The investigators hypothesize that spirulina-silicon supplementation will lead to an improvement in vasomotor endothelial function, followed by decreased arterial wave velocity on the aorta and central arterial pressure compared to placebo subjects.

Inclusion Criteria:

• The subject must have given their free and informed consent and signed the consent form
• The subject must be a member or beneficiary of a health insurance plan
• The subject is available for 6 months of follow-up
• The subject must not have any pre-existing chronic illness nor any revealed during the pre-inclusion visit, either treated or requiring treatment according to current recommendations

Exclusion Criteria:

• The subject is participating in an interventional study, or is in a period of exclusion determined by a previous study
• The subject refuses to sign the consent
• It is impossible to give the subject informed information
• The patient is under safeguard of justice or state guardianship
• Presence of a chronic cardio-vascular and/or metabolic illness, known or revealed by the pre-inclusion exam and requiring treatment in accordance to official recommendations (HAS)
• Any other chronic pathology requiring medical treatment
• History of uric acid metabolism disorders (hyperuricemia, gout, urolithiasis).
• Subject presenting a loss of limitation of autonomy
• Treated with hormone replacement therapy in females
• Active smoker or drug user
• Presence of an abnormality revealed by the pre-inclusion biological assessment of dyslipidemia justifying a prescription medication, diabetes or intolerance to glucose (insulin resistance).
• Presence of a stenosis (greater than 50% in diameter, NASCET method) or carotid occlusion revealed by the echo-Doppler screening test.
• Presence of an aneurysm (dilation> 30 mm) of the abdominal aorta revealed by the echo-Doppler screening test.
• Arteriopathy of the lower limbs (toe systolic pressure (tsp) <0.7) revealed by the screening test (SysToe™ device).
• Subject already taking a food supplement based on spirulina or silicon.
• History of cardio-vascular disease or heart attack
• Subject develops a chronic illness requiring medical treatment for more than 7 days or a surgical intervention leading to incapacity for more than 7 days,or a pathological event during the 14-day period before each follow-up visit, or a serious adverse event