PROTEIN
Soy Protein vs. Whey Protein During Endurance Effort
BY MARK TWIGHT
Read the title again.
Calorie replacement during endurance effort is critical to long term energy production and speedy post-effort recovery. I used to feed myself an exclusively carbohydrate diet during long days and it worked a lot better than my previous diet of water and will power. As the days got longer and I learned more I began putting protein and fat into my body during effort (only when my heart rate was low enough that compromised gastric emptying was not an issue).
48 hours into a 63-hour day, searching the pack for any remaining food
One of my goals during these punishing 12-60 hour non-stop efforts has been to reduce the ammonia production that results from muscle glycogen depletion (MacLean and Graham, 1993) and subsequent muscle cannibalization. When blood glucose levels dip gluconeogenesis (one process that steps up) uses protein to make glucose and if protein is not available in the blood the body goes after muscle to get it. One byproduct of muscle and BCAA breakdown is ammonia, which is toxic to the cells, a cause of premature fatigue, and processing it puts a lot of stress on the kidneys. It would seem that prophylactic protein intake to prevent muscle cannibalization is the answer but if you eat too much protein during effort the excess is converted to ammonia and you get whacked again. A proper protein-to-carb ratio is important and those in the know suggest eating or drinking a solution that contains 88-90% carbs and 10-12% protein. There are several supplements on the market that fit this profile.
Before you begin swilling one of these, check its ingredients to learn the source of the protein. Whey peptides have great bioavailability and an excellent amino acid profile, which is ideal for recovery but its concentration of glutamine contributes to the ammonia burden when consumed during effort. Soy protein does not readily produce ammonia. Soy isoflavones have a strong anti-oxidant effect. Soy protein's amino acid profile (lower lysine to arginine ratio) reduces the insulin to glucagon ratio, which can favor fat metabolism. Soy protein's amino acid profile also replenishes Leucine, Isoleucine and Valine, which are the main BCAAs burned during endurance effort.
Leucine, Isoleucine and Valine are also supplemented in many carbohydrate gels but whether the quantities are adequate is open to debate. On the ground carbohydrate gels work, period. One further justification (beyond supporting gluconeogenesis) for supplementing those amino acids is that Tryptophan competes for entry into the brain via the same amino-acid carrier as Leucine, Isoleucine and Valine and as they decline the Tryptophan crosses more easily. Studies also indicate that blood Tryptophan levels increase with free fatty acid concentrations, which follow muscle glycogen depletion (Weltan et al 1998). Higher Tryptophan levels induce sleep, depress motor neuron excitability, influence autonomic and endocrine function, and suppress the appetite - none of which help the endurance athlete.
Whether supplementing with soy protein to reduce catabolism or supplementing with carbohydrates to lower free fatty acid levels is the more effective counter-measure doesn't matter because the smart endurance athlete is going to do both. We have a lot of experience with carb gels and several different calorie replenishment drinks. Spiz and Perpetuem are used by Race Across America competitors, high altitude climbers, ski mountaineering racers, etc. and both products disguise the sorry taste of soy protein with palatable flavors. Neither has enough fat so supplement with almonds or sunflower seeds (both are relatively alkaline), fish oil capsules or a small bottle of olive oil. These days I make my own calorie replenishment drink by combining agglomerated maltodextrin and rice protein, which is easy to digest and doesn't give me bubble guts, with a bit of orange flavoring and a small dose of electrolytes.
Be smart, eat and drink intelligently and you'll race faster or survive longer.