The Problem of Protein Production
Athletes need a lot of protein — roughly 1.6–2.0 grams of protein per kilogram of body weight per day [1,2]. And most of that protein still comes from animal sources. The problem is that producing it comes at a steep environmental cost. A single kilogram of beef generates as much as 32 kg of CO₂ equivalents, and pound for pound, protein from beef and lamb produces roughly 250 times more emissions than protein from legumes like lentils or chickpeas [3,4]. With the global population expected to approach 10 billion by 2050, the current model of protein production simply can't scale.
A review by Tuna and Ersoy, recently published in Current Nutrition Reports, surveys the landscape of sustainable alternatives and asks which ones can realistically meet both athletic needs and environmental goals [5]. The paper examines five protein categories — plant proteins, mycoproteins, insect proteins, microalgae, and cultured meat — drawing on clinical trials, environmental assessments, and nutritional analyses. It's worth noting that the paper doesn't describe a formal systematic search methodology (no documented inclusion criteria or PRISMA diagram), so the evidence might be somewhat curated rather than exhaustive. That said, the breadth of sources it covers — 95 references spanning nutrition science, environmental assessment, and food technology — makes it a useful map of where things stand. The short answer: several alternatives can support muscle protein synthesis (MPS) — the process by which the body repairs and builds muscle tissue — at levels comparable to animal protein, but the strength of that evidence varies dramatically from one source to the next.
| Protein Source | Available Now? | Human MPS Evidence | Key Trade-Off |
|---|---|---|---|
| Plant proteins (soy, pea) | Yes | Strong — multiple randomised trials show comparable muscle gains to whey | Requires leucine matching and attention to iron, zinc, B12 |
| Mycoproteins (fungi) | Yes | Strong — outperformed milk protein for MPS in a randomised controlled trial | Consumer perception ("unnatural"), taste and texture limitations |
| Insect proteins | Limited | Promising — mealworm MPS comparable to milk protein in one trial | Cultural acceptance in Western markets; chitin can reduce digestibility |
| Microalgae (Spirulina, Chlorella) | As supplement | Mixed — some antioxidant and recovery benefits; null results in elite athletes | Strong marine taste limits usable quantity; inconsistent performance effects |
| Cultured meat | No | None — zero published human performance trials | High production costs, regulatory hurdles, unresolved safety questions |
What Athletes Can Use Today
Two categories already have enough evidence to act on. Plant proteins — particularly soy and pea — have been tested head-to-head against whey in randomised trials. Lynch et al. found no significant differences in muscle growth or strength between soy and whey supplementation over 12 weeks of resistance training when leucine content was matched [6]. A separate trial showed pea protein delivering equivalent improvements in muscle strength and mass to whey [7]. And a recent meta-analysis confirmed that plant-based diets do not compromise muscular strength compared with omnivorous diets [8]. The caveat is that matching matters: athletes who switch to plant protein without paying attention to leucine content, total intake, and micronutrients like iron, zinc, and B12 may fall short.
Mycoproteins — protein derived from fungi, most famously Fusarium venenatum — may be the most underappreciated finding in the review. Monteyne et al. demonstrated that 70 grams of mycoprotein sources (containing 31.5 grams of protein) stimulated MPS at a higher rate than 31 grams of milk protein (containing 26 grams of protein), both at rest and after resistance exercise [9]. In a follow-up study, a 35g mycoprotein drink enriched with BCAAs stimulated muscle protein synthesis at rest and after resistance exercise. Higher doses produced greater MPS, yet blood BCAA levels barely changed — suggesting the fungal food itself, not just its amino acids, was driving muscle growth [10]. Mycoproteins also come with a lower carbon footprint than conventional meats and are rich in dietary fibre. The main barriers are perceptual rather than nutritional: some consumers view them as "unnatural," and the taste needs work for broader adoption.
What's on the Horizon
Insect proteins are nutritionally excellent — 20–70% protein by dry matter, all essential amino acids, digestibility up to 96%, and a fraction of the environmental footprint of livestock [5]. In a double-blind randomised trial, Hermans et al. showed that 30 grams of mealworm protein stimulated postprandial MPS at levels comparable to milk protein [11]. But insect exoskeletons contain chitin (8–27% of dry weight), which functions as dietary fibre and can reduce protein digestibility when bound to muscle proteins [5]. Processing methods matter, and athletes considering insect-based supplements should check whether the chitin has been reduced. The bigger obstacle remains consumer acceptance — particularly in Western markets.
