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I’ve written and recorded a lot of evidence-based content over the years on just about everything you can imagine related to building muscle, losing fat, and getting healthy.

I’ve also worked with thousands of men and women of all ages and circumstances and helped them get into the best shape of their lives.

That doesn’t mean you should blindly swallow everything I say, though, because let’s face it—nobody is always right about everything. And especially in fields like diet and exercise, which are constantly evolving thanks to the efforts of honest and hardworking researchers and thought leaders.

This is why I’m always happy to hear from people who disagree with me, especially when they have good arguments and evidence to back up their assertions.

Sometimes I can’t get on board with their positions, but sometimes I end up learning something, and either way, I always appreciate the discussion.

That gave me the idea for this series of podcast episodes: publicly addressing things people disagree with me on and sharing my perspective.

Think of it like a spicier version of a Q&A.

So, here’s what I’m doing:

Every couple of weeks, I’m asking my Instagram followers what they disagree with me on, and then picking the more common or interesting contentions to address here on the podcast.

And in this episode, I’ll be tackling the following . . .

  • You say artificial sweeteners are potentially harmful and cite animal research. How does that apply to humans?


0:00 – Pre-order my new fitness book now for a chance to win over $13,000 in splendid swag: 

7:16 – Can artificial sweeteners be harmful to your health?

8:04 – What are some of the claims about artificial sweeteners?

14:41 – What about articificial sweeteners and cancer?

15:07 – Artificial sweeteners and headaches

15:50 – Artificial sweeteners and seizures

16:11 – Artificial sweeteners and gut health

23:22 – Conclusion

24:23 – Natural sweeteners

Mentioned on the Show:

Pre-order my new fitness book now for a chance to win over $13,000 in splendid swag: 

What did you think of this episode? Have anything else to share? Let me know in the comments below!


For decades now, most doctors have recommended cardio over strength training because they believed it produced more health benefits, stress to the body less, and it was more popular among the public. We now know though that strength training has multiple major advantages over cardio, and if you had to pick just one kind of exercise, it should.

Strength training. That said, there are good reasons to include cardio in your exercise routine as well. First, as the term implies, cardio boosts the health and the function of your cardiovascular system. For instance, while cardio and strength training are. About equally effective for reducing blood pressure.

Research shows that doing both reduces blood pressure the most. Additionally, cardio but not strength training helps keep your arteries flexible and responsive to changes in blood flow. And that’s why studies show that people who do the most cardio have these splt arteries, and that is crucial for maintaining healthy blood pressure.

And minimizing stress on your heart and blood vessels. Another circulatory downside to aging is the reduction of the capillary health and density of your muscles and other tissues. And studies show that cardio can significantly increase capillary density, which is the number of capillaries in an area of the body in muscle tissue, in just a.

Weeks cardio also burns substantially more calories per unit of time than strength training does. And that of course can help you lose fat faster and help you keep it off more effectively. Cardio is great for, uh, body composition maintenance for that reason. And when you combine strength training, And cardio together.

And when you combine them, especially in the way that I teach in my new book, muscle for Life, which you can learn about at Muscle for Life, muscle f o r life You can maximize fat loss without hindering. Muscle or strength gain. So the takeaway here is with moderate, sustainable and effective doses of strength training and cardiovascular exercise, you can build a body that looks, feels, and functions like a well-oiled machine and cardio’s easier to incorporate into your fitness regimen than.

Think too. In fact, in Muscle for Life, I share three simple principles that allow you to enjoy most of the benefits cardio has to offer with none of the potential downsides. And again, you can learn all about that book as well as the now it’s over $13,000 of Cool goodies, fitness goodies that I’m giving away to people who pre-order the book at Muscle for Life

Hello, hello, and welcome to Muscle for Life. I am Mike Matthews. Thank you for joining me today. Very quickly, if you have not done it yet, please do subscribe to the show in whatever app you are listening to me in so you don’t miss any new episodes. And it helps me because it boosts the ranking of the show in the various charts.

