Any diet restrictions with radiation? What were your side effects?

Eat blueberries. My wife found research that showed radiation is more effective when taking blueberries. It cannot hurt. I ate tones of blueberries while on radiation.

Research suggests that blueberries may enhance the effectiveness of radiation therapy for cancer treatment, including prostate cancer:

Radiosensitization: Blueberries contain resveratrol, which can make cancer cells more sensitive to radiation.
Antioxidants: Blueberries contain antioxidants that can reduce abnormal cell growth that contributes to cancer.

Inhibiting cancer cell growth: Blueberries can inhibit the growth of cancer cells.

Promoting cancer cell death: Blueberries can promote the death of cancer cells.

"One study found that combining blueberry extract with radiation therapy reduced the number of human cervical cancer cells by around 70%. In comparison, radiation therapy alone reduced the number of cancer cells by 20%, and blueberry extract alone reduced them by 25%."

Sloan says ONLY cooked fruit - including blueberries which I love. And absolutely NO antioxidants of any kind. Blueberries don’t have all that much compared to supplements so they are probably not contraindicated.
However, antioxidant supplements are to be avoided. The radiation actually creates free radicals (oxidants) in the cancer cells and causes their metabolism to malfunction, thus weakening their ability to reproduce. ANTI-oxidants may actually UNDO what the radiation is trying to accomplish!
I don’t think you have to worry if you took them during your treatment since most supplements are poorly absorbed in most cases or are in amounts totally inadequate to do the job.
Even the health benefits of resveratrol have been debunked as they are portrayed in wine consumption. You’d have to drink something like 10,000 bottles of wine in a single sitting to get the amount of resveratrol that might clean your arteries.
Great PR for the wine industry but not so good for us. Drink the wine because you like it!😊

Three days out from completing IMRT and my GI side effects appear to be subsiding. I had pizza last night (Yippee!) and, so far so good. During the treatments my insides could best be described as perpetually unsettled. Frequent bowel movements, loose stools, diarrhea. For the record, I also had pelvic lymph node radiation. So, more of my bowels took a radiation hit, and as expected, demonstrated greater symptoms. All of the rectal irritation from the bathroom visits led to my hemorrhoids joining the party too.

Diet wise, it didn't seem to matter what I ate (although I stuck to an ultra conservative, bland diet).

There are always conflicting studies. I read several people on this site commented that they believe xgeva prevents and or kills bone metastases. While there are studies showing that xgeva helps prevent metastases in men prior stage 4 metastasizing. It does not stop metastases from occurring in men that are already stage 4. My doctor has reiterated those facts to me as well. There are more studies that show that there are several foods that are considered cancer killing (let's just agree that cancer cells do not like) blueberries are high on the list and green tea. I say eat the blueberries before treatment. It helped me and when I questioned my radiologist oncologist she agreed, blueberries do help and they specifically helped me.

Whatever works- or whatever we ‘think’ works is good all around. But again, none of the studies of any of these things have been done in double blind studies with tens of thousands of patients over a multi year period. Of course blueberries are good for you -I eat them every single day cooked or raw.
A good friend had leukemia and refused mainstream treatment. Instead he found these green tea pills that were super concentrated and his leukemia actually improved - much to the surprise of his doctors.
However, he did get prostate cancer and the pills did nothing about that. If I had a nickel for every website extolling the virtues of green tea for prostate cancer prevention I would be a rich man indeed!
There are probably even people on this forum who believe in its curative powers, and as I said in the beginning, if you believe it works then no harm done, as long as it’s combined with known, proven medical procedures and medications that DO work!
Best