Vegans are deficient in vitamin A:

https://www.ncbi.nlm.nih.gov/pubmed/19103647
http://m.jn.nutrition.org/content/137/11/2346.full
http://healthybabycode.com/why-you-cant-get-vitamin-a-from-eating-vegetables (studies linked in the article)
https://www.sciencedaily.com/releases/2009/11/091118072051.htm
http://researchnews.osu.edu/archive/betacarotene.htm
http://ajcn.nutrition.org/content/71/6/1545.full
http://www.fasebj.org/content/23/4/1041.full
http://www.thehealthyhomeeconomist.com/beta-carotene-vitamin-a-myth
http://empoweredsustenance.com/true-vitamin-a-foods
https://www.westonaprice.org/health-topics/abcs-of-nutrition/vitamin-a-vagary
https://www.westonaprice.org/health-topics/abcs-of-nutrition/vitamin-a-saga
https://philmaffetone.com/vitamin-a-and-the-beta-carotene-myth

Calcium in Rats
https://www.ncbi.nlm.nih.gov/pubmed/3183773

Magnesium and Oxalates
https://www.ncbi.nlm.nih.gov/pubmed/15035687

Vegans have a lower sperm count than non vegans:

https://www.ncbi.nlm.nih.gov/pubmed/35465
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3257705/

Vegans have lower testosterone than non vegans:

https://www.ncbi.nlm.nih.gov/pubmed/1435181
http://m.ajcn.nutrition.org/content/42/1/127.abstract
https://www.ncbi.nlm.nih.gov/pubmed/159772
http://m.jap.physiology.org/content/82/1/49