The Protein Book: A Complete Guide for the Athlete and Coach este o carte interesantă, care oferă detalii despre nutriția optimă pentru un sportiv, mai ales de performanță, în ceea ce privește aportul proteic. Văzând titlul, cu toate că nu mă consider nici pe departe a fiind un sportiv de performanță, am considerat că ar fi bine să aflu ce sfaturi are Lyle McDonald de oferit și pot spune că nu am fost dezamăgit.

1. Definitions and Basic Background

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Where is dietary protein found?

With the exceptions of pure sugars and fats, protein is found in some amount in almost all foods, although the amounts can vary drastically. Generally speaking, animal source foods provide the most concentrated source of protein.

Red meat, chicken, fish and pork contain essentially no carbohydrate although the fat content can vary from extremely low to extremely high depending on the type and cut of meat. Skinless chicken breast is essentially fat free, containing nothing but protein while a fatty cut of red meat may contain a significant amount of fat along with its protein.

Dairy foods such as milk, cheese and yogurt also contain significant amounts of protein with highly variable amounts of carbohydrate and fat. Full-fat cheese is high in both protein and fat while fat-free cheese is almost pure protein. Milk and yogurt contain carbohydrates in addition to the protein; fat content can vary from high to low (or zero) depending on whether full-fat, low-fat or skim products are chosen.

There are also vegetable sources of proteins, with beans being the primary source; nuts and seeds also contain protein. Fruits and vegetables both contain trace amounts of protein as well.

In supplements, in the most general terms, protein is available in supplemental form as either protein powder or free form amino acids. Protein powders come in three primary forms: isolates (up to 90% protein), concentrates (around 80% protein with 5-6% carbs and fat) and hydrolysates.

Amino Acids

Bear in mind that in special circumstances, an inessential amino acid may become essential.

Leucine, isoleucine and valine are sometimes referred to as BCAAs and play a special role in human physiology and muscle growth.

Complete and incomplete proteins

This classification is redundant. With a few exceptions, all dietary proteins contain some amount of all of the amino acids, both essential and inessential. In that sense they are all “complete” proteins.

It is better to think in terms of having a limiting amino acid – the amino acid found in the lowest proportion to what is required by the body. The amount of this limiting amino acid will determine, to a great degree, how well that protein is used by the body.

A common example is that grains are low in the amino acid lysine but high in methionine while beans are low in methionine and high in lysine. So the limiting amino acid in grains is found in ample supply in beans and vice versa. By combining foods, a “complete” protein could be obtained.

2. Protein Digestion and Absorption

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It’s sometimes claimed in print advertising or articles that a given protein is digested with much higher efficiency than another.

Clearly animal source proteins are digested with extremely high efficiency in the 95% and further range; vegetable proteins show far worse digestibility. In terms of daily protein requirements, an increase in total protein intake of 10-20% may be required to offset the decreased digestibility of vegetable protein sources.

Outside the clear difference between animal and vegetable based proteins, there’s simply no reason to believe that one high-quality protein will digest with significantly greater efficiency than another.

Speed of digestion

As a general rule, whole proteins will take the longest to digest and start releasing amino acids into the system. Liquid whole proteins, such as protein isolates and concentrates, will digest somewhat faster than solid whole proteins (chicken, beef etc).

Fast and slow proteins

Casein became known as a slow/anti-catabolic protein and whey was a fast/anabolic protein. The general recommendation became to consume fast proteins like whey around workouts or first thing in the morning (when there was a need to get blood AA levels up rapidly). Casein was recommended at times when an athlete wanted to stave off catabolism or needed a slow rate of digestion (such as before bedtime).

Some authors have argued that a casein/whey blend would impact on both protein breakdown and synthesis. This theory does have some merits, but it’s still unclear.

Absorption speed of other proteins

There is a problem with the above values in real-world terms. With an average digestion rate of 6-7 g/h for protein, that would allow a maximum protein intake of 168 g/day. For a 100 kg individual, this would represent a maximum daily protein intake of 1.68 g/kg. There are clearly athletes who are consuming far more protein than this on a daily basis and it seems unlikely that any protein in excess of 168 g/day is simply going undigested. It also seems highly unlikely that skeletal muscle would be able to respond to a larger amount of protein than can be physiologically digested per day.

Is there a maximum protein intake per meal?

Although there appears to be no limit on the amount of protein that can be digested per meal (larger amounts simply take longer), there is some evidence for a limit to the amount of protein per meal in terms of maximally stimulating protein synthesis. Other factors also need to be considered, which might mandate higher protein intakes per meal.

3. Basic Protein Metabolism

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Under normal dietary circumstances, an average-sized individual may turn over roughly 300 grams of protein per day; that is a total of 300 grams of protein will be broken down with most of it being resynthesized back into tissue. Larger and smaller individuals will turn over more or less protein per day. This doesn’t mean that daily protein requirements are 300 grams per day.

