Salt is not recommended for breast cancer
Although salt is a necessity, U.S. consumers are unlikely ever to be deficient in salt (sodium). Our diets are heavily loaded with salt, the majority of which is derived from processed food, fast food, and restaurant meals. Increasing salt consumption is correlated with higher blood pressure in the majority of people, so that high salt consumption serves to promote heart disease and stroke. Salt consumption is also suspected of contributing to insulin resistance and metabolic syndrome, which themselves may be associated with increased risk of breast cancer. High salt consumption has been found to be associated with increased risk of pancreatic cancer. Consumption of highly salted foods (including fermented soybean products, pickled vegetables, preserved salted vegetables, and salted fish) has also been found to be associated with increased risks of ovarian and prostate cancer in China. Consumption of salted fish has been shown in several studies to increase the risks of nasopharyngeal and colorectal cancers, as well as stomach cancer. One South American study found the risk of esophageal cancer to increase with increasing consumption of salt.Breast cancer-related effects of consuming salt
The relationship between salt and cancer is related to two types of salt intake: high overall intake and high intake of very salty foods. The relatively high overall level of salt in the average U.S. diet contributes to cancer risk indirectly by promoting metabolic syndrome and reducing the potassium/sodium ratio in the diet, both of which are thought to increase the risks of various cancers.
The second type of cancer-promoting salt intake occurs when people consume highly salted specialty foods, condiments and snacks. These foods act directly on the digestive track and have been shown in numerous studies to cause stomach (gastric) cancer. Implicated foods include dried and salted fish and seafood, fermented/pickled vegetables, fish sauce, kimchi, salted preserved vegetables, salted and fermented soybean paste, salted fish preserves, salted fish roe, salted meat, salted shrimp paste, salty snacks, and salty soups. Many of the foods listed above are Asian: Since the rate of stomach cancer is relatively high in Asia, there has been great interest in investigating the causes. Note however, that European and South American studies also have found associations between heavily salted foods and stomach cancer.
There is some evidence that breast cancer survivors are at increased risk of developing stomach cancer and lobular breast cancer survivors in particular are vulnerable to gastric metastases. It makes sense for breast cancer patients, breast cancer survivors and those at high risk for breast cancer to limit their consumption of salt and highly salted foods.
Additional comments
Sodium nitrite and related compounds are routinely added to processed meats and some other salty foods to preserve their freshness and coloring. Sodium nitrite has been shown to react with chemicals in the stomach to produce nitrosamines, which are known to be cancer-promoting. However, the cancer-related effects of salt consumption are not dependent on the presence of sodium nitrite; this carcinogen simply worsens the cancer profile of salty foods that contain it.
Iodine deficiency is a major cause of preventable mental retardation found worldwide. Iodized salt is designed to prevent this deficiency. In men with recurring oxalate kidney stones, restricting consumption of salt and animal protein (combined with a normal calcium intake) has been found to provide greater protection than the low-calcium diet traditionally recommended.
Selected studies
Gastric malignancies in breast cancer survivors: Pathology and outcomes American Journal of Surgery, March 2009As the number of breast cancer survivors increases, so does the appearance of second cancers and unusual metastatic patterns. In particular, the study authors and others have noted gastric malignancies in breast cancer survivors. 19,049 breast cancer cases in three regional hospital system cancer databases were reviewed to determine the number, types, and outcomes of subsequent gastric malignancies. Twenty-eight patients developed gastric malignancies after breast cancer, representing 0.15 percent of breast cancer survivors; 82% of these patients had gastric symptoms. Overall survival for this group was 39%. Twenty-four patients had gastric primary malignancies. Four patients had gastric metastases, all had lobular histology in both their primary breast tumors and the metastatic lesions.
Ovariectomized female Dahl salt-sensitive rats exhibit features of the metabolic syndrome The FASEB Journal, 2009 23:968.9
The present study was designed to test the hypothesis that aspects of metabolic syndrome are estrogen receptor (ER) dependent. Menopause is known to be associated with increased salt-sensitivity of blood pressure and risk of metabolic syndrome. When Dahl salt-sensitive rats have their ovaries removed, they have increased blood pressure and body weight compared to similar intact female rats. The anti-diabetic drug rosiglitazone reduces blood pressure in humans and reduces the blood pressure response to high salt in ovariectomized rats. Rosiglitazone also trans-activates estrogen receptor alpha in human breast cancer cells. In the study, the authors (1) confirmed that the ovariectomized rats exhibited metabolic syndrome; and (2) tested the hypothesis that the ER antagonist, fulvestrant (Faslodex), inhibits the blood pressure-lowering effects of rosiglitazone. Blood pressure, body weigh, plasma insulin, leptin and cholesterol levels were measured in intact and ovariectomized rats. The rats were administered fulvestrant while on a low salt diet, and then were challenged by a high salt plus rosiglitazone diet for two weeks. The increase in blood pressure on the high salt diet was significantly higher in ovariectomized rats given fulvestrant and rosiglitazone together than in ovariectomized rats given rosiglitazone only. The authors conclude that ovariectomized Dahl salt-sensitive rats exhibit features of metabolic syndrome and the data suggest that the effect of rosiglitazone on blood pressure may be ER dependent.
