Caffeine and Your Health

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The health reports on coffee and caffeine seem to change on a regular basis. First caffeine is good, then it’s bad. To bring you up to date, I’m providing the latest information based on a recent scientific statement on caffeine and cardiovascular disease by the American Heart Association.

Caffeine and Heart Disease

Overall, caffeine — especially filtered coffee — seems to benefit the heart. I used that word “seems” intentionally because that’s what the current science indicates.

Caffeine, especially from coffee, has proven to reduce the risk of atrial fibrillation. On the other hand, caffeine in general seems to increase premature ventricular contractions (PVCs). Why it might decrease risk of one arrythmia while increasing another type is unknown, but that’s what the data suggest. Caffeine either has no impact or may even decrease the risk of coronary artery disease, heart failure, and stroke. The latter is most pronounced with coffee. While caffeine doesn’t seem to impact coronary artery disease, caffeine does release fatty acids from fat cells; that could raise LDL cholesterol, and again, may only be a factor for some people.

When it comes to blood pressure, the relationship has no established pattern at this time.  It can increase it in some people, depending on the amount consumed, or have no effect. It seems to be an individual response.

Good news: caffeine, especially coffee drinking, reduces the risk of type 2 diabetes.

The Bottom Line

My feeling is that it may all come down to genetics. If you have the combination of genes I mentioned Tuesday that result in fast metabolism, you likely will have fewer issues, especially with coffee. If you’re a slow metabolizer, caffeine stays in your bloodstream longer and that may elicit the negative impacts.

I’m going to continue to enjoy drinking my coffee within the guidelines some suggest: four to five cups of filtered coffee per day, which is less than 300 mg of caffeine.  Other sources of caffeine? I don’t use energy drinks or products with caffeine in them because they don’t work for me; however some drinks may have excessive amounts of caffeine in them. Check the chart in the reference for info on caffeine in other drinks, such as tea and soda, and other products like pain relievers. You can get your caffeine any way you want; just try to keep it under 300 mg per day.

Remember, coffee and tea have more phytonutrients in them than just caffeine; that may also have an impact on who can handle caffeine or not. I’ll keep you posted when more research is published.

What are you prepared to do today?

        Dr. Chet

Reference: Circulation. 2026;154:e345–e355. DOI: 10.1161/CIR.0000000000001454

Caffeine’s Effects

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I love coffee. I had my first coffee when still using a bottle; my mother would put coffee with milk and sugar in it, and that’s what I drank instead of water. I don’t know why, especially after having been around an infant for the first time — the last thing baby Riley needed was more energy from caffeine!

Recently the American Heart Association published an updated review of coffee and caffeine, so today let’s cover facts about caffeine and coffee:

  • Caffeine has a close to 100% bioavailability when taken in a drink like coffee and tea, but caffeine can also be absorbed through the skin and inserted rectally. Remember when coffee enemas were popular years ago? Maybe people felt better because of all the caffeine they absorbed. (Or maybe they were just glad it was over.)
  • Many over-the-counter drugs have caffeine in them such as pain relievers and hangover preparations.
  • If you drink coffee or caffeinated beverages when you eat, you may delay or diminish the effects of caffeine, especially with meals high in fat.
  • There are definite genetic variations in your ability to absorb and utilize caffeine. Single-nucleotide polymorphisms in the CYP1A2 and AHR genes determine whether a person metabolizes caffeine fast or slow. I’m a fast metabolizer — I can drink coffee and go right to sleep. How about you?

Today, I drink my coffee black with no additions. But what’s the story on coffee, caffeine, and your health? I’ll cover that on Saturday.

What are you prepared to do today?

        Dr. Chet

Reference: Circulation. 2026;154:e345–e355. DOI: 10.1161/CIR.0000000000001454

Manteniendo Tu Melón

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Tuesday, we talked about Maintaining Your Melon — or manteniendo tu melón in Spanish. The U.S. POINTER study demonstrated that cognitive decline could be reduced using two different approaches in over 2,000 subjects with an average age of 68. Based on the U.S. POINTER design, the Latin American Initiative for Lifestyle Intervention to Prevent Cognitive Decline (LatAm-FINGERS), was adapted for use in 11 Latin American countries. The results were similar to the U.S. POINTER study; both groups improved their global cognitive scores. The approach was slightly different.

