  Let $\Omega \subset \mathbb{R}^n$ be a convex domain and let $f:\Omega
\rightarrow \mathbb{R}$ be a subharmonic function, $\Delta f \geq 0$, which
satisfies $f \geq 0$ on the boundary $\partial \Omega$. Then $$ \int_{\Omega}{f
~dx} \leq |\Omega|^{\frac{1}{n}} \int_{\partial \Omega}{f ~d\sigma}.$$ Our
proof is based on a new gradient estimate for the torsion function, $\Delta u =
-1$ with Dirichlet boundary conditions, which is of independent interest.
