Selected Studies continued...
2. RS2 resistant starch promotes colonic health
Results of the Colorectal Adenoma/Carcinoma Prevention Program 2 (CAPP2) were published in the New England Journal of Medicine in December of 2008. This randomized, placebo-controlled trial used a two-by-two design to investigate the effects of aspirin, at a dose of 600 mg per day, and resistant starch (a combination of RS3 from high amylose corn and RS2 from high amylose corn) at a dose of 30 g per day. 727 individuals participated in 43 centers around the world over an average of 29 months (range, 7 to 74). Participants were patients with Lynch syndrome (hereditary non-polyposis colon cancer), an autosomal dominant genetic defect that confers a predisposition to colorectal cancer. Up to 5% of colorectal cancers result from the Lynch syndrome. Conclusions: The use of aspirin, resistant starch, or both for up to 4 years had no effect on the incidence of colorectal adenoma or carcinoma among carriers of the Lynch syndrome.
A recently published clinical study led by Dr. John Mathers at Newcastle University in Newcastle upon Tyne, UK, showed that RS2 and RS3 resistant starch from high amylose corn reduced cell proliferation in the upper part of colonic crypts in normal colonic tissue of individuals with colorectal cancer. Since cell proliferation in the upper part of the crypt is considered a pre-malignancy marker, its reduction by resistant starch in this study suggests cancer prevention benefits. They also found differences in the genetic expression of key cancer-related genes.
Another newly published clinical trial led by Dr. Balakrishnan Ramakrishna at the Christian Medical College in Vellore, India, demonstrated that the addition of RS2 resistant starch from high amylose corn decreased the duration of diarrhea by 55% and significantly reduced fecal weight after the first 12 hours of hypo-osmolar oral rehydration solution therapy in adults with cholera-like diarrhea. Two previous studies by this group have already been published demonstrated similar benefits in convention iso-osmolar oral rehydration solution.
A 2007 rat study led by Dr. Shusuke Toden, CSIRO Human Nutrition, Adelaide, Australia, and published in British Journal of Nutrition, showed RS2 resistant starch from high amylose corn prevents colonic DNA damage induced by a high protein diet. The study showed that higher dietary casein and soya increased colonocyte DNA damage. Dietary resistant starch attenuated protein-induced Colonocyte DNA damage in all groups. Dietary protein level did not affect colonic mucus thickness overall but the barrier was thinner in rats fed high dietary casein. This effect was reversed by feeding resistant starch.
[Burn J, Bishop T, Mecklin JP, Macrae F, Moslein G, Olschwang S, Bisgaard ML, Ramesar R, Eccles D, Maher ER, Bertario L, Jarvinen HJ, Lindblom A, Evans G, Lubinski J, Morrison P, Ho JWC, Vasen HFA, Side L, Thomas HJW, Scott RJ, Dunlop M, Barker G, Elliott F, Jas JR, Fodde R, Lynch HT, Mathers JC. Effect of aspirin or resistant starch on colorectal neoplasia in the Lynch Syndrome. New England Journal of Medicine, 2008;359;24:2567-78.
Dronamraju SS, Coxhead JM, Kelly SB, Burn J, Mathers JC (2008) Cell kinetics and gene expression changes in colorectal cancer patients given resistant starch – A randomized controlled trial. Gut Published Online October 31, 2008. doi: 10.1136/gut.2008.162933.
Ramakrishna, BS, Subramanian V, Mohan V, Sebastian BK, Young GP, Farthing MJ, Binder HJ. (February 13, 2008) A randomized controlled trial of glucose versus amylase resistant starch hypo-osmolar oral rehydration solution for adult acute dehydrating diarrhea. PLoS ONE 3(2): e1587. doi:10.1371/journal.pone.0001587.
Toden S, Bird AR, Topping DL, Conlon MA. Differential effects of dietary whey, casein and soya on colonic DNA damage and large bowel SCFA in rats fed low and high in resistant starch. British Journal of Medicine (2007), 97(3), 535-543.]
3. RS2 and RS3 from high amylose corn reduce the glycemic impact and insulin impact of foods when replacing rapidly digestible carbohydrates such as flour
Multiple studies have confirmed that when Hi-maize replaces flour or other rapidly digestible carbohydrates such as cornstarch, the glycemic and insulin impact of that food is reduced. Studies have been published by investigators around the world – i.e. Dr. M. Olesen at the University of Copenhagen and Dr. Manny Noakes at the CSIRO in Australia. Delayed or sustained energy release has also been demonstrated in some studies with consumption of resistant starch from high amylose corn. Studies published by Dr. Kay Behall and her colleagues at the US Department of Agriculture have shown that the reductions in glycemic and insulin response are relative to the amount of RS incorporated into the food and increase with increasing amylose content of the corn starch.
[Noakes M, Clifton PM, Nestel PJ, Le Leu R, McIntosh G. Effect of high-amylose starch and oat bran on metabolic variables and bowel function in subjects with hypertriglyceridemia. The American Journal of Clinical Nutrition 1996;64(6):944-51.
Olesen M, Rumessen JJ, Gudmand-Hoyer E. Intestinal transport and fermentation of resistant starch evaluated by the hydrogen breath test. European Journal of Clinical Nutrition 1994;48(10):692-701.
Behall KM, Scholfield DJ, Canary J. Effect of starch structure on glucose and insulin responses in adults.
The American Journal of Clinical Nutrition 1988;47(3):428-32.