So this episode is the latest installment in my Saysyou series where I ask people to. Things that they disagree with me on. And I usually do it on Instagram, although I do get material for says you from emails. Well, so if you’re not following me on Instagram, you want to participate in my collection of stuff to address here on the podcast, follow me at Muscle Life Fitness.

Or you can send me an email, mike Muscle for muscle f o r And. You can let me know if you disagree with any of my positions on really anything. I, I mostly focus on health and fitness stuff, obviously, but if you disagree with me on something related to my political or cultural commentary, I’m open to that.

Uh, business practices, marketing practices, I’m open to that. I’m really open to anything, and I don’t take any of it personally, by the way, because I am genuinely in. In hearing about people’s disagreements, because sometimes it allows me to refine my thinking or my position. Sometimes it allows me to learn something that I didn’t know previously, and sometimes it allows me to find out where I am wrong and where I can find out how to be more right, which is how I prefer to look at the process of continually updating.

Positions, updating information, updating facts and opinions. I don’t mind admitting that I was wrong because what that means is I am now more, right? And so in today’s episode, I am going to address a challenge from Wolf Nutrition over on Instagram. And he says, you say artificial sweeteners can be potentially harmful in cite a study where they gave rodents four to five x, the R D a.

How does that apply to humans? And he brings up a good point. He’s referring to the product pages over at legion’s website, legion, my sports nutrition company, because on those pages it says, I’m gonna paraphrase that artificial sweeteners are not as harmful as many people would have you believe.

But there is evidence that. Consuming too much of these chemicals too often can be harmful to our health and particularly our gut health. And there are a few studies that were cited to support those claims, but I wrote that copy years ago and I was going with the research that was available at the time.

That I knew was a bit speculative and I was very open about that, but that I still stood by based on the research that was emerging at the time. The findings that were coming out at the time. To me, there was clearly a trend, and now you fast forward a couple of years later and it would appear that.

Instinct was correct because there is now quite a bit more research that indicates that I was mostly right, that these chemicals are not as harmful as the alarmists would want you to believe. And I’m not one of those people, but. If you want to, let’s say, optimize your gut health, which isn’t just about the health of your gut, we now know that your gut health impacts many aspects of your health, including your mental health.

Then you probably don’t want to be consuming a lot of these artificial sweeteners. So quickly just to mention, I have updated these citations on all of Legion’s product pages, uh, to the most recent research that best supports the claims made on the pages. And we’re gonna get into those details here on this podcast.

So the question, can artificial sweeteners be harmful to your health? Yes, I do think they can be. I do think that that is supported by good evidence. However, I do not think that they are as harmful as many people claim. And one of the reasons many people claim that these chemicals are very harmful is marketing.

It is good market. To take a strong position on a controversial topic because it gets attention right before you can sell anybody on anything. You first have to get them to stop scrolling. You have to get them to read or listen. You have to get their attention. And extreme and unusual statements get a lot more attention than moderate and conventional.

So some of these more extreme statements about artificial sweeteners are that they contribute to weight gain, that they can increase the risk of diabetes, metabolic syndrome, cancer, that they can give you headaches, seizures. And mess up your gut health. Most of that though, is overblown and not supported by the scientific literature.

For example, you can find studies that seem to show that artificial sweeteners have a negative effect on weight gain, that they can lead to weight gain or increase the risk of weight gain. But they are observational studies and that’s important because observational studies cannot be used to determine.

Causation. They can only be used to determine correlation because you are watching a lot of people over a period of time, sometimes a long period of time, and you are simply noting that certain things are happening and that there might be relationships between these things. This type of research is good for coming up with hypotheses, but you don’t know.

