Table 1 Studies investigating the association between milk, dairy protein, and dairy products and IGF-I, stratified by study type and ordered by year of publication
Author (year) | Intervention or exposure | Length of follow-up | Total sample size | Age of subjects (years) | Ethnicity (% male) | Diet assessment | Measure | Effect estimate | Overall risk of bias |
|---|---|---|---|---|---|---|---|---|---|
RCTs | |||||||||
Cadogan (1997) [50] | Milk (1 pint supplement/day) versus usual diet | 18 months | 82 | 12.2 | Caucasian (0) | 7 days weighed food record | Difference in IGF-I between intervention and control | p = 0.023; significantly higher IGF-1 levels in intervention | Unclear |
Heaney (1999) [51] | Milk supplement (3 × 8 oz/day) versus no supplement | 12 weeks | 204 | 65.2 | Caucasian (35.3) | 3 days food record | Difference in IGF-I between baseline and follow-up in intervention and control | p < 0.001; IGF-I increased in intervention (+12 ng/ml), not in control (−2.0 ng/ml) | Unclear |
Ben-Shlomo (2005) [28] | Milk supplement (NS) versus no supplement | 25 years | 644 | 25 | Caucasian (53.6) | Questionnaire | Difference in IGF-I between intervention and control | p = 0.01; r= −9.5 (95% CI −16.6−2.27) | Unclear |
Zhu (2005) [52] | Ca milk (330 ml/sch.day); CaD milk (330 ml/sch.day) vs no supplement | 12; 24 months | 606 | 10 | Asian (0) | n/a | Baseline versus 24-month follow-up (Ca and CaD milk) | p < 0.001, significantly higher IGF-1 levels in both Ca and CaD milk compared to control | Unclear |
Non-randomized experimental studies | |||||||||
Hoppe (2004) [41] | Milk (1.5 l of skimmed milk/d) versus low-fat meat intake (250 g/day) | 1 week | 24 | 8 | Caucasian (100) | FFQ | Baseline versus 24-month follow-up | p < 0.001; 19% in increase IGF-1 at 24 months in milk intake arm | Unclear |
Rich-Edwards (2007) [30] | Mongolians: 710 ml milk/d for 1 month versus usual diet USA girls: 710 ml low-fat (2%) milk/d for 1 week versus macronutrient substitute for 1 week | 1 month; 1 week | 46 28 | 7.6 | Asian (50) | 7 days FFQ | Mongolia pre- vs postintervention USA substitute versus milk | Mongolians: p < 0.0001, significantly higher IGF-1 levels in intervention USA intervention: p = 0.35 | Low |
Prospective studies (cohort) | |||||||||
Colangelo (2005) [29] | Milk (servings/day): (ethnic subgroups) | 8 years | 459 682 | 31.5 32.5 | Black Caucasian (100) | FFQ (quantatative with interviewer) | Per quantile change in milk servings/day | Blacks: IGF-1 p = 0.05, increase in IGF-1 Caucasian: IGF-1 p = 0.31 | Unclear |
Martin (2007) [27] | Milk & milk products (g) | 65 years | 727 | 5.8 (baseline) | Caucasian (46) | 7 days household inventory at baseline; FFQ at follow-up | Percentage change in IGF-I per SD | p = 0.06; −3.2% (95% CI −6.5, 0.07) | Moderate |
Hrolfsdottir (2013) [54] | 0–150 ml milk/day versus > 150-600 ml milk/day | 20 years | 436 | Gest. wk30 (baseline) | Caucasian (51.9) | Questionnaire | Percentage change in IGF-I per SD | p = 0.12; 8.3% (95% CI −2.2, 20.0) | Unclear |
Joslowski (2013) [55] | Dairy protein intake (tertiles) | >18 years of age | 213 | 9–15 (baseline) | Caucasian (45.6) | 3 days weighed diet records (x2) | p value for trend in linear regression models | p > 0.9 | Unclear |
Tsilidis (2013) [34] | Dairy protein intake (% energy) | NS | 4105 | 60–69 | Caucasian (100) | Questionnaire | Per tertile change in circulating IGF-1 and IGFBP-3 concentrations by dietary protein sources | p = 0.01, increase in IGF-1 | Moderate |
Retrospective studies (cross-sectional) | |||||||||
Signorello (2000) [56] | Dairy products intake (g) | 1 year | 153 | 70–74 | Caucasian (100) | FFQ (interviewer administered) | Percentage change in IGF-1 is per one quintile intake of dairy products | p = 0.57; −1.7(95% CI −7.4, 4.4) | Unclear |
