Side effects of pea protein

Pea protein is usually well tolerated, which is precisely why it is often chosen by people for whom whey is not suitable. However, «well tolerated» does not mean «without side effects». Our editorial team examined which adverse reactions actually occur, what causes them and how to reduce their likelihood.

General safety profile

Pea protein is a food product obtained from ordinary peas, which humanity has eaten for thousands of years. Therefore, serious systemic side effects in healthy people are uncharacteristic of it. Most of the adverse reactions that occur are related to digestion, individual sensitivity or the quality of the specific product.

It is worth distinguishing three groups of risks. The first is reactions to the pea protein itself (allergy). The second is reactions to accompanying substances that remain after processing (oligosaccharides, fiber) or are added by the manufacturer (sweeteners, thickeners). The third is contaminants that can get into the product from the raw material, in particular heavy metals.

In clinical studies of pea protein in athletes, such as the work of Babault et al. (2015), no serious adverse events were reported. However, such studies lasted a few weeks or months and were not designed to detect rare reactions.

Below we will examine each group of risks separately and explain who should be especially attentive.

Digestive disorders: bloating, gas, discomfort

The most frequent complaint of pea protein users is bloating and increased gas formation. The main cause is legume oligosaccharides (raffinose, stachyose, verbascose), which belong to the group of galacto-oligosaccharides. Humans do not have the enzyme to break them down, so they reach the large intestine, where bacteria ferment them with the formation of gases.

These carbohydrates are part of the FODMAP group — fermentable short-chain carbohydrates that are poorly absorbed. As Gibson and Shepherd (2010) showed, in people with functional digestive disorders, in particular irritable bowel syndrome, it is precisely FODMAPs that often provoke symptoms. Therefore, for such people legumes and products made from them can be harder to tolerate.

During the production of the isolate, most oligosaccharides are washed out along with other soluble carbohydrates, so isolates are usually tolerated better than concentrates or flour. However, the residual amount, as well as individual sensitivity, can cause symptoms, especially with large portions.

Another source of discomfort is the ingredients added by the manufacturer. Sugar alcohols (erythritol, xylitol, maltitol), inulin and other prebiotic fibers, thickeners can themselves cause bloating and loosening of the stool. Sometimes the problem is not the peas, but precisely these additives.

Usually digestive symptoms are mild and resolve on their own. But if severe pain, blood in the stool, prolonged diarrhea or weight loss appear, this is not a typical side effect of protein, but a reason to see a doctor.

Allergy and cross-reactions

Pea is not on the list of 14 major food allergens mandatory for labeling in the EU, unlike peanuts, soy and lupin. However, pea allergy exists. Pea belongs to the legume family, and in people with an allergy to peanuts, lentils or chickpeas cross-reactions are possible due to the similarity of the proteins, in particular the vicilin globulins.

With the spread of pea protein in the food industry — in meat substitutes, plant milk, bars — allergists increasingly pay attention to this allergen. A person with a known allergy to legumes should discuss with an allergist the possibility of consuming pea protein before trying it.

The manifestations of allergy are the same as with other food allergies: itching in the mouth, hives, swelling, abdominal pain, nausea, and in severe cases — difficulty breathing and anaphylaxis. The EAACI guidelines (Muraro et al., 2014) emphasize that a suspicion of food allergy requires examination by an allergist, not self-experimentation.

Contaminants, sodium and purines

Heavy metals.Plants can accumulate lead, cadmium and arsenic from the soil. Therefore plant proteins, in particular pea, periodically end up in the news because of detected traces of metals. The level of contamination depends heavily on the growing region and quality control. For a person who consumes protein every day over the course of years, choosing a manufacturer with transparent laboratory analyses is an important element of safety.

Sodium.During the production of the isolate the protein is neutralized with alkali, and part of the products contains a noticeable amount of sodium. For most people this is not a problem, but those who limit salt because of high blood pressure or kidney or heart disease should check the sodium content on the label.

Purines.Legumes contain purines — compounds from which uric acid is formed in the body. For people with gout, controlling uric acid is important, and the guideline of the American College of Rheumatology (FitzGerald et al., 2020) considers dietary measures as a supplement to drug treatment. There is little data on the effect of pea protein isolate specifically on uric acid levels, so patients with gout should coordinate its use with a rheumatologist.

Load on the kidneys.In healthy people, pea protein, like any other, does not harm the kidneys. However, in chronic kidney disease total protein intake is restricted according to the KDOQI guideline (2020), and the addition of protein supplements is possible only by the decision of a nephrologist.

How to reduce the risk of side effects

Most troubles can be avoided by following a few simple rules.

• Start with half a portion during the first few days, gradually increasing to the required amount.
• Choose an isolate instead of a concentrate if you are prone to bloating.
• Avoid products with sugar alcohols and inulin if your gut reacts to them.
• Do not mix large portions of protein with other fiber-rich products in one intake.
• Buy products with independent laboratory testing for heavy metals and microbiology.
• If you have a legume allergy, consult an allergist before the first intake.

It is useful to keep a short diary: when and how much protein you consumed, what you mixed it with and how you felt. This will help determine whether the symptoms are related specifically to pea protein or to other components of the diet.

If even small portions of the isolate consistently cause discomfort, you can try other plant proteins (rice, blends) or animal ones, if they suit you.

Editorial conclusions

Pea protein has a favorable safety profile, and the most frequent side effects — bloating and gas — are usually mild and associated with oligosaccharides, additives in the composition or overly large portions.

A rare but most serious risk is allergy, especially in people with an allergy to other legumes. It is also worth remembering the quality of the raw material and the sodium content.

A gradual start, the choice of an isolate with a short ingredient list and a trusted manufacturer substantially reduce the likelihood of problems.

We also recommend reading our articles «Who should not take pea protein», «Pea protein: product forms and which to choose» and «Who should not take egg protein».

References

1. Gibson PR, Shepherd SJ. Evidence-based dietary management of functional gastrointestinal symptoms: the FODMAP approach. J Gastroenterol Hepatol. 2010;25(2):252–258.
2. Muraro A, Werfel T, Hoffmann-Sommergruber K, et al. EAACI food allergy and anaphylaxis guidelines: diagnosis and management of food allergy. Allergy. 2014;69(8):1008–1025.
3. FitzGerald JD, Dalbeth N, Mikuls T, et al. 2020 American College of Rheumatology guideline for the management of gout. Arthritis Care Res (Hoboken). 2020;72(6):744–760.
4. Ikizler TA, Burrowes JD, Byham-Gray LD, et al. KDOQI clinical practice guideline for nutrition in CKD: 2020 update. Am J Kidney Dis. 2020;76(3 Suppl 1):S1–S107.
5. Babault N, Païzis C, Deley G, et al. Pea proteins oral supplementation promotes muscle thickness gains during resistance training: a double-blind, randomized, placebo-controlled clinical trial vs. whey protein. J Int Soc Sports Nutr. 2015;12(1):3.
6. Regulation (EU) No 1169/2011 of the European Parliament and of the Council on the provision of food information to consumers. Official Journal of the European Union. 2011;L304:18–63.