Resistant starch

23/11/2021

Resistant starch: back to the future diet!

Authored by Dr. Leonardo Caputo (ISPA-CNR)

Glucose, as we know, is a sugar, a carbohydrate, but this word immediately makes us think to sweets, cookies, fat on the hips, thigh inside, buttocks (and why not?) to physical fatigue or to fasting. In short, al what most of us do to get back in fit. So, what would you think of very long chains made with a very large number of glucose molecules? Well, those molecules exist and we intake them every time we eat a pasta dish, a slice of bread or focaccia and biscuits.

“Something's just not right—our air is clean, our water is pure, we all get plenty of exercise, everything we eat is organic and free-range, and yet nobody lives past thirty.” Alex Gregory, The New Yorker (22 maggio, 2006).

 

However, in these foods we must refer to another compound: the starch. Starch is a carbohydrate like glucose. It is a complex molecule produced by plants and made up of 2 polysaccharides: amylopectin and amylose. Very long chains of glucose. From 2000 to 200,000 in amylopectin and from 300 to 3000 residues in amylose. Depending on the vegetable origin, the first represents about 4/5 of the starch, while the second is around 1/5. Thanks to the characteristics of these constituent carbohydrates, "raw" starch is particularly indigestible for us humans. Yes, you got it right. It is a source of energy but it resists digestion. For this reason, when, at the dawn of humanity, during the Palaeolithic, we were avid hunters / gatherers, we needed to walk a lot to find tubers, fruits, seeds, roots very rich in this precious nourishment, until we understood that fire (cooking, in short) made those foods tastier but above all more digestible and assimilable (Carmody et al., 2011; Humphrey et al., 2014). And later, we learned how to grow those plants to have seeds or tubers rich in starch always available and close at hand. Thus, agriculture was born and we are no longer interested in walking to find food. And this is where the problems begin (tooth decay, cardiovascular disease), but this is another story, also because our life expectancy was very short at that time. Today, we know what it means to eat a plate of pasta: energy or calories that are not always due to pasta alone. A plate of cooked spaghetti (dry weight 70 g) seasoned with tomato sauce generally brings about 350 Kcal. These are very useful calories for the body, but we must be careful to divide them well, considering that, during the day, as regards carbohydrates, we can assume up to 58% of the total calorie requirement which, for an adult man of 70 kg, is about 2200 Kcal. Therefore, from carbohydrates we should get around 1200 Kcal per day to our body. The rest of the calories must come from fats (26% or 572 Kcal) and proteins (16% equivalent to about 352 Kcal). Without forgetting that 1 gram of carbohydrates or proteins provide 4 Kcal, while 1 gram of fat provides 9 Kcal. The caloric needs and the breakdown of macronutrients are based on the intake of 3 meals a day interspersed with 2 snacks, one mid-morning and the other in the afternoon. In addition, since most of us are not athletes, it is better to stay below the caloric requirement of about 200-300 Kcal (caloric deficit). These calories, that we should eliminate from the daily requirement, can easily be divided between some renunciations (especially for foods or drinks with high amounts of simple sugars and fats) and with a little physical activity (1 h or 6 km of fast walking for example). Beyond these almost bizarre calculations, for us who live on the shores of the Mediterranean, the caloric breakdown of the above macronutrients should not be difficult. In fact, the Mediterranean diet help us; it is famous for being complete and widely varied, also providing many fibers, vitamins and mineral salts. Unfortunately, for more than 50 years, new highly unbalanced eating habits have emerged, including intakes of excessive quantities of highly assimilable carbohydrates and fats. Furthermore, a sedentary lifestyle and the reticence towards active mobility have compromised even more the state of health of Italians as other European people. In Italy, in fact, 18 million adults are overweight (35.5% !!!) and 5 million are obese, or one in ten. Furthermore, 3 out of 10 children (29.8%, European Childhood Obesity Surveillance Initiative - 2019 data) are overweight and 1 of them is obese (9.4%). In Europe, Italians are second only to Cyprus and almost on a par with Greece and Spain people, with a prevalence of overweight children in the Southern Italian regions. Over the past 30 years, the incidence of overweight and obesity has increased by 30 and 60% respectively. In the next 10 years chilling figures will be reached with a 70% increase in the overweight population. The clinical and economic impact will be enormous, given that obesity is one of the first risk factors for the onset of cardiovascular diseases, diabetes, neurodegenerative diseases and some cancers.

