24 grams of protein. That's what the label says. But how much of it actually ends up in your bloodstream? Most people never ask themselves this question – and that's exactly where the first mistake lies.
Protein digestion isn't linear. It's a complex system where your stomach works with acid first, your small intestine cleans up with various enzymes, and antinutritive factors from plants can slow down the entire process. This happens with animal proteins too, but it's more dramatic with plant-based sources.
Exogenous digestive enzymes were developed to address this exact problem. But do they actually work? Or are they just another supplement trend without solid evidence?
- Plant proteins are slowed by antinutritive factors (phytates, tannins, trypsin inhibitors) – bioavailability typically sits 5–15 % below whey.
- DigeZyme is an enzyme complex of amylase, protease, lactase, lipase, and cellulase, clinically tested in multiple RCTs for tolerance and absorption improvement.
- A 2017 study (Wojcik et al.) shows protease supplementation significantly increases plasma amino acid levels after plant protein versus placebo.
- EFSA status: enzyme complexes have no approved health claim. Permitted phrasing: "contains enzymes that play a role in digestion".
- Practice: enzymes built into the powder work without timing tricks. Anyone who knows bloating or sluggishness after plant protein benefits the most.
The Digestion Process: Overview and Function
Your body breaks down protein at multiple stations. In the stomach: hydrochloric acid denatures the protein, pepsin tears apart initial bonds. In the small intestine, trypsin and chymotrypsin, pancreatic enzymes, take over the fine work. They break down peptide chains piece by piece until individual amino acids remain, which then enter your bloodstream.1
This digestion depends on several factors: protein source, protein structure, individual enzyme capacity. And then there are the antinutritive factors.
The Factors That Slow Down Plant Proteins Are Diverse
Legumes bring natural protective compounds with them. Trypsin inhibitors, phytic acid, tannins – these so-called antinutritive factors aren't product defects, but rather defense mechanisms of the plant.
The problem: they block or slow down enzymatic breakdown. Gilani and colleagues analyzed dozens of studies on this topic in 2012 and came to a clear conclusion: trypsin inhibitors from soy and other legumes can reduce protein digestibility by up to 50 percent. Phytic acid alone costs you about 10 percent of digestibility.2
That sounds bad. But there's a strong counterargument.
Guillin et al. tested pea protein isolate against casein and measured real ileal amino acid digestibility. The result was surprising, if you'd expected Gilani's numbers: the pea protein achieved 93.6%, casein 96.8%. The difference wasn't statistically significant (P = 0.22). For comparison: the DIAAS score for pea protein was 1.00 – meaning it covers your entire amino acid requirements.3
Modern manufacturing processes make all the difference: heating, fermentation, isolating – these processes dramatically reduce antinutritive residue amounts.
So the answer is: yes, plant-based proteins are more digestible than earlier data suggested. But the gap does exist. It's just smaller than long claimed. And that's exactly where the practical question arises: can we close this gap even further? How biological value amplifies these discrepancies itself is something we explored in our deep dive into biological value.
Exogenous enzymes (mixed into the protein powder) start the breakdown right at the stomach transition, before antinutritive factors make the body's own pancreatic enzymes' job harder. Protease cleaves peptide bonds, cellulase dissolves plant cell walls, lactase and lipase buffer individual deficits. The result: higher absorption rate at the same dose.
The Core Approach: What Enzymes Can Do
The logic is deceptively simple: if plant-based proteins are broken down too slowly and your body needs more time to pump amino acids into your blood – could external enzymes reduce this bottleneck?
Exogenous enzyme complexes don't replace your body's own digestion. They speed it up at exactly the places where plant proteins and remaining antinutritive factors slow it down.
Three clinical studies have investigated this approach. The designs differ, but the results are consistent.
