I found this interesting article, though not exactly new news, explaining why milk can block the effects of levadopa completely.
The explanation is clearer than many and may explain why my sinemet isn't so effective after my morning bowl of cornflakes and milky coffee!
Kathryn Holden (the nutritionist) is really helpful. I took her advice and gave up milk entirely a year ago and am very happy with that.
An important artice. Clearly written!
I have seen the advice to avoid dairy (i.e., because it is said to be worse for levodopa availability than other types of foods with high protein content), and elsewhere a suggestion that vegetable proteins may be better than animal proteins, when it comes to levodopa availability... but I was unable to find any studies supporting these views...
Milk is a liquid food containing long strand, complex, large neutral proteins. L-Dopa is a singular amino acid protein. Proteins compete with one another within the small intestine to go into the blood stream to ultimately cross the blood brain barrier.
Therefore, it is prudent avoid any other complex protein foods or singular amino acids when you take L-Dopa medications for at least one hour, such as milk which is particularly high in glutamic acid or whey protein, etc.
I many respects, a meal of long strand, complex proteins (like found in milk which has a complete amino acid profile as does eggs) dwarf l-dopa because normally it has a very short lifespan with low bioavailability versus milk which is highly bioavailable (and whole eggs are even higher than milk).
If one takes an ER/CR med, such as some forms of sinemet, this issue becomes supposedly less problematic due to the carbidopa theory.
The "theory" is carbidopa and/or benserazide somehow protect the l-dopa from competing proteins for a certain amount of time. Obviously, something happens as people age or their PD progresses where this doesn't quite work out the way the theory suggests it should for a variety of reasons.
Sharon
I have some experience of a latte coffee blocking a Levadopa dose, so now avoid this after taking a dose
I don't use milk at all, due to lactose intolerance, and dislike yogurt, sour cream, etc. I do eat cheese and have read that some people with lactose intolerance can eat cheese. I don't find cheese affects levodopa absorption and med effectiveness, but meat protein (beef, pork, chicken) majorly affects, as do eggs. I limit all of these to dinner as best I can.
subcutaneous Levadopa delivery 
What PwP need is regular rigorous exercise motivations NOT more levadopa
Levadopa (Rytary) should I keep trying to cut back?
Yikes! According to RXlist.com you should NOT take Methylene Blue and Levadopa
DBS levadopa challenge. Glad its over, but it does raise a question. 
