MTNRI1B is involved in melatonin receptivity. Found mainly in the eyes and brain and involved in the body’s receptivity to melatonin, the 'sleep hormone' released in response to the onset of darkness. Melatonin is involved in several processes in the body including circadian rhythms, mood regulation, anxiety, sleep appetite, immune responses, and heart function. Variants are associated with disturbed sleep and increased risk of impaired blood glucose metabolism leading to type 2 diabetes.
If you have the GC allele, then you are more likely to experience disturbed sleep patterns, particularly early waking, increasing your risk of impaired blood sugar metabolism and type 2 diabetes. Your risk increases with low exercise and a diet high in simple carbohydrates (sugar). Aim to get between 7-9 hrs sleep per night, increase your physical activity, decrease/avoid intake of simple carbohydrates and bright light/ electronics (particularly before bed), and increase tryptophan-rich foods to encourage healthy melatonin production and activity.