Tag Archive for: bananas

Fruit: Variety is the Key

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I didn’t want to hold you in suspense, so I already revealed that you can put the banana in your smoothie if you like. I’ll tell you why, but first a little more about the study.

The biggest issue, which the researchers acknowledge, is the limited number of subjects. Eight subjects just aren’t enough, nor is 11 in the second study, to be able to make generalizations applicable to others. While it’s interesting, not every subject was impacted in the same way. The researchers didn’t use scatter plots so we could see exactly how the subjects were impacted individually.

The take-home message is don’t blend the fruit with the banana until you’re ready to drink it if you want to maximize polyphenol content, but there’s more to it than that.

Three Observations

Part of the reasoning the researchers had was that people may be selecting their foods based on the polyphenol or phytonutrient content. Have you ever selected the fruits you put in your smoothie, or even those you want to eat, based on the polyphenol levels? I haven’t. I eat fruit because it’s available, better tasting in season than not, and I want to reach that eight to ten servings per day. Polyphenols have never crossed my mind once in that decision.

While I’ve talked about the limited benefits of the study, there are three things we can take away from it.

  1. If you like a banana in your fruit-based smoothie, there’s no reason to change that approach. Even if this were a large study with enough subjects to increase the power and actually be meaningful, you’re not eating the same smoothie three or four times a day; either you’ll get tired of it or your body will adapt. To take a line from a movie, “Nature finds a way.”
  2. You should eat a variety of fruits and vegetables throughout the day. If you eat enough fruit from a variety of sources, you’ll get the polyphenols at some point. You don’t have to eat in some strange schedule to maximize phytonutrient content.
  3. If this study shows anything, it’s that taking phytonutrients in supplement form is an excellent way to complement a good diet. If you already use products with plant concentrates and phytonutrients in them, you may be ahead in the phytonutrient game. 

These studies were well thought out and well executed as pilot studies; let’s hope this is a prelude to a larger study from the same research group in the near future. One question I have is whether the consistent consumption of the same banana-blueberry smoothie consumed regularly over six months shows the same results or would there be some form of adaptation resulting in more polyphenol absorption? If I find out, you’ll hear it here first. What are you prepared to do today?

        Dr. Chet

Reference: Food Funct., 2023, 14, 8217–8228

Should You Skip the Banana?

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Over the years, I think I’ve made it clear that I don’t drink smoothies of any type. I’m also aware that it’s a preferred method for many people to get their fruit, protein, fiber, and other nutrients in a convenient manner. That’s why a recent press release for a study published in 2023 caught my attention; it claimed that bananas may impair the phytonutrient benefit of blueberries when blended in smoothies, specifically the polyphenols. Let’s look at the study.

The reason for the study was to test a specific enzyme known to reduce polyphenol content in fruit: polyphenol oxidase (PPO). Bananas contain a high amount of it; would it reduce the potential phytonutrient content of the berries? Researchers recruited subjects for two studies; eight volunteers for the first, 11 for the second. They tested whether a banana added to blueberries in almond milk impacted the phytonutrient content as well as the amount actually absorbed into the body. There were two controls: first, another smoothie made without banana, and a capsule with a specific flavanol content taken with almond milk. The second test did the same thing but did not blend the banana with the blueberry and milk.

The polyphenol capsule and the fruit without the banana came out about the same in polyphenol absorption.

The question is simple: does this really impact your morning smoothie with a banana? I’ll let you know on Saturday. Okay, I won’t make you wait—put the banana in the smoothie if you like it.

Tomorrow night is the Insider Conference call. You can still become an Insider or purchase a Guest Pass for $9.95 by 8 p.m. ET Wednesday, and a replay will be available within the following week if you can’t make it live. The topic is Sugar and Carbs—Fact or Fiction as well as answering your questions.

What are you prepared to do today?

        Dr. Chet

Reference: Food Funct., 2023, 14, 8217–8228

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