How does serum creatinine impact GFR measurements in studies, especially with high protein intake?

Many epidemiological studies use estimated GFR based on serum creatinine and age. A significant increase in animal protein intake can acutely raise serum creatinine levels, independent of actual kidney function. This variability makes it difficult for clinicians to detect meaningful changes in GFR using creatinine-based metrics alone, as the 'noise' from fluctuating creatinine can be substantial.

Is hyperfiltration a concern with high protein diets?

Hyperfiltration is when GFR is too high, potentially leading to irreversible kidney damage. While some studies associate higher protein intake with increased risk of hyperfiltration, raw data often shows only minor differences or even higher prevalence in lower protein groups once covariates are removed from the analysis. For healthy individuals, small fluctuations within the normal range due to adaptation are not necessarily pathological.

Do high protein diets impair kidney function in healthy individuals?

Based on the studies reviewed, for individuals with healthy kidneys and no underlying pathology, high protein diets do not appear to inherently impair kidney function. Raw data from studies often shows no significant differences in GFR decline between high and low protein groups, especially before complex statistical adjustments that can skew results.

Can dietary cholesterol improve muscle protein synthesis and strength gains?

Research suggests that dietary cholesterol, particularly from whole eggs, may acutely elevate muscle protein synthesis more than egg whites. Longitudinal studies, especially in older adults, have also indicated a potential, albeit not always perfectly linear, association between higher cholesterol intake and greater gains in lean mass and strength. However, the exact mechanisms and dose-response remain unclear.

What are the proposed mechanisms by which cholesterol might enhance hypertrophy?

Three main mechanisms are proposed: 1) Cholesterol increases cellular rigidity, potentially leading to more muscle damage which some link to hypertrophy; 2) It might increase rates of cellular repair after damage, aiding recovery; 3) It could help with the production of 'lipid rafts' which compartmentalize cellular processes for more efficient signaling. However, the scientific evidence for all these mechanisms is still under debate or needs more direct study.

What is the 'first finder effect' in scientific literature?

The 'first finder effect' describes how the initial study discovering a particular effect often reports a larger magnitude of that effect than subsequent studies. This can happen because large positive results are more likely to generate excitement and get published, while weaker or null results might be overlooked or not published, creating a bias towards stronger initial findings.

What are reasonable rates of weight gain during a bulk to minimize fat gain?

To minimize fat gain during a bulk, a conservative rate of weight gain is 0.25% of your body weight per week. For more aggressive bulking, especially if you have significant muscle to gain, 0.25% to 0.5% of body weight per week can be acceptable. The quicker you gain weight, the higher the percentage of that gain is likely to be fat.

Does being leaner enhance hypertrophy during a bulk due to insulin sensitivity?

There's a popular idea that staying leaner (and thus more insulin sensitive) enhances hypertrophy, but there's little direct evidence to support this. Real-world observations of highly muscular athletes like sumo wrestlers and super heavyweight powerlifters, who often have high body fat, contradict this notion. Insulin affects fat cells as well as muscle cells, so getting shredded doesn't guarantee all nutrients go to muscle.

What is CNS fatigue and how does it relate to feeling sick after intense training?

CNS fatigue, or central nervous system fatigue, refers to a general feeling of poor performance and lethargy that accumulates over time, often lasting beyond typical recovery from acute muscle fatigue. Mechanistically, it may involve reduced motor drive from the brain or impaired signal transmission. The feeling of sickness, often linked to CNS fatigue, could be due to the 'cytokine hypothesis of overtraining,' where intense training leads to chronic inflammation and immune system fatigue, making one more susceptible to infections like common colds.

What are some practical strategies for improving CNS recovery?

To improve CNS recovery, ensuring plenty of sleep and adequate nutrition, especially carbohydrates, is crucial. If localized glycogen depletion is a factor, carbs help replenish it. Additionally, continuing to exercise with easy, low-intensity activities rather than completely resting can accelerate recovery, as it prevents the body from becoming too sedentary while still allowing tissues to heal.

Should athletes cutting weight be concerned about micronutrient deficiencies?

Yes, everyone, especially athletes in a caloric deficit, should be mindful of potential micronutrient deficiencies. This is particularly important with low calorie intake or limited food diversity. Strategies include consuming a variety of food sources, considering a well-formulated multivitamin, ensuring adequate fat intake for fat-soluble vitamin absorption, and supplementing with marine-based omega-3s like fish oil when dietary fat is very low.

