As we dive in to discussions of food and nutrition, highlighting each of the macronutrients (protein, carbohydrate, fat) separately will hopefully aid in understanding the complex interplay between foods and their functions in the body.
But first, my protein story...
**Long before I began studying nutrition, I was completely ignorant of the role that food plays in the body and how different various foods are. I was living a sedentary lifestyle and choosing foods based solely on cravings or eating emotionally to fill a void. As I began making lifestyle changes to turn this destructive pattern around, my first major change was increasing physical activity. As I increased exercise and gym time, I was given generic advice to increase my protein intake, specifically eating more protein at breakfast and at every meal.
"Okay, no problem!"
I immediately went to the grocery store and walked up and down every aisle looking for an aisle or section with a sign saying 'Protein'. (Like I said, I was completely ignorant of food and just assumed 'protein' was a category for an aisle) After what felt like an eternity searching for the 'Protein aisle' I was relieved when I finally found a section that had protein bars and powders. "Oh this is what he meant!" So naturally I bought enough protein bars to eat with every meal for a few weeks.
A few weeks later I was asked how my diet was going. "I guess it's going well. I'm eating these protein bars with my breakfast and all of my meals now."
"What? What are you sponsored by these protein bars or something? Stop eating the protein bars and just get a protein powder to make a shake after you work out."
So I immediately went to a supplement store where the clerk sold me a giant tub of protein powder. I started drinking these protein shakes according to the serving size on the label (3 scoops with 20oz liquid=90g protein per shake) throughout the day. I was unknowingly consuming way more (total calories) than I needed (~3x more than my needs) and my weight loss halted.
Flash forward by one year, I had successfully lost a substantial amount of weight (~50lbs) and was experimenting with first a vegetarian diet and then a vegan and raw vegan diet. After the first 1-2 months of a raw vegan diet, I was feeling great but started noticing my energy levels dropping heavily throughout the day. My sleep was irregular (I would be wide awake at 3am and sleeping for the night before 7pm) My body was constantly in aches and pains and I had suffered with a flu that lasted about 6 weeks. My weight was at an all time low and I was hypotensive, anemic, and in constant fatigue. I made the decision to eat animal protein again and I immediately began to see improvements with my immunity, sleep, and energy levels.
I want to emphasize: it was NOT a specific diet that led to these issues, but rather a misunderstanding of food (and likely a deficiency in total calories, protein, iron, and vitamin B12 to name a few). I was not diligent in learning about and obtaining enough information about food before starting a vegan diet (or any diet) that I basically made myself sick. In hindsight, had I made protein intake a priority in my vegan diet, I very well could have continued it without the adverse effects.**
My history of misunderstanding protein and food in general is the driving force behind this blog post:
Protein is comprised of basic building blocks, or amino acids, and is critical to bodily functioning in maintaining and restoring skeletal muscle, organs, blood, enzymes, DNA and RNA, neurotransmitters, hormones and more. (Lord, 2012) There is a constant flux in protein balance where proteins are utilized for anabolic processes in cell or tissue building, or degraded and broken down for excretion to where there is a subsequent need to consistently maintain protein intake to balance for losses. In this sense, dietary protein is essential (which translates to a need to take in dietary protein to make up for regular losses) as the body cannot produce it nor can it store protein. This last point regarding an inability to store protein points to an important distinction in that eating high amounts of protein beyond your needs will not necessarily provide MORE protein for these processes (i.e. will not necessarily turn in to MORE muscle mass), but rather your body will use what it needs and excrete the remaining protein or convert the carbon skeleton for other uses. (Lord, 2012) In fact, the fate of excess metabolized amino acids includes the carbon skeleton being used for some energy production as glucose and ketone body production, cholesterol production and fatty acid production- none of which can act directly on tissue repair and synthesis. (Lord, 2012)
But what is considered the right amount of protein? Short answer: it depends.
The current RDA guidelines for a 'normal' adult (non-active, normal BMI) are 0.8g/kg body weight, which equates to about 54g protein for a 150lb adult, OR between 10-35% of total daily calories coming from protein. (Nelms, et al. 2011) As a point of reference, there are about 7g of protein for 1oz meat so a 4oz chicken breast would be roughly 28g protein. That protein calorie range (10-35% of total daily calories) however suggests a lot of room for interpretation and experimentation. These guidelines are going to vary from person to person based on their body composition (difference between body fat and lean body mass), activity level, height, presence of any injury or illness, age, and growth status. (Nelms, et al. 2011) In this sense, an individual who has an increased amount of tissue breakdown will need an increased amount of protein intake to make up for losses and to aid in cell and tissue synthesis to continue normal functioning (like in high amounts of physical activity, injury, illness, growth spurts, younger children and older adults, and taller individuals compared to shorter.) Just based on these criteria alone, it would seem as though the majority of the population requires an increased amount of protein, but how much more protein is actually needed?
