|Ripe or as in this case overripe bananas have little to no starch, green ones almost only starch and only little sucrose / fructose.|
What distinguishes whole grains and co from plain sugar, cornflakes and white bread is that they contain dietary fiber in its non-digestible form that is fermented in the colon, where the production short chain fatty acids (SCFA | learn more) triggers many of the well-established health benefits by direct and indirect effects on the gut-endocrine axis (Topping. 2001).
One of the best dietary sources of resistant starches are bananas... well, green bananas or rather the high resistant starch flour that's produced from green bananas. Although, it takes some processing to extract it from the bananas, it's classified as "RS2", i.e. naturally occuring resistant starch, because it is after all a native (vs. man-made) starch granule that is naturally highly resistant to digestion by α-amylase enzymes in the small intestine (Englyst. 1992).
|Figure 2: Effects of either 24 g of NBS dissolved in 240 mL of water per day or 24 g/day of soy milk dissolved in the same volume of water for 4 week (data represents within subj. comparisons | Ble-Castillo. 2010).|
Why is it important to test not just in obese subjects? This is a good question and one that actually touches on (one of) the root cause(s) of the obesity pandemic. For decades, obese individuals have been told to eat like lean people. People of whom scientists observed that they stayed lean and healthy on low(er)-fat, high(er) carbohydrate diets. The consequences were - at least in some cases - literally "fatal." Over the past decade, though, we've seen lean, athletic people make the opposite mistake when they assumed that the same low-to-no-carbohydrate diet and supplements like lipoic acid that help the obese lean out would help them stay lean or become even leaner (learn more). The assumption that diets, supplements and - as in this case - certain dietary nutrients necessarily do the same thing in obese and lean individuals, however, is unwarranted and in many cases simply wrong.In a more recent study, Guadalupe Jiménez-Domínguez repeated the Ble-Castillo study in a different, more diverse group of subjects:
Forty five subjects were screened for obese and lean participants. Anthropometric indexes and basic laboratory examinations were carried out. Participants for the obese group were included if they were healthy persons between 18 and 45 years of age, were obese, and had maintained stable weight during the three months prior to experimentation. Subjects in the normal-weight groups (lean group) were included if they were between 18 and 45 years of age, had 18.5–24.9 BMI values, had [normal fasting glycemia and]HbA1c values [...] and had maintained stable weight during the three months prior to experimentation. Subjects not included in this study were those with a previous diagnosis of diabetes, with fasting glycemia >126 mg/dL (> 7.0 mmol/L) or glycated hemoglobin > 6.5%, with digestive disorders, chronic diseases such as renal or hepatic, being pregnant, under psychiatric treatment, receiving medical or naturist treatment to reduce BW, practicing intense physical activity (> 90 min/week), receiving immuno-suppressants, or with a history of cigarette smoking or alcoholism. Thirty two participants were eligible for the study, 15 for the obese group and 17 for the lean group. However, only 10 subjects in each group completed the whole protocol" (Jiménez-Domínguez . 2015).In said study, the subjects received a higher dose of 38.2 g of native banana starch (NBS) or the same amount of corn starch twice daily yet for only four days, before, on day 5, a 3-h meal tolerance test (MTT) was performed to evaluate the acute effects glucose and insulin responses that may explain the benefits Ble-Castillo et al. had observed (see Figure 2).
"All of the subjects received low-fiber diets at breakfast and lunch from the Nutrition Department’s restaurant during days 1‒4 of the treatment period. The low-fiber diet consisted of avoiding whole-grain/wholemeal breads and cereals, legumes, nuts, and seeds, and of removing the skins from fruit and vegetables" (Jiménez-Domínguez. 2015).All subjects had to stick to the same baseline diet. Adherence to the diet and the randomly assigned supplements,
- the NBS beverage, which contained 38.39 g of NBS, 31.82 g of soy milk, and 240 mL of purified water, and
- the DCS beverage, which contained 38.39 g of DCS, 31.82 g of soy milk, and 240 mL of purified water,
both of which had to be consumed in the fasting state (7:00 A.M.–9:00 A.M.) and before lunch (1:00 P.M.–3:00 P.M.), by counting the unopened sachets, a query regarding the missed servings and daily food records all subjects had to fill everyday before they went to bed.
|Figure 3: The 4 days on natural banana starch had quite significant beneficial effects on the glucose and insulin response to a standardized test-meal. It is yet also obvious that the obese saw greater benefits (Jiménez-Domínguez. 2015).|
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