A Coarse Sieve
Subtle effects of daily human life are very difficult to observe and study with our current methods. I'm always interested to see reviews such as this one but it can be difficult to interpret the findings. It is so common today to see a report that a substance is bad for humans, then to find a report the next week that says the opposite. The silver lining is that contradictions make us think. My summary and thoughts on the above review hopefully will help this thinking process.
Overweight and obesity is a common risk factor for many cancers. This has emerged from many studies including in cancers of breast, colon, pancreatic tissue (and more). It is estimated that up to 1/5 of cancer deaths are related to overweight and obesity. Thinking needs to go deeper to understand this and the review does mention insulin growth factor (IGF) and metabolic triggers that spur cancer cell growth. Carrying too much weight increases inflammation and changes sugar and fat metabolism which have been linked to cancer repeatedly.
The review mentions a study on protein intake where low protein intake was associated with reduced cancer risk. This suggestion has come out of humanizing medicine for a century. Modern naturopaths also warn about too much protein when on the ketogenic diet (as well as healthy protein sources which is hardly studied at all).
The authors pull the party line on diet, suggesting a diet with "reduced calorie intake combined with a significant limitation in red and processed meats, refined grains, saturated fats, sugar, sugar-containing beverages." The sieve of science is coarse here and I worry that there are confounding elements. Saturated fats are often combined with high sugar foods. It may be that the fats are fine (even necessary) and the sugars potentiate the damage. Red meat varies greatly in inflammatory potential depending on if the animals are pastured or raised in factory farms.
The protective effects of vegetables and fruits have come out of several studies. There is potential confounding here too. The Gerson diet is diet very rich in vegetables and fruit. There are components in this diet that certainly can be helpful. Perhaps it depends on what is missing or needed in the patient. But the fact is that sugars are sugars in the end. All carbohydrates are metabolized to sugar whether processed or organic. Gerson does not limit sugar intake- in fact it may increase overall sugar intake. But Gerson will raise a person's intake of protective compounds like vitamin C, sulfurophanes and much more. These are potent substances but the picture is complicated and honestly poorly studied.
The article notes a study on high olive oil consumption and protective effect from post-menopausal breast cancer.
The review notes a possible deleterious effect of using antioxidant compounds in high risk populations (such as smokers at risk of lung cancer). Bata carotene has trended to be more risky in such populations and it is thought that cancer cell death may depend on some oxidative stress. Using these supplements might take the pressure off the bad cells.
Randomized controlled trials on fat intake are mentioned in regards to breast cancer recurrence. There seemed too be conflicting results with the consistent variable not being low fat but weight loss associated with greater survival. Other cancers are mentioned and the only consistent finding seems to be lower obesity. To me this is a sign that we see confounding of several variables.
I am happy that these reviewers mentioned some key supplements and noted positive data on them as well. Curcumin was mentioned as a supplement "not to be discouraged" due to recent positive studies showing it significantly impacted the cancer in 1/10 to 1/3 of patients that used it in trials. Meanwhile we have TV ads for super-expensive medicines (hundreds of thousands of dollars) that prolong life by a couple of months with their use!
This review also looks at quality fish oil and states these are "not to be discouraged" as there is evidence they can help against cancer. They were less positive with green tea and interestingly found vitamin c, especially intravenous high dose, to be promising. They were also optimistic about artemisinin- the antimalaria drug that has been given a new role in cancer. Vitamin D they were less excited about- though I will save my commentary for another place as I feel this is an important and complex subject. The reviewers did not really know what to say about fasting in terms of drawing conclusions- though they did point out some of the relevant positive literature they were worried about too much weight loss and too little intake of essential nutrients. It is unfortunate that these reviewers did not address the ketogenic diet at all. I understand very well the academic constraints on what researchers can say (or risk not getting their paper published) and their review does try to push the envelope of academic medicine- that I support. One has to pull the slow to change mainstream along slowly in the process of scientific advancement.