Behall KM, Hallfrisch J. Plasma glucose and insulin reduction after consumption of breads varying in amylose content. European Journal of Clinical Nutrition 2002;56(9):913-20.]
4. Resistant starch increases insulin sensitivity in healthy people and in individuals with insulin resistance and metabolic syndrome.
Dr. Denise Robertson and her colleagues at The University of Surrey showed that consumption of Hi-maize resistant starch significantly increased insulin sensitivity in individuals with insulin resistance and metabolic syndrome. The preliminary results from a 8-week randomized, crossover clinical trial were released in March at the Diabetes UK Annual Professional Conference and published in Diabetic Medicine. In this study, 10 overweight individuals with insulin resistance and metabolic syndrome consumed 40 grams of dietary fiber from Hi-maize resistant starch per day, which increased their hepatic insulin sensitivity by 54%, their peripheral (muscle) insulin sensitivity by 24%, and their glucose uptake into forearm muscle by 68%.
Previous work from Dr. Robertson had shown that consumption of Hi-maize resistant starch from high amylose corn increased insulin sensitivity in healthy people by 14% (measured by hyperinsulinaemic-euglycemic clamp) and by 33% (as measured by Meal Tolerance Test). This 2005 study confirmed that increased insulin sensitivity was still seen after four weeks of natural resistant starch consumption. A 2003 study found a 69% increase in insulin sensitivity (as measured by Meal Tolerance Test) in healthy people following consumption of 60 grams of dietary fiber from Hi-maize resistant starch. This is important because insulin resistance is an underlying risk factor in metabolic syndrome, with increased risk for developing diabetes, obesity, and cardiovascular disease.
[Robertson MD, Currie JM, Morgan LM, Jewell DP, Frayn KN. Prior short-term consumption of resistant starch enhances postprandial insulin sensitivity in healthy subjects. Diabetologia 2003;46(5):659-65.
Robertson MD, Bickerton AS, Dennis AL, Vidal H and Frayn KN. Insulin-sensitizing effects of dietary resistant starch and effects on skeletal muscle and adipose tissue metabolism. The American Journal of Clinical Nutrition 2005;82:559–67.
Robertson MD, Wright JW, Batt J, Russell-Jones D, and Umpleby AM. Dietary resistant starch is an insulin sensitizer A37(P37). Diabetic MedicineMarch 2009;26(1)(Suppl. 1):14.]
5. Resistant starch lowers calories, increases lipid oxidation and may impact body composition
Dr. Kay Behall and her colleagues at the US Department of Agriculture confirmed that high amylose corn RS2 yields between 2-3 kcal/gram instead of the full 4 kilocalories per gram typical of flour and other digestible carbohydrates. Thus, when natural resistant starch is used to replace flour, the caloric content of that food is reduced. The energy is partially delivered in the small intestine through the digestion of the starch portion and partially delivered in the large intestine in the form of short-chain fatty acid by-products through the fermentation of the resistant starch.
A 2004 clinical study published by Dr. Janine Higgins at the University of Colorado suggests that eating a meal containing high amylose corn RS2 resistant starch increased post-prandial lipid oxidation in healthy people by 20-25%. This study measured lipid oxidation by both indirect calorimetry (Change in Respiratory Quotient) as well as the production of 14CO2 from 14C-triglyceride tracer. Surprisingly, the dose-response curve was not linear. Additional studies are needed to confirm increased lipid oxidation and its potential impact on weight over the long-term.
Animal studies suggest that high amylose corn RS2 impacts body composition. Dr. Dorota Pawlak and her colleagues at Harvard Medical School in Boston, MA, demonstrated that obesity-prone mice fed natural RS2 from high amylose corn had approximately half as much body fat after 9 weeks as obesity-prone mice consuming a high glycemic cornstarch diet.
[Behall, KM, Howe JC. Resistant starch as energy. The Journal of the American College of Nutrition 1996;15(3):248-54.
Higgins JA, Higbee DR, Donahoo WT, Brown IL, Bell ML, Bessesen DH, 2004. Resistant starch consumption promotes lipid oxidation. Nutrition & Metabolism 1:8.
Pawlak DB, Kushere JA, Ludwig DS. Effects of dietary glycaemic index on adiposity, glucose homeostasis, and plasma lipids in animals. Lancet 2004;364:778-85.
6. Natural resistant starch is well tolerated and does not cause uncomfortable digestive side effects.
The entire daily recommended intake of dietary fiber (usually 25-35 grams depending upon individual countries) could be consumed from natural resistant without digestive side effects. Clinical studies have specifically shown that high levels of natural high amylose corn RS2 (even those exceeding the recommended intake of dietary fiber) can be consumed with modest or no digestive side effects.
[Giacco R, Clemente G, Brighenti F, Mancini M, D’Avanzo A, Coppola S, Ruffa G, La sorella G, Rivieccio AM, Rivellese AA, Riccardi G. Metabolic effects of resistant starch in patients with Type 2 diabetes. Diabetes, Nutrition & Metabolism 1998;11:330-5.
Robertson MD, Bickerton AS, Dennis AL, Vidal H, Frayn KN. Insulin-sensitizing effects of dietary resistant starch and effects on skeletal muscle and adipose tissue metabolism. American Journal of Clinical Nutrition 2005;82:559-67.
Kendall, CWC, Jenkins DJA, Emam A. Assessment of resistant starch tolerance: a dose response study. Abstract presented at 9th European Nutrition Conference, October 1-4, 2003, Rome, Italy.]