I'll wait for the scientists among us to give an official comment, but meanwhile I can say this much, based on my reading---
'Boost' doesn't have much of a medical meaning. I suspect you'd have to ingest a huge amount of vitamin C for it to affect autoimmune conditions. Remember too that most other fruits and veggies have a lot of C also, and I've never heard of too much of them in a normal diet.
As with anything else, moderation is important. I think you should enjoy 8 ounces a day of OJ and not worry. But do consider it's high-cal because of the natural sugar.
Supplement pills usually have a minimum of 250mg and many have 500 or 1000mg per tablet. Some people supplement with much higher doses.
The amount of vitamin C in your juice will vary by what kind it is (concentrate has higher levels), how it is packaged and how fresh it is (loses concentration of C as it approaches expiration date). I think it runs somewhere between 30-60mg a serving and the higher end of that comes close to the "minimum daily requirement."
You probably don't need to worry too much since cravings like this are usually a short term obcession and you need to get some vitamin C in your diet for health and healing. How much are you drinking? I'm thinking the sugar high and weight gain would likely become a problem before you could drink enough OJ to overboard your immune system.
It is like I have replaced my soda for orange juice but much more. Not sure why. I am drinking OJ all the time now. I was just curious if I was going to cause more harm than good. I really didn't think about the calorie thing. I have just been buying about a gallon of OJ every two days and then I remembered what I had read about too much vitamin C.
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