Thanks, Yanni. My hypothesis was also that vegetarians and vegans would benefit more from creatine supplementation, but it looks like there is no clear evidence for that. Below is the abstract of the systematic review of Kaviani et al. (2020) (emphasis mine).

Background: Creatine monohydrate is a nutritional supplement often consumed by athletes in anaerobic sports. Creatine is naturally found in most meat products; therefore, vegetarians have reduced creatine stores and may benefit from supplementation. Objective: to determine the effects of creatine supplementation on vegetarians. Data sources: PubMed and SPORTDiscus. Eligibility criteria: Randomized controlled trials (parallel group, cross-over studies) or prospective studies. Participants: Vegetarians. Intervention: Creatine supplementation. Study appraisal and synthesis: A total of 64 records were identified, and eleven full-text articles (covering nine studies) were included in this systematic review. Results: Creatine supplementation in vegetarians increased total creatine, creatine, and phosphocreatine concentrations in vastus lateralis and gastrocnemius muscle, plasma, and red blood cells, often to levels greater than omnivores. Creatine supplementation had no effect on brain levels of phosphocreatine. Creatine supplementation increased lean tissue mass, type II fiber area, insulin-like growth factor-1, muscular strength, muscular endurance, Wingate mean power output, and brain function (memory and intelligence) in vegetarian participants. Studies were mixed on whether creatine supplementation improved exercise performance in vegetarians to a greater extent compared to omnivores. Limitations: Studies that were reviewed had moderate–high risk of bias. Conclusions: Overall, it appears vegetarian athletes are likely to benefit from creatine supplementation.

The 2nd sentence I highlighted above refers to "exercise performance", but it is also unclear whether vegetarians and vegans benefit more from creatine supplementation with respect to cognitive function. From my post:

Sandkühler et al. (2023) “found no indication that our vegetarian participants benefited more from creatine than our omnivore participants (in fact, the creatine effect was smaller in vegetarians than omnivores to a non-statistically significant extent). This is in line with Solis et al. [22, 24] who did not find a difference in brain creatine content between omnivores and vegetarians”.

Thanks for the comment, Michael. I did not time myself, but 7.5 s/d is my guess for the difference between taking 5 capsules (including one of creatine; capsules are 23.5 $/year cheaper under my assumptions) and the 4 I already take after lunch (D3, Omega 3, iodine and a multivitamin; I take B12 before breakfast). I have all the supplements in the same place, so it would not take me much time to take another capsule.

I do not have a strong view either way. It depends on the details of the global health intervention. Note "I am not confident that saving human lives in China, India or Nigeria is harmful to animals. Even if it is so for farmed animals nearterm [my results refer to 2022], it can still be beneficial overall".

I have just published a break-even analysis of creatine supplementation. I estimate the improvement in cognitive function caused by creatine supplementation is worth it for a net income above 10.6 k$/year.

Thanks for the great clarifications, David! Strongly upvoted.

I think there's still enormous uncertainty that animal welfare interventions are better than human ones. Are you saying that's not the case?

I think it is clear that the best animal welfare interventions are much more cost-effective than the best human welfare interventions.

After the project decided to assume hedonism and dismiss neuron count, the cumulative percent of these 90 behavioral proxies became the basis for their welfare range estimates. Although the team used a number of models in their final analysis, these models were mostly based on different weightings of these same behavioral proxies.

The welfare range of chickens is higher than RP's median under the 2 models besides the neuron count one which do not rely on behaviour:

• For the quantitative model, it is 1.69 (= 0.641*0.876/0.332) times as high.
• For the equality model, it is 2.51 (= 0.953*0.876/0.332) times as high.

If one puts at least 10 % weight on the quantitative model, which "aggregates several quantifiably characterizable physiological measurements related to activity in the pain processing system", the welfare range of chickens will be at least 16.9 % (= 0.1*1.69) of RP's median.

Thanks for the discussion, JBentham, Ian and Nick.

I would wager less than 1% would endorse the view that we should let humans suffer and die because otherwise they might eat animals

This wording is very unfavourable to the animal welfare side, and does not exactly get into the action I would like people to change, which is how they donate, not how they relate to other humans. Given the answers "Yes", "Maybe" and "No" to the question "Donations to global health and development organisations may increase factory-farming nearterm via increasing human population. Factory-farmed animals live in very bad conditions, so such donations may increase animal suffering nearterm. Is this a good reason for donating to animal welfare instead of global health and development?", I guess more than 1 % would answer "Yes" or "Maybe".

In any case, I think the focus should be on increasing impartial welfare even if this does not correspond to what most people would do.

Thanks for doing this, Fabienne! Relatedly, readers may be interested in The effects of creatine supplementation on cognitive function in adults: a systematic review and meta-analysis, which was published this year, and includes your study.

Background: This study aimed to evaluate the effects of creatine monohydrate supplementation on cognitive function in adults and explore its potential role in preventing and delaying cognitive impairment-related diseases.

