To protect itself from undesirable substances in the blood, the brain has a complex set of mechanisms which control both the types of substances which enter the brain's extracellular fluid (fluid surrounding the cells) and the rate at which they enter, thus precisely regulating this fluid's chemical composition and minimizing the ability of harmful substances to reach brain tissues.

Water, carbon dioxide and oxygen readily cross the blood-brain barrier. Ketone bodies, amino acids and fatty acids cross more slowly, and other substances like proteins and hormones are highly restricted. Some areas of the brain lack a blood-brain barrier.

Blue-green algae (see Algae)

Boldo

A herb used as a gall bladder stimulant and mild diuretic.

Availability: From health food shops.

Borage oil

Borage oil, being a rich source of GLA, is often sold as a GLA supplement.