Caveman Doctor recently received a question asking how best to fight prostate cancer or cure it with diet. Caveman Doctor wasn’t sure how to fight or cure anything with his diet as he merely eats the foods that nature provided him for several million years. Regardless, he decided to take a closer look.
Protect Your Protector
The Prostate is an exocrine organ of the male reproductive system, whose main job is to secrete prostatic fluid. Prostate literally means protector in Greek. Androgens, which are hormones responsible for male sexual characteristics, act on the prostate to regulate its function. Dihydrotestosterone (DHT) regulates the activity of the prostate. This is the hormone that is often blocked with medications that are prescribed for benign prostate hypertrophy (BPH), such as Avodart and Proscar.
Prostate cancer is one of the most common cancers in the developed world, and is the most commonly diagnosed cancer in men. Curative therapies usually include surgical resection or radiation therapy, sometimes with the addition of hormone therapy. While these treatments often have some side effects, they are relatively successful when compared to other types of cancers.
Dietary Factors Associated with Risk of Prostate Cancer
Epidemiological data has traditionally associated prostate cancer with fat consumption, however results are inconsistent and far from conclusive.1 Prospective study results vary greatly as it is extremely difficult to accurately assess people’s diets through recall mechanisms. Studies often use food questionnaires, which are essentially a series of questions that attempt to assess what a person actually eats. They are prone to considerable error depending on who is filling them out and how the questions are asked,2-4 with studies showing some participants exaggerating their intake of certain foods by 230%! Unfortunately, most studies use this technique to examine food intake and results are nearly worthless. However, three of the larger studies examining this are:
- A study that randomized over 1,300 men to either a low-fat, high fruit, vegetable, and fiber diet, or gave them a standard brochure on a “healthy diet”. This questionable study fraught with intervention bias showed no impact on PSA and no evidence that a low fat diet affects the incidence of prostate cancer5.
- A study, that asked patients about their dietary habits using food questionnaires and compared this to their risk of prostate cancer.6 Their data showed a potential increased risk of prostate cancer with intake of saturated fat and alpha-linoleic acid (found in flax seed and walnuts), yet their conclusions were that we should eat less meat. In Caveman Doctor’s humble opinion, this study was also fairly bogus and it is difficult to draw real conclusions from it regarding prostate cancer and diet.
- A Norwegian study looked at 25,708 men again using food questionnaire techniques, and found no association between energy-adjusted intake of total fat, saturated fat, mono-unsaturated fat or poly-unsaturated fat and the incidence of prostate cancer.7 Interestingly and against “conventional” wisdom, a significantlyincreased risk of prostate cancer was associated with lower fat skim milk compared to whole milk.. Skim milk consumption was also associated with larger body mass index. No surprise there, as skim milk removes all the fat, leaving a large unchecked amount of carbohydrates. However, it is still difficult to draw tangible conclusions from this study.
While these studies do not provide conclusive evidence either way, with the knowledge that high-carb diets lead to obesity and chronic disease, it is no surprise that recent data has revealed a correlation with carbohydrate consumption and prostate cancer risk8. This is even truer with high glycemic-value carbohydrates.9
With food measurement issues so prevalent in dietary studies, perhaps we should take a step back and look at the bigger picture.
Do Insulin and Obesity Cause Prostate Cancer?
The connections between insulin and obesity are discussed at length on this site, as are the effects of high-carbohydrate foods on insulin level spikes and rises. Serum insulin levels are known to be reduced in general low-carb diets10 or even simply by replacing carbs with protein.11
Insulin Appears to Affect Prostate Cancer Cells in Several Ways:
1. Insulin causes hormonal changes that may fuel prostate cancer cells.
Insulin decreases hepatic synthesis of sex hormone-binding globulin (SHBG), resulting in the stimulation of testosterone and estrogen.12 This may seem like a good thing, especially for caveman. However, we need to realize that estrogen secretion is also stimulated by SHBG, and while the effect of testosterone on prostate cancer is incompletely understood and has been questioned,13-15 estrogen has been shown to cause cancer cells to proliferate and increases tumor growth.16,17 For those of you familiar with breast cancer, it has a propensity to have estrogen receptors on it and is treated with Tamoxifen, which works by blocking estrogen. Accordingly, this hormone stimulation is worrisome for more than just prostate cancer, and estrogen likely has an effect on several other cell types in our body.