This is a question that is continually being debated and researched. Traditional dietary guidelines would constitute a high protein intake to be consistent with 1.2.-2.0g/kg body weight, which for a 150lb adult would equate to 81g-136g protein/day. (Nelms, et al. 2011) There are theories that propose caution with a high protein intake as it is hypothetically attributed to stressing the kidneys and liver and leading to adverse effects on body composition (the theory that excess protein calories will lead to the remaining carbon skeletons being converted to glycerol for triglyceride formation and stored in adipocytes as body fat). However there are recent research findings that show much higher protein intakes (2.9-3.3g/kg body weight) having no adverse effects on blood lipid markers, markers of kidney and liver function, or adverse effects on body composition. (Antonio, et al. 2016) In this 2016 crossover trial, a sample of resistance trained men (ages 22-29yrs old) were randomized and instructed to follow their normal eating pattern for 8 weeks and a high protein diet for 8 weeks (or in reverse order) while tracking their intake daily. (Antonio, et al. 2016) The extra protein was from whey protein powder and they were instructed to continue following their own strength and conditioning program. (Antonio, et al. 2016) Despite being higher in protein and calories in the high protein phase of the study, the subjects showed no significant differences between their normal protein intake and the high protein intake in regards to their body composition, blood lipids, and markers of liver and kidney function, despite the high protein intake being three times higher than the traditionally recommended intake. (Antonio, et al. 2016) It is important to note however that the subjects' normal dietary intake for this sample still consisted of an already relatively high protein intake compared to the traditional recommendations (average of 2.0-3.4g/kg body weight) which when compared to an even higher protein intake (2.5-4.0g/kg body weight), showed no differences. (Antonio, et al. 2016) From my perspective, this could allude to the notion that there is a maximal, or ceiling effect, with protein intake where increases to a point may be beneficial for cell and tissue synthesis and recovery but beyond that threshold show no more additional benefit nor consequence (hence NO changes in body composition as fat mass gain or lean body mass gain). What is also noteworthy with a study like this and several others like it is the fact that these are resistance trained young men and thus their body composition and activity level are going to differ from other population groups. Due to these distinct characteristics of the study sample, the results of this study cannot be extrapolated to the rest of the population, but certainly warrant a second look at the claims against high protein intake.
But what if you are trying to alter your body composition?
When it comes to high protein intake and weight loss, according to a review of published data, high protein diets (1.5-3.0g/kg body weight) are suggested to increase satiety through increased activity of gastrointestinal hormones in rat studies, influencing reward mechanisms and hunger sensations in mice, and reductions in reward-driven eating behaviors in adolescent girls that previously skipped breakfast eating. (Cuenca-Sanchez, et al. 2015) As well, additional studies suggested that a high protein diet (25-35% of kcal) is associated with favorable changes in weight loss, fat loss, changes in serum triglycerides, fat free mass and self-reported increased satiety (and thus less overall caloric intake) compared to a 'standard' protein intake of 15% of kcal. (Cuenca-Sanchez, et al. 2015) These findings propose that hunger sensations can be mitigated through protein intake whereby increased satiety can decrease total caloric intake and affect body weight and composition.(Cuenca-Sanchez, et al. 2015) It is also worth noting that protein is more stimulatory for thermogenesis than carbohydrates or fat which means that you will use more energy (calories) to metabolize protein than you would the other macronutrients. (Cuenca-Sanchez, et al. 2015)
However, in my protein story, my weight loss halted when I was eating all of those protein bars and high calorie/high protein shakes. This was likely because I was eating more total calories than I was expending by adding ADDITIONAL calories from the supplementary foods (they were not being accounted for), not necessarily because of the protein itself.
This all sounds good, right? But what about those theories that high protein diets negatively impact the liver and kidneys? Or how high protein and phosphorus (like from animal proteins) can negatively affect bone health?
In terms of bone health, protein actually increases intestinal calcium absorption and has been shown to increase IGF-1 concentrations and support bone mineralization and maintenance in a healthy population. (Cuenca-Sanchez, et al. 2015) In elderly populations, protein intake was suggested to be inversely associated with fracture risk where those with the lowest protein intake showed the greatest risk for hip fracture and those with the highest protein intake showed the greatest absorption of calcium despite their total calcium intake being below the recommendations. (Cuenca-Sanchez, et al. 2015) When it comes to kidney function, protein does increase the glomerular filtration rate (GFR) which can be problematic for an individual with existing kidney dysfunction. (Cuenca-Sanchez, et al. 2015) However there is no current data to suggest that hyperfiltration in a normal kidney (not in the presence of chronic kidney disease or decreased renal function) is cause for concern, but rather an adaptive mechanism to clearing out the remaining products of protein metabolism. (Cuenca-Sanchez, et al. 2015) When amino acids are metabolized for excretion, they are deaminated (the amine group is removed) which produces ammonia that must be detoxified (via the urea cycle in the liver) and removed from the body (via the kidneys) safely to prevent toxicity. (Lord, 2012) It is because of this increased activity, or hyperfiltration, that can occur from increased protein output (whether from excess dietary protein or increased protein loss like in injury or infection) that leads to the notion that the kidneys are being stressed. But this may just be a matter of the kidneys performing their functions appropriately, not necessarily as a negative consequence. Where the real issue may lie is with hydration status as dehydration can come as a result of increased solute excretion via the kidneys, posing other potential complications like kidney stones. (Cuenca-Sanchez, et al. 2015) To this point I would say that in my opinion, hydration status in the presence of a high protein diet is more likely to affect kidney functioning than the high protein intake alone.
