Quote from Dr. Garrett Smith on November 11, 2018, 5:29 pm

This would seem pretty straightforward from multiple studies...higher retinol levels (blood and tissue levels) are associated with prostate cancer and Benign Prostatic Hypertrophy (BPH):

Serum Retinol and Carotenoid Concentrations and Prostate Cancer Risk: Results from the Prostate Cancer Prevention Trial

In this prospective analysis of serum retinol, carotenoids and prostate cancer risk, we found positive associations between serum retinol and total and high-grade prostate cancer, and between serum α-carotene and total prostate cancer, in the placebo arm of the PCPT.

In addition, a recent pooled analysis, which included data from the PCPT, reported a 13% increase in prostate cancer risk in the highest quintile of serum retinol, relative to the lowest (T. Key et al., unpublished observations).

CONCLUSION: In the placebo arm of this prospective study, high serum retinol and α-carotene concentrations were associated with increased risk of total and high-grade prostate cancers.

IMPACT:  Men with higher levels of serum retinol and α-carotene may be at increased risk for prostate cancer.

The MOST important thing to note about the research above is that they were NOT saying that any of these men actually HAD Poison/"Vitamin A" toxicity, just that the men who were HIGHER (still in normal range though!) levels of retinol and beta-carotene had HIGHER risks of cancer.  Note that this includes both serum retinol levels AND serum beta-carotene levels.  Don't fool yourself and think that carotenoids are somehow OK, they're not.

Serum retinol and risk of prostate cancer.

Men with higher retinol concentrations at baseline were more likely to develop prostate cancer (quintile 5 vs. quintile 1 hazard ratio = 1.19, 95% confidence interval: 1.03, 1.36; P(trend) = 0.009). The results were similar for aggressive disease.
[...]
In this largest study to date of vitamin A status and subsequent risk of prostate cancer, higher serum retinol was associated with elevated risk, with sustained high exposure conferring the greatest risk.

Abnormal level of retinoic acid in prostate cancer tissues.

Here we show that normal prostate, benign prostate hyperplasia (BPH), and prostate carcinoma tissues contain endogenous retinol and its biologically active metabolite retinoic acid. In our studies, the concentration of retinol was 2-fold elevated in BPH compared with the other two tissues.

Lower Prostate Cancer Risk in Men with Elevated Plasma Lycopene Levels

The only other notable association we observed in this matched set analysis was a higher geometric mean plasma retinol for all [prostate cancer] cases compared to controls (P = 0.02). However, this association was entirely confined to nonaggressive cases.

It should be noted that the association (quoted above) with increased retinol aka Poison/"Vitamin A" and prostate cancer was "conveniently" left out of the abstract...guess it didn't match the intended outcome the authors wanted to show!

The MOST important thing to note about the research above is that they were NOT saying that any of these men actually HAD Poison/"Vitamin A" toxicity, just that the men who were HIGHER (still in normal range though!) levels of retinol and beta-carotene had HIGHER risks of cancer.  Note that this includes both serum retinol levels AND serum beta-carotene levels.  Don't fool yourself and think that carotenoids are somehow OK, they're not.

Serum retinol and risk of prostate cancer.