How do low carb diets affect the risk of cancer

Healthy diet plan / Category / Emile Du Toit / May 9th 2014

As mentioned before, the literature on weight loss in general and the low carb diet debate in particular is somewhat dishonest and unreliable. In this article we are going to examine the various claims by the proponents and opponents of the low carb (Atkins diet) pertaining to the risk of cancer.

The argument for low carb high protein (Atkins) diets having a protective effect against cancer.

A theory has emerged that low carbohydrate diets might be able to suppress or at least delay the emergence of cancer, and that tumor growth could be slowed down. This argument makes the following points:

  • Contrary to normal cells, most cancer cells depend on glucose availability in the blood for their energy and biomass generating demand. They struggle to metabolize significant amounts of fatty acids or ketone bodies due to mitochondrial dysfunction.
  • High insulin and insulin-like growth factor (IGF)-1 levels resulting from chronic ingestion of high carbohydrate meals can directly promote tumor cell proliferation via the insulin/IGF1 signaling pathway.
  • Elevated ketone bodies when insulin and blood glucose levels are low appear to negatively affect growth of different malignant cells, or are not readily usable for metabolic demands by tumor cells.
  • Many cancer patients also appear to exhibit insulin resistance and it is hypothesized that they might benefit from an increased protein and fat intake.

  • Opponents to this view feel that low carb (Atkins) diets actually increase the risk of several ailments, including cancer.

  • Firstly there is some evidence that reducing glucose from carbs doesn’t solve the problem with cancer cells as they just switch over to using lactic acid in the blood for energy but at a much slower growth rate than with glucose. It appears that the liver may also then turn protein into sugar for the cancer cells. It may be though that altering the PH of the body might partially solve this problem.
  • High animal protein diets appear to predispose people to colorectal cancer. The Atkins (low carb, high protein) diet utilises even higher protein values in order to induce ketosis and/or make up the calorie deficit.
  • Meals high in saturated fat impair arterial compliance and therefore increase the risk of cardiovascular disease.
  • Ketosis itself affects the body’s acid-base balance, causing metabolic acidosis, which can lead to hypophosphatemia, reabsorption of calcium from bone, osteoporosis, and kidney stones. Hypophosphatemia is an electrolyte disturbance in which there is an abnormally low level of phosphate in the blood. In the about 1 in 4 people who have reduced kidney function research has shown that this can also result in kidney damage.

  • A few actual studies of cancer risk in low carb (Atkins) diets

    Breast cancer

    One particular study correlated breast cancer and carbohydrate consumption levels. 2 It compared a sample of 475 women on a low carbohydrate diet with 1391 control subjects. The conclusion reached was that ‘a high percentage of calories from carbohydrate, but not from fat, was associated with increased breast cancer risk.’

    Colorectal cancer

    A Harvard University study demonstrated that regular animal protein intake increases the risk of colorectal cancer by 300%.

    General cancer

    A longitudinal study (i.e. research over a period of time) with a large sample (22 944 healthy adults) investigated total mortality due to cardiovascular and cancer mortality.3 The results indicated that following a low-carb diet, or a low-carb high protein diet over a period of time placed the subjects at a significantly greater risk of mortality. It is not clear what the impact on cancer alone (as opposed to cardiovascular disease) was.

    Cancer of the kidneys

    Another study examined 2301 subjects of which 767 were suffering from renal cell carcinoma.1 The study found that bread (which tends to have a high glycemic index) was strongly correlated with cancer, with pasta and rice having a modest correlation. Vegetables had a negative correlation – and could be assumed to diminish cancer risk.

    What strikes me in this study is that all carbs are clearly not the same in terms of cancer risk (certainly for renal cell carcinoma). As an observation, the glycemic index of foods appears to be positively correlated with risk of cancer, and this might add weight behind a low GI rather than low carb diet.

    Recent high protein (and therefore low carb) studies show increased risk of cancer and all-cause mortality.

    You might want to read my article on how high protein diets may lead to higher levels of diabetes, cancer and all-cause mortality at this point. It explains the findings of the latest, cutting-edge research studies that demonstrate that higher protein levels may well increase the risk of all-cause mortality, and particularly cancer mortality.

    In the one 2014 study participants ingesting 20% or more calories from protein were 4X more likely to get cancer.

    Conclusions

    In my opinion the evidence on the effect that low carb (Atkins) diets have on the risk of cancer appears to quite strongly support a link between both low carbohydrate consumption and (separately) high protein consumption in increased mortality from cancer.

    It does appear that low carb diets might have merit in reducing tumor growth in persons who already have cancer, though it is less clear how effective this is over the longer term. In general though, combining the research on low carb diets with that from high protein diets I would be cautious in pursuing a low carb high protein diet, particularly if you have cancer in the family!

    References

    1. Bravi, F., Bosetti, C., Scotti, L., Talamini, R., Montella, M., Ramazzotti,V., Negri,E., Franceschi, S., & La Vecchia, C. (2006): "Food Groups and Renal Cell Carcinoma: A Case-Control Study from Italy". International Journal of Cancer 120 (3): 681–5 http://onlinelibrary.wiley.com/doi/10.1002/ijc.22225/abstract). (http://dx.doi.org/10.1002%2Fijc.22225).
      (//www.ncbi.nlm.nih.gov/pubmed/17058282).
    2. Romieu, I., Lazcano-Ponce, E., Sanchez-Zamorano, L.M., Willett, W., & Hernandez-Avila, M. (2004): ‘Carbohydrates and the Risk of Breast Cancer among Mexican Women’. Cancer Epidemiology Biomarkers & Prevention, Vol. 13, 1283-1289 (http://cebp.aacrjournals.org/cgi/content/abstract/13/8/1283)
    3. Trichopoulou A, Psaltopoulou T, Orfanos P, Hsieh CC, Trichopoulos D.(2007)’ Low-carbohydrate-high-protein diet and long-term survival in a general population cohort’. Eur J Clin Nutr. 61(5):575-81. (http://www.nature.com/ejcn/journal/v61/n5/full/1602557a.html)

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