New Study: Plant Protein Powders Are Inferior to Whey Protein
Plant-based diets are becoming increasingly popular; however, consuming enough dietary protein from whole plant food sources to support the rigors of training and promote muscle growth can be challenging for some.
The reason for this is that plant-based proteins generally contain less leucine compared to animal-based proteins.
This is important because leucine has been identified as the “anabolic” trigger of muscle growth, which means if your meal doesn’t contain enough leucine (or you don’t get enough) throughout the day, you are not maximizing muscle protein synthesis.
In order to achieve a similar leucine content to animal-based proteins, individuals would need to consume higher amounts of individual plant proteins (~50-60g).
Table 2: Representative amount of protein
However, with this higher overall food intake comes increased calorie intake, which may not be advantageous for those looking to maintain their weight or lose it.
There’s also the concern that plant proteins come with various “antinutrients”, such as phytates and tannins, which have been shown to reduce the digestibility and bioavailability of amino acids contained in protein.
The combination of incomplete/deficient amino acid profiles and the presence of antinutrients result in plant proteins typically having lower biological values and PDCAAS rating.
There’s also the consideration that consuming large quantities of food (like the amounts consumed by physically active people looking to increase performance and/or build mass) can become prohibitive at some point, meaning the foods are so voluminous that you get full, feel stuffed, and have trouble hitting your macro needs.
Consuming this many plant foods could also lead to bloating, flatulence, and/or GI distress (not exactly ideal).
For these reasons, individuals (including those that do and do not consume animal proteins) routinely turn to protein powder supplements.
Whey protein is the typical choice when it comes to purchasing a protein powder; however, amidst the rising popularity of plant-based diets, veganism and vegetarianism, as well as those seeking to diversify their protein sources, plant-based protein powders are becoming more mainstream.
As we mentioned, plant proteins are incomplete proteins, meaning they are deficient in one or more of the nine essential amino acids (generally, lysine and/or methionine).
They also tend to have lower leucine contents on a per-gram basis compared to animal proteins.
To circumvent these issues, and create a plant-based protein powder than can go toe-to-toe with whey protein, supplement companies and manufacturers have started creating vegan protein powder blends containing multiple plant protein sources.
The goal (hope) of these plant protein blends is to make some just as effective as whey protein.
And while this sounds promising in theory, will combining multiple plant proteins actually make something as effective as whey protein, which could arguably be considered as one of the most bioavailable protein sources available?
Well, a recently published study sought to answer that very question.
Purpose & Research Questions
The team of researchers hypothesized that a high-quality plant-based protein blend formulated to achieve a PDCAAS rating of 1.0 and similar leucine content would be bio-equivalent to whey protein isolate as defined by blood essential amino acid.
Therefore, the primary question the team was seeking to answer was:
Can a plant-based protein blend that’s formulated to match the leucine and PDCAAS of whey protein isolate produce similar increases in the blood of essential amino acids?
Researchers had a secondary object to assess the leucine kinetics over a 4-hour period of the plant protein blends in comparison to whey protein isolate.
Subjects & Methods
Researchers conducted a randomized, double-blind, 4 × 4 William square cross-over study to assess the bio-equivalence of the blood essential amino acid response over 4 hours post-ingestion of 3 distinct high-quality (PDCAAS = 1.0) plant-based protein blends versus whey protein isolate in healthy, resistance-trained adult men.
20 men, between the ages of 18–35, with a Body Mass Index (BMI) between 18.5 and 29.9 kg/m2 took part in the study.
Figure 1. Flow of participants through the study.
Participants were instructed to abstain from protein supplements for one day prior to each of their respective visits to the lab.
The four proteins used in the study were:
- Protein Blend #1 -- Pea, Pumpkin
- Protein Blend #2 -- Pea, Pumpkin, Sunflower Coconut
- Protein Blend #3 -- Pea, Pumpkin (hydrolysate)
- Control -- Optimum Nutrition whey protein isolate
To create Blend #3 researchers hydrolyzed the pea and pumpkin proteins used in Blend #1 using a food-grade enzyme sold by Novozymes North America, Franklinton, NC, USA.
To try to make the comparison as similar as possible (and give the plant proteins a chance to compete with whey protein), the researchers matched the leucine and total essential amino acid content, so that each protein had a PDCAAS of 1.0.
Subjects reported to the lab on four separate occasions to receive their protein shake. Each visit was separated by a washout period consisting of a minimum of four days but no more than 14 days.
Researchers measured blood levels of all nine essential amino acids for 4 hours following ingestion of the protein shake.
In the day preceding each lab visit, the men consumed a standardized dinner consisting of two frozen meals based on their individual body mass, age, and activity level (total nutritionals for both meals: Hungry-Man® Fajita Chicken, per serving: Calories 960, Carbohydrates 158 g, Protein 60 g, Fat 16 g), followed by an overnight fast that lasted 12 hours.
Subjects were also instructed to drink water ad libitum.
The research staff also collected a 24-hour dietary recall for each subject at the beginning of the trial. Researchers made a photocopy of the recall and gave it to each subject so that they could duplicate their same food intake before each subsequent visit.
This helps to keep blood amino acid levels similar between testing days and helps offset the possibility for any aberrations that may occur as a result of one’s daily diet.
The primary findings from this study were that even when matched for leucine (2.6g), essential amino acid content (12g), and PDCAAS ratings (1.0), the three plant-based protein blends were not bioequivalent to the WPI control, as assessed by tracking blood levels of leucine and essential amino acids over 4 hours post-consumption.
Figure 3. (a) Mean blood leucine over 4 hours per time point of each study product; (b) Mean and 95%CI total sum leucine iAUC (nmol/mL) by study product, obtained using the trapezoidal rule.