2. Insulin directly stimulates the growth of prostate cancer cells
Insulin also stimulates growth and progression of cancer cells18 by a more direct pathway through its circulating growth factor IGF-1, which causes cellular proliferation. In other words, insulin, which is secreted in response to high blood sugar, can directly cause prostate cancer cells to grow and advance. In fact, the level of IGF-1 can actually predict how bad a cancer is based on the measurement of a patient’s serum level.19 These results were actually from a study that followed men as they got treated (prospectively), giving these results much credence (thus why it was published in the highly esteemed journal Science). We do not have clinical trials to compare this versus a control, but one thought that immediately comes to mind is:
“What would happen if we tried to significantly decrease insulin levels in patients with prostate cancer?”
3. When insulin is blocked, prostate cancer cells die.
Insulin growth factor binding protein 3 (IGFBP-3) has been shown to have an anti-cancer role through its binding and blocking of IGF-1. It has also been shown to block cell growth and cause cell death (apoptosis).20 Patients with prostate cancer were even found to have lower levels of IGFBP-3.21
While it remains obvious to most people that obesity is detrimental to our general health, more and more studies are showing how it negatively affects prognosis in cancer patients. Recent data from both prospective studies and clinical trials for the treatment of cancer have shown increased mortality in obese patients.22 A recent randomized clinical trial for prostate cancer patients treated with radiation therapy for locally advanced prostate cancer has shown that obese patients did much worse with cancer treatment and had higher mortality than their leaner counterparts.23
Obesity is associated with high levels of circulating insulin, decreased insulin sensitivity, and insulin resistance24 and has been correlated with both higher incidence of prostate cancer and higher rates of cancer treatment failure.25-27 Randomized trials have shown an improvement in weight loss and cardiovascular health in nearly all trials comparing low-carb, high fat diets with conventional diets10,28-34, and while these low-carb diets were likely still suboptimal in my humble opinion, a low-carb caveman diet may provide prostate cancer patients with additional benefits as well.
Low-Carbs in Animals
It has become more obvious to health professionals (and hopefully everyone) that nutrition influences the incidence and treatment of cancer in general, but this may be especially relevant in prostate cancer. There aren’t many human clinical trials evaluating this connection, unfortunately. We are working to try to change this, but it is not easy.
While Caveman Doctor doesn’t like to experiment on animals, only eat them, several well-done animal studies do exist with important results. Animal studies are clearly inferior to human studies, however, animal studies usually must be done first and if and when they show results, human studies ensue. Right now, all we have is animal studies, so hopefully human trials will ensue…
Mice fed a no-carb ketogenic diet versus a low-fat or Western diet prior to and after injection with prostate cancer cells had significantly reduced tumor growth and longer survival compared to mice fed the Western diet.35 Mice on the ketogenic diet also had significantly lower levels of IGF-1 in their blood and an increase in IGFBP-3 (which blocks insulin, as discussed above).
2. Low-Carb #1
A similar study confirmed these results in mice on a low-carb, but not no-carb diet like the one above. Mice fed low-carb diets had increased survival and decreased activation of cellular tumor pathways. These mice also had increased IGFBP-3 and decreased levels of insulin, IGF-1, insulin resistance, obesity, and inflammation.36
3. Low-Carb #2
A third study revealed decreased bodyweight, tumor growth, serum insulin, and IGF-1 in low-carb versus high-carb fed mice. Markers signifying tumor growth were also increased in the high-carb mice37.
Some of these diets required the mice to go into ketosis, which is a state when carbohydrate consumption gets extremely low. Since blood glucose levels can drop very low, the body then breaks down fat in the liver and turns it into ketones, which are a sugar-like substance that the brain uses for energy. This fat breakdown is one of the reasons ketogenic or very low-carb diets often cause such dramatic weight loss. There are no long term studies on the safety of ketosis, but the short term studies listed above show it to be safe. Cavemen likely went into ketosis often when carb sources were not available or when food wasn’t available. Current caveman dieters like me go into ketosis periodically as well.
Does Low-Carb = No-Carb?
Recent data have revealed that non-ketotic low-carb diets may work as effectively as no-carb diets, resulting in similar survival, serum insulin levels, and PSA (prostate-specific antigen – the chemical that measures prostate cancer) levels in mice.38 A recent study showed a reduction in tumor growth with diets allowing 15% CHO in mice that were not experiencing ketosis.39 This is encouraging, as for most of us it can be tricky to routinely achieve an extremely low, or no-carb diet. This will also allow us to consume a significant portion of leafy, green vegetables and some fruit, while still easily remaining in the low-carb range.
A caveman diet, with its low-carb backbone, may work to decrease prostate cancer risk and more effectively cure it through several mechanisms that include weight loss and decreased serum insulin levels, as well as decreased tumor proliferation and aggressiveness in cancer cells. Once again, the diet that Mother Nature provided for us likely provides us with the most health benefits. In this case, she was trying to protect us from cancer.
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