How might protein excess, or the type of protein eaten, influence health?  What implications would this have for those on high protein diets?  Do you believe a high protein diet promotes health?  Why or why not?

Protein excess can occur when an individual is over-consuming the macronutrient protein, which is essential for tissue growth, maintenance, and repair. Delimaris (2013) conducted a meta-analysis of 32 electronic studies that contained the keywords ““high protein diet,” “protein overconsumption,” “protein overuse,” and “high meat diet”. Out of 22 human studies and 11 reviews, Delimaris (2013) identified that “The adverse effects associated with long-term high protein/high meat intake in humans were (a) disorders of bone and calcium homeostasis, (b) disorders of renal function, (c) increased cancer risk, (d) disorders of liver function, and (e) precipitated progression of coronary artery disease” (Delimaris, I. 2013). It is important to understand that a “high-protein diet” or “over-consumption” of protein would constitute consuming higher than the current Recommended Daily Allowance, which is currently 0.8g per 1/kg of body weight for generally healthy adults. This conflicts with protein dietary recommendations in the fitness nutrition industry, where higher consumption of protein is seen as critical for muscle and connective tissue anabolism and fat-loss.

Further, Nix (2017) explains that “high-protein diets are often higher in total fat, saturated fat, and cholesterol and lower in fiber and antioxidants” (Nix, S. 2017. p.53). As discussed in Chapter 3, elevated levels of consumed saturated fats, in conjunction with poor lifestyle factors, may lead to cardiovascular complications and other metabolic diseases. Further, fats, are the most energy-dense source in human nutrition, therefore if an individual is seeking to lose fat, overall energy intake must be taken into consideration. Nix (2017) discusses “that weight loss will require a reduction in total kilocalories consumed. The body still needs all of the essential nutrients to function and those nutrients come from a variety of foods – including fruits, vegetables, grains, and fats…if a weight-loss diet is designed such that most of the energy is supplied by protein-rich foods, there may not be enough kilocalories left to fit in all of the other food groups necessary to meet the body’s requirements for essential nutrients” (Nix, S. 2017. p. 53). Consuming too much protein may not only create an energy imbalance but may also create nutrient-deficiencies. It is possible that if protein intake is a priority focus within a prescribed diet, that we can sacrifice essential vitamins and minerals that we must retrieve from plant carbohydrate sources. An example of this would be the carnivore diet, where carbohydrates are completely restricted and fatty sources of protein are used to compose total daily calorie consumption.

The quality of protein that is consumed can also influence health. I think that two important methods when considering protein sources are the chemical score (or amino acid profile) and net protein utilization, which describes a food source’s bioavailability of digestible protein. We can use both measures in protein quality regarding animal or plant-based protein sources. Based on Nix (2017) Table 4-2, animal protein sources overall exhibit a higher chemical score and net protein utilization score than whole grain and vegetable sources of protein. In fact, eggs and cow’s milk are right at the top of the list for amino acid ratio and bioavailability (Nix, S. 2017. p. 51). However, Craig & Mangels (2009) also suggests that “Plant protein can meet protein requirements when a variety of plant foods is consumed and energy needs are met. Research indicates that an assortment of plant foods eaten over the course of a day can provide all essential amino acids and ensure adequate nitrogen retention and use in healthy adults…” Further, when considering a vegetarian-based diet, we must also look at other possible nutrient deficiencies. Protein, omega-3 fatty acids, iron, zinc, iodine, calcium, vitamin D, and vitamin B-12 nutrient intake should also be carefully analyzed when considering a vegetarian-based diet (Craig, WJ., Mangels, AR. 2009).

I think that choosing an appropriate macronutrient intake per the individual is important when setting up the overall calorie and macronutrient ratios to support optimal health. For starters or general population, the Recommended Dietary Allowance (RDA) for protein is 0.8g per kilogram of body weight. I personally work with athletic individuals who train rigorously outside of their normal activity level in the effort to build muscle, and protein requirements may differ from general RDA. Very common knowledge, or “bro science” for lack of a better term for athletic protein intake, is 1g per body weight pound. However, with obese individuals, protein goals set using this multiplier may be completely unattainable and may result in excess protein consumption and will likely also not be sustainable longterm. If a person weighs 300lbs, and we are using 1g/1lb, that would be this person would be required to consume 300g of protein.

