  We give a lower bound for the numerical index of the real space $L_p(\mu)$
showing, in particular, that it is non-zero for $p\neq 2$. In other words, it
is shown that for every bounded linear operator $T$ on the real space
$L_p(\mu)$, one has $$ \sup{\Bigl|\int |x|^{p-1}\sign(x) T x d\mu \Bigr| : x\in
L_p(\mu), \|x\|=1} \geq \frac{M_p}{12\e}\|T\| $$ where
$M_p=\max_{t\in[0,1]}\frac{|t^{p-1}-t|}{1+t^p}>0$ for every $p\neq 2$. It is
also shown that for every bounded linear operator $T$ on the real space
$L_p(\mu)$, one has $$ \sup{\int |x|^{p-1}|Tx| d\mu : x\in L_p(\mu), \|x\|=1}
\geq \frac{1}{2\e}\|T\|. $$
