Here is the design of a clinical trial:

Official Title: The Effects of Magnesium Salts on Vascular Stiffness: A Randomized Controlled Trial in Healthy Overweight and Slightly Obese Men and Women

Included conditions:
- Vascular Stiffness
- Blood Pressure

Study Armgroups:
- {'label': 'Magnesium Citrate', 'type': 'EXPERIMENTAL', 'description': '450 mg of Magnesium Citrate per day', 'interventionNames': ['Dietary Supplement: Magnesium Citrate']}
- {'label': 'Magnesium Sulfate', 'type': 'EXPERIMENTAL', 'description': '450 mg of Magnesium Sulfate per day', 'interventionNames': ['Dietary Supplement: Magnesium Sulfate']}
- {'label': 'Magnesium Oxide', 'type': 'EXPERIMENTAL', 'description': '450 mg of Magnesium Oxide per day', 'interventionNames': ['Dietary Supplement: Magnesium Oxide']}
- {'label': 'Placebo', 'type': 'PLACEBO_COMPARATOR', 'interventionNames': ['Drug: Placebo']}

Interventions:
- {'type': 'DIETARY_SUPPLEMENT', 'name': 'Magnesium Citrate', 'description': '450 mg of Magnesium Citrate per day (6 capsules per day) for 24 weeks', 'armGroupLabels': ['Magnesium Citrate']}
- {'type': 'DIETARY_SUPPLEMENT', 'name': 'Magnesium Sulfate', 'description': '450 mg of Magnesium Sulfate per day (6 capsules per day) for 24 weeks', 'armGroupLabels': ['Magnesium Sulfate']}
- {'type': 'DIETARY_SUPPLEMENT', 'name': 'Magnesium Oxide', 'description': '450 mg of Magnesium Oxide per day (6 capsules per day) for 24 weeks', 'armGroupLabels': ['Magnesium Oxide']}
- {'type': 'DRUG', 'name': 'Placebo', 'description': 'The placebo capsules will contain starch (Amylum solani) for 24 weeks', 'armGroupLabels': ['Placebo']}

Primary Outcomes:
- {'measure': 'Change in vascular stiffness', 'description': 'Measured from carotid-femoral pulse wave velocity (PWV). For this assessment, a SphygmoCor will be used (SphygmoCor v9, AtCor Medical).', 'timeFrame': 'Baseline, FU-1 (2 weeks), FU-2 (12 weeks), and FU-3 (24 weeks)'}

Please estimate the sample size based on the assumption: 
The sample size calculation is based on a significance level (probability) of 0.05, a power of 0.80, and a 10% dropout rate. Additionally, it is assumed that only 50% of the subjects included in the screening will meet all inclusion criteria and be willing to participate.
Sample size calculation
        The current study is powered on arterial stiffness, the primary endpoint. The required sample size for noninferiority testing is calculated based on a margin of 0.5âm/s, a probability of 0.05 and a power of 0.80. Therefore, 41 subjects per magnesium group are needed. To compare magnesium citrate with placebo, we assume that the number of subjects per group calculated for a two-arm trial (nâ=â24) is sufficient. Because a 10% dropout rate is expected, 162 will be recruited to start the study. By taking into account that only 50% of the subjects included in the screening will meet all inclusion criteria and are willing to participate, 324 subjects are expected to participate in the screening visits.
        This sample size calculation is based on an intra-subject variability of 0.9âm/s and a 1.0âm/s change in the PWVcâf after 24âweeks of magnesium supplementation found in our previous study [9]. The equivalence margin of 0.5âm/s is based on the observed effect [9], which is 50% of the magnesium citrate supplementation effect compared to placebo. For the calculation of the sample size, the formula of Julious [21] was used.