Why would they have to be cooled though? Sounds a bit dumb and unfounded.
I posted this in the potato thread, but figured since so many of you are tired of taters, I'd post here, too.
My latest rabbit-hole is resistant starches. Apparently these are very, very important but rarely talked about because they are so easy to get on the SAD. They are mostly found in grains, seeds, and legumes, but also in potatoes and rice. HOWEVER, the potatoes and rice must be cooked and cooled for the biggest effect.
This study shows resistant starches with meals increase fat oxidation that is biologically relevant and could be important for preventing fat accumulation in the long term by effecting total fat balance:
Resistant starch consumption promotes lipid oxidation
Resistant Starches also are converted to butyrates in the large intestine which are a short chain fatty acid. These short chain fatty acids feed the colon flora and protect against whole body and colon inflammation.
Read more: Whole Health Source: Butyric Acid: an Ancient Controller of Metabolism, Inflammation and Stress Resistance
"Butyrate has caused me to re-think my position on fiber-- which was formerly that it's irrelevant at best. I felt that fiber came along with nutrient-dense whole plant foods, but was not beneficial per se. I believed that the associations between fiber intake and a lower risk of a number of diseases were probably due to the fact that wealthier, more educated, healthier people tend to buy more whole grains, fruit and vegetables. In other words, I believed that fiber intake was associated with better health, but did not contribute to it. I now feel, based on further reading about fiber and short-chain fatty acids like butyrate, that the associations represent a true cause-and-effect relationship.
I also didn't fully appreciate the caloric contribution of fiber to the human diet. In industrialized countries, fiber may contribute 5 to 10 percent of total calorie intake, due to its conversion to short-chain fatty acids like butyrate in the large intestine (free full text). This figure is probably at least twice as high in cultures consuming high-fiber diets. It's interesting to think that "high-carbohydrate" cultures may be getting easily 15 percent of their calories from short-chain fats. Since that isn't recorded in dietary surveys, they may appear more dependent on carbohydrate than they actually are. The Kitavans may be getting more than 30 percent of their total calories from fat, despite the fact that their food is only 21 percent fat when it passes their lips. Their calorie intake may be underestimated as well."
So, please let your takeaway from this be: Think about adding a source of resistant starch to you diet...cooked and cooled potatoes and rice are specifically mentioned anywhere you see the term 'resistant starch'.
Why would they have to be cooled though? Sounds a bit dumb and unfounded.
from:Resistant starch - Wikipedia, the free encyclopedia
Resistant starch (RS) is starch and starch degradation products that escape digestion in the small intestine of healthy individuals. Resistant starch is considered the third type of dietary fiber, as it can deliver some of the benefits of insoluble fiber and some of the benefits of soluble fiber.
Some carbohydrates, such as sugars and most starch, are rapidly digested and absorbed as glucose into the body through the small intestine and subsequently used for short-term energy needs or stored. Resistant starch, on the other hand, resists digestion and passes through to the large intestine where it acts like dietary fiber.
Resistant starch has been categorized into four types:
RS1 Physically inaccessible or digestible resistant starch, such as that found in seeds or legumes and unprocessed whole grains
RS2 Resistant starch that occurs in its natural granular form, such as uncooked potato, green banana flour and high amylose corn
RS3 Resistant starch that is formed when starch-containing foods are cooked and cooled such as in legumes, bread, cornflakes and cooked-and-chilled potatoes, pasta salad or sushi rice. The process of cooking out the starch and cooling it is called retrogradation.
RS4 Starches that have been chemically modified to resist digestion. This type of resistant starches can have a wide variety of structures and are not found in nature.
