This is the type of vitamin D that circulates in the blood. Itâs considered a good reflection of how much vitamin D youâve absorbed from sun exposure and taken in from foods. Levels of vitamin D are expressed in nanomoles/liter (nmol/L) or nanograms/milliliter (ng/mL). According to the Office of Dietary Supplements (ODS), the results can indicate the following:
Other Health Conditions. On rare occasions, being tired after a meal or simply sleepy all the time could be a sign of another health problem. Diabetes, anemia, underactive thyroid, celiac disease, food intolerance, and sleep apnea can make post-meal drowsiness worse.
For anyone with anemia, drinking coffee/tea/red wine with a meal could be problematic in that it will reduce the iron absorbed from the food consumed. After a heavy meal the body is in the process of active digestion. Which means it requires a lot of blood supply to that area. One of the reasons people feel sleepy post lunch is because of this.