2.6 grams of leucine is the amount of leucine naturally occurring in the whey protein isolate used for the study.
This is noteworthy as the “threshold amount” of leucine needed to stimulate muscle protein synthesis (MPS) is between 2-3 grams of leucine per meal.[6,7]
While the researchers were able to administer a significantly smaller amount of plant-based protein to the men while still matching leucine levels (33–34 g instead of 50-60g), the subjects did not experience a similar rise in blood essential amino acid levels (including leucine, one of the nine EAAs) to that of whey protein isolate.
In fact, plant-based proteins yielded 30–40% lower in total essential amino acid area under the curve over 4 hours post-ingestion.
Figure 2. (a) Mean concentration of blood eAA over 4 hours following ingestion of each study product; (b) Mean and 95%CI total sum plasma eAA iAUC (nmol/mL) over 4 hours by study product. The area under the curve above baseline vs. time (minutes) was obtained by using the trapezoidal rule.
However, by the end of the 4-hour measurement plant-based protein blend #1 and blend #3 yielded similar blood leucine levels to that of whey protein isolate.
While previous studies have compared various plant-based proteins to whey protein matching total protein and/or leucine content, this study was able to match the leucine, total essential amino acids, and PDCAAS rating of whey protein with a considerably smaller total serving size of plant-based proteins.
However, despite matching the leucine, total EAAs, and PDCAAS of whey protein, none of the plant-based protein blends were able to match the blood leucine or total EAA kinetic response of whey protein isolate.
Previous studies have shown that hydrolyzing plant-based protein (e.g. wheat protein) leads to a considerable postprandial (after feeding) increase in blood amino acid availability; however, an equal amount of whey protein resulted in a greater postprandial increase in blood eAA concentrations.
In this study, the researchers only “mildly” hydrolyzed the plant proteins used in Blend #3 (~15%). Perhaps if they had more extensively hydrolyzed the pea and pumpkin proteins, they might have been able to match the leucine and EAA kinetic response of whey protein isolate.
However, the issue with greater hydrolysis is that it leads to adverse flavor changes (chemically, bitter taste).
Regarding the differences in postprandial blood amino acid levels, researchers attributed this to a mix of differing amino acid configurations and reduced digestibility compared to whey protein.
Additionally, the team also suggests the postprandial kinetics of dietary amino acids found in plant proteins may have also impacted the results. The reason for this is that previous studies have shown that plant-based proteins are transported into tissues at different rates than dairy proteins.
Despite the differences in immediate postprandial spike in blood amino acid levels between plant-based proteins and whey protein isolate, the researchers concluded that plant-based proteins are:
“...able to be absorbed by the blood stream with a good efficiency, thus proving to be a viable alternative to the consumption of animal proteins.”
Even though researchers cobbled together various plant-based protein sources to mimic the leucine, total EAA content, and PDCAAS of whey protein, all three blends failed to simulate the postprandial amino acid kinetics of good ole whey protein isolate.
One potential improvement that could be explored in future trials is to add additional free from L-Leucine to the plant-based protein powder to increase the leucine spike and see if it could match whey protein's leucine kinetics.
Additionally, further hydrolysis of the plant-based protein may have yielded similar postprandial leucine and total EAA kinetics, but then again, further hydrolysis would have made the taste of plant-based protein powders even worse than they already are.
Plus, hydrolysis adds a further step to the manufacturing process, which increases the overall cost of the product, and for those seeking “more natural” products, hydrolysis is a step in the opposite direction.
Despite whey protein isolate leading to greater initial spikes in amino acids (0-2 hours post ingestion), by the 4-hour mark, the difference between the blends was negligible.
One thing that the researchers did not test for, which would be a very interesting investigation for future trials, is to compare leucine, total EAA, and PDCAAS-matched plant-based protein blends vs whey protein on muscle protein synthesis.
So, as a consumer and connoisseur of protein powder, what does this mean for you?
Well, in my opinion, no matter how many plant proteins you “Frankenstein” together, they likely won’t ever be as good as what whey protein (or dairy proteins) have to offer.
Does this mean you can’t build muscle, promote recovery, and kick ass in life using only plant-based proteins?
Of course, not!
Research from Babault et al. showed that supplementation with pea or whey protein (50 grams per day) led to similar increases in muscle gain (as determined by biceps brachii) measurement.
(It's also worth noting that the study was funded by Roquette, producers of NUTRALYS pea protein. But the funding company had no part in the study design, data collection and analysis or preparation of the manuscript.
However, three of the researchers on the paper were employed by Roquette at the time of publication.)
However, realize that plant proteins by and large are less bioavailable than animal proteins, and plant-based protein powders almost always cost more than dairy-based protein powders.
A 2019 critical review comparing anabolic properties of animal-based vs plant-based proteins concluded:
"Plant-based protein sources that are rich in fiber and micronutrients may be valuable , but they have lower anabolic potential than animal-based proteins. Strategies to improve these properties by increasing protein intake or preferentially improving protein quality (i.e., their amino acid composition) include selective breeding, fortifying plant-based proteins with specific essential amino acids, mixing several plant proteins, and mixing plant- with animal-based protein sources."
Essentially, plant-based proteins can have their benefits, but head-to-head compared to animal-based protein powders they are inferior, unless they are mixed or heavily fortified to simulate the characteristics of whey protein and other animal-based proteins.
Plus, plant-based protein powders (typically) taste inferior.
If you’re looking to “optimize” your post-workout leucine and EAA spike, whey continues to be the way to go.
However, if you’re just looking to supplement your daily protein intake, either whey protein or plant-based protein could work.
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