Fortify

verb

1. To increase the defenses of; to strengthen and secure by military works; to render defensible against an attack by hostile forces.
2. To impart strength or vigor to.
3. To add spirits to wine to increase the alcohol content.

   "Sherry is made by fortifying wine."

4. To increase the nutritional value of food by adding ingredients.

   "Soy milk is often fortified with calcium."