Associations of dietary protein intake on subsequent decline in muscle mass and physical functions over four years in ambulant older Chinese people.

OBJECTIVE: To examine the association of dietary protein intake with 4-year change in physical performance measures and muscle mass in Chinese community-dwelling older people aged 65 and older in Hong Kong.

DESIGN: Prospective cohort study design.

SETTING: Hong Kong, People's of Republic of China.

PARTICIPANTS: There were 2,726 (1411 male, 1315 female) community-dwelling older people aged 65 and older.

MEASUREMENTS: Baseline total, animal and vegetable protein intakes were collected using a validated food frequency questionnaire. Relative protein intake expressed as g/kg body weight was calculated and divided into quartiles for data analysis. Baseline and 4-year physical performance measures (normal and narrow 6-meters walking speed and step length in a 6-meters walk) were measured and 4-year change in appendicular skeletal muscle mass (ASM) from baseline was assessed by dual-energy X-ray absorptiometry. Univariate analysis identified age and sex as significant factors associated with change in physical performance measures or ASM, thus adjustments for these factors were made for subsequent analysis of covariance.

RESULTS: Median relative total protein intake was 1.3 g/kg body weight in men and 1.1 g/kg body weight in women. After adjustment for age and sex, relative total protein intake and animal protein intake were not associated with change in physical performance measures and ASM. In contrast, participants in the highest quartile (>0.72 g/kg body weight) of relative vegetable protein intake lost significantly less ASM over 4-year than those in the lowest quartile of relative vegetable protein intake (<=0.40 g/kg body weight) (adjusted mean ± SE: 0.270 ± 0.029 vs. 0.349 ± 0.030 kg, ptrend=0.025). There was no association between relative vegetable protein intake and change in physical performance measures.

CONCLUSIONS: Higher protein intake from vegetable source was associated with reduced muscle loss in Chinese community-dwelling older people in Hong Kong whereas no association between total and animal protein intake and subsequent decline in muscle mass or physical performance measures was observed in this sample.