Learn Spanish (Spain): No como pan blanco, sino integral, porque tiene fibra. - I do not eat white bread, but whole grain, because it has fiber.

We use sino to make a direct correction or replacement. The first part of the sentence is negative (No como pan blanco), and the second part introduces the exact thing that replaces it (integral). If you used pero, it would sound like you are adding contrasting information rather than replacing the rejected item.

Why is it just sino and not sino que in this sentence?

You only use sino que when the correction introduces a brand new conjugated verb. Here, the verb como carries over from the first half, and you are only swapping the adjective (blanco for integral). Since there is no new conjugated verb right after the word 'but', you just use sino.

Why don't we need to repeat the word pan and say sino pan integral?

In Spanish, you can drop the noun if it is already clear from the immediate context. Saying sino pan integral is grammatically correct but sounds unnecessarily repetitive. By just saying sino integral, the word pan is smoothly implied.

Does integral always mean 'whole grain'?

In the context of food, yes. Integral is the standard word in Spain for 'whole wheat' or 'whole grain' (like arroz integral for brown rice or harina integral for whole wheat flour). In other contexts, it means 'comprehensive' or 'integral', just like in English.