Monday, September 12, 2011

Whey Protein Vs. Soy Protein...which is better?

I.  Introduction
II.  Experimental Design
III. Results
IV. Conclusion - Who's the Winner?
V. References
I.  Introduction

This article was another example of how some research papers do not COMPLETELY support their hypothesis and leave reasonable doubt.  In my opinion, there are certain aspects of this study that are just not up to par.  These aspects challenge the validity of these results.  Let’s dig in…

Whey Protein vs. Soy Protein…which is better for losing fat?  This study approached that question in a unique way.  Rather than coupling protein intake with one of the many fat loss diets (i.e. – calorie-restricted, complex carbs, high protein, etc.), subjects had totally unrestricted diets.  The authors’ primary objective was to “determine the effects of added supplemental protein to the habitual diet of free-living overweight and obese adults, without energy restriction, on body weight and composition.” 

This approach presents a HUGE amount of variability in the data!!  I’m not sure how I feel about that, not exactly scientifically sound, but we’ll get into that later…
II.  Experimental Design

Ninety overweight, but healthy subjects (BMI = 28-38) were randomly assigned to 3 groups, with each group consuming 1 pack of a whey protein (WP), soy protein (SP), or carbohydrate (CHO - control) supplement powder immediately prior to, during, or immediately after breakfast and dinner for a 23-week period. The total amount of energy from each supplement powder was 1670 kJ/d.  However, the subjects received “minimal instruction from a registered dietician on how to make dietary alterations to incorporate these products.”  But dietary intake was assessed every 10 days.  Other measurable were:

Physical Activity: measured every 2 weeks
Body weight and composition – measured every month
Waist and hip circumference – measured every month
Insulin, glucose, IGF-I, IGF binding proteins, Serum free thyroxine (T4) concentrations
and triiodothyronine (T3) uptake
III.  Results

     A.  Timing of Supplement Intake
There was a large variation in when the subjects consumed their supplements.  Here’s a quote: 

“At breakfast time, most packets were consumed immediately before or during the meal (44 and 41%, respectively) and fewer were consumed immediately after the meal (15%). At dinner time, over one-half of the packets (52%) were consumed immediately prior to the meal. The remainder dinner time packets were consumed with the meal (20%) or immediately after the meal (28%).” 

Consuming these packets before or after a meal could potentially affect how much food the subject eats during their meal.  Also, the other foods that are eaten with these packets can significantly alter the affect of the TOTAL meal on a subject’s body.  For example, drinking whey protein with a grilled chicken salad is much different than drinking whey protein with a double cheeseburger.  But I guess that was the point of studying “free-living” subjects. 

     B.  Dietary Intake

% Protein Energy
% Fat Energy
% Carb Energy
WP Group
SP Group
CHO Group (control)

Remember, these percentages were not planned.  These were what was reported to the authors BY the subjects.  Even more disturbing (at least to me), is that there is NO distinction as to what types of proteins, fats, or carbs are being consumed!  And on top of that, these subjects received “minimal instruction from a registered dietician on how to make dietary alterations to incorporate these products.”  So, I don’t know if subjects are eating oatmeal, brown rice, white rice, Starburst, or popsicles for their carb intake.  And the same issue exists with protein and fat intake.  So how do I know that any results I see are due to whey protein or soy protein treatment???  Maybe one group had more low GI carbs than the other.  Maybe one group ate more lean protein?  Or more healthy fats?  This is why I don’t see the point of using “free-living” subjects.

So, in my opinion, you should take the following results with a HUGE grain of salt!!

     C.  Physical Activity
There was no difference in physical activity between the treatment groups.  I guess that since protein, fat, and carb intake, and physical activity were similar between the whey protein and soy protein groups, the authors’ argue that any changes in body composition or biochemical factors is due to one of those proteins.  But with this experimental design??  Hmmm…that would be a very questionable conclusion.

     D.  Body Composition
Body weight was 4 lbs lower in the WP group than in the CHO (control) group.  Also, body fat was 5 lbs lower in the WP group than in the CHO group.  The SP group had lower body weight and body fat than the CHO group, but not as low as the WP group.  Basically, this data suggests that WP is better for losing body weight and body fat mass.  These responses did not differ between men and women. 

