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Today’s Health Upgrade
Does distance running cause cancer?
Eat this way, live 3 years longer
About those cycle-based workouts
The breakfast food (not eggs!) that can power your brain and improve decision-making
Health
No, Running Doesn't Cause Cancer
If you saw the headlines claiming marathon runners have "12.5 times higher" rates of pre-cancerous colon polyps, you'd be forgiven for wanting to cancel your next race. The claims seem to defy reality. And that’s because, to a certain extent, they did.
Exercise remains one of the most proven ways to reduce your cancer risk, and one small, unpublished study doesn't change decades of evidence showing that physically active people have lower rates of colon cancer.
Here's what actually happened to cause all the drama. Researchers gave colonoscopies to 100 ultramarathon and marathon runners and found that 15% had advanced pre-cancerous polyps. That "12.5 times" claim came from comparing their results to a benchmark from roughly 25 years ago, when screening technology was completely different.
Modern data from nearly 4 million colonoscopies puts the general population rate for the same age group at about 5%, which makes the real comparison roughly 3x, which is still interesting, but a very different story.
But here’s the bigger problem: the study also had no control group, didn't account for diet, alcohol, genetics, or any other risk factor, and hasn't been peer-reviewed. It's a conference abstract that the authors themselves call preliminary.
Most importantly, no cancer was found in any participant.
Meanwhile, a meta-analysis of 52 studies found that physically active people have a 24% lower risk of colon cancer. A separate analysis found 16% lower risk of developing polyps in the first place. Every major health organization — the WHO, the American Cancer Society, the AICR — lists exercise as a key cancer-prevention tool.
The one useful thing this study did surface: if you're a distance runner who notices bleeding after runs, don't wave it off as "runner's colitis." Talk to your doctor. A screening colonoscopy is straightforward and catches problems early. But don’t stop moving because of something you read. Instead, listen to your body, see a doctor if you’re concerned, and don’t overreact to potentially misleading headlines.
Longevity
The Diet That Could Add 3 Years to Your Life (Even If Longevity Doesn't Run in Your Family)
Scientists have spent decades arguing about the best diet. High-fat or low-fat. Vegan or Mediterranean. More protein, less protein. With so many conflicting messages, it's tempting to throw your hands up and eat whatever's closest.
But when researchers analyzed five different evidence-based eating patterns in over 103,000 people, all five were linked to living longer, and they agree on more than you'd think.
The study followed participants for roughly a decade and evaluated their diets using the Mediterranean, DASH, plant-based, AHEI, and Diabetes Risk Reduction patterns. People who scored highest on any of the five had up to a 24 percent lower risk of dying.
In other words, eating well is associated with approximately 1.5 to 3 additional years of life expectancy compared with those who scored lowest.
Researchers also tested whether genetics changed the picture. They mapped each person's longevity genes, and the dietary benefits held regardless. Even people without favorable genetics gained years by eating better. The Diabetes Risk Reduction Diet appeared especially protective for those genetically predisposed to shorter lifespans.
Despite their different philosophies, the five patterns converge on a few things. Every diet emphasized more vegetables, fruits, whole grains, legumes, and nuts. What they all minimize: sugar-sweetened beverages and processed meat.
That overlap matters because it suggests the foundation of a longevity-supporting diet isn't about picking the "right" team; it's about getting the basics consistently right.
This isn't about perfection or memorizing a meal plan. Start with whichever behavior feels easiest, focus on building the habit, and work on doing it repeatedly.
Fitness
Your Muscles Don't Check the Calendar
On Monday, Arnold promised to provide evidence that can’t be defined by a phase of life, and that they can set their own terms. If you've ever skipped a workout because an app told you it wasn't the right time in your cycle, you had good intentions. But even if you don’t feel like your normal self, your body is still doing everything it can internally to turn your efforts in the gym into results.
New research suggests the female body builds muscle regardless of where you are in your menstrual cycle.
Researchers at McMaster University, led by Dr. Lauren Colenso-Semple — a strength coach and PhD researcher who built her career specifically to close the gap in exercise research on women — designed a fascinating study. In it, menstruating women performed resistance training during the follicular phase and the luteal phase. (Each woman served as her own control, which eliminates a lot of the noise that weakens other studies.) Cycle phases were verified with hormone bloodwork, not assumed from a calendar.
The scientists measured muscle protein synthesis over a week and took muscle biopsies, which capture real-world building more accurately than older single-session lab methods. Exercise boosted muscle protein synthesis significantly, but the cycle phase made no difference. Protein breakdown didn't differ between phases either.
The finding aligns with a growing body of evidence. A 2023 review, a 2020 meta-analysis, and multiple systematic reviews all point in the same direction: normal hormonal fluctuations across the menstrual cycle don't meaningfully change how your muscles respond to training.
That doesn't mean your energy, mood, or comfort feel the same every week. Those experiences are real and can make it much harder to exercise or push the way you want. But the physiology underneath — the actual muscle-building machinery — keeps working no matter what day it is. Train when you can, adjust intensity based on how you feel, and drop the complicated calendar.
Foods Are Super
The Breakfast Brainpower Boost
A crossword puzzle or a cup of coffee is a great way to sharpen your mind to start your day. But a simple breakfast choice could give your brain some extra oomph when the afternoon slump tends to hit.
