Eating blood was forbidden under the Law of Moses (Lev. 7:26,27), but “we are not under the law, but under grace” (Rom. 6:15). It is true that men were told not to eat blood before the Law, but there was a reason for this. God told Noah,
“…flesh with the life thereof, which is the blood thereof, shall ye not eat” (Gen. 9:4).
When God expanded Adam’s vegetarian diet here (Gen. 1:29 cf. 9:3), He warned Noah not to eat the flesh of an animal with its blood, for the blood of an animal is “the life thereof,” and God had another purpose in mind for the life of animals:
“…the life of the flesh is in the blood: and I have given it to you upon the altar to make an atonement for your souls: for it is the blood that maketh an atonement for the soul. Therefore I said unto the children of Israel, No soul of you shall eat blood…” (Lev. 17:11,12).
The word “therefore” here clearly shows that the reason they weren’t to eat blood under the Law was because “it is the blood that maketh an atonement for the soul.” We know that this was also true before the Law, for animal sacrifices were required to be “accepted” by God before the Law as well (Gen 4:7).
But this is not true under grace! Now that Christ shed His blood to reconcile us to Himself (Col. 1:20,21), anyone who says we shouldn’t eat blood because the life of the flesh is in the blood must believe that the blood of animals still atones for men’s souls, for this is the only reason eating blood was prohibited.
This is similar to God’s prohibition against eating unclean animals. The only reason God said some animals were unclean (Lev. 11) was to teach Israel that some people were unclean, i.e., the Gentiles (Lev. 20:24-26 cf. Acts 10:9-16,28). That means anyone who says certain foods are unclean today must believe that the Gentiles are still unclean. And anyone saying we shouldn’t eat blood “for the life of the flesh is in the blood” must still believe that the blood of animals atones for men’s souls. source