As far as I know the only thing you can eat to "lose your milk" is certain cold medicines (phenylephrine and pseudoephidrine), which do reduce milk supply - but it usually comes back again. Pregnancy will cause a drop in milk supply, as can some oral contraceptive pills.
You need to be heading for malnutrition before you lose your milk from poor diet. Insufficient fluids can be a problem - but as long as you actually drink when you feel thirsty then that won't be an issue either.

Usually when youl feel like you are "losing your milk", you won't be - your baby may be ramping up what they are drinking!
If you feel your supply needs to increase then feeding them more often will do it.

Some people do have problems with low milk supply. Usually it is associated with babies that don't suck enough to stimulate milk production; there is also a condition where people don't actually have enough milk-producing tissue in their breasts, but it is quite rare.

As long as your baby are growing adequately, and weeing frequently, they are getting enough milk.