Tag Archive for: potatoes

Unusual Question: Resistant Starch and Food Prep

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Resistant starch (RS) has qualities that are somewhat unique. As it’s being touted today, RS will help reduce the glycemic response to some carbohydrate-based foods. The issue is that when and how an RS containing food is prepared and consumed seems to be important. Let’s take a look.

Food Preparation Methods

The most natural forms of resistant starch to eat, regardless of preparation, are beans, seeds, nuts, and legumes. The food preparation doesn’t seem to impact the RS in any way, so these are the best ways to get RS.

Eating bananas and plantains when they’re green provides a high amount of RS. The more they’re allowed to ripen, the higher the sugar content and the less RS.

Raw potatoes also seem to have a high amount of RS. Because most people don’t eat raw potatoes, the type of preparation impacts RS levels. The longer the potatoes are cooked, the more the starch is changed into sugars or starches that don’t contain as much RS. In a review study of potatoes, the cooking method that contains the most RS was baked, followed by deep-fried, and finally boiled. The problem with deep-fried is the additional fat.

Does Cooling Increase RS?

We rarely hear about nutrients being increased by food prep, but RS may be the exception. A lot of the recent focus on RS surrounds the possibility of increasing RS by cooking and then cooling the foods before eating. The RS that degenerates during cooking is partially restored in cooling, particularly in rice and pasta.

However, in a study that examined the difference between rice that was eaten immediately, kept at room temperature and eaten eight hours later, and cooled for 24 hours and then eaten, the amount of fiber increased by 0.64 grams, 1.3 grams, and 1.65 grams per 100 grams serving. Stated slightly differently, in a half-cup portion, there was an increase of one gram of fiber per serving. While it’s true, it’s not meaningful in the real world and probably not worth the additional effort.

RS and Type 2 Diabetes

Another benefit of RS is to reduce the amount of sugar that enters the blood stream. In the rice study, the cooked and cooled rice was fed to 15 healthy volunteers. Their glycemic response was reduced. While I think that’s great, there’s no indication that this will happen in T2D. On top of that, think about the additional steps required to achieve that. I think there’s a better way.

The Bottom Line

Resistant starch is legit; it acts as a prebiotic and reduces the glycemic response, but I don’t think we need to go out of our way to get more of it. Increasing our intake of beans, seeds, legumes, and nuts will increase our RS the most without jumping through hoops. If you like green bananas, eat them. Cook your pasta al dente and that maintains some of the RS in pasta. If you like to cook extra rice and pasta to use in later meals, now you know there’s a nutritional benefit. You don’t need to do anything else but eat the foods that naturally contain RS. Simply put, just eat better.

Next week is all your questions, so send them in if you haven’t already.

What are you prepared to do today?

        Dr. Chet

References:
1. Nutrients. 2018 Nov 14;10(11). pii: E1764. doi: 10.3390/nu10111764.
2. Asia Pac J Clin Nutr 2015;24(4):620-625.

Unusual Questions: Resistant Starch

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Recently an Insider asked what I knew about resistant starch and whether it can help control blood sugar in someone whose blood sugar was higher than normal. Here’s what I found.

Resistant starch (RS) is found in many vegetables and some fruits. It resists digestion and absorption, especially in the small intestine. One of the problems: RS is described on the Internet as not digested and absorbed, but that’s not accurate. It resists digestion and absorption in the small intestine but doesn’t block it completely. Because it doesn’t break down to sugar molecules, RS will not spike blood sugar the way non-resistant starch might.

RS is digested by gut bacteria in a fermentation process. Because the RS feeds healthy bacteria, it produces, among other substances, short-chained fatty acids—fats that can be used for energy without being processed by the liver. The highest amount of RS can be found in beans, grains, potatoes, bananas, and plantains.

However, it’s not quite as simple as that because food preparation happens to be important in this process. I’ll cover that as well as some other research on RS in Saturday’s Memo.

What are you prepared to do today?

        Dr. Chet

The Big Fried-Potato Question

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During the eight-year study, only 236 of the 4,400 subjects died; fewer than 30 per year. We don’t know what caused their deaths; one would expect it to be heart attacks and strokes but that data was not examined. The researchers adjusted the analysis for a number of variables including age, but it would have been more valuable to know whether fried-potato consumption was related to early mortality. That would give us more of an indication that there really was an increased mortality from eating french fries three days a week.


The Big Question

The big question is simply this: why are researchers from Italy examining the relationship between potato intake and mortality in a study about osteoarthritis? On the surface, it doesn’t make any sense. There was no overall strategy outlined in the reasoning for the study.

One reason they did it is because it’s open-access data: anyone can examine the data and use it for any type of analysis. All I had to do was register and I could download all the data related to any of their questionnaires including the FFQ. I’m not going to analyze the data, but I could.

The study was designed to examine osteoarthritis (OA) and the variables that are important to its prevention and treatment: “The purpose of this study is to examine people who have knee OA or are at high risk for knee OA; information will be used to better understand how to prevent and treat knee OA.” No mention of looking at potato intake and mortality.

