According to the guides on the Speedwell cavern tour, eating tallow candles gives you stomach cancer. Mind you, they also mention a young lad named 'Little Winster' who was made to work with a bucket of lead ore hanging from his neck and a candle in his mouth - though they did name a vein after him, so it wasn't all bad - I bet he was right chuffed about that bonus. This all gave a life expectancy of about 40 apparently, despite the gravestones in Castleton churchyard showing most made it to their 70s usually, unless they got squashed. Probably from the nutritious tallow-supplemented diet.