A leadless implantable medical device includes a housing formed from a battery and an end cap. The food supplements described comprise a substance which increases nitric oxide production in the body, and, a source of amino acids. The OEC a) is soluble in the liquid of the phase that partially fills the positive electrode pores, b) is electrochemically activated at a potential above the equilibrium cell voltage and c) is capable of evolving oxygen gas by oxidizing a metal oxide discharge product produced during discharge of the rechargeable metal-air battery.