The problem is that the authors of the study did not design the variables to examine; they had to use what was already in the study. The questions might have been different if they begin with a study to examine their research question: does potato intake affect mortality in North America? Here’s an example. The authors did not include data from potato chips in their analysis. To be fair, they couldn’t because all snacks were lumped together: potato chips, corn chips, pretzels, and other snack food. If you were starting from scratch, you would definitely include separate questions on the types of snack foods. But this is the type of problem that occurs when you don’t design the study; you take whatever is there, and maybe it works and maybe it doesn’t.


The Bottom Line

What can we gain from this research paper? Not much—it’s mostly meaningless in the real world. But we can do this: be realistic in how we prepare foods and what fast foods we choose to eat. Deep-fried foods can be a part of your diet; just make them a small, infrequent part of it. Every food can be a part of your diet as long as you control the amount and how often you eat it. Eat less. Eat better. Move more.

What are you prepared to do today?

Dr. Chet

 

Reference: Am J Clin Nutr doi: 10.3945/ajcn.117.154872

 

The Data Must Make Sense

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The data has to make sense before you do any type of statistical analysis; that’s why I always look at the mean and standard deviations. Let me explain what I found that seemed a little off in the Fried Potato Study.

The authors divided the data into quintiles based on potato consumption from less then once per month to greater than three days per week. The researchers reported 19 variables from age to calorie intake to the percentages of various diagnosed diseases in each quintile of potato intake.

I focused on the caloric intake and the Body Mass Index in each category of potato intake. As potato intake increased, the caloric intake increased 600 calories per day—from 1,150 calories per day to 1,750 calories per day. Keep in mind there are 3,600 calories in a pound, so that’s over a pound a week. In every quintile, as the potato intake increased, so did the caloric intake. That could make sense although we don’t know if the additional calories all came from potatoes.

What didn’t make sense was that the BMI for each quintile was about the same: 28.5. That makes no sense at all. If the calories increased, the BMI had to increase for each quintile. It did not. Physical activity could not explain it because those in the highest caloric intake were less active than those with the lowest potato intake. It would be wonderful if calories didn’t add up and we could eat all we want without gaining a pound. I’m sad to say it doesn’t work that way.

While the study leaves that question unanswered and many more, it still isn’t the single biggest question of all. Can you guess what it is—even without reading the study?

What are you prepared to do today?

Dr. Chet

 

Reference: Am J Clin Nutr doi: 10.3945/ajcn.117.154872

 

Fried Potatoes: Hazardous to Your Health

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The headline said: “Eating fried potatoes linked to higher risk of death.” My philosophy is that we can eat anything as long as we eat them in moderation, and I like French fries once in a while. My scientific curiosity tells me that I need to check this out. Let’s take a look at the study.

Researchers from Italy used data from the Osteoarthritis Initiative (OAI) to assess the relationship between potato intake and mortality. This is a multicenter study that recruited over 4,400 subjects from four medical centers in the North America. The eight-year study followed subjects who have osteoarthritis of the knee or are at high risk for developing it.

At the beginning of the study, data were collected on dietary intake using a Food Frequency Questionnaire. The dietary data were used to examine the relationship between potato intake and mortality rate. Non-fried potatoes were not related to increased mortality, but there was an increased risk of death for those subjects who ate fried potatoes. The risk was highest if someone ate fried potatoes more than three days per week.

Those are the results. But I have several questions of my own. I’ll cover that the rest of the week including the big question. Don’t forget: tomorrow night is the Fibromyalgia webinar; there’s still time to register.

What are you prepared to do today?

Dr. Chet

 

Reference: Am J Clin Nutr doi: 10.3945/ajcn.117.154872

 

Potatoes and Your Microbiome

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A Cherokee legend talks of two wolves inside us, one good and one evil. Which one will win? The one you feed. It applies to our microbiome as well. We have good and bad microbes within us at all times. Which ones dominate? It depends on how we feed them.

In a recent study, researchers tested a prebiotic made up of a harder-to-metabolize starch extracted from potatoes. The subjects were a group of elderly and middle aged men and women. The objective was to compare the types of bacteria that responded positively to the prebiotic.

At baseline, the elderly subjects had higher amounts of the bad microbes, proteobacteria such as E. coli, compared to middle-aged subjects. After three months of using the prebiotic, there was a decrease in the bad microbes in the elderly subjects while both groups experienced in increase in bifidobacteria, the good microbes. The conclusion was that the prebiotic helped create a better microbiome balance.

While this was a small study that focused on one type of prebiotic, there’s a lesson. If you have a diet that includes vegetables, beans, and some starchy root vegetables such as potatoes, you will get a variety of prebiotics including the type used in this study. They will help you feed the good microbes to create the right balance in your digestive system. Which microbes will win? Your diet determines which ones dominate.

What are you prepared to do today?

Dr. Chet

 

Reference: DOI: http://dx.doi.org/10.1016/j.clnu.2017.03.025