“Sugar feeds cancer.” We have all heard this a million times, yet what exactly do we do with this information? As data continue to accumulate, this question will eventually be answered with certainty. In fact, new data linking breast cancer and sugar increases our concern over diet’s effect – and the modern, food pyramid-driven diet – on cancer outcomes. Last week, I discussed a study revealing that metabolic health may be more important than a woman’s weight when it comes to breast cancer. This week, a new study adds more fuel to the fire.
High levels of blood sugar have been linked to worse outcomes in patients treated for many different types of cancer, including brain tumors1–3 and lung cancer.4 Even in patients with less “metabolic” cancers, like prostate cancer, data reveal that a man’s blood sugar value can predict how well he will do with treatment.5 Along these lines, men that are found to have high blood sugar before removal of their prostate (a prostatectomy) also experience a larger risk of their cancer returning afterwards.6
Breast Cancer and Sugar
Segueing to breast cancer, the data has been less clear. Dr. Pamela Goodwin and her group from the University of Toronto have shown that fasting insulin levels – the hormone that pulls sugar from the blood and into our cells – are correlated with an increased risk of breast cancer metastasizing and also with an increased risk of a woman dying after the diagnosis of breast cancer.7 A new study from the journal Cancer and Metabolism has shown that in non-diabetic women with breast cancer, elevated blood sugar is associated with poorer outcomes and an increased risk of death.8 We already know that metabolic dysfunction, exemplified by obesity and signs of metabolic syndrome, can lead to poorer outcomes for women with breast cancer.9 However, this study adds ammo to the smoking gun of the view of sugar “feeding cancer.”
The question remains whether the sugar is actually “feeding” the cancer cells or the metabolic response – insulin release, inflammation, obesity from consistently high blood sugar, and even others – is the cause. In my view, it is likely a combination of all of these factors.
Breast Cancer and Sugar – Dietary Strategies
Regardless of the exact significance of high blood sugar and the detriment in survival that accompanies it in multiple cancer types, what these studies are systematically telling us is to limit those foods that dramatically raise our blood sugar levels. Along these lines, it certainly seems reasonable to try to limit excess sugar spikes and the amount of insulin our pancreas is forced to secrete after a meal to lower our blood sugar. Over time, chronically elevated blood sugar and insulin levels are associated with poor cancer outcomes in multiple studies. Exercise also helps to lower blood sugar and insulin levels.10 This gives women two weapons against metabolic dysfunction.
What stands out from all of these studies is that we need to eat healthy to avoid and fight cancer. While this can be difficult during cancer treatment, we can aim for the easy targets to start. Then switch to refine the more difficult ones, by turning to healthy leafy greens and berries as our major carbohydrate sources.
Ignore the Easy Targets:
- Juices and soda
What this data may tell us is simply to ignore the decades of low-fat and high-carbohydrate recommendations. The evidence is piling up. Cancer loves a high blood sugar and the resulting insulin spikes that follow. Breast cancer and sugar continue to be caught conspiring against our health. While the studies continue to provide us with more answers, it only seems reasonable to follow a healthy diet and avoid sugar and other foods that spike blood glucose.
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- Derr, R. L. et al. Association between hyperglycemia and survival in patients with newly diagnosed glioblastoma. J. Clin. Oncol. 27, 1082–6 (2009).
- McGirt, M. J. et al. Persistent outpatient hyperglycemia is independently associated with decreased survival after primary resection of malignant brain astrocytomas. Neurosurgery 63, 286–91; discussion 291 (2008).
- Mayer, A. et al. Strong adverse prognostic impact of hyperglycemic episodes during adjuvant chemoradiotherapy of glioblastoma multiforme. Strahlenther. Onkol. 190, 933–8 (2014).
- Luo, J., Chen, Y.-J. & Chang, L.-J. Fasting blood glucose level and prognosis in non-small cell lung cancer (NSCLC) patients. Lung Cancer 76, 242–7 (2012).
- Wright, J. L. et al. Hyperglycemia and prostate cancer recurrence in men treated for localized prostate cancer. Prostate Cancer Prostatic Dis. 16, 204–8 (2013).
- Lee, H., Kuk, H., Byun, S.-S., Lee, S. E. & Hong, S. K. Preoperative glycemic control status as a significant predictor of biochemical recurrence in prostate cancer patients after radical prostatectomy. PLoS One 10, e0124761 (2015).
- Goodwin, P. J. et al. Fasting insulin and outcome in early-stage breast cancer: results of a prospective cohort study. J. Clin. Oncol. 20, 42–51 (2002).
- Monzavi-Karbassi, B. et al. Pre-diagnosis blood glucose and prognosis in women with breast cancer. Cancer Metab. 4, 7 (2016).
- Champ, C. E., Volek, J. S., Siglin, J., Jin, L. & Simone, N. L. Weight Gain, Metabolic Syndrome, and Breast Cancer Recurrence: Are Dietary Recommendations Supported by the Data? Int. J. Breast Cancer 2012, 9 (2012).
- Borghouts, L. B. & Keizer, H. A. Exercise and insulin sensitivity: a review. Int. J. Sports Med. 21, 1–12 (2000).
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