Protein is important!
This information is logical and should have reached everyone who values a healthy, high-performance body by now.
However, if you delve a little deeper into the subject, it becomes more difficult. You enter the world of protein myths that abound about the supposed positive and, above all, negative effects of protein.
We will address and clarify four of these myths in today's article.
MYTH 1
Protein above the RDA recommendation is harmful to the kidneys.
One of the most persistent myths about protein is that a higher intake (above the RDA) would cause kidney damage or promote kidney failure.
There are older studies that report an increased risk of microalbuminuria, kidney disease, increased glomerular filtration rate (GFR) and urinary nitrogen excretion.
Brenner et al. have suggested that these detrimental effects of excessive protein intake are the result of increased glomerular pressure and hyperfiltration (1-3).
The correct amount of protein intake for renal patients is controversial, with 'correct' being considered in the context of both 'necessary' and 'harmless' (4).
Research in healthy people shows that higher protein intake is not associated with negative effects on kidney health. In Antonio et al (5), resistance-trained men consumed a diet that provided up to four times more protein than recommended via the RDA (i.e. 2.6 to 3.3 g protein per kg body weight) for 8 weeks.
After an overnight fasting period, blood samples were taken on three separate occasions.
Renal function was assessed using laboratory markers such as blood urea nitrogen (BUN), globulin and the albumin/globulin ratio. No changes were found in either the normal or high protein groups. Serum creatinine, estimated GFR, BUN/creatinine ratio, globulin and albumin/globulin all remained within the normal range.
A follow-up study (6) investigated possible adverse effects of a 2-year high-protein diet with an average protein intake of 3.5 g per kilogram of body weight. Based on the group's laboratory values (i.e. glucose, BUN, creatine, eGFR, ALT and AST), the high-protein diet showed no adverse effects on liver and kidney function.
Poortmans et al (7) measured albumin excretion rate, nitrogen and calcium balance and GFR in male athletes normally consuming more than 1.35 g protein per kilogram body weight.
Albumin excretion rates and eGFR were within the normal range despite higher serum calcium concentrations.
Similarly, Knight et al (4) reported no changes in eGFR in healthy women with higher protein intakes.
The studies confirm that higher protein intake does not impair renal function in healthy individuals.
Although some studies report changes in eGFR, these are attributed to the natural response of the kidneys (8). In healthy people, changes in GFR are a normal response of the body to an increase in dietary protein and are not markers of an increased risk of kidney complications.
Higher protein intake does not affect kidney function in otherwise healthy people.
MYTH 2
Increased protein intake is detrimental to bone health.
A widespread claim sees a high protein intake as a trigger for negative effects on bone health.
The acid-base theory suggests that sulfur-containing amino acids create an acidic environment in the body (9). In an effort to maintain homeostasis, the body draws calcium from the bones, which acts as a buffer.
In fact, studies suggest that prolonged dependence on bone minerals to buffer the acidic environment can lead to lower bone mineral density (BMD) and a higher incidence of fractures (10 - 12).
On the other hand, adequate protein intake has been shown to be necessary for the development and maintenance of bone health (13, 14). Studies have also shown that a higher protein intake is not detrimental to bone health (8, 15 - 17).
On this topic, the scientific community is somewhat ignoring itself. Both hypotheses may be correct in the context of increased acid load and an impact on bone health:
- Protein is an important link for the development and maintenance of bone substance.
- Increased acid load, triggered by an overall unbalanced dietary pattern together with all the other factors that influence the overall acid load, can lead to minerals having to be released from the bone more frequently as a buffer.
Protein intake is one of many pieces of the puzzle when it comes to establishing a correlation between acid-base balance and bone health.
Increased protein intake does not necessarily harm bone health, as long as it is part of an overall balanced nutritional concept in terms of acid-base balance.
MYTH 3
Excess protein is stored as fat mass.
A large number of studies have shown the benefits of protein for weight loss or for gaining lean mass (21, 22).
Nevertheless, there are also studies that show that increased protein intake is able to increase body weight. This was observed in a cohort study that determined protein intake as a percentage of total calories (under 15%, 15-20%, over 20%), in an observational study that found such a correlation mainly for animal proteins, or in a study that only found a correlation when protein was replaced by carbohydrates but not by fats (18-20).
