The Wellness Brew - Issue 36

California passed a law in September that begins restricting supplement sales to anyone under 18 in January. It names no ingredient at all, covering anything whose label claims to build muscle, which puts creatine and protein powder in the same bucket as diet pills. Meanwhile a 15-year-old in that same state can buy as many energy drinks as they can carry, with no age restriction anywhere in the country.

But first, we filtered the noise — here's what's worth knowing this week.

Forty trained adults were randomly assigned to one of two rest schemes across eight weeks of supervised lower body training. One group rested a prescribed two to three minutes between sets. The other started the next set whenever they felt recovered. Both trained twice weekly, four sets per exercise, every set to failure. Muscle thickness rose in both groups with no clear difference between them, and strength and endurance gains were statistically indistinguishable too. What differed was time. Fixed sessions averaged 56 minutes, self-selected 78.5, and the gap widened as the weeks went on, from 19 minutes in week one to 32 by week eight. Forty participants is small, but worth setting a fixed rest time in between sets. — Mohan AE, Piñero A, Coleman M, et al., SportRxiv, 2026.

Two forever chemicals tracked with an aggressive breast cancer subtype

The Sister Study has followed 50,884 American women since 2003, all cancer-free at enrollment and all with a sister who had been diagnosed with breast cancer. Researchers measured 17 compounds in blood drawn years before any diagnosis, then compared 1,609 women who went on to develop breast cancer against 2,269 who didn’t. Women with the highest levels of PFOA had a 67% higher rate of estrogen receptor negative breast cancer than women with the lowest. For PFOS, the figure was 93%. The association showed up only for that subtype, not for breast cancer overall, but this is the harder subtype to treat because hormone therapies don’t work against it. The study is observational and every woman in it had a sister with breast cancer, so the group started at higher risk than average. PFOA and PFOS haven’t been used in the US in years, but can still be found in drinking water. Filter your water with a reverse osmosis filter or a filter certified NSF/ANSI 53 or NSF/ANSI 58. — Chang C-J, Pullella K, Keil AP, et al., Journal of Clinical Oncology, 2026.

In January, California begins restricting the sale of certain supplements to anyone under 18. The law is AB 2030, signed in September.

It covers any dietary supplement "labeled, marketed, or otherwise represented for the purpose of achieving weight loss or building muscle." That phrasing is the whole story. The law names no specific ingredient at all, meaning supplements like protein powder and creatine could both fall under this umbrella. [1]

New York passed a version of this in 2024 and carved out protein products. California's has no such exception, a point the American Herbal Products Association raised directly. So a tub of protein powder whose label says it builds muscle appears to land in the same category as a diet pill. Three other trade associations raised the same objection, and one noted the language is loose enough that a product's shelf placement, its ingredients, or even a third party's description of it could be enough to trigger the restriction. [2]

The case for restricting teen access isn't empty (though I'd argue it's misplaced). Supplements don't go through premarket approval, so nothing verifies what's in a container before it reaches a shelf. The American Academy of Pediatrics has cautioned against teen use. Eating disorder organizations backed the bill, and roughly one in ten young people report having used a weight-loss or muscle-building product. [1]

The problem is what the law includes alongside diet pills. For example, "Supports muscle growth" isn't a marketing flourish when it comes to creatine. It's an accurate description of what twenty-three randomized trials found.

There is no federal minimum age to buy an energy drink in the United States, and no state has set one. A 15-year-old can walk into any store in California and buy as many as he can carry.

