They're a wheatmeal biscuit, so probably like digestive biscuits. I had to google and found this on wikipedia:

The Graham cracker was originally conceived of as a health food as part of the Graham Diet, a regimen to suppress what he considered unhealthy carnal urges, the source of many maladies according to Graham. Reverend Graham would often lecture on "self-abuse" as it was commonly called at the time. One of his many theories was that one could curb one's sexual appetite by eating bland foods. Another man who held this belief was Dr. John Harvey Kellogg, the inventor of the corn flakes cereal
hmmm