The prostate is part of the male reproductive system – it basically helps produce semen. And unfortunately, it tends to get a lot of cancer. Prostate cancer is the 4th most common cancer in the world, and the 2nd most common in men. (If you’re wondering, the #1 spot for men is lung cancer).
Prostate cancer is often blamed on eating a high-fat diet, which makes it particularly interesting from a Paleo point of view. If fat or any particular type of fat really does increase the rate of prostate cancer or speed the progression of the disease, that’s a serious strike against it and not something we should ignore.
If you look at the studies on dietary fat and prostate cancer, the link between saturated/animal fat and prostate cancer is weak at best. But it does point to a stronger and possibly more significant link: inflammation.
This isn't a claim that any type of diet causes, prevents, or cures cancer, either prostate cancer specifically or cancer in general. There's no such thing as a food or a diet that causes, prevents, or cures cancer all by itself. But there are diets that can increase or reduce the risk of specific types of cancer - that's what we're talking about here.
The Case Against Fat
There are several studies showing an association between saturated fat consumption and prostate cancer. This review went over the anti-fat theory in detail, starting from the very first studies. Early on, researchers weren’t looking at saturated fat specifically. They were trying to find an association between dietary fat in general and prostate cancer. But it didn’t work very well:
“the results were mixed, with studies demonstrating positive, negative and no associations between dietary fat and the risk of prostate cancer.”
So total dietary fat probably doesn’t increase or decrease risk to any significant degree. But the review explains that these studies didn’t distinguish between different types of fat, and that’s admittedly an important distinction.
In 1993, an analysis of fat and prostate cancer risk broke down “fat” into different types and found that animal fat specifically was associated with the risk of advanced prostate cancer. Dairy fat, except for butter had no association. Since then, there have been plenty of other studies reporting an association between dietary animal fat and/or saturated fat and prostate cancer.
But later the review goes into more details:
“Some studies show increased risk of prostate cancer risk and progression [from eating saturated fat], while others are inconclusive. Animal models suggest that the quality of dietary fat, and, specifically, the PUFA content of dietary fat intake, may be an important prognosticator. Long-chain [saturated fats] may negatively affect prostate cancer, while short-chain [saturated fats] may be beneficial.” (bolding added)
So in other words, the evidence isn’t totally conclusive, and there may be differences between the types of saturated fat. And it might also be true that the effects of saturated fat depend on PUFA (namely that high saturated fat is only “bad” if PUFA is also high). But hang onto that PUFA connection, because buried deep in the review, you’ll find this:
"There is extensive research examining the role of PUFA in prostate cancer. It is reported that n-6 fatty acids increase prostate cancer risk, while n-3 fatty acids decrease prostate cancer risk."
So far we have some evidence that some types of saturated fat might be associated with an increased risk of prostate cancer in some contexts, compared to a lot of research showing that PUFA really matters.
(At this point, if you don't know what PUFA or Omega-3 or Omega-6 means, go here and check it out - you'll be totally confused otherwise).
Is it Saturated Fat, or Omega-6 PUFA?
The problem is that in the context of the typical American diet, a high intake of saturated fat typically goes hand in hand with a high intake of Omega-6 fats and a low intake of Omega-3 fats. Omega-6 fats come from industrial oils, like soy and canola oil. They were relatively scarce in our ancestral diet but they’re abundant in the modern diet.
Think about the typical high-saturated-fat diet in the US or another Western country. It’s the McDonald’s diet, where the burger (saturated fat) comes with fries (fried in vegetable oil – Omega-6 PUFA). In the typical American context, saturated fat and Omega-6 PUFA go together. But if there’s anything about that diet that increases prostate cancer, the evidence suggests that it’s more likely to be the Omega-6, not the saturated fat. Saturated fat is getting framed because it happened to be caught at the scene of the crime, but the actual villain might be Omega-6 PUFA.
