Flaxseeds: One of the best plant sources of omega-3 fatty acids, flaxseeds provide both soluble fiber, linked to reduced risk of heart disease, and insoluble fiber, which provides valuable roughage. They must be ground for your body to absorb the benefits. Whole flaxseeds have a longer shelf life (grind them in a clean coffee grinder or dry blender). Once ground, flaxseeds are highly perishable, so store them in a tightly covered container in the refrigerator or freezer. You can purchase whole seeds and ground flaxmeal in natural-foods markets or at bakerscatalogue.com.