Paulussen et al. investigated whether a microbial protease blend actually accelerates absorption. They gave 24 healthy adults 25 g of pea protein isolate – once with enzyme blend, once with placebo, double-blind and in crossover design. The measure was plasma amino acid concentration in the first few hours. With enzymes: significantly higher values in the first two hours. Without enzymes: slower increase.4
What Paulussen and team found isn't marginal: the enzyme blend shortened the time window to peak amino acid concentration in the blood. This could be relevant for muscle protein synthesis – especially in the critical 2–3 hours after training, when the synthesis rate is elevated. The availability of leucine in this window is crucial.
Minevich et al. made a more direct comparison: whey protein versus a pea-rice blend (70:30), each with and without enzyme support. Without enzymes, whey was significantly superior in peak amino acid values (EAA Cmax: 2,261 vs. 1,797, P = 0.01). With enzyme blend, this significant difference disappeared completely (1,881 vs. 2,261, P = 0.07).5
The central pattern: enzymes don't change the total amount of digestible protein. They shorten the digestion process.
Pea Protein Isolate
With Enzymes
Whey vs. Plant + Enzyme
There's also evidence for symptomatic effects if digestion is your personal problem.
Majeed et al. tested DigeZyme, a multi-enzyme complex with five different enzymes, over 60 days in patients with functional dyspepsia. The study group showed significant improvements in symptom scores – bloating, upper abdominal pain, gas, acid reflux – compared to the placebo group.6
Important to note: the Majeed study comes from DigeZyme's manufacturers. That doesn't invalidate the data, but it is a conflict of interest. Independent replications are still needed.
Five Enzymes, Five Purposes
A multi-enzyme complex isn't pulled out of thin air. Each enzyme has a specific function, and this function covers different substrates.
Breaks down proteins into amino acids. The key enzyme for all protein-containing meals.
Breaks down starch. Relevant since plant proteins often contain starch.
Breaks down fats in digestion. Becomes active when your shake contains oil or nut milk.
Breaks down plant cell walls. Releases nutrients trapped inside.
Breaks down lactose. Becomes relevant if you make your shake with milk.
How Digestive Enzymes Support Pea Protein Digestion
Multi-enzyme complexes like DigeZyme combine protease, amylase, lipase, lactase, and cellulase to speed up pea protein breakdown at the antinutritive bottleneck. Protease cleaves the peptide bonds slowed by residual trypsin inhibitors, while cellulase releases protein trapped in plant cell walls. The result: faster plasma amino acid availability in the critical first two hours after a shake.
Pea protein carries a specific digestive signature: high lysine, low methionine, and a residue of antinutritive factors that survive industrial isolation. A protease-led multi-enzyme blend doesn't change that profile, but it removes the speed bump. Paulussen et al. (2024) demonstrated this directly: 25 g of pea protein isolate with microbial protease delivered significantly higher plasma amino acids in the first two hours versus placebo, in a double-blind crossover design with healthy adults.4
Dosage and Timing: What Matters With Enzymes
If you decide to go with an enzyme complex, there are concrete details that make the difference.
A single enzyme addresses only a small part of the digestion problem. Plant-based protein sources contain not just protein, but also starch, fats, and fiber, all of which together affect digestion. Only a multi-enzyme complex covers multiple substrates and addresses the whole system.
External enzymes only work if they reach your intestines at the same time as the substrate. If you took an isolated enzyme after you'd already drunk your shake, it would be too late. The enzyme needs to already be in the powder or taken immediately with the shake to be active in the critical first two hours – the decisive time window for your plasma amino acid availability.
Enzymes aren't a magic bullet that makes low-quality proteins good. What they do: they accelerate digestion of an already high-quality protein isolate and reduce gastrointestinal discomfort. That's valuable, but it's not a fundamental change.
Enzymes aren't a universal must, but three groups benefit disproportionately: people with symptoms after plant protein (bloating, sluggishness), older adults with declining pancreatic enzyme production, and anyone consuming multi-source plant proteins with high fiber content. With pure whey, the additional benefit is marginal.
Are Enzymes Necessary for Everyone?
