Sunday, August 14, 2011

Hold the Starch?

Starch is that stuff that stiffens your shirts. It's also what most people eat for fuel. Wheat, rice, corn, oats, potatoes are all very starchy foods. Many popular diet plans call starch a second-rate food that should be avoided at all costs. No-starch and low starch diets are favored by irritable bowel communities, while former Weight Watchers, Jenny Craig and Atkins enthusiasts love the new Carb Lovers Diet praising starch. Yet, there may be something good about starch even for those with sensitive stomachs. 

Starch is a mixture of long and intermingled molecules digested with different rates and outcomes. Our bodies' response to eating starch depends on its amount and types along with our nature [1] and nurture, including intestinal microbes eating the leftovers [2].

Resistant Starch (RS), also called Functional Fiber, is a type of starch that may have beneficial physiological effects. It is further classified into four or five classes,  like RS2 in potatoes or RS3 (maltodextrin on food labels) formed when starchy foods are cooked and cooled. Resistant starch is not digested in the small intestine of healthy individuals. It is an effective prebiotic as it feeds and stimulates specific bacteria in the gut [3]. Bacteria consuming resistant starch raise levels of short-chain fatty acids (SCFA) and derivatives that can act as a source of energy [2,4] and provide other benefits like protection from inflammatory conditions of the bowel. 

Over 200 nutritional studies showed  that resistant starch increases satiety, reduces food consumption and can prevent weight regain, acting almost like exercise. It also lowered insulin levels and reduced the deposition of fat.

How much resistant starch do we need to eat?

Adults in most developed countries consume between 3-7 grams of resistant starch per day. The Carb lovers diet recommends 10-15 grams. According to an earlier Australian study [5], 20 grams per day may be even more beneficial. However, optimal levels of resistant starch in diet are very individual, depending on body weight, metabolism, microbial makeup and dietary preferences. Flatulence and belching are among potential side effects.

Resistant starch is like other types of fiber and prebiotics – everybody has their own individual threshold and every extra gram leads to production of excessive gas [6].
Fructooligosaccharides (FOS) and inulin, prebiotics selectively stimulating bacteria in the colon, usually lead to mild flatulence starting from about 10 grams per day. Isolated individuals experience discomfort even at 5 grams. 14-15 grams per day usually mark the threshold for significant increase in flatulence, stomach growling and cramping. Resistant starch may have slightly higher sensitivity thresholds [6].

Total starch,  per 100 g
  Resistant starch, per 100 g
Red kidney beans
Black-eyed peas
Potato chips
Long-grained rice, parboiled
Spaghetti, cooked for 9 mins
Mashed potatoes
Boiled potatoes
White bread
Rye crisps
Puffed wheat cereal
Medium-grained rice, boiled
Spaghetti, cooked for 12 mins
Oatmeal (Oat porridge)

Understanding what amounts are right for you takes careful analysis and evaluation  Don’t forget about the digestible starch that accompanies indigestible starch. Ideally, our enzymes can efficiently break down the digestible starch into glucose, but the process is so lengthy (5-7 hours) that overload could result in more starch leaking through pores in the small intestine before it has a chance to be digested. This leads to endotoxins and an excess of methane and carbon dioxide, in addition to other metabolic end products, in your system.  

So remember:  there are different types of starch and they usually come packaged with other food components for which you might have separate sensitivities. In other words, your mileage may vary.


[1] Perry GH, Dominy NJ, Claw KG, Lee AS, Fiegler H, Redon R, Werner J, Villanea FA, Mountain JL, Misra R, Carter NP, Lee C, Stone AC.   Diet and the evolution of human amylase copy number variation. Nat Genet. 2007 Oct;39(10):1256-60. Epub 2007 Sep 9.

[2] Bird AR, Conlon MA, Christophersen CT, & Topping DL (2010). Resistant starch, large bowel fermentation and a broader perspective of prebiotics and probiotics. Beneficial microbes, 1 (4), 423-31 PMID: 21831780

[3] Gray, G. Dietary fibre – from definitions to public health messages (pages 159–161). Article first published online: 13 Aug 2008 | DOI: 10.1111/j.1467-3010.2008.00702

[4] Donohoe, DR, Garge, N, Zhang, X, Sun, W, O'Connell, TM, Bunger, MK, Bultman, SJ. (2011). The Microbiome and Butyrate Regulate Energy Metabolism and Autophagy in the Mammalian Colon. Cell Metabolism 13 (5): 517–26

[5] Baghurst PA, Baghurst KI, Record SJ, Dietary fibre, non-starch polysaccharides and resistant starch – a review. Food Australia, 1996 Vol 48, No. 3:S1-S35.

[6] Brighenti F, Pellegrini N, Casiraghi MC, Testolin G (1995) In vitro studies to predict physiological effects of dietary fibre. European Journal of Clinical Nutrition 49, Suppl. 3, S81±S88

[7] Elmståhl, L.H. Resistant starch content in a selection of starchy foods on the Swedish market. European journal of clinical nutrition: 2002 Jun;56(6):500-5.