PGF2 [alpha], An F2-Isoprostane, on Endothelin-1 Release.” Journal of cardiovascular pharmacology 26 (1995): S51-52.