How eating affects protein synthesis and breakdown

On a day-to-day basis, perhaps the single largest impact on skeletal muscle metabolism comes from the simple act of eating a meal. Proper training “tells” the body to store more protein, which would have been lost otherwise. Combined with sufficient building blocks (calories and protein) this leads to increases either in skeletal muscle mass or in the proteins and enzymes involved in endurance performance.

The effects of training on protein metabolism

Resistance training affects both protein synthesis and breakdown with both being increased following training. Immediately after training the body is in a net catabolic state, breaking down more protein than it is synthesizing. Properly performed, resistance training has a net anabolic effect on the body – leading to increased levels of muscle mass (with sufficient protein and calories).

In contrast, endurance training has a profoundly different impact on skeletal muscle. The proteins synthesized following endurance training are primarily enzymes and mitochondrial proteins which enhance energy production during activity.

4. Protein Requirements

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Despite decades of work, there is still argument among researchers over the true human requirements for protein, both for the average non-training person as well as the athlete.

How should protein intake recommendations be given?

Don’t go with macronutrient percentages, as they may or may not have any relevance to the actual nutrient requirements of an individual. It’s more appropriate to make recommendations in terms of grams of a given nutrient per kilogram of body weight.

A question that often comes up is whether protein (or carbs or fat) recommendations should be made relative to total body weight or lean body mass (LBM). LBM is determined by subtracting the total amount of body fat from the total weight; everything that is left is considered LBM and this includes skeletal muscle, bone, organs, body water etc. The distinction between total body weight and LBM becomes increasingly important at higher body fat levels.

It makes most sense that LBM would be the primary determinant of protein requirements. However, this has to be weighted against the general difficulty in getting a good estimate of body fat percentage and body fat (necessary to determine true LBM); methods can vary drastically and many are inappropriate for athletes.

Traditionally, bodybuilders have long used an intake of 2.2 g/kg of lean body mass as a rough estimate for daily protein requirements.

But the “requirement” is context specific: endurance athlete, strength athlete, strength/power athlete. Answering the question of “How much protein is required?” depends entirely on the context. For strength/power athletes, an intake of 2.5-3 g/kg protein per day should be more than sufficient to support any and all needs, without causing any negatives. Once again, this assumes adequate calorie and carbohydrate intake.

Protein needs when dieting

As calories go up, the body retains more protein; as calories go down, the body retains less and more protein is required, thus protein intake needs to go up when dieting to cover the additional requirement.

How much extra protein is required for athletes to maintain mass or performance while dieting is currently unknown. Sedentary individuals may require 1.5 g/kg versus 0.8 g/kg. Bodybuilders have often increased protein by 50-100% over baseline from a traditional 2.2 g/kg to 3.3-4.4 g/kg or even higher while dieting.

Athletes should have a protein intake of 3-3.3 g/kg, as it should generally suffice.

In short, a male strength/power athlete will need a habitual 2.5-3 g/kg of protein per day and for dieting, 3-3.3 g/kg.

5. Protein Quality

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The quality of protein is directly related to the physiological needs of the subject being studied. It is context specific.

There is no single protein that can be rated as the highest quality protein for all situations.

No methods of measuring protein quality have been developed to be perfect for human use.

6. Amino Acid Requirements

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Both strength/power and endurance training increase overall protein requirements.

Although weight training, in general, does not use protein for energy, glycogen depletion is known to activate the enzyme involved in oxidizing BCAAs. Therefore, it seems plausible that the glycogen depletion seem with weight training might increase BCAA oxidation (more true for bodybuilding).

Ensuring optimal muscle glycogen stores and providing carbohydrate during a workout (such as with the consumption of a dilute carb drink) should prevent any oxidation of BCAAs during exercise. The provision of protein before and/or during workout may also limit protein breakdown.

With certain types of strength/power training there can be large increases in lactic acid, which could potentially affect glutamine status. An increased need for glutamine will be felt. But strength/power training is suggested not to have a real impact on glutamine stores, and thus, the importance of glutamine for strength/power athletes is highly debatable.

As long as athletes obtain sufficient amounts of both protein and essentials amino acids by consuming the recommended amounts of varied high quality protein, there is little reason to believe that any one protein will have a greater impact on growth than any other based on the EAA profile alone. Quality is more important than quantity.

Soy and whey had equivalent effects on muscle mass gains over 6 weeks in one study although another found that milk protein showed a slight benefit over soy in terms of mass gains. A recent study found that milk generated better mass gains than soy over 12 weeks when combined with resistance training.

Both casein and whey stimulated similar gains in protein synthesis following training. In an unpublished abstract, whey, soy, casein or maltodextrin (all given at 0.7 g/kg) all had the same impact on muscle size and strength. Some researchers feel that a casein/whey mix (or milk) might give the best benefits overall.

7. Meal Frequency

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Bodybuilders are probably the most obsessive of all athletes when it comes to eating protein (and calories) in small amounts throughout the day (often eating every 2.5-3 hours or so) with the belief that this is necessary for optimal protein utilization, growth or fat loss.