The answer to the initial question can be found in studies such as that of Antonio et al (21), in which resistance-trained men were given a diet with a normal amount of protein for 6 months and a higher amount of protein for 6 months, including a 400 kcal increase in calories.
Despite the protein-related increase in calories, the test subjects did not gain fat mass. In hypocaloric diets, a high-protein diet has a consistently positive effect on body composition. In some studies, high-protein diets have been shown to result in greater fat loss and better preservation of fat-free mass (23, 24).
Current research shows that an increased protein intake promotes an increase in lean body mass in both hypocaloric and hypercaloric diets and does not necessarily result in an increase in fat mass.
MYTH 4
Only 30 g of protein can be consumed in one meal.
Many different publications claim that the body can absorb a maximum of 30 g of protein per portion. Anything more than this is either excreted, used for energy or stored as fat.
In terms of maximizing protein synthesis, previous studies have shown that 20 to 30 g per serving provides the maximum benefit (25, 26). This is now relativized at least by the age factor.
If a lot of protein is consumed at once, protein turnover increases, a larger amount of nitrogen is retained and more amino acids, especially leucine, are oxidized. Protein is broken down into amino acids and can then enter various metabolic pathways in the body.
- An excess can be converted into metabolic substrates such as glucose via the process of gluconeogenesis.
- Other endogenous protein compounds and transport proteins can be synthesized from amino acids.
From an evolutionary point of view, the "30 g per portion" claim is probably a misconception. For hunter-gatherers and even Paleolithic man, food was a scarce and seasonal commodity. As a result, people ate considerably more during times of increased availability in order to be better equipped for times of food shortage.
Estimates assume a protein intake of around 2.5 g per kilogram of body weight per day in the Palaeolithic period during times of increased food availability (27 - 29).
There is no evidence that humans could only consume a maximum of 30 g of protein in one meal. Presumptions suggest that the "optimal" administration of protein in terms of the utilization of protein synthesis has been confused with the "maximum possible" intake per serving, which is how this protein myth came about.
Sources
(1) https://pubmed.ncbi.nlm.nih.gov/7731172/
(2) https://pubmed.ncbi.nlm.nih.gov/14993863/
(3) https://pubmed.ncbi.nlm.nih.gov/7050706/
(4) https://pubmed.ncbi.nlm.nih.gov/12639078/
(5) https://pubmed.ncbi.nlm.nih.gov/26778925/
(6) https://www.researchgate.net/publication/323257734_Case_reports_on_well-trained_bodybuilders_Two_years_on_a_high_protein_diet
(7) https://pubmed.ncbi.nlm.nih.gov/10722779/
(8) https://pubmed.ncbi.nlm.nih.gov/25979491/
(9) https://pubmed.ncbi.nlm.nih.gov/29690515/
(10) https://www.mdpi.com/2072-6643/10/4/517
(11) https://pubmed.ncbi.nlm.nih.gov/15546911/
(12) https://pubmed.ncbi.nlm.nih.gov/12612169/
(13) https://www.researchgate.net/publication/279064249_Chapter_4_Bone_Modeling_and_Remodeling
(14) https://pubmed.ncbi.nlm.nih.gov/28686536/
(15) https://jissn.biomedcentral.com/articles/10.1186/s12970-018-0210-6
(16) https://pubmed.ncbi.nlm.nih.gov/15546911/
(17) https://pubmed.ncbi.nlm.nih.gov/28003538/
(18) https://pubmed.ncbi.nlm.nih.gov/25886710/
(19) https://pubmed.ncbi.nlm.nih.gov/21139559/
(20) https://pubmed.ncbi.nlm.nih.gov/24942843/
(21) https://www.researchgate.net/publication/309026102_A_High_Protein_Diet_Has_No_Harmful_Effects_A_One-Year_Crossover_Study_in_Resistance-Trained_Males
(22) https://pubmed.ncbi.nlm.nih.gov/22215165/
(23) https://pubmed.ncbi.nlm.nih.gov/16046715/
(24) https://pubmed.ncbi.nlm.nih.gov/26817506/
(25) https://pubmed.ncbi.nlm.nih.gov/23459753/
(26) https://pubmed.ncbi.nlm.nih.gov/19056590/
(27) https://pubmed.ncbi.nlm.nih.gov/10702160/
(28) https://pubmed.ncbi.nlm.nih.gov/8648449/
(29) https://pubmed.ncbi.nlm.nih.gov/9104571/