If what you are seeing, if the, if the apparent relationships that you are seeing are. Just coincidences or causes and effects. To determine causes and effects you have to move to clinical trials, RCTs, randomized controlled trials. Now those studies can determine causation. Because they are carefully designed to control, or in many cases, eliminate potentially confounding variables and specifically investigate the hypothesis that you have created and the variables that will prove that hypothesis to be correct or incorrect.

And just to give you a simple real world example of how this works, consider people who have lost a lot of weight by following the keto diet and who assume that it was successful because they ate less carbs. They assume that carbs drive fat, gain carbs make you fat. They keep you fat. And that’s because people, many people at least, who push the keto.

Claim that. And as proof for that claim, these people say, Hey, just cut basically all of the carbs outta your diet and see what happens if you lose a bunch of fat. And if you find it easier to stay lean, well then my hypothesis or the hypothesis of carbs driving fatness is correct. Right? And so people.

Give it a go. They get rid of most of the carbs in their diet. They lose weight and think, well, I guess that is correct. Then I guess I should just not eat carbs. If you look to the scientific literature though, we know that is not correct. We know that the reduction of carbohydrate intake is simply a correlation in the outcome of weight loss.

It is not the driving factor. It is not causative. It contributed to the weight loss, of course, but the weight loss did not occur because. Fewer carbs were eaten. It occurred because fewer calories were eaten. It occurred because calorie intake dropped to a point where energy in was consistently lower than energy out, uh, a calorie deficit.

That is the true causative factor, and one way of creating a calorie deficit is, Getting rid of a lot of the foods that you like to eat, which in many cases are high carb foods, and that, of course is conducive to just eating less food. Another way is to not make such a dramatic reduction in carbs, to eat less carbohydrate, but also eat a bit less fat as well.

Another way is to eat a lot less food a couple of days per week, and then just eat normally a couple of days per week, like a, a five two approach, right? Where you just eat normal maintenance calories basically five days per week, and then you eat very little food or no food two days a week. So that’s an intermittent fasting, uh, method of intermittent fasting.

That’s another. of creating a weekly calorie deficit. So if you looked at your calories in versus calories out, not, uh, in the, in the day-to-day, but in the week to week, that’s a way of going about it. And there are other ways too, but the key is if you don’t create a calorie deficit, you are not going to lose fat.

And that is true regardless of how. Little carbohydrate you eat. And that is why many people fail to lose weight on the keto diet or even gain weight on the keto diet. In some cases, average daily calorie intake actually goes up on the keto diet because they’re eating a lot of these fatty foods that are very calorie dense and in some cases are not very filling.

And so it actually makes it easier for them to overeat by getting rid of, uh, a lot of. Carbs that they normally eat, they are generally less full and they just tend to now eat more calories than before. So anyway, coming back to artificial sweeteners, now we have these observational studies that suggest that they can lead to weight gain.

But when we look at randomized controlled trials, we normally find that the opposite is true. So the weight of the evidence goes in the other direction. When you look at rct. People who consume artificially sweetened foods and drinks actually lose more weight on average than those who eat sugar sweetened food and drink sugar sweetened drinks, of course, because the latter have more calories, it just makes it easier to overeat.

And the same goes for studies that. Purport to link artificial sweeteners with diabetes and metabolic syndrome. There are some observational studies that would suggest there is a cause for concern, but most of the high quality research, most of the randomized controlled trials shows that there probably isn’t a major reason for concern that there probably isn’t a cause and effect relationship.

And as far as claims about artificial sweeteners increasing the risk of cancer, those are largely based, at least the ones that I’ve seen, they’re largely based on animal research. Uh, there are a few human trials that have suggested there might be a link there. But again, if we look at the weight of the human research, it shows that artificial sweeteners do not increase your risk of cancer.

Now as far as headaches go, this is a little bit less conclusive because some research does suggest that some people are susceptible to getting headaches and migraines after consuming artificial sweeteners. Uh, but most research shows that there is no connection there. That’s said this is pretty simple for you to conclude for yourself because if you notice that you tend to get headaches after consuming these chemicals, then.

