Quick answer

For most healthy adults, yes at usual amounts. NIH lists no known side effects of protein and no safety concerns up to about 2.0 g per kg of body weight a day. The cautions are allergies, fava bean protein for anyone told to avoid fava beans, two kinds of medicine, and traces of lead in plant powders.^1,2,3

Key facts

No upper intake level has been set for protein, because the danger from protein in food is very low.¹
Plant-based protein supplements averaged about three times the lead of dairy-based ones in a 2026 study of 30 products.³
Milk and soy are major food allergens that labels must name; pea is not on that list but can still cause reactions.^4,5
Protein can reduce how much levodopa is absorbed, according to its label.⁶

At usual amounts

NIH lists no known side effects of protein and reports no safety concerns at intakes up to about 2.0 g per kg of body weight a day.¹

High-protein diets of two to three times the RDA do not appear to harm kidney function, bone health or hydration in healthy people, and trained adults eating up to about 3.3 g per kg a day for up to a year showed no change in kidney or liver markers. People with severely reduced kidney function may need to limit protein.^1,7,8

Protein raises the calcium lost in urine, but NIH says this appears to have no lasting effect on bone and is easily offset by slightly more calcium.¹

No tolerable upper intake level has been set for protein, because the risk of harm from protein in food is very low. NIH still advises caution with high intakes from foods and supplements combined, since data are limited, and reports no safety concerns up to about 2.0 g per kg a day.¹

Allergies

Allergic reactions can occur. Milk, soy and peanuts are major food allergens, and peas, lentils, lupin and other legumes can also cause reactions, sometimes severe and sometimes in people already allergic to peanut.^4,5

Pea and fava are legumes. Reactions to pea and lupin have been severe in some cases, and some come from cross-reactions with peanut, so people with a peanut or legume allergy should ask an allergist before trying a legume protein powder.⁵

Fava bean protein and G6PD deficiency

Fava beans contain vicine and convicine, which make red blood cells break down in people with G6PD deficiency. Nursing babies with the condition have been harmed after their mothers ate fava beans.²

Most reported cases come from around the Mediterranean and the Middle East, where G6PD deficiency is more common. If you have it, or are nursing a baby who might, avoid fava bean protein unless your doctor says it is safe.²

Lead and cadmium

Plants can take up lead from the environment. In a 2026 study of 30 protein supplements, plant-based products averaged about three times the lead of dairy-based ones (0.18 against 0.06 mg per kg).^3,9

A 2020 risk assessment based on published tests estimated that one to three servings of protein powder a day would not raise health risks from arsenic, cadmium, mercury or lead.¹⁰

FDA's interim reference levels for lead from all food are 2.2 micrograms a day for children and 8.8 micrograms a day for women of childbearing age.⁹

FDA's advice is to eat a variety of foods so that no single one supplies much of any contaminant. If you use a plant protein every day, and especially if you are pregnant or could become pregnant, ask the maker what its lab results show for lead per serving.⁹

Medicines

Ask your pharmacist or doctor first

Protein can lower how much levodopa is absorbed. The carbidopa and levodopa label says levodopa competes with certain amino acids to cross the gut wall, so a high-protein diet may delay its absorption and reduce the amount that reaches the blood.⁶

On the medicine's label

Ask your pharmacist or doctor first

The label of phenelzine, an MAO inhibitor, tells people to avoid high-protein foods that have been aged, fermented, pickled or smoked, along with yeast extract and fava bean pods, because of the tyramine or dopamine they can contain. Ask before using a protein powder made with fermented yeast or fava bean protein.¹¹

On the medicine's label

Who should ask first

Anyone with kidney disease, or who has been told to limit protein
Anyone pregnant, nursing or under 18
Anyone allergic to milk, soy, peanuts, peas, lupin or other legumes, or to yeast
Anyone with G6PD deficiency, or nursing a baby who may have it, before using fava bean protein²
Anyone taking levodopa or an MAO inhibitor

Questions people ask

Is pea protein safe for the kidneys?

In healthy people, high-protein diets do not appear to harm kidney function, according to NIH. If you have kidney disease or reduced kidney function, ask your doctor, because protein limits may be part of your care.^1,8

Is plant protein safe during pregnancy?

Ask your doctor or midwife first. FDA's reference level for lead from food for women of childbearing age is 8.8 micrograms a day, set partly to protect a baby before a pregnancy is known, and plant powders tend to carry more lead than dairy ones.^3,9

Is whey protein safer than plant protein?

Neither has known side effects at usual amounts. Whey is a milk protein, so it is out for people with a milk allergy, while plant powders averaged more lead and cadmium in testing.^1,3,4

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Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.