Each macronutrient seems to have gotten it’s share of being demonized in the health and fitness industry, as well as with the general public. Fat was deemed bad for us early on. Then we discovered the Atkins diet (and subsequently keto rose to fame), so carbs became the evil macro to avoid. While protein hasn’t been deemed bad by the general public, it has faced a different form of scrutiny and has been the victim of some confusing misinformation. Do we get enough? Do we eat too much? How much should we consume each day? Is there a limit to how much we can absorb at one time? Does high protein damage our kidneys? What exactly is a high protein diet?
How much protein should you consume?
To begin sorting through the misinformation, let’s start with the current recommendations for protein. Currently, the Recommended Dietary Allowance (RDA) for protein is 0.8 g/kg of body weight or 0.4 g/lb. The RDA, which can be found for almost every essential nutrient, is the adequate amount required to meet the average nutritional needs of most healthy people. Basically, it is the minimum amount needed not to see any deficiencies. This recommendation does not take into account physical activity levels, resistance training, or the demands of an athlete. So, if the bare minimum is what you strive for, then you are getting enough. However, if you prefer to thrive instead of just survive, keep reading.
The current recommendations from the ISSN (International Society of Sports Nutrition) for physically active individuals is 1.4-2.0 g/kg of body weight. This is 2-3 times the RDA mentioned above. Just to put it in perspective, a person weighing 180 lb (80 kg) would be eating a measly 65 g of protein if following the RDA but would be eating 115-160 g of protein under the ISSN recommendations. To many, this would be considered a high protein diet, however, this same researcher suggests that anything over 2.0 g/kg should be considered high. Even this term starts to get ambiguous. Some of the definitions of high protein are: anything over 15% of total calories, anything over the RDA, or 35% or more of total calories.
Using a percentage of calories is a mistake in my book. If someone were on a 1400 kcal diet (low, but somewhat common in weight loss) 35% of their diet would be 115 g. This is likely at or below the 2.0 g/kg mark for someone eating these calories. On the other side, an athlete eating 4000 kcal would be crushing 350 g of protein if hitting 35% of calories from protein, likely well over the 2.0 g/kg mark. For this reason, when you are deciding how much protein to consume, you should use the g/kg body weight recommendations and not a percentage of total calories.
Is it possible to consume too much protein?
Now, how much protein is too much? The short answer is: we don’t know. A study investigating high protein intake in resistance trained individuals showed some surprising results. One group was fed within the standard ISSN range (1.4-2.0 g/kg) while the other group was consuming 4.4 g of protein per kg of body weight. The groups showed no difference in fat mass, fat-free mass, or body weight changes even though the high protein group consumed 800 calories per day MORE THAN the control group. The same lab conducted another study in which the subjects were placed on a heavy resistance training protocol and assigned to normal or high (3.4 g/kg) protein groups. While there was still no significant difference in the fat-free mass, the higher protein group showed significant reductions in fat mass compared to the control although they consumed 400 calories more per day.
How much protein to consume per meal
Another area of uncertainty is surrounding the amount of protein per meal. I often hear people claim that the body can’t absorb more than 20 g of protein at a time. Absorption describes the passage of nutrients into systemic circulation, so the amount of protein that can be absorbed is basically unlimited. How much is being utilized by the body is a better question. Where this 20 g limit originated is an older study showing feedings of 10 g, 20 g, or 40 g of protein at decreasing frequency and the results showed muscle protein synthesis (MPS) peaked at 20 g per feeding with no added benefit in the 40 g group. A later study showed a 20% increase in muscle mass in the 40 g group compared to the 20 g group. Another study examined feedings of 40 g or 70 g, and while MPS was the same, muscle protein breakdown was lower in the 70 g group.
What we can take from these studies is that 20 g per feeding isn’t terrible, but it should be viewed as a minimum baseline. Some researchers argue that total daily protein is more important than what you get per meal. Aiming for 0.4 g/kg for each meal and post-workout will not only optimize protein turnover but also set up good habits for hitting that 1.4-2.0 g/kg range. Don’t have to twist my arm to get me to eat more protein. This is just validating my existing behaviors.
Is protein bad for your kidneys?
Finally, let’s look into the idea that protein is bad for your kidneys. The whole idea stems from a study showing that rats who had one kidney removed showed renal damage when fed a high-protein diet and another group showed no damage but had renal hypertrophy. A more recent study showed rats supplemented with high protein had no negative effects on liver or kidney health and instead may improve liver health compared to rats not receiving protein.
Well, the problem with rat studies is that almost all of the rats are bred with certain issues to be more sensitive to damage, disease, and death. Plus, humans and rats differ greatly, so the results aren’t always transferable.
In a different, year-long study subjects followed 6 months of either high or normal protein intake, then switched for a further 6 months. The high protein group consumed ~3 g of protein per kg. The study reported no negative effects from either group. Protein is most often limited in the case of chronic kidney disease in which the patient is not undergoing dialysis. The main reason for this is because of the extra work the diseased kidneys do to filter proteins from the system, not an effect of protein itself. Once on dialysis, the recommendation is to increase protein.
So, current research tells us that we can not only increase our dietary protein intake 5-fold, but (provided we do not have a kidney disorder) we also aren’t destroying our kidneys while doing it. YAY! If you’re looking for a high-quality protein powder to supplement your dietary protein intake, check out Bodylogix® Natural Isolate with 25 g of protein per scoop.
One of my favorite things to do is combat common misconceptions with science, but I also caution using one study to prove a point. Research is definitely in favor of higher protein intake, but let’s stick to the ISSN recommendations for the most part. Higher protein can be used to reduce muscle breakdown on heavy workout days. However, sticking to that 1.4-2.0 g/kg range is your best advice. It’s sustainable. You’ll likely hit your goal of 0.4 g/kg per meal. Plus, it leaves room in your diet for carbs and fat to fuel your workouts. Delicious, delicious fuel.