Yes, black seeds can cure candida and yes you must still go on the diet. If you have cancer and you are taking black seeds, can you eat sugar? No. Black seeds can cure candida, but you need to follow the diet of our Prophet.
If your candida is bad take the oil instead of the seeds. If you are mixing it with honey, do not take store bought honey as store bought honey is 70% sugar. You can mix the oil with the juice of one orange and take it before breakfast and before sleeping.
Go on a very strict candida diet for two weeks with the oil and gradually start adding back in fruit. At first no fruit, after two weeks you can have grapefruit, After 4 weeks you can add in tangerines, strawberries, berries and no more than one kiwi. After 6 weeks you should be on the road to recovery.
Some people will have candida for years and years. With the use of black seeds you will be cured in a short time. Keep in mind that black seeds are to be taken like a vitamin pill so should be taken for life. My mom who is 80 years old takes them every day.
Now if you have seeds, I suggest taking the seeds once and the oil the second time. In order to take the same amount of seeds you will need 2.5 as much. So with the seeds you are consuming more sugar in either honey or juices.
Hope this helps.