A Meal-based Comparison of Protein Quality, Complementary Proteins and Muscle Anabolism

The investigators will test the following hypotheses in middle-aged men and women (45-60)
years old using a randomized, cross over design. All study objectives will be met
concurrently:

1. Meals containing 30 g of high quality, predominantly beef-protein (PRO-A) will stimulate
acute (i.e., single meal response) and 24 h skeletal muscle protein synthesis
[confirmatory hypothesis]

2. Meals containing 30 g of complementary plant-based proteins (PRO-B: complete essential
amino acid profile at each meal) will stimulate acute and 24 h skeletal muscle protein
synthesis, but to a lesser extent than beef-protein.

3. A single meal containing 30 g of an incomplete plant-based protein source (PRO-C:
lacking one essential amino acid) will fail to acutely stimulate skeletal muscle protein
synthesis

4. Meals containing 30 g of plant-based protein that are incomplete at each separate meal,
but complementary over a 24 h period, will fail to stimulate 24 h skeletal muscle
protein synthesis.

5. Beef-and plant-based meals will have a similar effect on satiety and 24 h blood glucose
[descriptive]

If these hypotheses are correct, the investigators will demonstrate that meals containing a
moderate amount of high quality protein, such as beef, are an efficient and effective way to
augment a largely plant based diet and stimulate skeletal muscle protein synthesis - a
prerequisite for outcomes related to physical function, performance, successful aging and
metabolic health.

Inclusion Criteria:

1. All races and ethnic backgrounds

2. Men and women, age 45-60 years

3. Generally healthy (see exclusion criteria)

4. Able and willing to provide informed consent

5. Ability to speak and read English (* the study procedures, e.g., muscle biopsy,
duration of each acute study, e.g. overnight stay; and multiple dietary questionnaires
require sound written and spoken English)

Exclusion Criteria:

1. Sarcopenia (defined by: European Working Group on Sarcopenia in Older People, EWGSOP
(44))

2. Clinically significant heart disease (e.g. New York Heart Classification greater than
grade II; ischemia)

3. Peripheral vascular disease

4. Pulmonary disease

5. History of systemic or pulmonary embolus

6. Uncontrolled blood pressure (systolic BP>170, diastolic BP>95 mmHg)

7. Impaired renal function (creatinine >1.5 mg/dl)

8. Anemia (hematocrit <33)

9. Untreated thyroid disease (abnormal TSH)

10. A recent history (<12 months) of GI bleed

11. Diabetes mellitus or other untreated endocrine or metabolic disease

12. Electrolyte abnormalities

13. Any history of stroke, hypo- or hyper-coagulation disorders

14. Recent (3 years) treated cancer other than basal cell carcinoma

15. Systemic steroids, anabolic steroids, growth hormone or immunosuppressant use within
12 months

16. Recent (6 months) adherence to a weight-loss or weight-gain diet

17. Weight change of 5% or more in previous 6 months

18. Body mass index >30 or excess body fat that compromises muscle biopsy collection

19. Body mass index <20 or recent history (<12 month) of disordered eating

20. Dietary preferences or practices that preclude the consumption of the study meals

21. Acute infectious disease or chronic infection

22. Alcohol or drug abuse

23. Any other condition or event considered exclusionary by study physician

24. Pregnancy