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Table 3 Prospective Observational Studies that met the Inclusion Criteria

From: Causal assessment of dietary acid load and bone disease: a systematic review & meta-analysis applying Hill's epidemiologic criteria for causality

Study Year Population Exposures Outcomes Results Potential confounders controlled or stratified Potential confounders not controlled
Feskanich 1996 Women 35 to 59 years Protein intake Fractures Protein intake was associated with increased risk of forearm fracture; no association between protein intake and hip fractures. Age, BMI, change of BMI, estrogen status, smoking, energy intake, physical activity, calcium, potassium, and vitamin D intakes. Family history of osteoporosis, baseline BMD
Munger 1999 Postmenopausal women Protein intake Hip fractures Protein intake was associated with lower hip fracture risk. Age, body size, parity, smoking, alcohol intake, estrogen use, physical activity Weight loss during follow-up, family history of osteoporosis, baseline BMD, vitamin D status, calcium intake
Tucker 2001 Adults 69 to 97 years Fruit & vegetable nutrients, & protein Change of BMD Potassium, fruit & vegetable intakes among men were associated with less BMD loss. Protein intakes were associated with less BMD loss. Energy intake, age, sex, weight, BMI, smoking, caffeine, alcohol intake, physical activity, calcium intake, calcium and/or vitamin D supplements, season, current estrogen use. Weight loss during follow-up, family history of osteoporosis, baseline BMD
Promislow 2002 Adults 55 to 92 years Protein intake Change of BMD Protein intake was associated with increased BMD over 4 years. Energy intake, calcium intake, diabetes, number
of years postmenopausal, exercise, smoking, alcohol,
thiazides, thyroid hormones, steroids, and estrogen,
body weight change
Family history of osteoporosis, baseline BMD
Kaptoge 2003 Adults 67 to 79 years Fruit, vegetables, vitamin C Change of BMD No associations between nutrients and BMD loss. In women, vitamin C was associated with less BMD loss. No associations for fruit and vegetable intakes. Sex, age, BMI, weight change, physical activity, smoking, family history, energy intake. Baseline BMD, estrogen status, vitamin D status, calcium intake
Rapuri 2003 Women 65 to 77 years Protein intake Change of BMD No association between protein intake and the rate of bone loss. Age, BMI, intakes of calcium, energy, fiber, vitamin D status, and alcohol, smoking, physical activity. Weight loss during follow-up, baseline BMD, family history of osteoporosis
MacDonald 2004 Premenopausal women Fruit & vegetables nutrients Change of BMD Among menstruating and perimenopausal women, intakes of vitamin C and magnesium, but not potassium, were associated with change of BMD. Age, weight, change in weight, height, smoking, physical activity, socioeconomic status, baseline BMD. Family history of osteoporosis, calcium intake, vitamin D status
Dargent-Molina 2008 Postmenopausal women Protein & diet acid load Fractures No overall association between protein intake and acid excretion with fracture risk; in the lowest calcium intake quartile, protein intake was associated with fracture risk Age, BMI, physical activity, parity, maternal history of hip fracture, hormonal therapy, smoking, alcohol, energy intake. Weight loss during follow-up, baseline BMD, vitamin D status.
Thorpe 2008 Peri- and Postmenopausal women Protein Wrist fractures Protein intake was associated with lower risk of wrist fracture, for both vegetable and meat protein. Age, height, weight, BMI, education, any fracture since age 35, parity, smoking, alcohol use, diabetes mellitus, rheumatoid arthritis, physical activity, years since menopause. Estrogen status, calcium intake
Pedone 2009 Women 60 to 96 years Potential renal acid load Change of BMD Protein intake was associated with a lower loss of BMD. Physical activity, energy intake, renal function, vitamin D status, estrogen status, baseline BMD. Weight loss during follow-up, family history of osteoporosis, calcium intake.
Beasley 2010 Women 14 to 40 years Protein intake Change of BMD No association between protein intake and change of BMD. Age, race-ethnicity, age of menarche, time since menarche, family history of fracture, BMI, physical activity score, calories, dietary calcium, phosphorous, dietary vitamin D, magnesium, fluoride, alcohol, smoking, contraceptive use, prior pregnancy, and education  
Fenton 2010 Adults 25 years+ Urine pH, urine potassium, sodium, calcium, magnesium, phosphate, sulfate, chloride, and acid excretion, controlled for urine creatinine Change of BMD and fractures No associations between urine pH or acid excretion and either the incidence of fractures or change of BMD Age, gender, family history of osteoporosis, BMI, change in BMI, baseline BMD, estrogen status, kidney disease, smoking, thiazide diuretics, bisphosphonates, physical activity, calcium intake, and vitamin D status, urine creatinine,.  
  1. * BMD = bone mineral density; BMI = body mass index