What about the type of protein? Plants and animals are not the same...
When protein is metabolized, it is broken down into those amino acid building blocks. Dietary protein in general consists of 20 amino acids, 9 essential (must be obtained in the diet) and 11 non-essential (can be derived from other intermediates). Animal proteins like meats, seafood, poultry and dairy are considered complete proteins because they contain all of these essential amino acids. Plant proteins like grains, legumes, nuts and seeds are considered incomplete proteins as they are missing some of the essential amino acids, however when combined properly they can balance out. As an example of incomplete plant proteins, legumes lack the essential amino acid methionine while cereal grains lack the essential amino acid leucine, but when you combine legumes with grains (like beans and rice) the combination balances out and provides all of the amino acids. There are some exceptions to this where plant foods like soy and quinoa do offer all of the essential amino acids and are therefore considered complete proteins. It is important to note however that with plant proteins, there is typically an equal amount of carbohydrates present in the foods as there is protein which would translate to an overall comparatively higher carbohydrate intake (and calorie intake) if eating plant proteins to meet specific protein requirements, compared to animal proteins which do not contain carbohydrates. (Imagine eating 4oz of steak to equal ~28g protein compared to eating 1 cup black beans +2 cups rice to equal the same amount of protein. The steak is providing roughly 240 calories from protein and fat, depending on the cut and method of preparation. The beans and rice are providing roughly 560 calories from carbohydrates and protein.) This difference would play a role in total calories and volume of food eaten when comparing the same protein intake from either animal sources or plant sources.
It goes without saying that the debate between animal and plant protein sources has been a popular trend with observational findings of increased risk of cancer and theoretical environmental impacts of a diet high in animal protein compared to a diet high in plant protein. In my opinion, it is not necessarily the source of protein that should be a cause for concern, but the overall lifestyle whereby a diet that is high in plant protein is likely to also be high in fiber and nutrient-dense foods where a typically high animal protein diet may be lacking in. Thus observational study findings of cancer associations may be based on completely different lifestyles of the subjects, and not warranted on the type of protein source alone. There are actually some recent study findings to suggest that isocaloric diets (same calories for both diets) and with same macronutrient ratios (30% protein, 40% carbohydrate, 30% fat) showed no significant differences between animal protein or plant protein in reducing non-alcoholic fatty liver disease in type 2 diabetics. (Markova, et al. 2017) In this study, both groups (animal protein and plant protein) showed reductions in liver fat, decreased inflammation, and increased insulin sensitivity. (Markova, et al. 2017) This deserves some explanation though...
These diets consist of the same calories and same macronutrient ratios which means that both groups are eating the same amount of protein regardless of whether it is animal or plant origin. (Markova, et al. 2017) What stands out the most in this study is the fact that fiber content was the same between both groups. (Markova, et al. 2017) This last point should be a giant exclamation point (!) where a diet with plant proteins is certainly likely to be high in fiber, but for a diet with animal proteins to also be (equally) high in fiber and to show equal benefits to a plant protein-based diet certainly raises some flags regarding those observational studies that alluded to ill health from a diet high in animal protein.
This was merely an intro to protein to highlight some of the most frequent misunderstandings. Future posts will dive further into questions like protein for physical activity. Take away from this what you will, but never stop learning.
Antonio J, Ellerbroek A, Silver T, et al. The effects of a high protein diet on indices of health and body composition- a crossover trial in resistance-trained men. Journal of the International Society of Sports Nutrition. 2016; 13:3. https://jissn.biomedcentral.com/articles/10.1186/s12970-016-0114-2
Cuenca-Sanchez M, Navas-Carrillo D, Orenes-Pinero E. Controversies Surrounding High Protein Diet Intake: Satiating Effect and Kidney and Bone Health. Advances in Nutrition. 2015; 6: 260-266. http://advances.nutrition.org/content/6/3/260.full
Lord, R. Laboratory Evaluations for Integrative and Functional Medicine. Metametrix Institute. Duluth, GA. 2012.
Markova M, Pivovarova O, Hornemann S, et al. Isocaloric Diets High in Animal or Plant Protein Reduce Liver Fat and Inflammation in Individuals with Type 2 Diabetes. Gastroenterology. 2017; 152(3): 571-585. http://www.gastrojournal.org/article/S0016-5085(16)35229-5/fulltext?referrer=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2F
Nelms M, Sucher K, Lacey K, et al. Nutrition Therapy and Pathophysiology. Wadsworth, Cengage Learning. 2011.