Due to my high PSA, I am always on the hunt for new Prostate Cancer preventative measures, especially "easy" ones that are lifestyle-related. One of the best ones that I have come across recently is alpha-carotene consumption. There is a class of phytonutrients, i.e. plant-based chemicals in food, that called carotenoids. These include a lot of heavy hitters that many of you health fanatics will have come across in your reading, including alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein, zeaxanthin and lycopene.
Lycopene, for example, already has some solid study results (coupled with soy) against men with existing prostate cancer. I plan to cover that in another page soon. But what about its lesser known cousin, alpha-carotene? Well, there have been two studies to date, including a very recent one, that look very promising:
1. 2005 Carotenoid Study. This study looked at a broad range of carotenoids and concluded that five major carotenoids - alpha-cryptoxanthin, alpha-carotene, trans-beta-carotene, and lutein and zeaxanthin - would help prevent prostate cancer but not necessarily treat it.  In other words, consuming these before you have full-blown PC will likely help but not necessarily after. Notice that alpha-carotene is in this list.
This study looked at plasma levels of these compounds, i.e. this was based primarily on food and digestion. By the way, it is not that shocking that it does not help after one is diagnosed with prostate cancer. This is quite common, because medium and larger-sized tumors are notoriously tough to treat.
NOTE: If you have existing prostate or other cancer(s), be sure to run any changes by your doctor first. Cancer is tricky stuff. Also, if you are a smoker, you should take note that those cigarrettes deplete carotenoids from your plasma! In other words, the population that probably needs these phytochemicals the most is selectively removing them from their system...
2. 2014 Study on Japanese Men. This study found that vegetable consumption and beta-carotene consumption did not improve prostate cancer risk. However, both the highest and second highest beat-carotene quintiles had about half the risk of developing prostate cancer.  This is a HUGE drop for just one nutrient. Again, this study looked at plasma levels, which is measuring what these men digested through food, and was only looking at prostate cancer prevention (not treatment). Clearly, this is indicating that alpha-carotene is likely a big gun in the battle against prostate cancer.
COOKING: Let me tell you what is beautiful: alpha-carotene (along with beta-carotene and lycopene) are made more bioavailable by cooking. This is not that common but is the reason that catsup and tomato paste are actually potent sources of lycopene for example.
FOOD SOURCES: So how do you get alpha-carotene? Is it in food? Of course, many men know that beta-carotene is prevalent in carrots and sweet potatoes and lycopene in tomatoes and watermelon. However, few guys can name a vegetable with alpha-carotene in it - at least I couldn't. It turns out that, while there are many vegetable sources of alpha-carotene, only a couple of them are pretty significant in size: carrots and pumpkin. A cup of canned pumpkin will supply, for example, 11.7 mg of alpha-carotene.  I always wondered why pumpkin was on Dr. William Li's anti-angiogenesis foods.  Now I know! Besides the fact that canned goods here in the U.S. usually have Toxic Bisphenol-A, pumpkin is just not something that most men consume on a regular basis. The only way most men get pumpkin is in pumpkin pie, which hardly can be classed as a cancer preventative. So that essentially leaves carrots.
I am proud to say that I snack on organic baby carrots from Trader Joe's almost every day. I find them to be an easy snack food that is low glycemic and, of course, packed with nutrients. Little did I know that I was getting a decent dose of alpha-carotene while I was at it. A medium carrot supplies about 2.1 mg of alpha-carotene and I am eating probably a half bag of baby carrots on average. I don't know how many medium carrots that translates to, but I'd guess around 4.
So the bottom line is start munching on those carrots - hopefully organic - and get some solid cancer prevention going on!.
1) Nutr Cancer, 2005, 53(2):127-34, "Relationship between plasma carotenoids and prostate cancer"
2) Br J Cancer, 2014 Feb 4, 110(3):792-6. doi: 10.1038/bjc.2013.685. Epub 2013 Oct 29, "Relationship between vegetable and carotene intake and risk of prostate cancer: the JACC study"