If someone were to put a pint of beer and a pint of carrot juice in front of you, telling you to pick the safer option, you'd go for the carrot juice, right? You fool! Sure, beer is full of alcohol, but compared to carrot juice it's relatively free of something else — radioactivity.
When you drink a pint of beer you take on its attendant chemical and behavioral dangers, and a hidden danger as well. Beer is very slightly radioactive. The radioactivity comes from a wholesome source, potassium.
Potassium is an element, and as an element in comes in different forms. One of these forms is Potassium-40, with twenty-one neutrons and nineteen protons. It's an unsavory isotope that tends to decay, and it decays in several ways. Most of the time it gives off a relatively low-energy ray, and an electron. No problem. About eleven percent of the time, it decays by giving off a gamma ray and a neutrino. Gamma rays can do damage to the body, so this is more of a concern. About 0.1 percent of the time, Potassium-40 decays by emitting a positron and a neutrino. This doesn't do direct damage, but a positron is antimatter, and when it hits an electron in your body, the two particles annihilate, giving off a gamma ray.
This isn't something to be worried about. Many foods give off small levels of radiation. When fears about radioactivity started getting out of hand, experts started pushing the term "Banana Equivalent Dose" to let people understand that small amounts of radiation are natural and normal. Beer puts off about 390 picoCuries of radiation per killogram, which is around one tenth the Banana Equivalent Dose. (Though you're more likely to consume a kilogram of beer than a kilogram of bananas.)
There's something else that has about ten times the radiation per kilogram of beer. Carrots suck up potassium, and put off about 3,400 picoCuries per kilogram. So a glass of carrot juice, based purely on radioactivity, is ten times as bad for you as a glass of beer. Drink up.
[Via Potassium: A Radioactive Element, 10 Common Naturally Radioactive Foods.]