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Table 1 Study and participant characteristics

From: Effectiveness of interventions to promote healthy diet in primary care: systematic review and meta-analysis of randomised controlled trials

Study (Year)

Country

Study design

Selection of participants

Number of practices

Participants randomised (% Female)

Eligible age range (mean) years

Ethnicity and socioeconomic status

Diet assessment tool

Baron (1990) [33]

UK

RCT

Randomly selected participants registered with a family practice

One group general practice

437 randomised 368 participated (49)

25-60 (41.7)

Social class 1 or 2: controls, 30% men, 24% women; intervention 39% men, 43% women.

Self-administered food frequency questionnaire

Beresford (1997) [35]

USA

Cluster RCT

Participants attending routine visits without major illness

28 physician practices within 6 clinics

2121 (68)

26% > 65 years

White: 91%; Some college education: 73%. Family income below $25000 per year: 28%.

Telephone interview administered food frequency questionnaire

Coates (1999) [28]

USA

RCT

Post menopausal women volunteers, consuming at least 36% energy from fat

University clinical centres in three states

2208 (100)

50-79 (60)

White (55%), Black (28%), Hispanic (16%); <High School (11%), High School (20%), Post high school with no college degree (35%), graduate /post graduate (33%)

Self-administered food frequency questionnaire

Fries (2005) [34]

USA

RCT

Randomly selected participants from physicians’ lists

Three rural Virginia physician practices

754 (64)

18-72 (46.34)

White: 61%, African American: 37%; 8th grade: College degree: 24%; Income < $10,000: 14.69%, ≥$41,000:19%.

Telephone interview administered fat and fibre behaviour questionnaire

Gann (2003) [36]

USA

RCT

Women volunteers aged 20–40 years recruited through advertising and direct mail in Chicago.

One clinic

213 (100)

20-40 (33.4)

76% White, 13.5% Black, 4% Hispanic, 5.5% Asian, 1.5% other; 85% completed college

Telephone interview administered food frequency questionnaire, based on 24 hr diet recall on each of three days

Kristal (2000) [32]

USA

RCT

Randomly selected patients enrolled with an HMO.

Health maintenance organisation

1459 (50)

18-69 (45.8)

White (85.9%), Black (4.5%), Asian (5.8%), Hispanic (3.0%), Other (0.8%); Household income < $25,000 12.2%, ≥$70,000 21.7%.

Telephone interview administered Food Frequency Questionnaire (FFQ) and Diet Habits Questionnaire

Roderick (1997) [29]

UK

Cluster RCT

Unselected patients attending GP surgery practices

8 family practices

956 (50)

35-59 (47.3)

Non-manual occupation, intervention 60%, control 49%; rented accommodation intervention 11%, control 25%.

Self-administered food frequency questionnaire.

Sacerdote (2006) [30]

Italy

RCT

Unselected patients, not obese, no chronic disease

33 general practitioners

3179 (50)

18-65 (44.5)

Not reported

Family physician administered food frequency questionnaire

Stevens (2003) [31]

USA

RCT

Women with recent negative mammogram and total cholesterol ≥200 mg/dl

Health maintenance organization (HMO)

616 (100)

40-70 (53.8)

Minority groups: 7%; College graduates: 40%

Self-administered fat and fibre behaviour questionnaire (FFBQ)

Takahashi (2006) [27]

Japan

RCT

Healthy volunteers in two rural villages, advice given after annual health checks

Not reported

550 (68)

40-69 (56)

Not reported

Self-administered diet history questionnaire (DHQ)