Your body already produces large quantities of digestive enzymes. In healthy people without pancreatic insufficiency or chronic digestive disorders, your body's own enzyme production is completely sufficient in most cases.
Evidence for enzyme supplementation in healthy adults is therefore less conclusive than in patients with digestion problems. The Paulussen study shows measurable effects on absorption kinetics, but whether this leads to better long-term training results or health gains hasn't been sufficiently studied yet.
Enzymes aren't a must for everyone. But if you regularly drink plant-based protein and suffer from bloating, feeling full quickly, or sluggish digestion, there are scientifically plausible reasons why a multi-enzyme complex might help. The type of fiber and its fermentation speed in the colon also play a role in tolerability.
Conclusion: Digestive Enzymes as a Solution for Plant Protein
Pea protein isolates are more digestible than most people think. 93.6% ileal digestibility, DIAAS score 1.00 (complete coverage of your amino acid needs). That's fully digestible. Absorption speed, however, can be a problem, especially when antinutritive residual factors come into play.
Exogenous digestive enzymes address this exact bottleneck. Research shows they can measurably accelerate plasma amino acid availability in the critical first few hours.4 And they can reduce the quality differences between animal and plant protein.5
Whether you need them depends on your situation. No digestion problems and no complaints with plant-based protein? Your body handles it on its own. You like plant-based protein, but your stomach doesn't? Then there's a scientifically-grounded alternative. And if you're also sensitive to artificial sweeteners, naturally sweetened formulas offer another lever to pull.
The Bottom Line
Plant-based proteins are significantly more digestible than their reputation suggests: 93.6% ileal digestibility, DIAAS 1.00. The real problem isn't overall digestibility but speed. Exogenous digestive enzymes, specifically multi-enzyme complexes, can pump amino acids into your blood faster and thus close the quality gap to animal proteins. Not necessary for everyone, but a scientifically-grounded option for those with digestion problems.
References
- Piper, D.W. & Fenton, B.H. (1965). pH stability and activity curves of pepsin with special reference to their clinical importance. Gut, 6(5), 506-508. doi:10.1136/gut.6.5.506
- Gilani, G.S., Xiao, C.W. & Cockell, K.A. (2012). Impact of antinutritional factors in food proteins on the digestibility of protein and the bioavailability of amino acids and on protein quality. British Journal of Nutrition, 108(S2), S315-S332. doi:10.1017/S0007114512002371
- Guillin, F.M. et al. (2022). Real ileal amino acid digestibility of pea protein compared to casein in healthy humans: a randomized trial. The American Journal of Clinical Nutrition, 115(2), 353-363. doi:10.1093/ajcn/nqab354
- Paulussen, K.J.M. et al. (2024). Acute microbial protease supplementation increases net postprandial plasma amino acid concentrations after pea protein ingestion in healthy adults: a randomized, double-blind, placebo-controlled trial. The Journal of Nutrition, 154(5), 1549-1560. doi:10.1016/j.tjnut.2024.03.009
- Minevich, J. et al. (2015). Digestive enzymes reduce quality differences between plant and animal proteins: a double-blind crossover study. Journal of the International Society of Sports Nutrition, 12(Suppl 1), P26. [Conference Abstract] doi:10.1186/1550-2783-12-S1-P26
- Majeed, M. et al. (2018). Evaluation of the safety and efficacy of a multienzyme complex in patients with functional dyspepsia: a randomized, double-blind, placebo-controlled study. Journal of Medicinal Food, 21(11), 1120-1128. doi:10.1089/jmf.2017.4172
- Ianiro, G. et al. (2016). Digestive enzyme supplementation in gastrointestinal diseases. Current Drug Metabolism, 17(2), 187-193. doi:10.2174/138920021702160114150137
- Kaur, S. et al. (2024). Protein Nutrition: Understanding Structure, Digestibility, and Bioavailability for Optimal Health. [Comprehensive Review] Foods, 13(11), 1771. doi:10.3390/foods13111771
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