The following three types of trademarks can be used for the word "Jian":

1. Medical nutritional products belong to Category 5, such as vitamin preparations, cod liver oil, tonics (medicines), medical lecithin, Edible plant fiber, medical nutritional food, medical nutritional beverage, mineral food additives, etc.

2. Non-medical nutritional products belong to Category 30, such as spirulina, non-medical nutritional drinks, non-medical nutritional capsules, non-medical nutritional powder, etc.

3. Health care services belong to Category 44, such as medical massage, health care, medical assistance, physiotherapy, medical care, medical consultation, psychologists, aromatherapy, telemedicine services, dietary nutrition guidance, etc.

In short, the "Jian" size trademark can be used in multiple categories, depending on the type and category of the trademark involved. It should be noted that when choosing a trademark, you should ensure that the trademark name is legal and easy to remember, and the trademark pattern must also comply with relevant laws, regulations and industry standards.