Key Moments

Protein & Kidney Function; Cholesterol & Training Adaptations (Episode 49)

Stronger By Science

Education5 min read134 min video

Nov 5, 2020|7,735 views|167|16

Stronger By Science Podcast

Save to Pod

Key Moments

TL;DR

High protein diets unlikely to harm healthy kidneys. Whole eggs may aid muscle growth more than egg whites.

Key Insights

High protein intake in healthy individuals does not appear to significantly impair kidney function based on current research, with raw data showing no alarming differences between low and high protein groups.

While some studies show higher protein intake associated with a faster decline in Glomerular Filtration Rate (GFR), the effect size is small and becomes more pronounced only when numerous confounding variables are introduced into statistical models.

Dietary cholesterol, primarily from whole eggs, may offer slight benefits for muscle protein synthesis and strength gains compared to egg whites, though the evidence is not overwhelmingly strong.

The strongest evidence suggesting a significant impact of dietary cholesterol on muscle adaptation comes from the initial studies, potentially illustrating the 'first-finder effect' where initial findings are often more pronounced.

Central Nervous System (CNS) fatigue is likely a combination of peripheral factors like low-frequency fatigue and systemic inflammation (cytokines), rather than a direct central impairment, and can be managed with adequate sleep, nutrition, and low-intensity exercise.

Creatine supplementation does not require cycling for efficacy, and while leucine supplementation might offer theoretical benefits for muscle protein synthesis, it's likely unnecessary for most individuals consuming adequate protein.

Behavior-based dietary interventions can be more effective than strict macronutrient targets for many individuals, especially those new to tracking, by focusing on actionable habits.

The relationship between dietary cholesterol and blood lipids/heart disease is less direct than previously thought, with current guidelines de-emphasizing strict limits on dietary cholesterol intake.

There is no strong evidence to suggest that high body fat percentage inherently prevents maximal lean mass gains during a bulk; individual preferences and health dictate body fat management.

Encouragingly, Arctic whales are reportedly having a happier year due to reduced cruise ship traffic during the pandemic. A blue whale remains the largest animal to hypothetically fight.

HIGH PROTEIN DIETS AND KIDNEY FUNCTION

The podcast segment addresses concerns about high protein diets potentially harming kidney function. Research reviewed suggests that for individuals with healthy kidneys, high protein intake does not appear to be a significant risk factor. Raw data from epidemiological studies show minimal difference in Glomerular Filtration Rate (GFR) decline between individuals consuming low versus high amounts of protein. While some models indicate a faster GFR decline with higher protein, this effect is likely influenced by numerous confounding variables, and the raw data does not support a strong negative correlation.

UNDERSTANDING GLOMERULAR FILTRATION RATE (GFR)

GFR is a key measure of kidney function, reflecting how efficiently the kidneys filter blood. As people age, GFR naturally declines. Chronic kidney disease is typically concerned when GFR drops below 60. The measurement, often estimated using serum creatinine, can be influenced by factors like muscle mass and animal protein intake, making it an imprecise marker for broad populations. Hyperfiltration, where GFR is unusually high, is also a concern as it might indicate kidney damage.

DIETARY CHOLESTEROL AND TRAINING ADAPTATIONS

The discussion explores the impact of dietary cholesterol, particularly from whole eggs, on resistance training outcomes. While some studies show no significant differences between whole egg and egg white consumption, subtle trends favor whole eggs for body composition and strength gains. Acute studies suggest whole eggs may promote greater post-exercise muscle protein synthesis. Longitudinal research in older adults indicates potential benefits for lean mass and strength with higher whole egg consumption, although the evidence is not definitively conclusive and may be confounded by protein intake.

MECHANISMS AND INTERPRETATION OF CHOLESTEROL RESEARCH

Several theoretical mechanisms propose how dietary cholesterol might influence muscle hypertrophy, including increased cellular rigidity, enhanced repair after muscle damage, and improved signaling through lipid rafts. However, these mechanisms are not definitively proven. The strongest evidence linking dietary cholesterol to significant gains comes from initial studies, potentially subject to the 'first-finder effect.' The research is generally positive overall, but often confounding factors like protein intake or other components in eggs make it difficult to isolate cholesterol's specific effect.

