Oak is a fairly safe and very useful tree for humans, but internal use should be guided by a qualified herbal physician.

As with all natural remedies consumption of Willow
should be guided by a qualified herbalist or physician.
This information here is for information purposes only,
and certainly not for prescription.

best use ...  

first aid, crush and mash twigs, acorns and leaves, to stop bleeding after an accident

qualities of Oak are said to be ...

astringent - reduces fluid loss, constricts tissues, such as stop bleeding
styptic - stops bleeding
tonic - builds strength

toxicity? ...  as all plants have a nourishing level and toxic level

Raw acorns can make us feel a bit ill. There is a preparation for cooked acorns, but its not very tasty.

For the rest of the Oak plant material, some folk remedies recommend making a tea with the leaves and acorns to drink as a tonic to build strength like the oak, but really you must consult a qualified herbalist to be guided to and enjoy these benefits. For some people, consuming oak can make you actually feel weak and ill for a couple of days.

to read about the crafting potential of Oak, please click here