Increasing Calcium Dietary Intake Helps to Control Blood Presure and Body Weight

Mediterranean diet is relatively poor in calcium (about 700 mg/daily) whilst there are several reports indicating beneficial effects of calcium-rich diets. Aim of the preset study is to evaluate the effects of a low-sodium, low-lipid diet enriched in calcium, mainly from vegetables instead of dairy products, on blood pressure, body weight a main parameters of the glucose and lipid metabolisms.

This study is a randomized, parallel group trial that will be performed in the Outpatient Clinic. At least 150 patients with arterial hypertension and/or increased body weight (IMC\> 28 kg/m2) will enter the study program. After a 3 month low-lipid low-salt diet that will be prescribed to all patients, they will be divided in two groups. The first will change the diet to that similar for total calories, percent composition of macronutrients and salt but enriched in calcium (about 1200 mg/daily) whilst the alternative group will continue the first diet. The observation period will be of 1 year with anthropometric (body weight and height, waist circumference), hemodynamic (blood pressure and heart rate) and metabolic (cholesterol, triglycerides, fasting blood glucose, uric acid, calcium, phosphorus, sodium and potassium) controls after 3-6 and 12 months.

The DASH Study showed that the antihypertensive effects of a low-salt, low-lipid diet were significantly potentiated when the diet was enriched in calcium. This target may be reached either increasing the daily consumption of low-lipid milk and dairy products or increasing the daily consumption of calcium-rich vegetables.

In the Italian population the mean daily consumption of calcium is rather low, not exceeding 700 mg/daily whilst it would be desirable a daily consumption of 1200 mg/daily. Unfortunately there are in Italy very few dairy products (particularly low-lipid cheese) that would ensure a variable and palatable calcium-rich diet.

Aims of the present study are:

1. to prepare a low-sodium (about 3 g/daily) diet enrich in calcium (about 1200 mg/daily) and to compare the effects on blood pressure with those of a low-sodium diet similar to it in macronutrients but with a calcium content typical of the Mediterranean diet (no more than 700 mg/daily) (see Table 1);
2. to verify if this diet is able to improve the control of body weight and of the main parameters of the glucose and lipid metabolisms;
3. to evaluate if this diet is palatable enough to be prescribed in a long term study.

Patients:

At least 150 patients with arterial hypertension and/or overweight /obesity (IMC \> 28 kg/m2) will be enrolled.

Methods:

1. evaluation of nutritional habits by an adequate frequency questionnaire at baseline, after a 3-month low-lipid low-sodium diet;
2. anthropometric measures (body weight, height, waist circumference);
3. measurements of blood pressure and heart rate;
4. measurements of serum total and HDL cholesterol serum triglycerides, fasting blood glucose, serum sodium potassium calcium and phosphorus.

Design of the study:

This is a randomized parallel-group study performed in the Outpatient Clinic. Patients enrolled in the study will be prescribed a low-sodium low-lipid diet for 3 months. At the end of the first phase they will be randomly divided in two groups:

1. Group A: patients will change their diet in a diet similar for total daily calories, sodium and macronutrients but enriched in calcium (1200 mg/daily) and will be followed up to 1 year with an intermediate control after the first 3 months;
2. Group B: patients will continue the low-lipid, low-sodium diet up to 1 year with an intermediate control after the first 3 months.

At baseline, after 3, 6 and 12 months of observation, patients will repeat the measurements 1-4 described in the Methods.

Composition in macro and micronutrients of the two diets

NUTRIENTS LOW-SODIUM DIET LOW-SODIUN CALCIUM- ENRICHED DIET PROTEINS (%) 17 17 LIPIDS (%) 27 28 SATURATED FATTY ACIDS (%) 7 7 MONOUNSATURATED (%) 16 17 POLTYUNSATURATED (%) 4 4 CHOLESTEROL ( mg) 132 140 CARBOHYDRATES (%) 56 54 SOLUBLE CHO (%) 18 17 FIBRE (g) 39 42 Na (mg) 1397 1377 K (mg) 3973 4067 Fe (mg) 16 21 Ca (mg) 650 1211 P (mg) 1285 1501

Eligibility Criteria:
Inclusion Criteria:

* age 30-70 years
* IMC \>28 and \< 35 kg/m2
* pharmacological treatment unchanged in the last 3 months

Exclusion Criteria:

* chronic kidney disease
* liver or chronic inflammatory bowel disease
* tumor