The aim of the study is to compare the effects of powdered skim milk containing A2 β-casein only versus conventional powdered skim milk containing A1 and A2 β-casein milk on cognition, inflammation, and dietary intake in adults aged 65-75 years.

For inclusion in the study, participants must meet all of the following criteria:

1. Adults aged 65-75 years;
2. Complaint of memory loss for more than 6 months;
3. Base on the Chinese version of Mini Mental State Examination (MMSE), cognitive ability score is lower than the standard cut-off value according to age and education levels: MMSE score≤ 17 points if years of education is 0 year; ≤ 20 points if 6 years or less of education; ≤ 24 points if more than 6 years of education
4. Living and social functions are reduced: activities of daily living (ADL) score ≤18;
5. Not meeting the diagnostic criteria for dementia (Diagnostic and Statistical Manual of Mental Disorders - Fourth Edition), Alzheimer Disease (National Stroke Institute for Neuropathic Speech Disorders and Association for Alzheimer Disease and Related Disorders); no mental disorder, brain damage, or other physical disorders that can lead to cognitive impairment.
6. Agreed not to participate in another interventional clinical research study during the present study;
7. Signed informed consent

Participants must be excluded from the study if they meet any of the following criteria:

1. <65 years; or >75 years
2. Neurological examination showed focal signs of central nervous system disorder such as hemiplegia, dysesthesia, aphasia; history of cerebrovascular diseases (including hemorrhagic and ischemic types), internal brain trauma or fracture;
3. Asthmatic bronchitis, severe hypertension, angina and severe infection;
4. Mental disorders such as depression and anxiety; endocrine system diseases (such as hyperthyroidism, hypothyroidism, systemic lupus erythematosus, rheumatoid arthritis);
5. Newly diagnosed, progressing or advanced tumors;
6. Visual, reading, hearing impairment or language communication difficulties that significantly affect cognitive function tests;
7. History of alcohol dependence and abuse of psychoactive substances (e.g., antipsychotics, benzodiazepines, cholinesterase inhibitors, sedatives), or use of drugs that affect cognitive function;
8. Neurological diseases (e.g. Parkinson's disease, epilepsy);
9. Antibiotic treatment in previous 2 weeks;
10. Administered immunosuppressive drugs in the 4-weeks preceding screening;
11. Allergy to milk or dairy;
12. Diagnosed lactose intolerance;
13. Other diseases that investigators judged as unsuitable to participate the study.