There is little to no data on a connection between breast cancer and salt. Sugar, on the other hand, has been shown to be associated with breast cancer, and in my recent posts (here and here) I have been keying in on the role of sugar and breast cancer for several reasons. Firstly, many patients are curious about this link and it is one of the most common questions that I am asked by patients regarding diet and cancer. Secondly, as more and more studies reveal the role that sugar and blood glucose play in cancer initiation and progression, we need to pin down optimal dietary changes to reduce this risk. The silver lining is that if simple lifestyle and dietary changes can actually help us to avoid cancer, this is powerful news.
However, a recent study on the effects of salt caught my eye. While studies on the connection of salt and breast cancer are limited, these data may reveal some connections and raise some questions. Could a low salt diet increase the risk for breast cancer?
Breast Cancer and Salt – The Study
In this study, 152 healthy men and women were placed on a low salt diet. A key here is that these were healthy individuals with no known medical issues, yet they were placed on a low salt diet per many modern dietary recommendations. After seven days, a plethora of studies were performed on the participants to see the effect of the dietary change.
Norepinephrine, our stress hormone, was increased from the salt restriction as the unwanted stress appeared to activate these participants’ renin-angiotensin-aldosterone and sympathetic nervous systems, or more simply, the “fight or flight” response. More worrisome was the insulin resistance that they experienced from the low salt diet.1 These participants required more insulin to lower their blood sugar than before starting the low salt diet. A further study by the same group also revealed that a low salt diet raised both insulin and blood sugar levels.2
Insulin is a hormone secreted from the pancreas to lower the amount of sugar in our blood. If blood sugar becomes too high, insulin shuttles some of the sugar into our cells as high blood sugar can be fatal. High blood sugar3 and high insulin levels4 have been found to be associated with elevated breast cancer risks and worse outcomes after treatment for breast cancer. Based on this study, a low salt diet in healthy individuals increases both. Such findings are certainly worrisome.
Breast Cancer and Salt– The Takeaways
I dedicated an entire chapter of my book, Misguided Medicine, to debunking the myths of the effect of salt and our health. As you will read throughout the chapter, not only have many studies shown no benefit from lowering salt intake, but many large studies have shown significant harm. Insulin resistance and raising blood sugar levels only adds to this harm and may connect breast cancer and salt restriction.
Furthermore, if we consume a lower carbohydrate diet, we actually may need to eat more salt as insulin – secreted to lower blood sugar – acts on the kidneys to retain sodium. When synthesizing this information, it becomes clear that the data on a low salt diet is shaky at best and dangerous at worst.
This is certainly not a green light to eat processed foods. However, when a diet consists of real whole foods and a reasonable amount of carbohydrates (i.e. much lower than the food pyramid and most modern health sources would recommend) we actually need more salt to support our cardiovascular and nervous system, while supporting healthy metabolism.
- Garg, R. et al. Low-salt diet increases insulin resistance in healthy subjects. Metabolism 60, 965–968 (2011).
- Garg, R., Sun, B. & Williams, J. Effect of low salt diet on insulin resistance in salt-sensitive versus salt-resistant hypertension. Hypertension 64, 1384–7 (2014).
- Monzavi-Karbassi, B. et al. Pre-diagnosis blood glucose and prognosis in women with breast cancer. Cancer Metab. 4, 7 (2016).
- 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).
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