A walnut-rich breakfast led to faster reaction times and improved memory later in the day.
Researchers gave participants two breakfasts on separate days: one with 50 grams of walnuts (about 12-15 whole walnuts) and another without nuts (with butter) that provided the same number of calories. Researchers measured cognitive performance, mood, blood markers, and brain activity using EEG scans at baseline and 2, 4, and 6 hours after eating.
At the 2-hour mark, participants actually performed worse on memory tasks after the walnut breakfast. But by 6 hours, that flipped, and walnut eaters outperformed the control group. Reaction times were consistently faster throughout the day in the walnut group on executive-function tasks such as decision-making. EEG scans also showed meaningful differences in brain activity, particularly in regions responsible for attention and memory.
Researchers think walnuts' combination of omega-3 fatty acids, polyphenols, and protein may work together to support brain function, partly by helping your body maintain steadier blood sugar levels throughout the day. That smoother energy supply could explain why cognitive benefits grew stronger as the hours passed.
Not a walnut fan? You're not stuck. Blueberries, chia seeds, and other flavonoid-rich foods have shown similar cognitive benefits in research. Even pairing a handful of almonds with some berries in your morning yogurt or oatmeal checks many of the same nutritional boxes (healthy fats, polyphenols, and protein working together). The bigger takeaway: a nutrient-dense breakfast that combines these elements may give your brain an edge, whether or not walnuts are part of it.
If you’re looking for an easy way to sneak walnuts into your morning routine, sprinkle them into yogurt, oatmeal, or a smoothie.
Better Today
Take any of these tips from today’s email and put them into action:
1. Running Doesn't Cause Cancer. Here's What the Headlines Got Wrong.
One unpublished study claimed that marathon runners faced elevated cancer risk, but the headlines didn’t tell the full story. A meta-analysis of 52 studies found that physically active people have a 24% lower risk of colon cancer, while a separate analysis found a 16% lower risk of developing polyps — evidence that directly contradicts viral headlines claiming marathon runners face elevated cancer risk. Those headlines relied on comparing a small, unpublished, uncontrolled study of 100 runners to a benchmark from 25 years ago, when screening technology was fundamentally different. The evidence on exercise and cancer prevention hasn't changed.
2. Five Different Diets Were Studied in 103,000 People. They All Agreed on the Same Thing.
An analysis of five evidence-based dietary patterns (Mediterranean, DASH, plant-based, AHEI, and Diabetes Risk Reduction) over a decade found that high adherence to any of the five was associated with up to a 24% lower risk of dying and approximately 1.5 to 3 additional years of life expectancy compared to low adherents. All five patterns converge on the same foundation: more vegetables, fruits, whole grains, legumes, and nuts; less sugar-sweetened beverages and processed meat, which means the argument about which diet is "right" has been distracting people from the basics that actually matter.
3. The Science Behind Cycle-Phase Training Apps Doesn't Hold Up. Here's the Research
A study led by Dr. Lauren Colenso-Semple measured muscle protein synthesis and obtained muscle biopsies from menstruating women during both the follicular and luteal phases. The study found that resistance training significantly increased muscle protein synthesis in both phases, with no meaningful difference between them; protein breakdown rates were also identical across phases. Energy, mood, and comfort vary across the cycle, and those experiences are real, but the muscle-building machinery underneath keeps working every day, so train when you can and adjust intensity based on how you feel, not what a calendar says.
4. The Cognitive Case for Eating Walnuts at Breakfast (The 6-Hour Delayed Energy Boost)
In a crossover study where participants consumed either a 50-gram walnut breakfast (approximately 12–15 whole walnuts) or a calorie-matched butter-based control on separate days, cognitive performance, memory tasks, and reaction time testing showed that walnut eaters performed better 6 hours after eating, with consistently faster reaction times throughout the day on executive-function tasks, including decision-making. Researchers attribute the delayed cognitive advantage to walnuts' effect on stabilizing energy and improving the brain's access to glucose — its primary fuel source — rather than producing an immediate stimulant-like effect.
The Positive Corner of The Internet
About Arnold’s Pump Club Editorial Standards
We do things a bit differently here, starting with transparency.
The Content: All APC emails are researched, written, and fact-checked by the APC editors (see bottom of the email), with written contributions from Arnold (noted with “Arnold’s Corner”). Links take you to original studies (not second-hand sources).
Does AI play a role? Not for the primary content, but it is used in two ways. The main items are original content written by the APC team. The summaries at the end are AI-generated based on the human-written content above. We also use an AI tool to review our interpretations of the research and ensure scientific accuracy. We don’t assume AI is right, but we use technology to hold ourselves accountable.
Yes, we have partners (all clearly noted). Why? Because it allows these emails to remain free. We first test products, and then reach out to potential partners who offer ways to help you improve every day. The bar is set high, and to date, we have turned down millions in ad deals. (Example: we will not partner with any non-certified supplements or those without evidence in human trials). If we won’t buy the product, we won’t recommend it to you. And if there’s no evidence it works, then there’s no place for it here.
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Publisher: Arnold Schwarzenegger
Editors-in-chief: Adam Bornstein and Daniel Ketchell
