You will be provided with a reference and some statements. Please determine whether each statement is 'supported', 'unsupported', or 'unknown' with respect to the reference. Please note:
First, assess whether the reference contains any valid content. If the reference contains no valid information, such as a 'page not found' message, then all statements should be considered 'unknown'.
If the reference is valid, for a given statement: if the facts or data it contains can be found entirely or partially within the reference, it is considered 'supported' (data accepts rounding); if all facts and data in the statement cannot be found in the reference, it is considered 'unsupported'.

You should return the result in a JSON list format, where each item in the list contains the statement's index and the judgment result, for example:
[
    {
        "idx": 1,
        "result": "supported"
    },
    {
        "idx": 2,
        "result": "unsupported"
    }
]

Below are the reference and statements:
<reference>
1. Am J Clin Nutr. 2016 May;103(5):1260-6. doi: 10.3945/ajcn.116.131466. Epub
2016  Apr 6.

Long-term magnesium supplementation improves arterial stiffness in overweight 
and obese adults: results of a randomized, double-blind, placebo-controlled 
intervention trial.

Joris PJ(1), Plat J(2), Bakker SJ(3), Mensink RP(4).

Author information:
(1)Department of Human Biology, NUTRIM School of Nutrition and Translational 
Research in Metabolism, Maastricht University Medical Center, Maastricht, 
Netherlands; Top Institute of Food and Nutrition, Wageningen, Netherlands; and 
p.joris@maastrichtuniversity.nl.
(2)Department of Human Biology, NUTRIM School of Nutrition and Translational 
Research in Metabolism, Maastricht University Medical Center, Maastricht, 
Netherlands;
(3)Top Institute of Food and Nutrition, Wageningen, Netherlands; and Department 
of Internal Medicine, University of Groningen, University Medical Center 
Groningen, Groningen, Netherlands.
(4)Department of Human Biology, NUTRIM School of Nutrition and Translational 
Research in Metabolism, Maastricht University Medical Center, Maastricht, 
Netherlands; Top Institute of Food and Nutrition, Wageningen, Netherlands; and.

BACKGROUND: Epidemiologic studies have suggested a protective effect of 
magnesium intake on cardiovascular disease risk. However, intervention trials of 
magnesium supplementation on blood pressure and conventional cardiometabolic 
risk markers are inconsistent. Effects on vascular function markers related to 
cardiovascular disease risk have rarely been studied.
OBJECTIVE: The objective was to evaluate the effects of long-term magnesium 
supplementation on arterial stiffness.
DESIGN: We performed a 24-wk, randomized, double-blind, placebo-controlled 
intervention study. Fifty-two overweight and slightly obese individuals (30 men 
and 22 postmenopausal women, mean ± SD age: 62 ± 6 y) were randomly allocated to 
receive either 3 times daily magnesium (3 × 117 mg or 350 mg/d) or placebo 
capsules. Twenty-four-hour urine collections and 24-h ambulatory blood pressure 
assessments were performed at the start and end of the study. Carotid-to-femoral 
pulse wave velocity (PWVc-f) was assessed at baseline, after 12 wk, and at week 
24.
RESULTS: Serum magnesium concentrations did not differ after 12 wk but tended to 
increase after 24-wk magnesium supplementation compared with placebo by 0.02 
mmol/L (95% CI: 0.00, 0.04 mmol/L; P = 0.09). Twenty-four-hour urinary magnesium 
excretion increased by 2.01 mmol (95% CI: 1.22, 2.93 mmol; P < 0.001) at week 
24. PWVc-f was not changed after 12 wk (0.0 m/s; 95% CI: -0.6, 0.5 m/s; P = 
0.90) but was improved in the magnesium compared with the placebo group by 1.0 
m/s (95% CI: 0.4, 1.6 m/s; P = 0.001) after 24 wk. Office and 24-h ambulatory 
blood pressure levels were not changed. No adverse events were observed.
CONCLUSION: Our data indicate that a daily magnesium supplement of 350 mg for 24 
wk in overweight and obese adults reduces arterial stiffness, as estimated by a 
decrease in PWVc-f, suggesting a potential mechanism by which an increased 
dietary magnesium intake beneficially affects cardiovascular health. This trial 
was registered at clinicaltrials.gov as NCT02235805.

© 2016 American Society for Nutrition.

DOI: 10.3945/ajcn.116.131466
PMID: 27053384 [Indexed for MEDLINE]
</reference>

<statements>
1. A 24-week randomized, double-blind, placebo-controlled trial in overweight and obese adults (mean age 62 years) found that daily supplementation with 350 mg magnesium reduced carotid-femoral pulse wave velocity (PWV) by about 1.0 m/s compared with placebo, indicating improved arterial stiffness. Blood pressure did not change significantly, and no serious adverse events were reported.
2. Magnesium, zinc, and selenium supplements are widely available, inexpensive, and have been used in many trials, demonstrating practical feasibility for chronic administration. Adherence is generally good, although gastrointestinal side effects (especially with magnesium) can limit tolerability.
3. Magnesium stands out as the metal ion with the most consistent observational, genetic, and mechanistic support for a protective role in cardiovascular disease, and supplementation appears to improve some cardiovascular risk factors and surrogate markers in certain populations. However, large randomized trials with hard endpoints (MI, stroke, CVD mortality) are still needed before magnesium supplementation can be widely recommended as a primary preventive therapy.
</statements>

Begin the assessment now. Output only the JSON list, without any conversational text or explanations.