PROTEIN MYTHS – Have you fallen for them, too?

Protein is important!

This information makes sense and should by now be common knowledge to anyone who values a healthy, high-performing body.

But if you dig a little deeper into the subject, things start to get complicated. You enter the world of protein myths, which abound—covering supposed positive effects, but especially the negative effects of protein.

In today’s post, we’ll address and debunk four of these myths.

MYTH 1

Protein intake above the RDA is harmful to the kidneys.

One of the most persistent myths about protein is that a higher intake (above the RDA) causes kidney damage or contributes to kidney failure.

There are older studies that report an increased risk of microalbuminuria, kidney disease, elevated glomerular filtration rate (GFR), and nitrogen excretion in the urine.

Brenner et al. have suggested that these harmful effects of excessive protein intake are the result of increased glomerular pressure and hyperfiltration (1–3).

The appropriate amount of protein intake for people with kidney disease remains controversial, whereby “appropriate” must be considered in the context of both “necessary” and “harmless” (4).

Research in healthy individuals shows that a higher protein intake is not associated with negative effects on kidney health. In a study by Antonio et al. (5), men who regularly engaged in resistance training followed a diet for 8 weeks that provided up to four times more protein than recommended by the RDA (i.e., 2.6 to 3.3 g of protein per kg of body weight).

After an overnight fast, blood samples were collected on three separate occasions.

Kidney function was assessed using laboratory markers such as blood urea nitrogen (BUN), globulin, and the albumin-to-globulin ratio. No changes were observed in either the normal-protein or high-protein groups. Serum creatinine, estimated GFR, BUN/creatinine ratio, globulin, and albumin/globulin ratio all remained within the normal range.

A follow-up study (6) investigated potential adverse effects of a 2-year high-protein diet with an average protein intake of 3.5 g per kilogram of body weight among the participants. Based on the group’s laboratory values (i.e., glucose, BUN, creatinine, 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 who typically consume more than 1.35 g of protein per kilogram of body weight.
Albumin excretion rates and eGFR remained within the normal range despite higher serum calcium concentrations.

Similarly, Knight et al. (4) reported no changes in eGFR among healthy women with higher protein intake.

These studies confirm that a higher protein intake does not impair kidney function in healthy individuals.

Although some studies report changes in eGFR, these are attributed to the kidneys’ natural response (8). In healthy individuals, 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.

A higher protein intake does not impair kidney function in otherwise healthy individuals.

 

MYTH 2

A high-protein diet is harmful to bone health.

A widespread claim suggests that a high protein intake triggers 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.

Studies do indeed suggest that long-term reliance on bone minerals to buffer the acidic environment can lead to lower bone mineral density (BMD) and a higher incidence of bone fractures (10–12).

On the other hand, an 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 does not harm bone health (8, 15–17).

On this topic, scientific research is slightly missing the mark. Both of the hypotheses put forward may be correct in the context of an increased acid load and its impact on bone health:

1. Protein is a key component in the development and maintenance of bone mass.
2. An increased acid load—triggered by an overall unbalanced dietary pattern, along with all other factors that influence total acid load—can lead to an increased release of minerals from the bones to act as buffers.
   Protein intake is just 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, provided it is part of a holistically balanced dietary approach that takes acid-base balance into account.

 

MYTH 3

Excess protein is stored as body fat.

Numerous studies demonstrate the benefits of protein for weight loss or the gain of lean body mass (21, 22).

Nevertheless, there are also studies showing that increased protein intake can lead to weight gain. This was observed in a cohort study examining protein intake as a percentage of total calories (less than 15%, 15–20%, over 20%), in an observational study that found such a correlation primarily for animal proteins, and in a study that found a correlation only 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 by Antonio et al. (21), in which men who regularly engaged in resistance training were placed on a diet with a normal protein intake for 6 months and a diet with a higher protein intake—along with a 400 kcal increase in caloric intake—for another 6 months.

Despite the protein-induced increase in calories, the participants did not gain fat mass. On hypocaloric diets, a high-protein diet consistently has a positive effect on body composition. Some studies have demonstrated that high-protein diets result in greater fat loss while better preserving lean body mass (23, 24).

Recent research findings show that increased protein intake promotes gains in lean body mass on 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 a single meal.

A wide variety of publications put forward the theory that the body can absorb a maximum of 30 g of protein per serving. Anything beyond that is either excreted, used for energy, or stored as fat.

With regard to maximizing protein synthesis, earlier studies have shown that 20 to 30 g per serving provides the greatest benefit (25, 26). This finding is now qualified, at least in relation to age.

When a large amount of protein is consumed at once, protein turnover increases, a greater amount of nitrogen is retained, and more amino acids—particularly leucine—are oxidized. Protein is broken down into amino acids and can then enter various metabolic pathways in the body. 

• Any excess can be converted into metabolic substrates such as glucose through the process of gluconeogenesis.
• Other endogenous protein compounds, as well as transport proteins, can be synthesized from amino acids.

From an evolutionary standpoint, the “30 g per serving” claim is likely a misconception. For hunter-gatherers and even for people in the Paleolithic era, food was a scarce resource available only seasonally. This meant that during periods of increased availability, people ate significantly more in order to be better prepared for times of food scarcity.

Estimates for the Paleolithic era suggest a protein intake of about 2.5 g per kilogram of body weight per day during periods of increased food availability (27–29).

There is no evidence that humans can consume more than 30 g of protein in a single meal. Speculation suggests that an “optimal” intake of protein—in the sense of maximizing protein synthesis—has been confused with the “maximum possible” intake per serving, leading to the emergence of this protein myth.

 

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/