While they also used a similar demographic for age, health issues, and diminished global cognitive status, and a structured approach and self-guided approach, they tailored it for every country, which I think was brilliant. It’s similar to the approach used in studies that teach the Mediterranean diet but adapted for specific countries and culture.

Why try to teach people to focus on eating wholegrain pasta when the primary source of carbs in that country is wholegrain rice? That applies to the types of vegetables, fruits, protein sources, and spices used in cooking. But that’s not all. They also used forms of movement most likely to get greater participation for the exercise program. Salsa, tango, and large-group outdoor exercise programs were incorporated into the exercise program if it was part of the culture. I think that approach should be universal for all lifestyle programs.

The question could be raised as to why the structured program was more beneficial in any of the countries where this type of study was used. Although the programs didn’t answer that, in my opinion, it’s the personal attention that the subjects received with diet and exercise. Those participants benefit the most because they can get personalized direction exactly at the time they need it. Keep that in mind when you think you’re ready to change your lifestyle. What are you prepared to do today?

        Dr. Chet

Complementar Su Dieta

P.S. If Spanish is your first language, this downloadable MP3 may be just what you need to make sure your supplements are the right ones for your lifestyle. Check out Complementar Su Dieta at drchet.com for only $8.95 (Member and Insider discounts apply).

Reference: Lancet, 2026; 408 (10553): 417 DOI: 10.1016/S0140-6736(26)01278-X

Maintaining Your Melon

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Changing one’s lifestyle is difficult to do, and I think it’s especially challenging if the benefits could be years in the future — specifically doing those things that need to be done now to reduce the decline in cognition that happens as we get older. Two recently published studies have demonstrated how that’s possible. The characteristics of both were a structured program of changes in diet, exercise, learning and remembering, and social interaction with intermittent personal guidance from nutrition and exercise specialists. That regimen was compared with a control group who was provided with the same information but without the personalized assistance.

U.S. Study to Protect Brain Health Through Lifestyle Intervention to Reduce Risk (U.S. POINTER) was adapted for the U.S. based on a Finnish study. The primary outcome was a combination of surveys typically used to measure global cognitive status as well as other health metrics tested before and at six-month intervals for two years. Over 2,000 subjects between 60 to 79 were recruited from five sites throughout the U.S.; subjects were randomly assigned to the structured program or the self-guided program.

After two years, both groups experienced an improvement in the global cognitive status; those in the structured program experienced a greater improvement than the self-guided group. In fact, every sub-group experienced a mean improvement in cognition. That can result in reducing or delaying dementia and Alzheimer’s disease if sustained over the remainder of their lifespan. While these results were great, could there be an even better way to protect your melon? I’ll let you know on Saturday.

What are you prepared to do today?

        Dr. Chet

Bottom Line on Alzheimer's Disease

P.S. Is Alzheimer’s disease a concern for you or your family? Learn more about it with The Bottom Line on Alzheimer’s Disease at drchet.com; get the MP3 or PDF for only $2.99 (free for Insiders).

Reference: AMA. 2025;334(8):681-691. doi:10.1001/jama.2025.12923

Is Xylitol Dangerous?

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Over the past few years, research papers have suggested that sugar alcohols, specifically erythritol, may increase blood clotting and potentially lead to a major adverse coronary event or MACE for short. It gave me pause — to the extent that I stopped using sugar-free gum when I work out. The same research group recently presented a paper at a major heart disease conference suggesting that xylitol may do the same. I’m going to present some facts about what I’ve found, and you can make your own decision.

The Facts on Xylitol

Xylitol is a sugar alcohol. It is not an artificial sweetener. Some discussions have labeled it as such, but that’s wrong.

Our body makes xylitol along with other sugar alcohols. The amounts vary, but on average, the amount is 5 to 10 grams per day.

