Vegans are deficit in b12:
http://jamanetwork.com/journals/jamaneurology/fullarticle/78...

High fiber diets reduce serum half life of vitamin D3:
https://www.ncbi.nlm.nih.gov/pubmed/6299329

Vegans have weaker bones due to lower calcium intake and vitamin D3 levels:
http://jamanetwork.com/journals/jamainternalmedicine/fullart...
https://www.ncbi.nlm.nih.gov/pubmed/21092700

Vegans have a worse memory compared to non vegans due to creatine deficiency in vegans:
https://www.ncbi.nlm.nih.gov/pubmed/21118604
https://www.ncbi.nlm.nih.gov/pubmed/14561278

Vegans have less gains compared to non vegans:
http://m.ajcn.nutrition.org/content/70/6/1032.full

Vegans are deficient in omega threes:
https://www.ncbi.nlm.nih.gov/pubmed/16087975
https://www.ncbi.nlm.nih.gov/pubmed/16188209
https://www.ncbi.nlm.nih.gov/pubmed/12323090
https://www.ncbi.nlm.nih.gov/pubmed/12323085

Vegans are deficit in carnitine:
https://www.ncbi.nlm.nih.gov/pubmed/21753065
https://www.ncbi.nlm.nih.gov/pubmed/2756917
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1628441/
https://www.ncbi.nlm.nih.gov/pubmed/11043928

Vegans are deficient in taurine:
https://www.ncbi.nlm.nih.gov/pubmed/3354491

Vegans are deficient in iodine:
https://www.ncbi.nlm.nih.gov/pubmed/12748410
https://www.ncbi.nlm.nih.gov/pubmed/21613354

Vegans are deficient in Coenzyme Q10:
https://www.ncbi.nlm.nih.gov/pubmed/16873950

Vegans are deficient in iron due to the fact that iron from plant sources is less bioavailable than iron from meat sources:
https://ods.od.nih.gov/factsheets/Iron-HealthProfessional/
https://www.ncbi.nlm.nih.gov/pubmed/11269606

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-e... (studies linked in the article)
https://www.sciencedaily.com/releases/2009/11/091118072051.h... 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...
http://empoweredsustenance.com/true-vitamin-a-foods https://www.westonaprice.org/health-topics/abcs-of-nutrition...
https://www.westonaprice.org/health-topics/abcs-of-nutrition...
https://philmaffetone.com/vitamin-a-and-the-beta-carotene-my...

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

Veganism causes loss of libido and erectile dysfunction:
https://www.ncbi.nlm.nih.gov/pubmed/21353476

Children who are raised on strict vegan diets do not grow normally:
https://www.ncbi.nlm.nih.gov/pubmed/4067152
https://www.ncbi.nlm.nih.gov/pubmed/8005079

Children develop rickets after prolonged periods of strict vegetarian diets:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1874810/pdf/canm...

"There are some links between vegetarians and lower birthweight and earlier labour"
https://www.ncbi.nlm.nih.gov/pubmed/7788369

Most recent studies using more sensitive techniques for detecting B12 deficiency have found that 68% of vegetarians and 83% of vegans are B12 deficient, compared to just 5% off omnivores.
https://www.ncbi.nlm.nih.gov/pubmed/12816782
https://www.ncbi.nlm.nih.gov/pubmed/10966896
https://www.ncbi.nlm.nih.gov/pubmed/10552882

---------------------------------
These are case studies:

Cerebral atrophy in a vitamin B12-deficient infant of a vegetarian mother:
https://www.ncbi.nlm.nih.gov/pubmed/25076673

Severe megaloblastic anemia in child breast fed by a vegetarian mother:
https://www.ncbi.nlm.nih.gov/pubmed/8442642

Consequences of exclusive breast-feeding in vegan mother newborn - case report:
https://www.ncbi.nlm.nih.gov/pubmed/19748244

Nutritional vitamin B12 deficiency in a breast-fed infant of a vegan-diet mother:
https://www.ncbi.nlm.nih.gov/pubmed/3948463

"We report the case of a 7 month-old girl that presented with acute anemia, generalized muscular hypotonia and failure to thrive. Laboratory evaluation revealed cobalamin deficiency, due to a vegan diet of the mother."
https://www.ncbi.nlm.nih.gov/pubmed/18293883