Debunking Myths

As I mentioned in a previous post, I am taking a Sports Nutrition class this quarter.  I have been shocked, flabbergasted, and frustrated regarding the misconceptions of protein intake.  So, listen up!

It’s Story Time with Stephanie: Protein Myths!

The Myth:  “An athlete needs meat in their system to get adequate protein.”

How It Actually Works:

When an individual consumes food, the mouth begins mechanical digestion through chewing.  Food is propelled down the esophagus and into the stomach where chemical digestion of protein begins.  Gastric juices denature proteins and break down cell walls of plant foods forming large polypeptides.  As the contents of the stomach empty into the small intestine, pancreatic enzymes break the large polypeptides into smaller polypeptides and individual peptides.  It is not until polypeptides and peptides encounter brush border enzymes on the villi on the small intestine that they are broken down into amino acids.  The amino acids diffuse into blood circulation and enter the amino acid pool (the body’s total supply of free amino acids).  The body uses the amino acid pool as it’s source for protein synthesis (building of muscle tissue and other structural components, plus a few other things).  A complete set of amino acids must be present for protein synthesis to occur.  So you see, the body does not distinguish between “meat” versus “powerbar” versus “plant.”  As long as an individual has consumed all of the essential amino acids, the body can happily do it’s job.


The Myth:  “Energy comes from things found in meats.”

How It Actually Works:

As you probably know, a calorie is a unit of energy measurement.  One dietary calorie (kcal or Cal) is approximately the energy required to raise 1,000 g (1 kg) of water by one degree Celsius.

All the macronutrients we consume provide the body energy, not just Protein or meat. Protein renders 4 calories of energy per each gram consumed, Carbohydrates 4 Cal, and Fats 9 Cal.

Individuals who engage in regular physical activity, carbohydrates should supply about 60% (400-600g) of total daily calories.  During intense training, carbohydrate intake should increase to 70% of total calories consumed.”  400 – 600g of carbohydrates is the equivalent of 1,600 to 2,400 calories.  Quite a lot of energy, wouldn’t you say?  And remember, muscle glycogen (stored polysaccharides) serves as the major source of carbohydrate energy for active muscles during exercise.

 Most Americans consume too much protein. 
Are you?

RDA* 0.8 g of protein per kilogram of body mass (1 kg = approx. 2.2 lb)
Endurance athletes 1.2 – 1.4 g/kg of body mass
Resistance training 1.8 g/kg of body mass
*Recommended Dietary Allowance – standard nutrient intake for the majority of healthy individuals

For example:
A 160 lb, healthy man would require only 58 g of Protein.

160 lb / 2.2 lb = 72.7 kg
72.7kg * 0.8 g = 58 g of Protein

A can of tuna and a cup of low fat cottage cheese provides more than enough protein for the entire day (68 g total; providing 10 grams extra!)

Here is a list of a few common protein sources:
  • Chicken Breast (medium size): 30 g of Protein
  • Tuna: 6 oz can – 40 g
  • Tilapia Fillet: 6 oz – 45 g
  • Pork Chop (medium size): 25 g
  • Steak: 6 oz – 47 g
  • Deli Turkey: 1 slice – 5 g
  • Large Egg – 6 g
  • Skim Milk: 1 C – 8.5 g
  • Lowfat Cottage Cheese: 1 C – 28 g
  • Nonfat Plain Yogurt: 1 C – 14 g
  • Soy Beans: 1/2 C cooked – 14 g
  • Peanut Butter: 2 Tablespoons – 8 g
  • Whole Wheat Bread: 1 slice – 3 g
  • Whole Wheat Bagel: 11.5 g 
  • Brown Rice: 1 C cooked – 5 g
  • Black Beans: 1 C cooked – 12 g
  • Garbanzo beans: 1 C – 12 g
  • Lentils: 1 C cooked – 47 g
  • Peas: 1 C cooked – 9 g
  • Oats: 1 C – 26 g
  • Almonds: 1/4 C – 7.5 g

The Myth“My friend lost a ton of weight by cutting carbohydrates.  You can lose major lbs by only eating protein.”
How It Actually Works: 
Your friend was most likely in metabolic ketoacidosis.  This is an accumulation of ketone bodies in the blood occurring during times of inadequate carbohydrate intake.

Gluconeogenesis is the process of forming new glucose molecules from noncarbohydrate sources such as lipids or protein, allowing the brain (which is fueled only by glucose) and other body tissues to maintain functioning.

Lipolysis is the process of breaking down stored fats into glycerol and fatty acids.  Glycerol is converted to glyceraldehyde phosphate, which can then enter the Kreb’s cycle for fuel.  Fatty acids are broken down into acetic acid which then is converted into acetyl CoA.  Typically, acetyl CoA would be picked up by a carbohydrate substrate (oxaloacetic acid) and enter the Kreb’s Cycle to continue the metabolic process.  In the absence of carbohydrates, acetyl CoA accumulates in the blood.  The liver converts acetyl CoA into ketone bodies which are then released back into the blood.

When the lack of carbohydrate intake continues over time, weight loss is bound to happen, along with liver and kidney damage, respiratory distress, and dangerously low blood pH levels which can depress the nervous system, leading to coma or death.

Ketoacidosis (DKA or diabetic ketoacidosis) is also found in patients with diabetes.  Without insulin, glucose can not enter cells to begin the energy production process, and so the body switches to burning lipids for fuel.

Not exactly a healthy diet, I would say.

So now you know!  Don’t strain your liver and kidneys through over-consumption of protein.  Be good to your body and it’ll be good to you!


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