Those drinks are not benign. A review of nineteen clinical trials found energy drinks lengthen the QT interval, which is the window the heart takes to reset between beats. A longer window raises the odds of a dangerous rhythm. The same review collected 32 published case reports of cardiac events after energy drinks, including arrhythmias and torn coronary arteries, in patients as young as 13. Three were fatal. Case reports can't establish cause, and no trial has studied children directly, which is its own kind of answer. The American Academy of Pediatrics has recommended against energy drinks for children and teenagers since 2011. [3]

Other countries have drawn a line when it comes to energy drinks, and two of them drew it at exactly the same place. Poland amended its Public Health Act in 2023 to bar energy drink sales to anyone under 18, along with sales in schools and in vending machines, defining an energy drink as anything carrying more than 150 milligrams of caffeine per liter. [4] England announced its own ban this July using that identical threshold, setting the age at 16 and covering shops, vending machines and online sales, with fines up to £2,500 for retailers who break it. The government's estimate was that about 100,000 English children were drinking them every day. [5]

American regulators have looked at this. The Senate held a hearing on energy drink marketing to young people. The American Medical Association called for a ban on marketing them to teens. Neither produced a rule.

So starting in January, the teenager who can buy energy drinks will need an adult for creatine. I could use the same example with countless other food products and ingredients shown to cause adverse health impacts, but I'll avoid belaboring the point.

This is the part that isn't in dispute and is more than a marketing claim.

A 2024 meta-analysis pooled 23 randomized trials in adults under 50. Every trial compared creatine plus resistance training against a placebo plus identical training, so the question was never whether lifting works. It was what creatine adds on top of it.

Upper body maximum strength gained about 10 pounds more in the creatine groups. Lower body gained about 25 pounds more. What makes those numbers unusual is how consistent they were across trials: the standard statistical measure of disagreement between studies came out at zero for both outcomes, which almost never happens in nutrition research. [6]

One caveat to be clear about. Across all 23 trials there were only 49 women, so this is largely a finding about men. [6]

Additionally, the benefits seem to be smaller for older adults. A 2026 meta-analysis of 11 trials in adults over 60 found creatine added a small strength benefit to resistance training, while muscle mass and physical function both came out statistically non-significant. [7]

On dosing, more isn't faster in any way that matters. Three to five grams a day saturates muscle in about four weeks. A loading phase of 20 to 25 grams daily for five to seven days gets there sooner, and nothing is lost by skipping it. Creatine on its own, without resistance training, doesn't build anything. [8]

This one is harder to answer.

Start with what holds up. A 2024 meta-analysis of 16 trials found memory improved, with an effect size of 0.31 and what the authors graded as "moderate certainty." [9] The sharpest single result came from a study that gave 15 adults one dose of about 28 grams during 21 hours of sleep deprivation and measured improvements in memory and processing speed. [12] The pattern running through both is that creatine shows up when the brain is working against something.

Dose matters more here than it does for muscle, and the reason is physical. Muscle tissue holds roughly eight times the creatine the brain does, and creatine crosses into the brain slowly because the transporters that carry it are sparse at the blood-brain barrier. Supplementing raises muscle creatine by around 20% and brain creatine by around 10%. [13]

Higher doses do reach it. German researchers gave six adults 20 grams a day for four weeks in 1999 and measured total brain creatine up 8.7%, with the thalamus up 14.6%. A later study in adolescents compared 2, 4 and 10 grams a day across eight weeks and found frontal lobe phosphocreatine rose 4.6%, 4.1% and 9.1%, so ten grams roughly doubled what four grams managed. [13]

What hasn't followed is the part that matters. A creatine manufacturer applied to European regulators for permission to advertise that creatine improves cognitive function, and the European Food Safety Authority concluded cause and effect could not be established. Of ten trials in healthy people, one showed an effect, on a single measure, at 20 grams a day. The European Union formally refused the claim in May. [10][11] A separate trial gave healthy young adults 10 or 20 grams daily for six weeks and found no cognitive benefit at either dose. [14] And in the same meta-analysis that found the memory effect, overall cognitive function did not reach statistical significance. [9]

So putting more creatine in the brain and improving how the brain performs are two different results, and only the first one is settled.

