DEAR DR. ROACH: I am a 68-year-old male who weighs 130 pounds and is 5 feet, 7 inches tall. I am in good shape and work out regularly. I had my prostate removed in 2023 after about six years of active surveillance, and I just finished radiation treatment.

I’ve taken vitamins for as long as I can remember. I take Centrum Silver multivitamins, fish oil, calcium, and vitamin D for osteoporosis. When doing some research, I read that selenium and vitamin E are not good to take if you have prostate cancer, and they are included in Centrum Silver. The fish oil had conflicting information, with some saying it was good and others saying it wasn’t good to take if you have prostate cancer.

Should I continue taking these vitamins, or should I stop? Could these have made my cancer worse?

–Anon.

ANSWER: Several supplements have been associated with an increased risk of prostate cancer. The evidence is moderately strong with vitamin E. A large study designed to look for benefits had to be stopped by the safety committee, and an analysis showed a 17% increased risk of prostate cancer with vitamin E.

Some studies found an increase in prostate cancer risk with fish oil, while others didn’t. In my opinion, men with prostate cancer should not take vitamin E. Unless you are clearly recommended fish oil based on your triglyceride level or for some other clinical indication, I don’t recommend it either.

Because your multivitamin contains vitamin E and selenium, another mineral that may increase prostate cancer risk, I recommend against it for any man with prostate cancer. There is no need to taper off it slowly.

DEAR DR. ROACH: I am a 78-year-male in overall good health. Based on certain symptoms (foamy urine and a previous eGFR of 55), my nephrologist has instructed me to have a metabolic blood test. Regarding the blood test, his instructions regarding the blood test were not to fast. I have never taken a metabolic test without fasting.

My research revealed that by fasting, your test results are more realistic. What should I do? Fast or not?

— B.E.

ANSWER: Clearly you should heed the instructions of your nephrologist. Blood tests without fasting provide a measure of what your body chemistry is like under the most usual conditions. You are right that creatinine isn’t much affected by diet, although heavy meat consumption will make the creatinine reading a bit higher.

Blood sugar and lipid tests are most affected by fasting, and while lipid tests are generally standardized to the fasting state, blood sugar tests need to be interpreted according to whether a person is fasting or not.