Comprehensive Protein and Sarcopenia: Sources, Requirements, and Effects in Adults

What is the daily protein requirement for young healthy adults?

Roughly 50 to 60 grams of protein each day.

What are the primary sources of dietary protein in high-income countries?

Meat, poultry, seafood, eggs, and dairy products.

What is the significance of essential amino acids?

They cannot be synthesized by the human body in sufficient amounts and must be included in the diet.

What is protein-energy malnutrition (PEM)?

A term that covers a range of protein deficiency conditions, including pure protein deficiency or protein deficiency plus energy deficiency.

What is Kwashiorkor?

A condition resulting from pure protein deficiency.

What is Marasmus?

A condition characterized by energy (calorie and nutrient) deficiency, often referred to as starvation.

How are amino acids absorbed in the body?

Amino acids are absorbed into portal circulation and delivered to the liver.

What is the role of proteins in the human body?

Proteins function as enzymes, hormones, antibodies, transporters, structural components, storage components, and contractile fibers.

What is the nitrogen balance in relation to protein intake?

Negative nitrogen balance occurs when losses exceed intake, while positive nitrogen balance occurs when intake exceeds losses.

What are the acceptable macronutrient distribution ranges (AMDR) for protein?

10% to 35% of total daily calories, roughly 50-175 grams/day based on a 2,000-calorie intake.

What is the recommended protein intake for athletes?

Twice the protein RDA may be appropriate for athletes.

What are common sources of food allergies related to proteins?

Milk, eggs, tree nuts, peanuts, sesame, wheat, soy, fish, and shellfish.

What is anaphylaxis?

A rapid, severe allergic reaction triggered by the absorption of undigested proteins.

What are the waste products of protein deamination?

Ammonia and urea.

What is the role of leucine in protein synthesis?

Leucine is an essential amino acid that stimulates muscle synthesis.

What is the significance of consuming protein-rich foods every 3 to 4 hours?

It helps maintain a robust amino acid circulatory system and supports muscle synthesis.

What is the caloric value of protein?

4 calories per gram.

What should individuals with intestinal diseases be aware of regarding protein?

They are prone to allergies because their damaged intestine allows for the absorption of protein fragments.

What are some recommended protein sources for athletes?

Legumes, tofu, chicken, turkey, fish, beef, pork, yogurt, and milk.

What is the role of protein in fluid balance?

Proteins help maintain fluid balance in the body.

What is the relationship between protein intake and satiety hormones?

Sufficient protein increases production of satiety hormones like GLP-1, CCK, and PYY, and reduces ghrelin.

What is the impact of a country's economic improvement on dietary protein sources?

As a country's economy improves, the proportion of animal foods in the diet increases.

What percentage of body weight is skeletal muscle in young adults?

37% to 46%

How many kcalories does skeletal muscle use at rest per pound per day?

6 kcalories

What is the primary composition of skeletal muscle?

75% Water, 20% Protein, 4% Fat, 1% Glycogen

What is sarcopenia?

The progressive loss of skeletal muscle associated with aging.

At what age does muscle loss typically begin?

In the late 30s or early 40s.

What is the annual rate of muscle loss due to sarcopenia?

About ½ pound (¼ kg) or 1% of muscle every year.

List two consequences of gradual muscle loss.

Decreased muscle mass and strength; increased risk of chronic diseases.

What are some modifiable factors contributing to sarcopenia?

Inadequate calories, protein, vitamin D, low physical activity.

What are some non-modifiable factors contributing to sarcopenia?

Fewer motor nerve cells, lower hormone production, genetic differences.

What is the daily protein requirement for young adults?

0.8 grams of protein per kilogram of body weight.

What is the daily protein requirement for older adults?

1.0-1.25 grams of protein per kilogram of body weight.

How much protein might older adults with significant sarcopenia need?

As much as 1.8 grams of protein per kilogram of body weight.

What is the optimal level of protein intake for aging adults?

Greater than the RDA, with evidence suggesting 1.6 g/kg body weight.

What amino acid is crucial for triggering protein synthesis in skeletal muscle?

Leucine.

What is the recommended amount of leucine per meal for muscle synthesis?

2 to 3 grams.

How does physical activity affect protein intake in older adults?

It enhances muscle anabolism when combined with high biologic value protein meals.

What nutritional components does cow's milk have more of compared to plant milks?

Calcium, vitamin D, iodine, riboflavin, pantothenic acid, and biotin.

Can protein needs be met on a purely plant-based diet?

Yes, if sufficient legumes, grains, seeds, nuts, and vegetables are consumed.

What dietary strategies can help meet protein needs?

Include lean poultry and fish, choose low-fat dairy, and add nuts and seeds.

What is the impact of low-grade metabolic acidosis on muscle health?

It can lead to less muscle protein synthesis and increased proteolysis.

What are some chronic diseases associated with sarcopenia?

Type 2 diabetes, heart disease, hypertension, osteoporosis.