Protein: The Facts, the Myths, and the Real Science

Everyone has an opinion about protein, and the myths surrounding it are rampant. That's why sorting the facts from the crap will lead to better choices regarding your own diet and protein intake. Answer the questions below and see if you've been falling for the myths.

Fact or Myth?

The RDA (Recommended Dietary Allowance) protein suggestions are just fine for people who work out.

Hint: The RDA guideline for protein is 0.8 grams per kilogram of bodyweight per day. So if you weigh 190 pounds (86 kilograms) you'd need about 69 grams of protein.

The Answer: Lifters and athletes concerned with their performance or physique require more protein than what's recommended by the RDA. So it's a myth (and a joke) that the RDA protein recommendations are adequate for ass-kicking individuals.

Here's Why: RDA protein recommendations are too low for certain groups. Those recommendations were never intended for people attempting to enhance performance, maintain, or gain muscle. In fact, a higher protein intake may have positive benefits regarding different health ailments including obesity, type 2 diabetes, osteoporosis, heart disease and muscle wasting.

The RDA guideline reflects the minimum daily needs of protein required to maintain short-term nitrogen balance in healthy, moderately active people. Nitrogen balance compares the amount of nitrogen coming into the body (from dietary protein) to the amount being lost. It's often used as a measurement of protein balance since protein is 16 percent nitrogen.

If you're consuming the same amount of nitrogen that you're losing, you're in nitrogen balance. If you're consuming more than you're losing, you're in positive nitrogen balance. If you're losing more than you're consuming, you're in negative nitrogen balance and are losing protein.

Nitrogen balance studies often involve examining urinary nitrogen levels. Approximately 90 percent of the nitrogen in urine is urea and ammonia salts – the end products of protein metabolism. The remaining nitrogen is accounted for by other nitrogen-containing compounds.

This nitrogen balance method is useful, but it has problems: Urine collections tend to underestimate nitrogen losses, dietary intake tends to be overestimated, miscellaneous skin and hair losses are prone to error, and the response to increased protein intake varies tremendously.

The Really Geeky Stuff

1. In a review published in the International Journal of Sports Nutrition, researchers concluded, "Those involved in strength training might need to consume as much as 1.6 to 1.7 grams of protein per kilogram per day (approximately twice the current RDA) while those undergoing endurance training might need about 1.2 to 1.6 grams per kilogram per day (approximately 1.5 times the current RDA)."
2. In another article published in Nutrition & Metabolism, researcher Donald Layman argued that the dietary guidelines should be improved and reflect new understandings about protein requirements. According to him, "During the past decade a growing body of research reveals that dietary protein intakes above the RDA are beneficial in maintaining muscle function and mobility." Diets with increased protein have been shown to improve adult health when it comes to treatment or prevention of obesity, type 2 diabetes, osteoporosis, heart disease and muscle wasting.
3. A review published in the International Journal of Sport Nutrition and Exercise Metabolism was conducted to evaluate the effects of dietary protein on body composition in energy-restricted resistance-trained athletes, and to provide protein recommendations for these athletes.

The researchers concluded that "...the range of 2.3 to 3.1 grams per kilogram of FFM (fat free mass) is the most consistently protective intake against losses of lean tissue." In other words, for every kilogram on your body that's not fat, you should be consuming 2-3 grams of protein in order to preserve lean tissue. So if you have 190 pounds of lean tissue, up to 258 grams of protein would be optimal for you.

In addition, the goal of the athlete should be considered. Leaner athletes or those having a primary goal of maintaining maximal FFM should aim toward intakes approaching the higher end of this range. Even higher levels of protein than those recommended in the review are not uncommon in exercising individuals. It's unlikely that negative health consequences will follow from higher levels of intake, assuming there are no related health problems that would suggest limiting intake.

Fact or Myth?

The thermic effect of protein is the same as it is for carbs and fat.

Hint: The thermic effect of feeding or diet induced thermogenesis (DIT) is the amount of energy your body has to expend in order to digest and assimilate food. So picture a lean chicken breast (mostly protein), a bowl of rice (mostly carb), and tablespoon of butter (mostly fat). Which do you think your body will have to work hardest to digest?

The Answer: Among the three macronutrients, protein ranks highest in diet induced thermogenesis. So it's a myth that they're all equal in terms of their thermic effect. That means it'll cost you more calories to digest and absorb protein than it would fat and carbohydrate.

Here's Why: The consumption of protein requires an expenditure of 20-30% of the calories derived from protein. So, if 200 calories of protein are eaten, 40-60 calories are burned during digestion. DIT from carbohydrate is 15-20% and 2-5% for fat.

Fact or Myth?

Protein is more satiating (filling) than fat or carbohydrate.

