Plant proteins or whey: no difference detected in five studies in resistance-training beginners

A comparison in adults starting resistance training

The researchers selected studies comparing plant protein supplementation with whey supplementation in healthy adults aged 18 to 59 who were taking part in resistance training. Body composition was assessed using dual-energy X-ray absorptiometry, or DEXA.

The review was registered in PROSPERO and conducted according to PRISMA guidelines. Five studies were included in the synthesis and meta-analysis. However, the available abstract does not specify the total sample size, intervention durations or protein doses used.

No difference detected does not mean equivalence demonstrated

For both types of supplementation combined with training, the authors report favorable changes in lean mass and fat mass, with no statistically significant difference between groups. The abstract does not provide effect sizes or their uncertainty intervals.

This lack of a detected difference is not enough to prove equivalence. Without this information, it is impossible to determine what potential difference the data can rule out. Measured lean mass should not be confused with a direct measurement of strength, either.

The comparison concerns two types of supplementation alongside resistance training. On its own, it cannot attribute the changes to supplements rather than training, or determine whether a supplement was necessary.

Soy, pea and chia do not have the same level of support

The authors consider soy and pea proteins possible nutritional options for adults starting resistance training who want to avoid whey. This does not allow the finding to be generalized to every commercial formulation or to already-trained athletes.

For chia, the evidence is limited to a single study, which showed no significant change in lean mass. This finding is not enough to establish its effectiveness or to conclude definitively that it is ineffective.

What we can take away

In resistance-training beginners, this synthesis finds no evidence that whey is superior to the plant proteins studied. Soy and pea appear to be possible alternatives, without formally demonstrated equivalence.