Most of the discoveries in Chinese herbal medicine were made right at the beginning of TCM (Traditional Chinese Medicine) and acupuncture over 2000 years ago. Ever since, incremental changes have been made. Back in ancient China when experimentation eventually became established rules, there were certain herbs that could not be used together, and if they were, they would become poisonous to humans. Some herbs can only be taken for a certain amount time or at a certain dosage because otherwise, they could be fatal. There were some other herbs that people had to avoid using together because otherwise their strength would be decreased. This is not to say all herbs are so restrictive — most herbs can help people.
Ancient Chinese doctors had a spectrum of classifcation on what is considered just food, just herbs, or foods that are also herbs (or vice versa). What they understood was that food is for our normal needs, and the herbs are for our herbal normal needs (meaning to balance our body in times of trouble). Certain foods can have a detrimental effect on the absorption and activity of the herbs. Mung beans can work either way, meaning it is a food but also an herb. But for the Chinese, everybody knows that you are supposed have mung beans more in the summertime and less or none at all in the winter. They do this because mung beans are naturally cold. They can slow our metabolism and make us feel chilly. However, the other aspect of mung beans that many people don’t know is that mung beans can also detox our bodies or lessen the capabilities of other herbs. That means if you take a Chinese herbal formula for feeling cold easily/feeling fatigued/low spirited, it’s best you don’t have any mung beans or mung bean-derived products. Otherwise, the herbal formula won’t work well for you. In the same way, radishes will easily get rid of the capabilities of ginseng. If you take a formula containing ginseng, then it will be rendered useless if radishes are eaten in the same timeframe. For teas, the effect will vary. Generally, it is better to avoid drinking teas when taking a Chinese herbal formula but if you are taking a formula for tonification/energy/feeling cold easily, you can drink red tea at the same time and it will be fine. If you are taking an herbal formula for overheating easily/hot flashes/etc. then perhaps you can have green tea too. Otherwise, it will be detrimental towards the formula.
In daily practice, there are much more complicated situations. If you found a good TCM practitioner or acupuncturist, they can tell you much more detailed information.