Welcome to Straight Talk on Health. I’m your host Dr. Chet Zelasko. Straight Talk on Health is a joint production with WGVU in Grand Rapids MI. With a PhD in exercise physiology, I’ve been teaching people how to improve their health through diet, exercise, and supplementation for over 30 years. I look at the science behind all the headlines and social media, and let you know whether it’s something to consider or not. You can check out other things that I do on my website Drchet.com and sign up for my free emails.
I’ve made it clear that I don’t drink smoothies of any type. I’m also aware that it is 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. Bananas added to smoothies may impair the phytonutrient benefit of blueberries when blended in smoothies. Let’s look at the study.
Researchers recruited subjects for two studies; 8 volunteers for the first, 11 for the second. They tested whether a banana added to blueberries in almond milk impacted the polyphenol content as well as the amount of polyphenols absorbed into the body. There were two controls: first, another blueberry smoothie made without banana, and a capsule with a specific flavanol content taken with almond milk. The second study differed slightly. They blended the blueberries with half the almond milk and the rest of the almond milk with the banana. When they drank the shakes, they alternated sips between each shake until the total amount from both shakes was finished.
Why do this study to begin with? The reason was to test a specific enzyme known to reduce polyphenol content in fruit: polyphenol oxidase (PPO). Bananas contain a high content of PPO thereby reducing the potential polyphenol content of the berries a great deal. That didn’t happen without the bananas; in fact, the polyphenol capsule and fruit without the enzyme came out about the same in polyphenol absorption.
The question is simple: does this really impact your morning smoothie if you choose to include a banana in the blend? I won’t hold you in suspense: you can put the banana in your smoothie if you like them. 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 isn’t enough, nor is 11 in the second study, to be able to make generalizations applicable to a population in general. While it is interesting, we don’t know whether 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 dispersion pattern would have been helpful. While the mean reduction was significant, not pre-blending the banana with the blueberries and milk did not reduce the polyphenol content very much. That was where they alternated sips from each shake. The take home message to me is don’t blend the fruit with the banana until you’re ready to drink it. Many people say they blend their smoothie the night before and leave it overnight. Maybe put the ingredients in the blender without the liquid and banana and store it in the fridge overnight. But there’s more to it than that. Here are three observations I had.
Part of the reasoning the researchers did the study was that people may be selecting their foods based on the polyphenol or phytonutrients content. Have you ever selected the fruits you put in your smoothie, or even those you want to eat in a salad or a meal based on the polyphenol levels? For the most part, I don’t although I will admit I try to get at least of one serving of brassica vegetables every day. I eat fruit and vegetables because it’s available, better tasting if in season than if not, and I want to reach that 8-10 servings per day. Polyphenols never cross my mind in that decision, the exceptionthe brassica veggies I mentioned earlier. While I’ve talked about the limited benefit of the study, there are three things we can take away from it.
First, If you like a banana in your fruit-based smoothie, there is no reason to change that approach if you like it. 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 3-4 times per day. Either you’ll get tired of it or your body will adapt. To take a line from a movie “Nature finds a way.”
Second, 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.
Third, 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 a product or 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 6 months show the same results or would there be some form of adaptation resulting in more polyphenol absorption. That’s what I would like to know. I also had another question. Why was a press release about research that included a polyphenol dietary supplement sent out three years after the study was published? Just seems curious to me.
Let’s turn to another topic that I’ve been thinking about and that’s bioengineered foods and our DNA. I don’t know if you’ve noticed it but apples are sweeter than they used to be. I prefer Empire apples because of the tartness but eating a honey crisp apple seems to be a lot sweeter than any other apple I’ve eaten. The same holds true for corn this past summer. One variety we got seemed almost too sweet to eat. When it comes to those foods, they have been created through normal plant husbandry for the most part. But many products including corn, soybeans, canola, sugar beets, and potatoes have been have been made via GMO or bioengineered techniques. That raises the question in some people minds: Could the DNA from the bioengineered foods end up mixed with my DNA in some way?
The answer is no. Cooking and processing the plants will break apart the cell structure including the plants DNA. That’s one limitation. In addition, while there is DNA from the plants or animals we eat in our food that is not processed or cooked, most is digested and broken down in the gut. Further, there is no greater probability that a DNA sequence is more likely to be a problem from GMO food than from non-GMO food. In fact, it is more likely to happen with non-GMO food because we eat so few foods that are bioengineered.
On top of that, if somehow it happened, it wouldn’t necessarily be harmful. If it were harmful, the immune system would attack to eliminate the altered cell because that’s what the immune system does. While a different topic, we make approximately 10,000 cancer cells per day and the immune system eliminates them all most of the time. I think that the odds of any permanent alterations to our DNA shouldn’t be a concern at this or any time for that matter.
That’s all the time I have for this episode. If you like this podcast, hit the like button and send a link to your friends and colleagues about it. Until next time, this is Dr. Chet Zelasko saying health is a choice. Choose wisely today and every day.
Reference:Food Funct., 2023, 14, 8217–8228
