I am not aware that taking folic acid (or any vitamin supplement) can increase the risk of prostate cancer.

The only nutritional supplement that has been associated with an increased risk of prostate cancer is calcium. Men that take calcium supplements are more likely to consume more daily calcium. And studies have shown a higher rate of advanced prostate cancer in men that consume large amounts of calcium every day.

It's important to note that eating a diet low in calcium does not decrease prostate cancer risk. And getting enough calcium has many important health benefits.

Other foods you eat play a role in prostate cancer risk. Men that eat a lot of red meat and high-fat dairy products (like full fat milk and cheese) appear to have a greater chance of developing prostate cancer.

On the flip side, men that eat lots of fruits and vegetables and only a little red meat and minimal high-fat dairy products may have a lower prostate cancer risk.

Keeping a healthy body weight and exercising regularly appear to decrease the risk of developing the more aggressive and potentially deadly stage of prostate cancer.

Until recently, there was hope that vitamin E and selenium supplements might decrease cancer risk. But a large study failed to show any benefit from either one.