Leyla Weighs In: Oolong Tea, Supplement Absorption, and How Gut Signals Shape Memory

Nutritionist Leyla Muedin answers a listener question about taking many supplements with oolong tea, explaining that tea tannins can interfere with vitamin and mineral absorption; because oolong is partially oxidized, its tannin level falls between green and black tea, so she recommends taking supplements with water and separating them from tea or coffee by at least an hour (ideally 1.5–2 hours). She then reviews research in Nature Communications from USC on how gut signals via the vagus nerve may influence which food experiences become memories: in rats, nutrient-rich foods increased acetylcholine signaling to the hippocampus, supporting memory for food location, while sweetness without calories did not. Over time, high-fat/high-sugar diets weakened this gut–hippocampus communication and memory performance, with implications for obesity, diabetes/prediabetes, and cognitive decline, and possible future vagus-nerve-based approaches.