Diet and lifestyle choices, notably the Western-type diet, are implicated in oxidative stress and inflammation, factors that elevate the risk of cardiovascular diseases (CVDs) and type 2 diabetes mellitus (T2DM). In contrast, the Mediterranean of diet, rich in antioxidants, appears to have protective effects against these risks. This article highlights the dual role of diet in generating molecular hydrogen (H{}_2) in the gut, and H{}_2’s subsequent influence on the pathophysiology and prevention of CVD and T2DM. Dietary fiber, flavonoids, and probiotics contribute to the production of liters of H{}_2 in the gut, functioning as antioxidants to neutralize free radicals and dampen inflammation. In the last two decades, mounting evidence has demonstrated that both endogenously produced and exogenously administered H{}_2, whether via inhalation or H{}_2-rich water (HRW), have potent anti-inflammatory effects across a wide range of biochemical and pathophysiological processes. Recent studies indicate that H{}_2 can neutralize hydroxyl and nitrosyl radicals, acting as a cellular antioxidant, thereby reducing oxidative stress and inflammation—leading to a significant decline in CVDs and metabolic diseases. Clinical and experimental research support the therapeutic potential of H{}_2 interventions such as HRW in managing CVDs and metabolic diseases. However, larger studies are necessary to verify the role of H{}_2 therapy in the management of these chronic diseases.