On a related note, I'm note sure I've EVER liked the term "safe starch." There may be less than optimal sources (grains and beans for sure), but it's not the starch that's the issue here as much as the other goodies that get packaged along with it. Starch is starch. It's is either, as you say here, resistant or not. But in either case, the body uses it. Excessive amounts of starch in any form may not be warranted, but I don't think you can draw the line and say "this starch is good" or "this starch is bad." It is the source of starch that is the problem, not the starch itself. Maybe I'm being nitpicky, but the whole "safe" vs. "unsafe" starch reflects a lack of understanding of chemistry.
And among the paleo/primal community it may even be an unnecessary term to use. If you're eating paleo/primal diets, you should already know which sources of starches are to be avoided. Pretty obvious to me. If a fellow primal advises me to add starch to my diet, I'm not going to think he means pasta.
"No dude, not pasta, I mean a safe starch!"
Just had to get that off my chest.
Oh, and you know what ELSE promotes fat oxidation? Fasting.
In Paul Jaminet's new Perfect Health Diet book (with an intro by Mark Sisson), he says to eat up to 1 pound of 'safe starches' a day. His list of safe starches is: Taro, Sago, Tapioca, Plantain, Sweet Potato, Potato, and Rice.
He might as well just listed Potatoes, Sweet Potatoes, and Rice, because I have never heard of or eaten the rest--they certainly aren't US staples.
Concerning rice, I'm surprised it made his list. I think it is thought of as a benign starch, but potatoes and sweet potatoes are much better. Rice also has little fiber and resistant starch, not nearly as much as the potato.
The cooking and cooling issue is what really threw me for a loop on the resistant starches. Here's another weird fact; vinegar aids in the conversion of resistant starch to butyric acid. So, cold potatoes and vinegar--isn't that German Potato Salad?
Agree on the safe starch issue. Much more appropriate to talk about safe sources of starch. Otzi, any sense of how you would differentiate between white and sweet potatos in terms of resistant starch? (also, hard to get my head around the idea of vinegar on a sweet potato, but who knows?)
This study:Novel Resistant Potato Starches on Glycemia and Satiety in Humans
Has undertaken a way to make RS4, the ones that don't occur in nature, to be added to food to give them better satiety and glucose/insulin control. If you read the study, they keep coming back to potato starch as the gold-standard for resistant starches...
"Diabetes, obesity, and cardiovascular diseases are interrelated, with diet being one factor that links them all together. Specifically, the current obesity epidemic has been suggested to be a result of increased carbohydrate intake , while dietary fat has frequently been touted as the primary dietary culprit in the cause of many deleterious metabolic conditions. As a nation, we increased carbohydrate consumption during the latter years of the past century as the obesity epidemic began to surge . While it is laudable to try to change the behavior of individuals so they choose other foods, it might be more effective in the short term to address this nutritional issue by providing bioactive compounds that “behave” like traditional starch yet elicit more favorable metabolic outcomes (acutely and chronically). In other words, let people continue to choose some of the foods they prefer, but make those foods healthier by incorporating bioactive ingredients.
To that end, incorporating resistant starches into foods by substituting them for the typical starch has been shown to acutely decrease postprandial glucose and insulin . There are five types of resistant starch, with RS types 2, 3, and 4 tending to be studied more frequently. Also, there are varieties of resistant starch within each type . Gram for gram, some resistant starches have been reported to elicit minimal glucose and insulin excursions compared with similar amounts of dextrose  and are easily incorporated into regular food items with minimal aversion by consumers ..."
The sweet potato is recognized as a health-promoting food, owing to its richness in functional components such as dietary fiber; however, only a few studies have been conducted on resistant starch (RS) levels in the sweet potato. Now, the sweet potato is expected to have potential as a renewable resource for bio-ethanol production. The enzymatic digestibility of raw starch appears to influence the conversion rate of starch to sugar in the first step of ethanol production. In this study, the RS content of gelatinized starch, digestible starch (DS) content of raw starch and other starch properties were investigated using 21 sweet potato cultivars and lines to assess varietal variations and to estimate relationships among these starch properties. The RS content of gelatinized starch ranged between 1.8 and 9.5%.