Mucci (2001) [35] | Dairy products (1 serving/day increment) | 1 year | 112 | 67.7 | Caucasian (100) | FFQ | Percentage change in IGF-I per 1 serving/day increment | p = 0.41; 2.4% (95% CI −3.2, 8.3) | Moderate |
Ma (2001) [36] | Skim/low-fat milk (8 oz glasses) | 18 weeks | 318 | 40–84 | Caucasian (100) | 19-item food report | p value for trend in tertiles of skim/low-fat milk intake | p = 0.0003, increase in IGF-1 | Moderate |
Holmes (2002) [37] | Milk intake (servings/day) | NA | 1037 | 50.5 | Caucasian (0) | FFQ | p value for trend in quartiles of milk intake | p = 0.01, increase in IGF-1 | Moderate |
Giovannucci (2003) [38] | Milk intake (1 serving increment/day) | NA | 753 | 41–86 | Caucasian (100) | Semi-quantitative FFQ | Change in plasma IGF-1 per 1 serving/day increment | p < 0.05; Δ 5.4 ng/ml, increase in IGF-1 | Moderate |
Gunnell (2003) [39] | Dairy products (g/week) | NA | 344 | 62.2 | Caucasian (100) | FFQ | Change in IGF-1 per SD increase | p = 0.09; r = 4.4 (95% CI −0.8, 9.7) | Moderate |
DeLellis (2004) [40] | Total milk intake (g/1000 kcal/day) | NA | 490 | 65 | Caucasian (100) | Questionnaire | P value for trend in quartiles of total dairy intake (g/1000 kcal/day) | p = 0.66 | Moderate |
Hoppe (2004) [41] | Milk intake (g/day) | 1 week | 90 | 2.5 | Caucasian (60) | Questionnaire | Change in IGF-1 per unit increase in milk intake | p = 0.045; b = 0.049 (SE 0.024) | Moderate |
Larsson (2005) [57] | Total milk (g/day) | 1 year | 226 | 60.5 | Caucasian (100) | 24 h telephone interviews (x14) | Difference in IGF-I serum concentration per SD | p = 0.61; b = −1.7 (95% CI −8.2, 4.8) | Unclear |
Morimoto (2005) [42] | Milk (servings/week) | NA | 333 | 59.8 | Caucasian (40.2) | Questionnaire | Per quantile change in milk servings/day | p < 0.05, increase in IGF-1 | Moderate |
Rogers (2006) [43] | Milk intake; dairy product intake (g) | NA | 744 | 7–8 | Caucasian (54.3) | 3 days unweighted diet record | Percentage change in IGF-1 per 100 g increase in cows milk/dairy product | p = 0.24; 1.11 (95% CI 20.70, 2.94) | Moderate |
McGreevy (2007) [31] | Dairy (servings/day) | NA | 233 | 61 55 | Caucasian Black (100) | 2000 Brief block questionnaire | Per quantile change in milk servings/d | Caucasian: p = 0.82 Black: p = 0.03, increase in IGF-1 | Moderate |
Norat (2007) [44] | Milk & milk beverages (NS) | 12 months | 2109 | 54.5 | Caucasian (0) | Questionnaire | P value for trend in quintiles of milk intake | p = 0.007, increase in IGF-1 | Moderate |
Budek (2007) [45] | Milk intake (g/day) | NA | 56 | 8.1 | Caucasian (100) | 3 days weighed food record | Change in IGF-1 per unit increase in milk/dairy protein intake | p = 0.03; b = 0.05, increase in IGF-1 | Moderate |
Crowe (2009) [46] | Dairy protein intake (% energy) | NA | 1142 | 59.9 | Caucasian (100) | Questionnaire | P value for trend in quintiles of dairy protein intake (%) | p < 0.001, 2.4% increase in IGF-1 | Moderate |
Esterle (2009) [32] | Milk intake (ml/day) | NA | 98 | 15.7 | Caucasian (0) | 7 days food recall, nutritionist | Difference between lowest (<55) and highest (>260) tertiles of milk intake | p < 0.015, increase in IGF-1 | Serious |
Maruyama (2009) [47] | Milk 3–4 servings/week plus | NA | 10,350 | 63 | Asian (100) | FFQ | p value for trend in quartiles of milk intake | p < 0.001, increase in IGF-1 | Moderate |
Young (2012) [48] | Dairy products (g) | 12 months | 1798 | 62 | Caucasian (100) | FFQ (12 months) | Percentage change in IGF-I per SD | p < 0.001; 4.88% (95% CI 2.52, 7.23) | Moderate |
Thorisdottir (2013) [33] | Dairy protein intake (% energy) | 6 years | 137 | 6 | Caucasian (0) | 3 days weighed food record | Dairy protein positive predictor of IGF1 in 6 year old girls | p = 0.0002; Δ 5.4 ug/l (95% CI 2.5, 8.2), increase in IGF-1 | Serious |