Creatine is widely used to improve muscle mass and athletic performance, but it may not be appropriate for everyone. While generally considered safe in healthy individuals, concerns remain for patients with kidney disease, diabetes, hypertension, dehydration, or those taking medications that affect renal function. This article reviews potential risks, explains who should exercise caution, and discusses safer alternatives for preserving muscle mass and healthy aging.

Vitamin D is commonly thought of as a simple nutrient, but medically it functions as a steroid hormone with effects far beyond bone health. Unlike true vitamins, vitamin D is synthesized in the skin, activated through the liver and kidneys, and acts on receptors throughout the body to regulate gene expression. This hormonal role explains its influence on immune function, muscle strength, cardiovascular health, and brain function. Because deficiency is widespread and supplemen