However, it’s less clear whether a higher meal frequency actually results in differences in how well or poorly the body utilizes nutrients and protein.

Meal frequency and health

There is certainly no harm to spreading daily calories into smaller, more frequent meals (outside of possible convenience issues related to meal preparation) but there may not automatically be a benefit from a health perspective.

Meal frequency and body weight / metabolic rate

Meal frequency has no real impact on energy expenditure given an identical caloric intake; eating the same number of calories in a few small meals will cause the body to expend the same number of calories during digestion and metabolism as if they are eaten in many smaller meals.

Practical aspects of meal frequency

Regardless of potential health benefits related to meal frequency, there may be practical reasons to eat more or less frequently.

For younger people, it’s better to spread their protein intake throughout the day, while for older people it’s better to have most of it at lunch.

8. Nutrient Timing Around Workouts

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Regardless of the athlete or sport, nutrient timing around training encompasses 4 specific phases:

the pre-workout meal generally consumed 1-4 hours before a workout

• ensures optimal levels of muscle and liver glycogen and blood glucose
  
• protein, fat and fiber should generally be part of this meal
  
• 3-4.5g carbs / kg eaten 3-4 hours before training; 2.2 g/kg if 1 hour before training
  
• 20-40g of protein
  
• fat, fiber (fruits and vegetables)

immediate pre-workout nutrition (immediately before training to 30 minutes before training)

• 0.3-0.5 g/kg with equal amount of protein – 30 minutes before strength/power training
  
• 3-5 g of creatine can be added

during workout nutrition (anything consumed during the workout itself)

• mix 32-36 oz of water and sip throughout the workout at a rate of 8-9 oz every 15 minutes
  
• 12-15g / hour whey protein (or use soy)
  
• 30-45g / hour dextrose or sucrose
  
• small amounts of potassium and sodium can also be added to improve flavor and drink more

post-workout nutrition (nutrients consumed immediately after training – especially if old – until 1-2 hours later)

• 0.3-1.5 g/kg carbs should be sufficient and may be excessive depending on total training volume and intensity
  
• 0.3-0.5 g/kg of whole protein

Sufficient carbohydrate and protein intake around training is important for almost all athletes. The specifics of different types of training affect whether relatively more carbohydrate or protein should be consumed.

Strength / power athletes will tend to need relatively more protein and less carbohydrate around training.

10. Whole Food Proteins

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Overall, an athlete’s daily protein intake should come primarily from whole food sources.

• Fowl (chicken, turkey, duck, goose and others)
  
• Fish
  
• Red meat (beef, lamb, emu, bison, buffalo etc)
  
• Pork (bacon, ham, pork tenderloin etc)
  
• Egg
  
• Dairy (milk, yogurt, cheese, cottage cheese, ice cream, kefir, condensed milk, dried milk powder)
  
• Soy (soybeans, tofu, soymilk, soy protein isolate, texturized vegetable protein)
  
• Other proteins (grains, vegetables, fruit etc)

It is best to mix the food sources.

11. Protein Powders

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While athletes should rely on whole foods for the majority of their protein needs, protein powders can offer a number of benefits in terms of price, convenience, dietary control etc. They are also preferred immediately before and during training.

While why has been the current top protein, it should be clear that casein and MPI/CMDI offer significant advantages due to their slower digestion time.

Soy protein powder can be used, but its total intake should be limited to some degree. Dairy proteins still appear to be superior.

12. Supplements

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Supplements should be considered only after overall protein intake (including both whole food proteins and powders) has been taken care of. Food comes first, supplemental protein powders second, any individual supplement should be considered last.

Glutamine

• 5-10 grams/day to protect the immune system function during periods of high-volume training (for all athletes)

Tyrosine

• 1-3 grams of l-tyrosine + 200 mg of caffeine and a high glycemic index carb like sugar (small amount) taken 30-60 minutes prior to training or competition = stimulant effects like the EC stack with performance increase (at least 5% more)

BCAA/Leucine

• don’t bother, stick with quality protein intake and you will get your BCAAs from there

Essential Amino Acids

• don’t bother if you consume enough quality protein

Creatine monohydrate

• 20 grams per day for 5 days – standard loading phase
  
• insulin is important for creatine uptake – taking creatine with a simple carb or carb and protein may increase update
  
• adding lipoic acid (1 g / day) to creatine with carbs may also increase uptake and storage
  
• 3-6 grams per day – maintenance dose with at least one dose (3-5 grams) put into the post-workout carb/protein shake
  
• after loading, a maintenance dose of 3-5 grams/day would be used post-workout on training days, or with any meal on non-training days

Carnitine

• 3-4 grams/day taken for multiple weeks to months, taken immediately before high intensity activity
  
• include it in the pre- or post-workout nutrition

Acetyl-l carnitine

• 1-3 grams/day immediately before training or first thing in the morning, on empty stomach