Stop consuming them. Pretty simple. Who cares what the research says, really? Right? If you notice that consistently, if you have some, or maybe too much of this stuff, you tend to get a headache, then just stop having it. Just leave it at that. And the same thing goes for seizures. Most research shows no link, but at least one study has shown that artificial sweeteners.

May exacerbate a condition in children that’s characterized by brief staring spells where the kid is not aware or responsive. It’s known as childhood absence epilepsy. And so that brings us to gut health, which is one of the more hotly debated. Topics, uh, relating to artificial sweeteners and how they can affect our health.

And it’s an important one because having a healthy gut should be a, a top priority if you want to optimize your health and wellbeing because studies show that poor gut health is associated with many different. Health issues, including weight gain, type two diabetes, compromised immune function, poor sleep quality, inflammatory diseases like inflammatory bowel disease and rheumatoid arthritis, cardiovascular disease, several cancers, the list rattles on Now, if we look to the scientific literature, we find that.

There are a lot of studies on this. There are a lot of studies on how artificial sweeteners can affect our gut microbiome, which is all of the microorganisms that live in our gut and that are vital to its health and to its functions. So this includes bacteria, viruses, fungi, and other things. According to some research, there are about a hundred trillion bacteria in our gut.

And for the sake of comparison, consider that there are about 30 trillion human cells in our body. So over three times as many bacteria in our gut as human cells in our body, wild, right? Anyway. As I was saying, there are quite a few studies looking at how artificial sweeteners affect the gut microbiome in all of those little creepy crawlies in it.

And some of those studies would say or suggest that artificial sweeteners are completely safe. But some of that research was funded by PepsiCo. Not that that automatically invalidates it, but it should be noted. However, there are many other studies that suggest that these chemicals are not. For our guts.

For example, in one study that was conducted by scientists at Weisman Institute of Science, seven healthy participants consumed three 120 milligram doses of saccharin per day for six consecutive days. And that 360 milligrams of saccharin that the people consumed every day is equal to the FDA’s maximal acceptable daily intake, which is five milligrams per kilogram of body weight per day.

Uh, but it, it’s. An unrealistic amount given the quantities that are normally found in many processed foods and drinks that contain saccharin. And at the end of the study, what the researchers found is that four out of the seven people had developed abnormally high blood sugar levels and a compromised gut microbiome.

Another study that was conducted by scientists at George Mason University found that consuming just 112 milligrams of as peram per day. Or 33 milligrams of Ace Suame K, which by the way, that is not that much. That is about eight ounces of diet soda. And so just that amount of these chemicals was enough to alter the overall bacterial diversity.

In the gut. Now, the researchers did not go as far to say that these changes would cause health issues, but they did recommend more research to be done because that is not very much. We’re talking again about eight ounces of diet soda and the changes were significant. And so of course the question is, well, what if you are having.

six of these diet sodas per day. And what if you were doing that four or 5, 6, 7 days per week? What would that do to your gut microbiome? And it’s research like this that makes me inclined to want to proceed with caution with these chemicals because of how important it is to maintain a. Gut, if that were not the case, if our gut microbiome didn’t impact so many different elements of our health and wellbeing, then I would be less concerned.

But because that is not the case, the opposite is true and more and more research is coming out on just how profoundly our gut health affects so many other aspects of our physiology. This is an emerging field of research, so, 10 years from now, researchers, doctors, and dieticians might rank maintaining a healthy gut microbiome up there with maintaining good sleep hygiene, for example.

It might prove to be that important, and so why gamble with that? . That’s my position with artificial sweeteners. Now, if you’re gonna have some here and there, of course that’s not a problem. But if you look at many fitness folk who take pre-workout, intra-workout, post-workout, BCAAs, multiple scoops of protein powder per day, uh, greens supplement and whatever else, and they do that 5, 6, 7 days per week and it’s all artificially sweetened.

