Mendel studied classics, economics and the humanities, as well as biology and chemistry at Yale University and graduated with honors in 1891.

[2] He then began graduate work at the Sheffield Scientific School on a fellowship and studied physiological chemistry under Russell Henry Chittenden.

In 1913, along with the American biochemists Elmer McCollum and Marguerite Davis, he discovered a fat-soluble factor in cod liver oil and butter, now known as vitamin A.

In promoting Mendel, Yale made him one of the first high-ranking Jewish professors in the United States.

In their early work, they studied the deadly poison ricin which is classified as a type 2 ribosome inactivating protein (RIP) from castor beans.

[9][10] He won the American Institute of Chemists Gold Medal in 1927 "for his outstanding contributions to chemistry."

[11] He won the Conné Medal of the Chemist's Club of New York in 1935 "for his outstanding chemical contributions to medicine."