It's worth knowing who is saying what here. Darren Candow co-authored the meta-analysis the manufacturer submitted in support of its claim. While he said the regulators' rejection was justified and that it is too early to conclude creatine improves cognition, he also sits on the scientific advisory boards of two creatine manufacturers. [11] He co-authored the 2025 review arguing higher doses are likely better for the brain as well. [13]

A word on taking more than five grams, since brain findings tend to push people toward bigger scoops. The safety record is long. The International Society of Sports Nutrition, a body with substantial ties to supplement manufacturers, found no compelling evidence of harm at up to 30 grams a day for five years, and clinical trials have given patients 21 to 56 grams daily for years without serious adverse events. [15] So there's no real penalty for taking 10 grams, and it demonstrably puts more creatine in your brain than five does. There's just no outcome attached to it yet. Five grams is the dose with the evidence under it. Ten is a cheap bet on an open question, which is a fine bet to make as long as you know that's what you're making.

A short list, because it is a short list.

Servings larger than about 10 grams at once can cause stomach upset and diarrhea. Splitting the dose solves it. There's some early weight gain from water pulled into muscle cells, more noticeable if you load than if you start at five grams and stay there. [8]

The one that catches people out is a blood test. Creatine breaks down into a compound called creatinine, and creatinine is the number laboratories use to estimate how well your kidneys are filtering. Taking creatine raises it. Across 22 studies, 12 found no rise at all, 8 found a rise that stayed inside the normal range, and 2 found a rise above it. [8]

That doesn't mean your kidneys are struggling. It means the estimate is being thrown off by something you swallowed. Two things help here. Take a break from creatine before blood work, so the number isn't skewed when it's drawn. And tell your doctor you take it, because plenty of them won't account for it on their own. Both are worth doing, since the same effect that creates a false alarm can also hide a real problem. If kidney function genuinely needs checking, there's a different marker called cystatin C that creatine doesn't affect.

The last risk isn't about creatine at all. It's about what's in the container. Because supplements aren't approved before sale, the only verification a buyer gets comes from third-party testing, and most products don't carry any. The last time ConsumerLab tested this category, three creatine products contained unacceptable levels of creatine breakdown compounds, and two of those delivered only trace amounts of actual creatine. [16] Buy from a brand carrying NSF Certified for Sport or Informed Sport on the label. Those programs test the finished product rather than taking a manufacturer's word for what went into it.

Three things you can do this week:

1. Five grams a day if you’re training.

Three to five grams daily saturates muscle in about four weeks, and a loading phase only gets you there faster without changing where you end up. The part worth being clear about is that creatine doesn’t build anything on its own. Every trial behind those strength numbers paired it with resistance training, so without the training you’re buying expensive powder. If you want to chase the brain findings, ten grams a day sits well inside the safety range and does put more creatine in your brain than five. It hasn’t been proven yet, so treat the second five grams as optional rather than better.

2. Take a break before blood work, and tell your doctor either way.

Creatine raises creatinine, which is the number your lab uses to estimate kidney function, so a normal result can come back looking abnormal. Stopping for a stretch before a blood draw gives you a clean number. Telling your doctor you take it matters regardless, because the same effect that creates a false alarm can also hide a real problem. If kidney function genuinely needs assessing, ask about cystatin C, a marker creatine doesn’t influence.

3. Buy something tested by someone other than the manufacturer.

Supplements don’t get approved before they go on sale, so nothing verifies what’s in the container unless a third party does it voluntarily. The last time ConsumerLab looked at this category, two products delivered only trace amounts of the creatine on their label. NSF Certified for Sport and Informed Sport both test the finished product rather than trusting the ingredient list. Either mark on the tub is worth more than any claim on the front of it. I use Momentous.

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Wellness, filtered.

The Wellness Brew

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Disclaimer: The Wellness Brew is for informational purposes only and does not constitute medical advice. The content published here is not intended to diagnose, treat, cure, or prevent any disease or health condition. Always consult a qualified healthcare professional before making any changes to your diet, supplement routine, or lifestyle.