Hints: Protein has an influence on CCK (cholecystokinin) and ghrelin. Protein may stimulate cholecystokinin (CCK) and decrease ghrelin. CCK is secreted mostly from the inner layer of the gastrointestinal tract has been shown to act as a satiety signal. The satiating effect of CCK was first demonstrated when administering CCK to rats. It "dose dependently" reduced meal size. Ghrelin is produced primarily in the stomach and has appetite increasing properties. Ghrelin levels are relatively high prior to a meal and they decrease after a meal.

The Answer: It's a fact that protein is usually more satiating than fat or carbs. When comparing protein, fat, and carbohydrate, protein is generally reported as the most satiating (satisfying to a point of full or beyond) and fat as the least satiating.

Here's Why: Research indicates that one of the primary factors involved with the satiating effects of protein is the thermic effect of feeding, mentioned above. Though protein's influence on ghrelin and CCK may play a large role in its satiating effects, more research needs to be conducted in these areas, as findings have been indecisive. Future research should concentrate on different levels of protein, different types of protein, and consumption of proteins in short and long term.

The Really Geeky Stuff

1. A review published in Nutrition & Metabolism reported that protein induced thermogenesis has an important effect on satiety. "Protein plays a key role in body weight regulation through satiety related to diet-induced thermogenesis."
2. A study published in Physiology & Behavior investigated the relative satiating effect of the macronutrients in lean women. On four separate occasions, the composition of an iso-caloric lunch "preload" was controlled in 12 lean women. Macronutrient composition had a significant effect on short-term hunger – the women were less hungry after the protein preload compared to the preloads with the other macronutrients. They also ate less after the protein preload.
3. A study published in the American Journal of Clinical Nutrition tested the prediction that increasing protein while maintaining the carb content of a diet lowers body weight due to decreased appetite and decreased calorie intake. The study showed when increasing the protein intake from 15% of diet to 30% of diet (while eating the same amount of carbs) there was a decrease in appetite and fewer calories were consumed.
4. The Journal of Clinical Endocrinology & Metabolism published a study that compared the effect of different proteins and carbohydrates on indicators of appetite and appetite regulatory hormones. CCK level was one of the primary outcomes measured.

Calorie intake was higher after the glucose preload compared with lactose and protein preloads. CCK level was higher 90 minutes after the protein preloads compared with glucose and lactose level. Researchers concluded that "acute appetite and energy intake are equally reduced after consumption of lactose, casein, or whey compared with glucose."

One Quick Caveat

The research sometimes gets a little messy. For example, some studies are indecisive when it comes to protein intake and ghrelin levels. This is why you need to rely on your own reasoning, logic, and experience while gathering info from the research.

References

1. Blom, A.M., Lluch, A., Stafleu, A., Vinoy, S., Holst, J., Schaafsma, G., & Hendriks, H. (2006). Effect of high-protein breakfast ont he postprandial ghrelin response. The American Journal of Clinical Nutrition, 83(2), 211-220.
2. Bowen, J., Noakes, M., Trenerry, C., & Clifton, P.M. (2006).Energy intake, Ghrelin, and Cholecystokinin after Different Carbohydrate and Protein Preloads in Overweight Men. The Journal of Clinical Endocrinology & Metabolism, 91(4).
3. Helms, E., Zinn, C., Rowlands, D.S., & Brown, S.R. (2014). A Systematic Review of Dietary Protein During Caloric Restriction in Resistance Trained Lean Athletes: A Case for Higher Intakes. International Journal of Sport Nutrition and Exercise Metabolism, 24, 127-138.
4. Layman, D.K.(2009). Dietary Guidelines should reflect new understandings about adult protein needs. Nutrition & Metabolism, 6(12), Lemon, P. (1998). Effects of exercise on dietary protein requirements. International Journal of Sports Nutrition, 8(4), 426-447.
5. Lucas, M, & Heiss C.J.(2005) Protein needs of older adults engaged in resistance training: A review. Journal of Aging and Physical Activity, 13(2), 223-236.
6. Moran, L.J., Luscombe-Marsh, N.D., Noakes, M., Wittert, G.A., Keogh, J.B., & Clifton, P.M. (2005). The Satiating Effect of Dietary Protein Is Unrelated to Postprandial Ghrelin. The Journal of Clinical Endocrinology & Metabolsim, 90(9).
7. Poppitt, S.D., McCormack, D., & Buffenstein, R. (1998).Short-term effects of macronutrient preloads on appetite and energy intake in lean women. Physiology & Behavior, 64(3), 279-285.
8. Weigle, D.S., Breen, P.A., Matthys, C.C., Callahan, H.S., Meeuws, K.E., Burden, V.R., & Purnell, J.Q. (2005). A high-protein diet induces sustained reductions in appetite, ad libitum caloric intake, and body weight despite compensatory changes in diurnal plasma leptin and ghrelin concentrations. The American Journal of Clinical Nutrition, 82(1), 41-48.
9. Westerterp, K.R. (2004). Diet induced thermogenesis. Nutrition & Metabolism, 1, 1-5