Microalgae like Spirulina are impressive on paper: up to 70% protein by dry weight, yields of 15–30 tons per hectare versus soy's 1.5–3.0 tons, and a rich supply of omega-3s and antioxidants [5]. But the performance evidence is genuinely mixed. A trial in trained cyclists found 21 days of Spirulina supplementation at 6 g/day enhanced sprint power output [12], yet a study in elite rugby players found 5.7 g/day for seven weeks produced no significant effects on body composition, strength, or aerobic capacity [13]. The marine taste also becomes hard to mask at meaningful protein-serving quantities, making microalgae more suited as a supplementary ingredient than a primary protein source for now.
Cultured meat — grown from animal stem cells in a lab — carries the most dramatic environmental promise: potentially 78–96% less greenhouse gas emissions and 99% less land use than conventional meat [14]. But at the time of writing, there are no published human trials examining how cultured meat affects athletic performance, recovery, or MPS. It's a technology to watch, not one to bet your training diet on.
The practical takeaway is that the science already supports diversifying your protein sources. Soy, pea, and mycoproteins can match — and in one case outperform — dairy for muscle building when intake and amino acid balance are managed. Insect protein is close behind. None are magic bullets, and each requires informed choices about processing and complementary nutrition. But for athletes looking to reduce their environmental footprint without compromising their training, the evidence base for the top two categories is now strong enough to make that switch with confidence.
References
- Jäger R. et al. "International society of sports nutrition position stand: protein and exercise", Journal of the International Society of Sports Nutrition 14 (2017) 20. https://doi.org/10.1186/s12970-017-0177-8
- Kerksick C.M. et al. "ISSN exercise & sports nutrition review update: research & recommendations", Journal of the International Society of Sports Nutrition 15 (2018) 38. https://doi.org/10.1186/s12970-018-0242-y
- Raihan A. "The influence of meat consumption on greenhouse gas emissions in Argentina", Resources, Conservation and Recycling Advances 19 (2023) 200183. https://doi.org/10.1016/j.rcradv.2023.200183
- Godfray H.C.J. et al. "Meat consumption, health, and the environment", Science 361 (2018) eaam5324. https://doi.org/10.1126/science.aam5324
- Tuna T. & Ersoy N. "Future Protein Sources in Sports Nutrition: Sustainable Solutions", Current Nutrition Reports 15 (2026) 12. https://doi.org/10.1007/s13668-026-00734-8
- Lynch H.M. et al. "No significant differences in muscle growth and strength development when consuming soy and whey protein supplements matched for leucine following a 12 week resistance training program in men and women: a randomized trial", International Journal of Environmental Research and Public Health 17 (2020) 3871. https://doi.org/10.3390/ijerph17113871
- Singh R.G. et al. "Efficacy of pea protein supplementation in combination with a resistance training program on muscle performance in a sedentary adult population: a randomized, comparator-controlled, parallel clinical trial", Nutrients 16 (2024) 2017. https://www.mdpi.com/2072-6643/16/13/2017
- López-Moreno M. & Kraselnik A. "The impact of Plant-Based proteins on muscle mass and strength performance: a comprehensive review", Current Nutrition Reports 14 (2025) 37. https://doi.org/10.1007/s13668-025-00628-1
- Monteyne A.J. et al. "Mycoprotein ingestion stimulates protein synthesis rates to a greater extent than milk protein in rested and exercised skeletal muscle of healthy young men: a randomized controlled trial", American Journal of Clinical Nutrition 112 (2020) 318–333. https://doi.org/10.1093/ajcn/nqaa092
- Monteyne A.J. et al. "Branched-chain amino acid fortification does not restore muscle protein synthesis rates following ingestion of lower- compared with higher-dose mycoprotein", Journal of Nutrition 150 (2020) 2931–2941. https://doi.org/10.1093/jn/nxaa251
- Hermans W.J. et al. "Insects are a viable protein source for human consumption: from insect protein digestion to postprandial muscle protein synthesis in vivo in humans: a double-blind randomized trial", American Journal of Clinical Nutrition 114 (2021) 934–944. https://doi.org/10.1093/ajcn/nqab115
- Gurney T., Brouner J. & Spendiff O. "Twenty-one days of spirulina supplementation lowers heart rate during submaximal cycling and augments power output during repeated sprints in trained cyclists", Applied Physiology, Nutrition, and Metabolism 47 (2021) 18–26. https://doi.org/10.1139/apnm-2021-0344
- Chaouachi M. et al. "Spirulina platensis provides a small advantage in vertical jump and sprint performance but does not improve elite rugby players' body composition", Journal of Dietary Supplements 18 (2021) 682–697. https://doi.org/10.1080/19390211.2020.1832639
- Tuomisto H.L. & de Teixeira M.J. "Environmental impacts of cultured meat production", Environmental Science & Technology 45 (2011) 6117–6123. https://doi.org/10.1021/es200130u