ADDITIONAL NAMES
Retinol, Retinoic Acid
SUMMARY
Taking Vitamin A combined with Vitamin D was the first thing I took that I actually noticed that consistently improved my health. Prior to taking this combination, I was also prone to getting regular coughs and colds. Taking Vitamin A & D together reduced the frequency of illness very significantly. I also noticed that my sexual function was improved. This has been my staple for almost a decade and forms one of the key components of my personal regimen.
The published data regarding Vitamin A and testosterone (mainly from animal studies) suggests that a deficiency of Vitamin A will considerably reduce testosterone production. Whether going above sufficiency will actually lead to higher and higher levels of testosterone is unclear. I've not personally noticed any beneficial effect of going much higher than my regular dose. I take 3 Holland and Barrett Cod Liver Oil capsules in the evening, along with 3000IU of Vitamin D, along with a chunk of butter from grass fed cows (Kerrygold).
TESTOSTERONE
Significant correlation between a testosterone metabolite and Vitamin A in male twins
https://www.ncbi.nlm.nih.gov/pubmed/3360302
Type of Study: Cross sectional, twin study
Participants: 72 male identical and 83 non-identical twin pairs
Measures: Food frequency questionnaire and blood samples for hormones
Finding: Testosterone glucuronide (a natural human metabolite of testosterone) is correlated with Vitamin A. What the hell this means, I'm not actually sure.
Additional info: Fat intake also showed a significant association with testosterone
Vitamin A deficiency reduces testosterone in Guinea Pigs
https://www.ncbi.nlm.nih.gov/pubmed/11055546
Study Design* Randomised Controlled Trial, Animal Study
Participants: Guinea Pigs
Methods Divided guinea pigs into groups, one was a diet with retinyl palmitate (a form of Vitamin A), the other diet was the same, but lacked the retinyl palmitate.
Results Vitamin A deficiency led to reduction of plasma testosterone.
Vitamin A deficiency reduces testosterone in rats*
https://www.ncbi.nlm.nih.gov/pubmed/2513446
https://www.ncbi.nlm.nih.gov/pubmed/3935184
https://www.ncbi.nlm.nih.gov/pubmed/6418843
Dihydrotestosterone (DHT)
In vitro study: Retinol stimulates 5AR
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1132824/pdf/biochemj00131-0210.pdf
"Retinol, 13-cis-retinoic acid and 13-cis-retinol showed 58 % stimulation at 200 uM but no stimulation or
inhibition at 40 uM."
In vitro study: Large dose of all-trans-retinoic acid increase didhydrotestosterone (DHT) production
https://www.ncbi.nlm.nih.gov/pubmed/10423178
Retinoic acid (RA): an inhibitor of 5 alpha-reductase in human prostatic cancer cells.
https://www.ncbi.nlm.nih.gov/pubmed/3695521
Relevance unclear.
Problems with Cod Liver Oil
persistent organic pollutants (POPs) derived from cod liver oil
https://www.ncbi.nlm.nih.gov/pubmed/21722693
IMPROVING VITAMIN A UTILIZATION
https://academic.oup.com/ps/article-abstract/36/6/1313/1531524/Effects-of-Antioxidants-DPPD-and-BHT-on-Health?redirectedFrom=PDF
"levels of vitamin A studied, storage of the vitamin in the liver was enhanced two to five times when DPPD was in the feed, and plasma vitamin A also was increased but not so markedly."
ZINC Zinc is needed to covert vitamin A into its active form
READ: https://www.ncbi.nlm.nih.gov/pubmed/22818093
GOOD BRANDS
A lot of people talk about fermented cod liver oil from Green Pasture, or the extra virgin cod liver oil from Rosita, however, I've taken both and been impressed by neither. The best brand I've found in terms of producing actually noticeable immune and testosterone boosting effects is from Holland and Barrett. Very cheap, but to me at least, it's more effective than anything else I've tried. Also, unlike other brands I've tried, the Holland and Barrett capsules do not give me fishy burbs or leave a fishy aftertaste in my mouth.
Other studies
http://www.reproduction-online.org/content/124/2/173.long