How do you say "serving" in Chinese, as in 1 serving of vegetables or 3 servings of bread, as it relates to nutrition? If you could give an example sentence too then that would be great! Thanks so much.
If it is restaurant food or fast food, you can use either '份' or the corresponding count word (量词). For example, 每份套餐, 每份薯条, 每个汉堡, 每份红烧肉, etc.
If it is a snack or drink, we directly use the mass or volume for 'serving'. For example: 每 100 mL 可乐 (cola)，每 100 g 薯片, etc.
Below is an empty nutrition label (used as the standard format) published by Ministry of Health of P.R.C. (中国卫生部). See http://www.gov.cn/gzdt/2008-01/11/content_856260.htm. What you want is the title of the second column.
For macroscopic semantics
Q: What is included in this set meal? A: 一份火腿，两份蔬菜，两份果汁 Q: What else you want to order, sir? A: 一例番茄炒蛋，一例糖醋排骨，一例果盘
You can also just use corresponding unit for each object to express " serving of "
like "一盘水果" "一瓶饮料" "一块排骨" "一条鱼"
For microscopic semantics
Q: What is included in this bottle of drink A: 100毫克维生素，10毫克碳水化合物，20克糖
Here under microscope, scientific unit is often used like "gram 克" "milligram 毫克"