CENTRAL NERVOUS SYSTEM (CNS) FATIGUE AND RECOVERY

CNS fatigue is often misinterpreted as a direct impairment of the central nervous system. More likely, it involves peripheral factors such as low-frequency fatigue (related to muscle calcium handling) and systemic inflammation from overtraining. These can lead to feelings of lethargy and reduced performance. Improving recovery involves adequate sleep, sufficient carbohydrate intake to address glycogen depletion, and continued, low-intensity exercise. Addressing inflammation via reduced training stress and proper recovery is crucial.

SUPPLEMENTATION AND DIETARY STRATEGIES

Key takeaways from the Q&A include that creatine cycling is unnecessary, and while leucine supplementation has theoretical benefits for muscle protein synthesis, it's likely not required for most individuals eating adequate protein. Citrulline malate's effects are not expected to diminish with continuous use. For soft tissue injuries, providing a mechanical stimulus through training is beneficial, but excessive inflammation or blood flow is not the primary driver of recovery. Lastly, behavior-based dietary interventions can be highly effective, often surpassing strict macronutrient targets for adherence and results.

WEIGHT MANAGEMENT AND HORMONAL CONSIDERATIONS

MICRONUTRIENTS AND DIETARY DIVERSITY

Regardless of calorie intake, attention to micronutrient intake is essential. Athletes, especially those in a caloric deficit or with limited food variety, should be mindful of potential deficiencies. A well-formulated multivitamin can serve as a safety net, particularly if meticulous dietary tracking is not feasible. Ensuring adequate fat intake is crucial for absorbing fat-soluble vitamins, and omega-3 supplements may be beneficial during periods of very low fat and calorie intake.

Mentioned in This Episode

●Supplements

●Software & Apps

●Companies

●Organizations

●Books

●Concepts

●People Referenced

Common Questions

GFR is a measure of the rate at which substances are filtered through the glomeruli in your kidneys. It's a key indicator of kidney function, with values typically high in younger individuals (90s-100+) and declining with age. A GFR below 60 suggests chronic kidney disease, while below 15 indicates end-stage renal failure.

Topics

Protein Intake Health & Longevity Nutrition & Diet Human Performance Strength Gains Kidney Health Muscle Protein Synthesis Dietary Cholesterol Bulking Strategies CNS Fatigue

Mentioned in this video

companyFacebook

A social media platform where Stronger By Science listeners can join a group.

companyReddit

A social news aggregation, web content rating, and discussion website where Stronger By Science listeners can join a subreddit.

companyBulkSupplements.com

An online retailer for supplement needs; mentioned as a sponsor where listeners can save 5% using a code.

personRich Piana

A bodybuilder and founder of the 5% Nutrition company, mentioned by Greg.

personGordon Ramsay

A chef known for his aggressive approach to cooking shows, contrasted with The Great British Baking Show.

mediaAmerican Idol

An American singing competition television series, mentioned as a show where a formula of drama worked.

studyG and colleagues

Authors of the first study reviewed, which explored the effects of protein diets on kidney function in over 9,000 subjects.

softwareWikipedia

An online encyclopedia, quoted for its definition of lipid rafts.

organizationMcMaster University

A Canadian university where research suggesting muscle protein synthesis might be directed towards damage repair when muscle damage is high.

supplementCreatine

A well-known ergogenic aid, used for comparison with the potential effects of cholesterol on hypertrophy, and later discussed in a Q&A.

organizationWorld Health Organization (WHO)

An international organization that has updated its stance on dietary cholesterol's effect on blood lipids.

supplementLeucine

An amino acid discussed for its role in optimizing muscle protein synthesis, with the suggestion that supplementing it at every meal is likely unnecessary for most.

supplementCitrulline Malate

A supplement discussed regarding whether its effects decrease with continuous use; the speaker highly doubts this, expecting potential long-term benefits.

supplementCollagen

A supplement taken to help repair soft tissue; discussed in the context of training stimulus.

toolMultivitamin

A supplement suggested to help avoid micronutrient deficiencies, especially with low calorie intake or limited food diversity.

supplementFish oil

An omega-3 supplement recommended for periods of very low calorie and fat intake to ensure adequate essential fatty acids.

conceptCOVID-19

The pandemic responsible for fewer cruise ships in the arctic, leading to happier whales.