An exploratory study into the acute and long-term effects of high-protein supplementation on postprandial muscle protein metabolism in healthy elderly.

1. Age 65 y or older;

2. Male;

3. BMI from 20 through 30 kg/m2;

4. Willingness and ability to comply with the protocol;

5. Written informed consent.

1. Prior or current participation in any other clinical study using phenylalanine stable isotopes;

2. Indications related to inadequate glycemic control;

3. Co-morbidities:

A. All co-morbidities interacting with mobility and/or muscle metabolism of the lower limbs and hands;

B. Any malignant disease during the last five years except for adequately treated prostate cancer without evidence of metastases, localized bladder cancer, breast cancer in situ or non-melanoma skin cancer;

C. Any (history of) gastrointestinal (GI) disease that interferes with GI function;

D. Known kidney failure;

E. Known liver failure;

F. Moderately severe and severe anaemia;

G. Diabetes Mellitus type I or II;

H. (Chronic) inflammatory status;

I. Any known food allergy to the ingredients of the breakfast consumed during study visits;

J. Dementia: Mini Mental State Examination <25.

4. Medication:

A. Use of oral or systemic antibiotics within 3 weeks prior to study visit;

B. Current oral or systemic use of corticosteroids, testosterone, growth hormone, immunosuppressants, tricyclics, opiates, barbiturates or insulin.

5. Malnutrition:

A. Severe weight loss (>3 kg in the last 3 months);

B. Severe loss of appetite.

6. Dietary or life style characteristics:

A. Adherence to a weight loss diet three months before and during the study;

B. Adherence to a high energy or high protein diet three months before starting and during the study;

C. Use of protein containing or amino acid containing nutritional supplements within one week of study entry and during the study;

D. Participation in a muscle strengthening program three months before starting and during the study;

E. Current or recent (within past 3 months) smoking;

F. Current alcohol or drug abuse in opinion of the investigator.

7. Indications related to the study product:

A. A cumulative monthly dose of more than 140 ìg (5600 IU) of vitamin D supplementation administrated according to a weekly or monthly regimen during the last three months;

B. More than 5 ìg (200 IU) of daily vitamin D intake from medical sources (including food supplements and vitamin supplements);

C. More than 500 mg of daily calcium intake from medical sources;

D. Known allergy to milk and milk products;

E. Known galactosaemia.

8. Contraindications related to muscle biopsy procedure:

A. Blood diseases;

B. Use of anticoagulants;

C. Allergy for lidocaine;

D. Prostate hypertrophy (Prostate specific antigen > 4 ìg/L) ;

E. Glaucoma.

9. Blood donation within 2 months of study entry, during the study and 1 month after study completion;

10. Investigator's uncertainty about the willingness or ability of the subject to comply with the protocol requirements;

11. Participation in any other study involving investigational or marketed products concomitantly or within 4 weeks prior to entry into the study.