That is a lot of these chemicals to be consuming. Regularly, and in the end it might not have any noticeable impact on their health. It might not make any difference whatsoever, but I would say the trend of the research suggests that it is negatively affecting their health, even if they don’t realize it, and that they would be in better health if they had.

Less of those artificial sweeteners, and that’s why my sports nutrition products, my legion products, have always been naturally sweetened and naturally flavored and no artificial food dies, uh, or other chemical junk since the beginning. And the beginning was about eight years ago. When the theories about how artificial sweeteners can impact gut health and why that would matter, were much more speculative.

But I didn’t want to take the risk with my own body because I do try to optimize as many aspects of my lifestyle as I can to maximize my health and wellbeing and performance. And so of course then I didn’t wanna sell products that I wasn’t gonna use myself, or that I wasn’t comfortable using myself, and I didn’t want to sell those products to other people.

I didn’t want to tell people to do something that I wasn’t doing myself or that I wasn’t comfortable doing myself. And so I committed to all natural products, which has been very expensive. And it continues to be very expensive. For example, in some cases it costs me three, four upward of $5 per bottle just to sweeten and flavor a powder product like the entire bottle.

And if I were to go artificial, I could cut those costs down to 50 cents. It could go from several dollars to 50 cents per bottle, and that would be very nice for margins, but not very nice for my conscience. And so Legion will always be all natural. And so where does all of this leave us? Well, I do think it’s smart to at least limit your consumption of artificial sweeteners.

Maybe try not to have a bunch of these chemicals every day. Maybe try to have them just here and there. Some people, for example, have very little or no artificial sweeteners when they’re maintaining and lean gaining, but when they’re cutting, what they find is that having the occasional diet Coke just helps.

Cravings for sweet things, and that helps them stick to their diet. That of course makes sense, and I would recommend that if that works well for you. But I would not recommend having five per day, for example, if it can be avoided. Now, if you did do that for a couple of months and then you stopped having five cans of Diet Coke per day, Yes, you will be fine.

And if you have harmed your microbiome at all, it is not permanent. Simply cutting the chemicals out will allow your body to normalize your gut. Now if you like to use artificial sweeteners to sweeten drinks, maybe like tea or foods like oatmeal, you could try some natural alternatives. You could try stevia, you could try erythritol.

You could try fruit extracts like monkfruit, for example. And studies show that these are not only safe, but actually can confer. Benefits, including better insulin sensitivity, a lower cholesterol profile, improved blood glucose control. There are potential anti-cancer effects. Uh, these substances can lower blood pressure, they can lower inflammation levels and more.

So if you can find a natural sweetener, uh, calorie. Sweetener that you like, then it’s a win-win. Or if you prefer sugar, you could just use that. But of course you have to account for the calories, and I would not recommend going over about 20 to maybe 25 grams of sugar, added sugar like sucrose per day.

So that would be sugar that you add. Two foods and drinks as well as foods and drinks that contain sucrose added to them. And the reason for that limit is research shows that if you consistently eat more sugar than that, it can negatively impact your health. Now, a lot of that research was done with sedentary people, and of course I understand that you can’t directly extrapolate that to those of us who are fit and who exercise regularly.

But I do still think that it is a reasonable cutoff. Well, I hope you liked this episode. I hope you found it helpful, and if you did subscribe to the show because it makes sure that you don’t miss new episodes. And it also helps me because it increases the rankings of the show a little bit, which of course then makes it a little bit more easily found by other people who may like it just as much as you.

And if you didn’t like something about this episode or about the show in general, or if you. Uh, ideas or suggestions or just feedback to share. Shoot me an email, mike muscle for, muscle f o r and let me know what I could do better or just, uh, what your thoughts are about maybe what you’d like to see me do in the future.

I read everything myself. I’m always looking for new ideas and constructive feedback. So thanks again for listening to this episode, and I hope to hear from you.

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