Methods: Following the PRISMA 2020 guidelines, a systematic review with meta-analysis was conducted. Randomized controlled trials (RCTs) published between 1993 and 2024 were retrieved from PubMed, Scopus, and Web of Science databases. The study protocol was registered with PROSPERO (registration number: CRD42024533557). The impact of creatine supplementation on overall cognitive function, memory, executive function, attention, and information processing speed was assessed using standardized mean differences (SMD) and Hedge’s g with 95% confidence intervals (CI).

Results: Sixteen RCTs involving 492 participants aged 20.8–76.4 years, including healthy individuals and patients with specific diseases, were selected. Creatine monohydrate was the form used in all included studies. Creatine supplementation showed significant positive effects on memory (SMD = 0.31, 95% CI: 0.18–0.44, Hedges’s g = 0.3003, 95% CI: 0.1778–0.4228) and attention time (SMD = −0.31, 95% CI: −0.58 to −0.03, Hedges’s g = −0.3004, 95% CI: −0.5719 to −0.0289), as well as significantly improving processing speed time (SMD = −0.51, 95% CI: −1.01 to −0.01, Hedges’s g = −0.4916, 95% CI: −0.7852 to −0.1980). However, no significant improvements were found on overall cognitive function or executive function. Subgroup analyses revealed that creatine supplementation was more beneficial in individuals with diseases, those aged 18–60 years, and females. No significant differences were found between short- (<4 weeks) and long-term (≥4 weeks) interventions for improving cognitive function. Low-to-moderate risk of bias was found, and no significant publication bias was detected. The GRADE assessment indicates that the certainty of evidence for memory function is moderate, suggesting a reasonable level of confidence in the positive effects of creatine on memory. However, the evidence for processing speed, overall cognitive function, executive function, and attention is of low certainty, indicating that further research is needed to confirm these potential benefits.

Conclusion: Current evidence suggests that creatine monohydrate supplementation may confer beneficial effects on cognitive function in adults, particularly in the domains of memory, attention time, and information processing speed. Larger robust clinical trials are warranted to further validate these findings. Furthermore, future research should investigate the influence of different populations and intervention durations on the effects of creatine monohydrate supplementation, as well as elucidate the precise mechanisms underlying its potential cognitive-enhancing properties.

I liked this post, Joey.

For example, if we aimed to launch ten animal charities a year (rather than ten charities across all the cause areas we currently focus on), I do not think the weakest two would be anywhere near as impactful as the top two, and only a small minority of them would secure long-term funding. With animal charities making up around a third of those we have launched, it’s likely we're already approaching some of these limitations. This means that even if we thought animal charities were, on average, more impactful than human ones, the difference would have to be substantial for us to think that adding a ninth or tenth animal charity into the ecosystem would be more impactful than adding the first or second human-focused charity.

I do not know whether Ambitious Impact (AIM) should be starting more or fewer animal welfare organisations due to them competing for funding. However, how about starting animal welfare organisations with more seed funding (instead of starting more of them)?

If we were to consider one cause area to be significantly superior to others by a factor of thousands, it is possible that the tenth charity within that area, despite having less impact, could still outperform the highest impact charity of another cause area. However, we find this assertion to be bold and unsupported, as we will discover when we look at the examples.

I did not find your examples convincing. I estimate:

• Broiler welfare and cage-free campaigns are 168 and 462 times as cost-effective as GiveWell’s top charities.
• The Shrimp Welfare Project is 64.3 k as cost-effectivene as GiveWell’s top charities.

How would you concretely modify these analyses to conclude that the best animal welfare interventions are less than 3 times as cost-effective as GiveWell's top charities?

Hi Nick.

I think it is helpful to make these difficult comparisons but only with deep humility and huge acknowledged uncertainty.

I think acknowledging uncertainty implies that the best animal welfare interventions are way more cost-effective that the best human welfare interventions. Below are RP's welfare ranges of chickens conditional on sentience for the 12 models RP has considered. I estimate broiler welfare and cage-free campaigns are 168 and 462 times as cost-effective as GiveWell’s top charities using Rethink Priorities' (RP's) median welfare range of chickens of 0.332. The welfare range of chickens under the neuron count model, the one leading to the lowest welfare range, is 0.528 % (= 0.002*0.876/0.332) as large as the one I assumed, in which case I would estimate cage-free campaigns to be 2.44 (= 462*5.28*10^-3) times as cost-effective as GiveWell's top charities. The welfare range of chickens under the cubic model, the one leading to the 2nd lowest welfare range, is 40.1 % (= 0.152*0.876/0.332) as large as the one I assumed, in which case I would estimate cage-free campaigns to be 185 (= 462*0.401) times as cost-effective as GiveWell's top charities. As a result, the best animal welfare interventions are way more cost-effective than the best human welfare interventions under 11 of the 12 models RP considered. I think one has to be super confident that the neuron count model, or other outputting a similarly low welfare range, is right for the best human welfare interventions to be competitive. I suspect people supporting human welfare interventions would not be that confident on such models on reflection.