Micronutrients
Several micronutrients found in coffee, including magnesium, potassium, niacin, and vitamin E, could contribute to the observed health effects of coffee consumption. According to the USDA Nutrient database, 8 oz (∼240 ml) of brewed coffee provide 7 mg of magnesium and 1 oz (∼30 ml) of espresso provides 24 mg of magnesium. 22 Thus, one cup of coffee could contribute 1–5% of the recommended dietary allowance (RDA) for magnesium (420 mg/d) in adult men. 23 An 8-oz cup of brewed coffee is reported to provide 116 mg of potassium and a 1-oz shot of espresso 34 mg, 22 suggesting that one cup of coffee contributes only 1–2% of the adequate intake (AI) for potassium (4700 mg/d) in adults. 24 Trigenolline in coffee beans is demethylated to form nicotinic acid during the roasting process. 25 Coffee has been reported to provide 1–3 mg of nicotinic acid per cup. 25 Thus, one cup of coffee could contribute 6–18% of the RDA for niacin (16 mg/d) in adult men. 26 Coffee does not appear to be an important source of dietary vitamin E since one cup provides about 0.2 mg of α-tocopherol and 0.2 mg of γ -tocopherol, 22 about 0.1% of the adult RDA for vitamin E (15 mg/d of RRR-α -tocopherol). 27