Do Artificial Sweeteners Destroy Your Gut? Here's What a 12-Month Trial Actually Found

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Today’s Health Upgrade

• This is failure

• Do artificial sweeteners destroy gut health?

• How to improve your HRV (heart rate variability)

• Change this habit, improve your brain aging

Show Your Work
This Is Failure (And Also Success)

Editor’s Note From Ketchell: We lead from the front, and Arnold asked for #ShowYourWork videos. This one was easy for me.

Over the past 5 years chasing a 400, then 500, then 600-pound trap bar deadlift, I have had many brutal failures and a few really ugly successes (I didn’t realize my back looked like a question mark the first time I hit 500 until I made this).

For people who just saw my Father’s Day post hitting the goal, you saw a guy who pulled 600 pounds and looked like he knew how to deadlift. Behind that Ketch were a bunch of Ketches who deadlifted like they didn’t know a spine was kinda important.

I loved the path so much, I’m doing it again with a traditional deadlift now. Back to the failing.

Instagram post

Follow Arnold’s lead, share your success (and your failures), and use the hashtag #ShowYourWork. Arnold will be resharing the best videos all week.

On Our Radar
Do Sweeteners Wreck Your Gut Bacteria?

You've probably seen the headlines warning that artificial sweeteners destroy your gut. It sounds scary enough to stick, and it's kept a lot of people from reaching for diet sodas or sugar-free options when trying to cut back on sugar.

But it might not reflect what keeps on showing up in research. 

A 12-month clinical trial found that replacing sugar with sweetener-containing foods and drinks helped maintain weight loss, increased beneficial gut bacteria, and showed no negative effects on blood sugar, insulin, or cholesterol.

Researchers studied overweight or obese individuals who had already lost at least 5 percent of their body weight. Over 10 months, half of the participants switched to sweetener-containing foods and beverages, while the other half used sugar versions. The sweetener group maintained 1.6 kg (about 3.5 pounds) more weight loss. Not dramatic on its own, but the gut findings were the real story.

The sweetener group showed higher levels of bacteria that produce short-chain fatty acids. These compounds are associated with reduced inflammation and stronger gut barrier function. 

The outcome led us to dig into where the fear that artificial sweeteners cause gut health issues began. The widely cited 2014 study behind the "sweeteners ruin your gut" narrative relied mostly on mice, with just seven human participants. 

This new study followed participants for a full year, eating real food rather than just beverages. It directly challenges the World Health Organization’s 2023 recommendation against sweeteners for weight control, but that was based on observational data that can't establish cause and effect.

Participants who used sweeteners most consistently saw the biggest benefits, which aligns with a common principle: the strategy you stick with tends to be the one that works.

If cutting sugar is on your list, swapping in diet drinks, sugar-free flavored water, or reduced-sugar snacks appears to be a safe and helpful option. Not a magic solution, but one more tool that makes the whole process a little easier.

If the sweeteners don’t sit well with you, or you prefer not to include them in your diet, then they are relatively easy to avoid and not something you need to eat, either.

Health 
Why Your Heart Needs More Than Resistance Training

Lifting weights gets a lot of love. And it should. But if you think strength training alone is enough to keep your heart healthy as you age, a systematic review suggests you're missing a big piece.

Aerobic and coordinative exercise like walking, swimming, Tai Chi, or dancing, done 2 to 3 times per week, appears to be more effective than resistance training alone for improving heart rate variability (HRV), a key marker of how well your cardiovascular system handles stress and recovers.

Researchers reviewed 13 studies involving older adults to compare how different exercise types affect HRV. Think of HRV as your nervous system's ability to shift between "go" and "recover" mode. Higher HRV generally means a more adaptable, resilient cardiovascular system.

Endurance training, dancing, and Tai Chi all improved HRV markers tied to your body's built-in recovery system (parasympathetic function). The studies used 2 to 3 sessions per week, with interventions ranging from 6 weeks to 12 months.

However, resistance training alone did not result in significant improvements in HRV across the studies. However, only a few studies were included. So it’s possible that strength training helps, but the evidence is limited. 

In other words, don't ditch your dumbbells. In the same review, every type of exercise improved at least one marker of cardiovascular health, whether blood pressure, body composition, aerobic capacity, or walking distance. Lifting still matters for plenty of reasons. It just doesn't appear to be the best tool for strengthening your heart's autonomic control.

Aerobic and coordinative exercise may work through several pathways: lowering norepinephrine, reducing oxidative stress, boosting nitric oxide production, and improving vascular flexibility. Those shifts help your heart handle stress and recover faster as you age.

Aim for two to three days of aerobic movement like walking or swimming, and consider adding Tai Chi or dancing for coordination benefits. Keep strength training in the mix for muscle, bone, and body composition. Several studies have shown measurable changes within 6 to 12 weeks, though longer interventions continue to show benefits.

If you need a place to start, two or three walks this week is a solid place to build momentum. 

Instant Health Boost
The Thinking Habit That Can Slow Down Brain Aging

You know those mental loops where you replay an awkward conversation, obsess over something you said, or spiral about what might go wrong? Turns out, that habit might be doing more than ruining your afternoon.

Research suggests that repetitive negative thinking — the tendency to ruminate on worries and dwell on negative experiences — is linked to cognitive decline.

A study measured how often people get stuck in repetitive worry loops and struggle to disengage from negative thoughts. The scientists used an evaluation tool that assessed memory, attention, language, and executive function. 

Those who scored highest on measures of repetitive negative thinking had significantly lower cognitive function scores compared to those with minimal negative thought patterns. The association held even after researchers accounted for age, education, income, and lifestyle factors. The connection was particularly strong for memory, abstract thinking, and visuospatial function.

The scientists believe that chronic worry and rumination keep stress hormones elevated, and prolonged exposure to the neurochemical reactions of negativity isn't great for brain health.

This builds on earlier research that found persistent negative thinking patterns were associated with both cognitive decline and the accumulation of Alzheimer's-related proteins in the brain.

This particular study was cross-sectional, meaning researchers captured a snapshot rather than tracking people over time. So we can't say for certain that negative thinking causes cognitive decline. It's possible the relationship works in reverse, or that something else drives both. But the pattern keeps showing up across multiple studies, which makes it worth paying attention to.

The good news: you are in control of rumination. Mindfulness practices, cognitive behavioral techniques, and even simple pattern interrupts (like going for a walk when you notice yourself spiraling) can help break the loop. 

You don't need to eliminate negative thoughts entirely. But learning to notice when you're stuck in a mental rut and gently redirect is a skill worth building, especially if you're playing the long game with your brain health.

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Publisher: Arnold Schwarzenegger​

Editors-in-chief: Adam Bornstein and Daniel Ketchell