Yes and no. The binding energy of atoms is tied to E=mc^2, thus c increasing dramatically slows nuclear decay, but keeps the overall energy output constant. A 2,000,000 fold increase in c, which is the minimum needed for fitting starlight into 6,000 years, would make the half-life of 14C about 2x10^16 years, but would make each decay about 4x10^12 times more energetic. A 70 kg person normally gets about 40,000 Bq from the 14C in them, with a total energy of 10^-9 W. They would now experience one decay every three years, each of which would have an energy of 0.01 J. So, not likely to kill you, but not good for you either.