Among the solutions put in place to stem this real food and health catastrophe, there are certainly those innovations that aim to reduce the glycaemic index and the caloric density of foods. In this regard, an interesting solution that is increasingly gaining ground is the replacement of a part of the starch present in starchy products with at least 14% of resistant starches. Above this percentage, foods such as bread, pasta, biscuits can get the health claim ID 681 on the label: “Reduces post-prandial glycaemic and insulin response” (EFSA, 2011). These starches, in fact, pass intact the gastro-intestinal digestive process and they are partially and lately hydrolysed by the intestinal microbiota which metabolizes them to short-chain fatty acids (SCFA), very useful for the health of colorectal cells ( DeMartino and Cockburn, 2020). The lack of calories has a significant impact on blood sugar, but also on the insulin response with positive effects on the satiety index (second course effect). Researches also conducted at the CNR-ISPA have shown that the percentage of resistant starch increases in relation to a high ratio of amylose / amylopectin in flours (Quintieri et al., 2012). Depending on the germplasm of origin, long linear chains of amylose take on a conformation that makes them inaccessible to amylases (resistant starch type II or "High amylose"), but after cooking they can lose this resistance, except for those corn flours called " high-amylose starch” (50-94% amylose) which instead partially gelatinizes at cooking temperatures (Sajilata et al., 2006; Birt et al., 2013). Thanks to these characteristics, these flours were used by CNR-ISPA researchers to fortify a "synbiotic" beverage, based on whey proteins and with the addition of probiotic bifidobacteria. The growth of these bacteria was promoted by resistant starch addition (Baruzzi et al., 2017). In a previous study the same researchers focused on mixtures of cereal flours with moderate concentrations of amylose (> 10%) which, upon specific gelatinization conditions (water / solute ratio, gelatinization temperature and cooling times), showed to get high percentages of resistant starch (retrograded or type III). This resistant starch, besides "resisting" the amylase hydrolysis, cannot be back gelatinized during subsequent cookings. Based on these studies, CNR-ISPA has developed a process to obtain a fermented vegetable beverage, alternative to milk-based ones, but with a high resistant starch content (35-57%) and the possibility of get the health claim 681. Furthermore, this methodology allows the production of flours that can be used in the bread-making and pasta-making processes or to produce snacks with beneficial effects on blood sugar control and caloric intake (Quintieri et al., 2014a and b).

 

References

Baruzzi, F., de Candia, S., Quintieri, L., Caputo, L., & De Leo, F. (2017). Development of a synbiotic beverage enriched with bifidobacteria strains and fortified with whey proteins. Frontiers in microbiology, 8, 640.

Birt, D. F., Boylston, T., Hendrich, S., Jane, J. L., Hollis, J., Li, L., ... & Whitley, E. M. (2013). Resistant starch: promise for improving human health. Advances in nutrition, 4(6), 587-601.

Carmody RN, Weintraub GS, Wrangham RW. Energetic consequences of thermal and nonthermal food processing. Proceedings of the National Academy of Sciences. 2011 Nov 29;108(48):19199-203.

DeMartino, P., & Cockburn, D. W. (2020). Resistant starch: impact on the gut microbiome and health. Current opinion in biotechnology, 61, 66-71.

EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). (2011). Scientific Opinion on the substantiation of health claims related to resistant starch and reduction of post‐prandial glycaemic responses (ID 681),“digestive health benefits”(ID 682) and “favours a normal colon metabolism”(ID 783) pursuant to Article 13 (1) of Regulation (EC) No 1924/2006. EFSA Journal, 9(4), 2024.

Humphrey LT, De Groote I, Morales J, Barton N, Collcutt S, Bronk Ramsey C, Bouzouggar A. Earliest evidence for caries and exploitation of starchy plant foods in Pleistocene hunter-gatherers from Morocco. Proceedings of the National Academy of Sciences. 2014 Jan 21;111(3):954-9.

Quintieri L., Monteverde A., Baruzzi F. Morea M., Caputo L. (2014b). Bevande fermentate contenenti elevate quantità di amidi resistenti. Industrie delle Bevande, 25:5-7.

Quintieri, L., Monteverde, A., & Caputo, L. (2012). Changes in prolamin and high resistant starch composition during the production process of Boza, a traditional cereal-based beverage. European Food Research and Technology, 235(4), 699-709.

Quintieri, L., Monteverde, A., Baruzzi, F., Morea, M., Caputo, L. (2014a). Fermented cereal-based beverages with high resistant starch content. Ingredienti Alimentari, 13(73), 16-20.

Sajilata M.G., Singhal R.S. e Kulkarni P.R. (2006). Resistant starch — A review. Compr Rev Food Sci F, 5:1–17, 

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