The Precision Nutritional Management for Diabetes trial (PNMD; NCT03708887) is a randomized clinical trial in 415 diabetic patients investigating whether taking daily dietary supplements of omega-3 fatty acids (1.5 or 3 grams) improves glucose and lipid homeostasis in Chinese diabetic patients. This ancillary study is being conducted among PNMD participants and will examine whether fish oil supplements affect A) cognitive function, B) sleep quality, and C) bone mineral density. Cognitive function, sleep quality, and bone mineral density will be evaluated at baseline and post-intervention. The Mini-Mental State Exams (MMSE) will be conducted to evaluate the cognitive function of participants. The Pittsburgh Sleep Quality Index (PSQI) will be calculated through questionnaires to evaluate sleep quality. The Dual-emission X-ray Absorptiometry (DXA) will be assessed to measure the bone density.

Inclusion Criteria:

• Diagnosed type 2 diabetes according to WHO diagnostic criteria or those on the use of diabetic medications;
• Between 40 and 75 years old (postmenopausal women);
• Have never used n-3 PUFA supplements before or have stopped using them for more than six months.

Exclusion Criteria:

• Type 1 diabetes;
• Coronary heart disease, stroke, cancer, hepatic or kidney disease;
• Pregnancy or lactation;
• Allergy to fish;
• Have participated in other clinical trials in the last three months.