Waist circumference was significantly lower (by 2.4 cm) in the WP group than the CHO and SP groups.  The SP group’s waist circumference was almost exactly the same as the CHO group.

     E.  Biochemical Changes
No differences in glucose were observed between groups.  Insulin concentrations were lower in the WP and SP groups than the CHO group (as expected), but there was no significant difference between WP and SP groups.  However, WP subjects had lower concentrations of the hunger-stimulating hormone, ghrelin, than SP and CHO groups. 

The authors also measured IGF-I, IGF binding protein (IGFBP)-1, and IGFBP-3 concentrations, which are important for overall growth.  While IGFBP-1 concentrations were relatively similar, IGF-1 concentrations were at its highest with SP treatment (87 ug/L).  WP treatment still produced greater IGF-I values than the CHO group (77.8 ug/L)IGFBP-3 concentrations were also at its highest with SP treatment (2.04 mg/L).  WP treatment actually produced the lowest concentration of IGFBP-3 (1.82 mg/L) with CHO treatment falling in the middle (1.98 mg/L).

Lastly, the authors also measured T3 uptake and free T4 concentrations.  These prohormones play a role in growth, development, and many metabolic processes in the body.  They increase protein synthesis, glycogen breakdown, lipolysis, and basal metabolic rate.  Interestingly, the WP group (T3 uptake = 30.9%; T4 = 13.7 pmol/L) had lower T3 uptake and free T4 concentrations than the SP (T3 uptake = 32.5%; T4 = 14.5 pmol/L) and CHO (T3 uptake = 31.4%; T4 = 14.1 pmol/L) groups

So, compared to the CHO control, soy protein increased IGF-1, IGFBP-3, T3 and T4, while WP had no effect or decreased them.  I wouldn’t think that is desirable.  All the more reason to actually control the subjects’ diet!!
IV.  Conclusion - Who's the Winner?

This article suggests that “Whey Protein but Not Soy Protein Supplementation Alters Body Weight and Composition in Free-Living Overweight and Obese Adults.”  In my opinion, using “free-living” subjects is pointless.  In my opinion, there’s NO way to definitively say that a dietary treatment works when all of your subjects are eating different things!  How can your data be completely accurate??  Therefore, even though I believe that whey protein is better, this article DOES NOT prove that.

Other studies have proven that both whey and soy protein, combined with resistance training, increase muscle mass and strength, whether they are consumed as shakes (Candow et al., 2006) or protein bars (Brown et al., 2004).  However, in regards to optimal muscle recovery, a study by Tang et al., (2009) may give whey protein a slight edge.  This study indicates that whey protein consumption results in larger essential amino acid, branched-chain amino acid, and leucine concentrations in the blood following resistance exercise.  Skeletal muscle protein synthesis with whey protein consumption was also 18% greater than soy protein at rest and 31% greater following resistance exercise.  This increased amino acid availability and protein synthesis may lead to increased fat loss as well, but the featured study in this article didn't prove it.  Nonetheless, these studies suggests that whey protein is better than soy protein for muscle recovery.
Dr. O 
"I don't live to eat...I eat to live!"

V.  References   

1.   Baer, D.J., et al., Whey Protein but Not Soy Protein Supplementation Alters Body Weight and Composition in Free-Living Overweight and Obese Adults. Nutrition, 2011. 141: p. 1489-1494. 

2.   Brown, E.C., et al., Soy verses whey protein bars: Effects on exercise training impact on lean body mass and antioxidant status. Nutrition, 2004. 3(22): p. 1-5. 

3.   Candow, D.G., et al., Effect of whey and soy protein supplementation combined with resistance training in young adults. Int J Sport Nutr Exerc Metab, 2006. 16(3): p. 233-244. 

4.   Tang, J.E., et al., Ingestion of whey hydrolysate, casein, or soy protein isolate: effects on mixed muscle protein synthesis at rest and following resistance exercise. J Appl Physiol, 2009. 107: p. 987-992.


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