Effect of changes in food groups intake on magnesium, zinc, copper, and selenium serum levels during 2 years of dietary intervention.

BACKGROUND: Essential elements in serum are related to specific changes in food groups intake. OBJECTIVE: To address the effect of 2-year food intake changes in an intervention study on serum concentrations of magnesium, zinc, copper, and selenium. METHOD: Two hundred thirty-one participants, a subgroup of the Dietary Intervention Randomized Control Trial (DIRECT) study (age = 52 years; body mass index = 32.8 kg/m(2); 85% males) randomized to low-fat, Mediterranean, or low-carbohydrate diets in a 2-year dietary intervention trial were followed for serum concentrations determined using inductively coupled plasma-mass spectrometry. Changes in the intake of 11 food groups were evaluated by food frequency questionnaires. RESULTS: Using multivariate regression models, adjusted for age, sex, baseline body weight (kg), and changes in intakes of 11 food groups (g/d), at 12 months, serum element elevations were observed mainly in the low-carbohydrate group: selenium, by increasing consumption of fats and oils (ß = 0.415, p = 0.009) and legumes (ß = 0.183, p = 0.010) and decreasing fruit intake (ß = -0.438, p = 0.030); copper, by increasing consumption of legumes (ß = 0.453, p = 0.018) and dairy products (ß = 0.320, p = 0.039); magnesium by increasing fish consumption (ß = 0.374, p = 0.042) in the low-carbohydrate group and in the entire study population (ß = 0.237, p = 0.016); and zinc exclusively in the low-fat group by decreasing consumption of fats and oils (ß = -0.575, p = 0.022). At 24 months, serum elements were elevated mainly in the low-fat diet group, mostly by decreasing intake of snacks, sweets, and cakes: zinc (ß = -0.570, p = 0.027), copper (ß = -0.649, p = 0.012), and selenium (ß = -0.943, p < 0.001). Also in this group, magnesium levels were elevated by increasing vegetable intake (ß = 0.395, p = 0.041), copper by increasing fruit intake (ß = 0.375, p = 0.025), and selenium by increasing consumption of bread, pasta, and cereals (ß = 0.751, p = 0.011). The entire group, further adjusted to assigned diet type, increased selenium (ß = 0.294, p = 0.004) and copper (ß = 0.220, p = 0.038) by increasing consumption of bread, pasta, and cereals; selenium level was also predicted by decreasing consumption of snacks, sweets, and cakes (ß = -0.256, p = 0.014). Introducing energy expenditure, expressed in metabolic equivalents (MET = 1 kcal·kg(-1)·h(-1)), as an additional variable emphasized the negative effect of sweets and cakes on increasing serum concentrations of zinc, copper, and selenium after 24 months (ß = -0.549, p = 0.021; ß = -0.669, p = 0.012; ß = -0.982, p < 0.001, respectively), especially in the low-fat diet group. No significant associations between changes in food groups intake and the 4 elements were found in the Mediterranean diet group. CONCLUSIONS: During this 2-year intervention, serum concentrations of 4 essential elements were associated with a diversity of food group intake patterns. Comprehensive predictors for elevating zinc, copper, and selenium in serum included decreasing consumption of sweets and cakes while increasing consumption of bread, cereals, and pasta.

Weight loss with a low-carbohydrate, Mediterranean, or low-fat diet.

BACKGROUND: Trials comparing the effectiveness and safety of weight-loss diets are frequently limited by short follow-up times and high dropout rates. METHODS: In this 2-year trial, we randomly assigned 322 moderately obese subjects (mean age, 52 years; mean body-mass index [the weight in kilograms divided by the square of the height in meters], 31; male sex, 86%) to one of three diets: low-fat, restricted-calorie; Mediterranean, restricted-calorie; or low-carbohydrate, non-restricted-calorie. RESULTS: The rate of adherence to a study diet was 95.4% at 1 year and 84.6% at 2 years. The Mediterranean-diet group consumed the largest amounts of dietary fiber and had the highest ratio of monounsaturated to saturated fat (P<0.05 for all comparisons among treatment groups). The low-carbohydrate group consumed the smallest amount of carbohydrates and the largest amounts of fat, protein, and cholesterol and had the highest percentage of participants with detectable urinary ketones (P<0.05 for all comparisons among treatment groups). The mean weight loss was 2.9 kg for the low-fat group, 4.4 kg for the Mediterranean-diet group, and 4.7 kg for the low-carbohydrate group (P<0.001 for the interaction between diet group and time); among the 272 participants who completed the intervention, the mean weight losses were 3.3 kg, 4.6 kg, and 5.5 kg, respectively. The relative reduction in the ratio of total cholesterol to high-density lipoprotein cholesterol was 20% in the low-carbohydrate group and 12% in the low-fat group (P=0.01). Among the 36 subjects with diabetes, changes in fasting plasma glucose and insulin levels were more favorable among those assigned to the Mediterranean diet than among those assigned to the low-fat diet (P<0.001 for the interaction among diabetes and Mediterranean diet and time with respect to fasting glucose levels). CONCLUSIONS: Mediterranean and low-carbohydrate diets may be effective alternatives to low-fat diets. The more favorable effects on lipids (with the low-carbohydrate diet) and on glycemic control (with the Mediterranean diet) suggest that personal preferences and metabolic considerations might inform individualized tailoring of dietary interventions. (ClinicalTrials.gov number, NCT00160108.)