Pure xylitol powder contains 4 grams of xylitol. The highest processed food source is sugar-free dark chocolate at 1.2 grams of xylitol per ounce of chocolate. None of the studies collected data on sugar alcohol intake.

The research on xylitol and other sugar alcohols is limited to large observational studies. No randomized controlled trial exists. Therefore, while the relationship proposed between MACE and sugar alcohol intake is curious, it’s going to take specific randomized controlled trials to determine any cause and effect.

The problem with the current state of research is that it doesn’t preclude that some people may naturally produce more endogenous xylitol than others. That has to be separated out at some point in time.

One thing is true: xylitol can be lethal for dogs, even in small amounts like chewing gum! Make sure you keep any sugar alcohol products including gum away from all animals.

The Current Bottom Line on Sweeteners

I think that the research on sugar alcohols should continue but without the hyperbole. What’s often not stated is the impact sugar alcohols can have on gut bacteria. Even if sugar alcohol can have some role in MACE, the gas production can keep consumers from using it in excessive amounts. As for me, I still chew gum while I work out, but my gut works overtime producing gas if I eat foods with sugar alcohols in them. I’d rather pass on the sugar alcohols than pass gas, so it’s regular old gum for me.

A Note on the Memo

While I love writing the Memos and helping you live a healthier life, drchet.com is still a business, so I’m hoping to increase product sales. If I have a product in the store that relates to the Memo’s subject, I’ll be highlighting it in a P.S., starting today with an option if you decide xylitol isn’t for you.

What are you prepared to do today?

        Dr. Chet

Bottom Line on Sucralose

P.S. If you’re going to stop using xylitol, you’re going to need another sweetener. Sucralose has been widely criticized, but is it warranted? Check out The Bottom Line on Sucralose at drchet.com; get the MP3 or PDF to learn more for only $1.99 (free for Insiders).

References:
1. CVD Res 2025. (121)1319–1329 https://doi.org/10.1093/cvr/cvaf091
2. Eur Soc Cardiology 365. 2026. Poster: The association of Xylitol and incident cardiovascular events: the CLSA and EPIC-Norfolk cohort studies

The Memo: AI-Free Zone

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I’m still bugged about the topic I wrote about last week, polyphenols in fruit. It’s not that I don’t think it was an interesting topic. It was. Why did it show up in press release now when it was published in 2023? My sense is that AI was involved, based on what I’ve read and what I’ve researched in the past. I’m going to change the way I select topics to write about.

But that’s not the real reason I’m writing this. It is to let you know that everything that’s posted on my website was written by me. I do use a specific AI to search for background research on topics (one expert said to think of AI as an eager research assistant, and that’s how I use it). I read research papers that AI finds, and I know the field well enough to know a good source from one that’s bad. Once I read enough research, I write about the topic. Then my editor of 36 years verifies what I’ve written makes sense or recommends changes that makes it clear what I intended to write. Then it goes to you.

It’s not that AI doesn’t offer to write something, but it doesn’t have a database of life experiences in addition to my knowledge base. It cannot think, has never run a marathon, got a knee replaced, or dealt with any of the human conditions we face. If you read what it writes, it sounds hollow because when AI writes, it’s not choosing the best word—it’s giving you the most common word to occur in that particular phrase.

One area is not free from AI: the illustrations. Paula says it’s almost impossible to find art that hasn’t been touched by AI. It’s not just the image of a hippo in a track suit eating ice cream; it’s almost every image, no matter how ordinary, but we work hard to make sure the images aren’t misleading and try to exclude anything made with generative AI.

Just know that the Memo and everything I write or say originated with me. This is an AI-free zone and is going to stay that way.

What are you prepared to do today?

        Dr. Chet

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

Carbs and Insulin: Diet Matters

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On Wednesday, I told you about a study of people who experienced an energy crash after eating carbs. The next study was more pragmatic: we have non-diabetic people who seem to have reactive hypoglycemia (RH), but can we treat it with diet alone? This is a concern because many believe that RH in these people may be a precursor of pre-diabetes and type 2 diabetes. This time, the researchers recruited 40 normal-weight subjects with RH symptoms to see if a dietary intervention could improve symptoms over a year. After testing all subjects, only 12 subjects actually had blood sugars below 55 mg/dl, the more-or-less agreed upon lower boundary for blood sugar.

