This study seeks to enlist healthy volunteers to form a validation cohort. The purpose is to confirm the observed correlations between the gut microbiome and the capacity to produce trimethylamine N-oxide (TMAO), which will be assessed using the oral carnitine challenge test (OCCT).

Carnitine, a nutrient widely found in meat, can promote the use of fatty acids by mitochondria to produce energy in the human body. It was previously thought to be beneficial in helping the body consume fat for energy and might be helpful for muscle training or weight loss. However, some human populations have harmful bacteria in their intestines that compete with the body for the use of carnitine. These bacteria metabolize carnitine to produce potentially harmful Trimethylamine N-oxide (TMAO). This might be one of the reasons why long-term consumption of red meat, which is rich in carnitine, is associated with a higher risk of cardiovascular disease. Therefore, understanding the functional state of one's gut microbiota and whether it is suitable to consume foods rich in carnitine can greatly aid in long-term dietary and health planning. In recent years, we have established an oral carnitine challenge test that (OCCT) can distinguish whether the intestinal bacteria in a subject produce a large amount of TMAO in the body. This was published in the Gut journal in 2019 and is expected to provide dietary or nutritional supplement recommendations for personalized nutrition for the test subjects. However, the value of the carnitine challenge test in distinguishing between high TMAO producers and low TMAO producers, and whether it can serve as an effective reference for whether a subject is suitable to consume large amounts of meat or take carnitine supplements, still needs further experimental verification. This study seeks to enlist healthy volunteers to form a validation cohort. The purpose is to confirm the observed correlations between the gut microbiome and the capacity to produce TMAO, which will be assessed using the OCCT.

Inclusion Criteria:

• adults aged 20 and above who are willing to participate in the trial.

Exclusion Criteria:

1. Under the age of 20
2. History of gastrointestinal surgery
3. History of malignant tumors
4. Those who have used antibiotics, probiotics, or carnitine supplements within the past month will be excluded
5. Liver cirrhosis
6. End-stage kidney disease

Healthy individuals undergoing health examinations at the Health Management Center of National Taiwan University Hospital.