Remember from above that butter was the only type of dairy fat associated with a higher risk of prostate cancer? Could that be because butter is the dairy fat most tied up in a junk-food diet? Meanwhile, the exact same type of saturated fat from yogurt is prostate-neutral because yogurt is “health food” and it isn’t a marker for a junk-food, high-O6, low-O3 diet.
The Omega-6 connection is especially convincing because Omega-6 fats are inflammatory, and there’s already a huge link between inflammation and prostate cancer.
Inflammation and Prostate Cancer
Inflammation is generally associated with prostate cancer, and systemic inflammation is associated with earlier death from prostate cancer. This study explains that inflammation might actually turn off the genes that help protect and repair DNA. This leaves the cells of the prostate unable to produce antioxidants, so the prostate is vulnerable to oxidative damage.
Systemic inflammation can come from anywhere (air pollution, overexercise, sleep deprivation, stress, medication…) but there’s also evidence specifically connecting dietary inflammation to prostate cancer. Take this study, which followed 6,542 subjects for over a decade. The study found that the inflammatory potential of a subject’s diet was strongly associated with his prostate cancer risk.
A very brief list of some dietary factors that...
Cause inflammation:
- Gut irritants
- Sugar and refined carbohydrates
- Trans fats
- ...and our old friends Omega-6 PUFA.
Reduce inflammation:
- Antioxidants
- Fresh fruits and vegetables
- Omega-3 PUFA
- Some vitamins and minerals (e.g. selenium)
(Learn more about inflammation here if you're new to this)
Omega-6 fats are notoriously inflammatory. So if there’s any kind of dietary fat that contributes to prostate cancer, you’d expect it to be Omega-6 fats…which is basically what the review of dietary fat above found out.
“Low-fat” Study Diets Improve Prostate Health…Because they’re Really Low-Inflammation Diets.
With inflammation in mind, it’s time for a closer look at some of the actual “low-fat” diets that improved markers of prostate health. A bunch of them had all kinds of anti-inflammatory interventions as well. The effects of these low-fat diets could easily be explained by their other anti-inflammatory features, not necessarily by anything to do with the reduction in fat.
Just for example, in this study, 20 men started a Mediterranean diet after a diagnosis of prostate cancer. The Mediterranean diet was basically the typical olive oil/fish/fruits and vegetables/legumes/whole grains deal, but with the addition of the definitely non-Mediterranean green tea because the researchers thought the antioxidants would help. Adherence to the Mediterranean dietary pattern overall was associated with a lower rate of DNA damage.
In this study, 13 subjects with recurring prostate cancer were encouraged to eat a “plant-based” diet: more whole grains, fruit, vegetables, and beans; less meat and dairy. They were also taught meditation and stress-relief techniques and encourage to practice those. The men did increase their intake of whole grains and of vegetables, and this seemed to slow the progression of the cancer.
But these diets represented huge anti-inflammatory changes. Adding more vegetables and healthy fats (olive oil) to any diet will probably reduce inflammation. In fact, even the whole grains are probably protective against prostate cancer, if they’re replacing refined grains. Paleo might not be very positive about grains in any form, but if you’re comparing whole wheat bread to Wonderbread, then the whole-wheat bread is probably a relative improvement.
Studies on actual humans support the idea that a diet specifically designed to be anti-inflammatory and also reduce saturated fat is beneficial for preventing and treating prostate cancer. But it looks like the anti-inflammatory part might be much more important than the saturated fat part.
Summing it Up
Early studies blamed “dietary fat” for prostate cancer, but the results were totally scattershot, with some research pointing to an effect and other research pointing to nothing going on. More recent research has suggested that inflammation, not dietary fat might be the real culprit. Today, people in the industrialized world who eat a lot of animal fat aren’t eating it as part of a Paleo diet. They’re eating it as McDonald’s burgers that they wash down with a Coke (inflammatory sygar) and fries (inflammatory Omeag-6 fats).
The Western diet really is associated with prostate cancer, but that's probably because it's inflammatory. It might be the Omega-6 PUFA, but it's probably not the saturated fat.
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