After assessing their initial diet, subjects met with a dietician four times over the next six months. They were taught the nuances of a Low Glycemic Index Diet in private sessions with a dietician. The subjects were asked to follow that diet for the next three months, with a follow-up session with the dietician midway to fine-tune the diet. The same pattern was followed for the Mediterranean diet. The subjects were tested for RH symptoms after each diet; then for the next six months, they were told to follow any diet they chose based on what they’d learned. All subjects were tested again after 12 months.

A couple of results stood out to me. After six months, the subjects ate an average of four times per day instead of the three times before the study began. Second, they allowed more time between each meal than they had before. While they were instructed on portion sizes during the training periods on each diet, there were no limitations on how much they ate or and no counting calories.

When it comes to the symptoms associated with RH, five of the seven tested were significantly reduced. The researchers attributed it to a healthier eating pattern. After the 12-month study, 80% of the subjects leaned toward the less-complicated Mediterranean diet, which increases the number of whole grains, vegetables, beans, and nuts.

What do we know now that we didn’t know then? Two things: diet matters when it comes to hypoglycemia in non-obese, non-diabetic subjects. Further, individual attention, even just four sessions within six months, is enough to help people make better choices. Whether that lasts more than a year is unknown, but we also know this: the most powerful hormone in the body—insulin—doesn’t cause the insulin overshoot phenomenon in otherwise healthy people. The search for the cause continues.

The Insider Conference call will be next Wednesday September 16 at 9 p.m. ET, and the topic will be Sugar and Carbs—Fact or Fiction. Some of the facts and fictions covered will be:

  • Does eating sugar cause diabetes or pre-diabetes?
  • Can type 2 diabetics eat sugar?
  • Which organ wants and uses more sugar than any other?
  • What are hidden sources of sugar on nutrition labels?
  • Can overeating carbohydrates cause non-alcoholic liver disease?
  • And even more, plus answers to your questions.

The Guest Pass for this Insider Conference call will be available just like last month for $9.95. Sign up before 8 p.m. Wednesday to be included, and a replay will be available within the following week.

GuestPass

Click on the ticket
to sign up!

What are you prepared to do today?

        Dr. Chet

Reference: Nutrients 2022. (14) 497. https://doi.org/10.3390/nu14030497

Carbohydrates and Insulin

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On a typical busy morning, a person has a fairly good dose of carbohydrates in the form of a sugary cereal, a bagel, a pastry, or a breakfast sandwich from a drive-thru. Then a couple of hours later, they seem to crash—not their car, but their energy seems to drain away. Maybe they start to sweat and even get some brain fog. If it happens with regularity, people get concerned and may even see their doctor. Is this a food problem? A metabolic problem? We’ll spend some time talking about it; let’s begin with a couple of studies.

The first study recruited a group of healthy subjects who had symptoms like I mentioned. They were tested, together with a healthy control group that had never responded that way, for a condition known as “reactive hyperinsulinemia,” also called the insulin overshoot phenomenon. In short, that means too much insulin is released and can drop the blood sugar below 55 mg/dl.

The researchers tested all subjects for problems in processing carbohydrates: oral glucose tolerance test, mixed meal tolerance test and a bunch more.

They found no specific pattern in either group of subjects:

  • Some in both groups had symptoms, but their blood sugar never went too low.
  • Some had their blood sugar go below 55 mg/dl with no apparent symptoms.
  • In subjects with glucose lower than 55 mg/dl, none had a high insulin level to cause that effect.
  • Not one subject responded with problems to the mixed meal tolerance test.

The conclusion was that a lot more research has to be done to find out why what everyone thinks is happening really isn’t happening in everyone. Fortunately, this same research group did an interesting follow-up. We’ll talk about that on Saturday.

What are you prepared to do today?

        Dr. Chet

Reference: J. Pers.Med. 2021,11,276. https:// doi.org/10.3390/jpm11040276