Norton & Baker (2018) show an excellent table in their e-book illustrating perhaps more optimal protein ratios based on recent evidence:

Norton, L. & Baker, P. (2018). The complete contest prep guide. 1st edition. Tampa, Florida: Biolayne, LLC

Norton & Baker (2018) explain that “Since it’s the LBM [lean body mass] component of your body mass that requires the majority of tissue turnover, it would make sense that protein intake should be based on your LBM rather than just total body mass, especially for people who may have more body fat than the average person” (Norton, L., Baker, P. 2018. p. 48-49).

The inclusion of optimal protein intake can positively impact overall health in that we have a better chance of preserving our lean body mass, especially as we age. Norton & Baker (2018) state that “in cases of a caloric deficit, or even advancing age, that number will actually go up to preserve the LBM that you might lose due to the catabolic nature of age (sarcopenia) and a caloric deficit” (Norton, L., Baker, P. 2018. p. 48-49). The table above illustrates optimal protein macronutrient intake as age increases and includes energy intake as a weighing factor in determining protein levels. We could assume that an individual who is seeking to lose weight or build muscle would be engaging in some sort of physical activity, therefore, I find that these levels are appropriate. It is important to understand that these recommended protein intakes can also be used to preserve lean body mass during a dieting phase. Frestedt et al. (2008) conducted a 12-week study in which a specialized whey protein was used in a within a 500-calorie deficit. Although the amount of weight lost after 12 weeks was not significantly different, the test group lost significantly less lean body mass and that the percentage of fat lost in comparison to lean body mass was greater (Frestedt, J., Zenk., J., et al. 2008).

Further, the thermogenic effect of protein may positively impact energy output and fat loss. Halton & Hu (2004) discovered that out of 15 participants, “All 6 studies that assessed the thermic effect of food as a percentage of ingested energy reported a greater energy expenditure for the higher protein versus the lower protein diet. All 3 studies reporting the thermic effect in kilojoules reported a significantly greater effect for higher protein versus higher fat or higher carbohydrate meals. All 6 studies that used a variety of other measures to assess the thermic effect reported increased effect for higher protein diets” (Halton, TJ., Hu, FB. 2004).

However, for general population who are generally healthy and living perhaps sedentary to light-moderately active lives, the RDA of .8g/1kg of body weight is sufficient in combination with an appropriately calculated overall macronutrient balance to ensure that our bodies are able to retrieve essential amino acids from diet and produce non-essential amino acids needed to build tissue, balance water, support metabolic processes, and support our immune system.

References:

Craig, WJ., Mangels, AR., American Dietetic Association. (2009, Jul). Position of the American Dietetic Association: Vegetarian diets. Journal of the American Dietetic Association, 109(7),1266-1282. Retrieved from: https://www.ncbi.nlm.nih.gov/pubmed/19562864

Delimaris, I. (2013, Jul 18). Adverse effects associated with protein intake above the recommended dietary allowance for adults. ISRN Nutrition. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4045293/

Frestedt, J., Zenk, J., Kuskowski, M., Ward, L., Bastian, E. (2008, Mar 27). A whey-protein supplement increases fat loss and spares lean muscle in obese subjects: a randomized human clinical study. Nutrition & Metabolism. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2289832/

Halton, TJ., Hu, FB. (2004). The effects of high protein diets on thermogenesis, satiety and weight loss: a critical review. Retrieved from: https://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0021577/ 

Nix, S. (2017). William’s basic nutrition and diet therapy. Missouri: Elsevier.

Norton, L. & Baker, P. (2018). The complete contest prep guide. 1^st edition. Tampa, Florida: Biolayne, LLC