Salt-preserved foods and risk of gastric cancer Medicina (Kaunas), 2006;42(2)
The aim of the present hospital based case-control study was to evaluate the relationship between gastric cancer and consumption of salt and salt-preserved food. Gastric cancer is a major health issue in Lithuania. Gastric cancer risk factors are believed to be related to nutrition and the environment. The study included 379 new gastric cancer cases and 1,137 controls that were free both of cancer and of gastric diseases. The cases and controls were matched by gender and age (±5 years). Information on possible risk factors was collected using a questionnaire. The odds ratios (OR) and 95% confidence intervals (CI) for gastric cancer were calculated using conditional logistic regression. The gastric cancer cases were found to have significantly lower education level on average and mostly resided in villages. After adjusting for other dietary habits, smoking, alcohol consumption, family history of cancer, education level, and area of residence, higher risk of gastric cancer was found for those adding salt to prepared meals and those who liked salty food. After also controlling for body mass index at 20 years of age and physical activity, intake of salted meat (OR=1.85, 95% CI=1.12–3.04, 1–3 times/month vs. almost never; OR=2.21, 95% CI=1.43–3.42, 1–2 times/week vs. almost never), smoked meat (OR=1.79, 95% CI=1.23–2.60, 3–4 times/week vs. 1–2 times/week), and smoked fish (OR=1.70, 95% CI=1.13–2.53, 1–2 times/week vs. 1–3 times/month) were found to be significantly associated with an increased risk of gastric cancer. Intake of salted mushrooms was also found to increase the risk of gastric cancer, however, this increase was not statistically significant. The authors conclude that people who like salty food, salt-preserved meat, or salt-preserved fish were found to have a higher risk of gastric cancer.
Diet and cancer of the stomach: A case-control study in China International Journal of Cancer, July 2006
The present case-control study was designed to evaluate the association between single food items and stomach cancer in the Heilongjiang area of China. The study included 241 patients with histologically verified stomach cancer and an equivalent number of controls (with non-cancer-related diseases) who were matched by age, sex and area of residence. The participants were interviewed during a two-year period regarding their economic status, occupation, history of smoking and of drinking, diet and dietary habits and medical history. Detailed data concerning the average frequency and quantity of intake of single food items were also obtained by the same interviewer. An inverse association between the intake of vegetables and stomach cancer was found. In particular, Chinese cabbage was found to play an important role in reducing the risk of developing stomach cancer. On the other hand, frequent consumption of potatoes and of salted and fermented soybean paste appeared to be high-risk factors.
Do preserved foods increase prostate cancer risk? British Journal of Cancer, April 2004
The present case-control study was designed to determine whether there was an association between preserved foods and prostate cancer risk. The study was conducted in southeast China during 2001 and 2002 and included 130 confirmed prostate cancer cases and 274 inpatient controls without any type of cancer. Total amount of preserved food consumed was positively associated with prostate cancer risk, with adjusted odds ratio of 7.05 (95% CI: 3.12–15.90) for the highest relative to the lowest quartile of consumption. In particular, the intake of pickled vegetables, fermented soy products, salted fish, and preserved meats was associated with a significant increase in prostate cancer risk and the risk increased with increasing levels of consumption for each of the foods.
Fish consumption and colorectal cancer: a case-reference study in Japan European Journal of Cancer Prevention, April 2003
The current epidemiological study was designed to clarify the relationship between fish consumption and the likelihood of developing colorectal cancer. Studies have suggested that fish oil supplementation can suppress the proliferation of colorectal mucosa and thereby help prevent the development of colorectal cancer. However, evidence concerning fish consumption and colorectal cancer risk is limited and inconsistent. The authors conducted a large case-control population study with 928 cases of colon cancer, 622 cases of rectal cancer and 46,886 cancer-free outpatient controls aged 40 to 79 years. Frequent raw or cooked fish intake was found to be associated with decreased risk of colon cancer (odds ratio (OR) 0.68 with 95% confidence interval (CI) 0.47-0.99), especially for males over 60 years old, smokers, and frequent meat eaters. A marginal decrease in risk (OR 0.58, CI: 0.31-1.07) also was found for female rectal cancer, especially in the subgroup that performed regular physical exercise. However, frequent dried or salted fish intake was found to be associated with increased colorectal cancer risk in females younger than 60 years old and alcohol drinkers. The authors conclude that frequent raw or cooked fish intake may decrease the risk of colorectal cancer while dried or salted fish intake may increase it.
Consumption of Salted Fish and Other Risk Factors for Nasopharyngeal Carcinoma (NPC) in Tianjin, a Low-Risk Region for NPC in the People's Republic of China Journal of the National Cancer Institute, February 1990
The current case-control study was designed to assess the association between diet and lifestyle factors and nasopharyngeal cancer in Tianjin City, People's Republic of China. The study participants included 100 patients with histologically confirmed nasopharyngeal carcinoma and 300 neighborhood controls who were individually matched to the patients with respect to age, sex, and race (i.e., Han). The dietary habits, alcohol and tobacco use, occupational exposures, and medical histories were collected from study participants. Exposure to salted fish was found to be significantly associated with an increased risk of nasopharyngeal cancer. Four characteristics of salted fish consumption independently contributed to the increased risk: (1) earlier age at first exposure; (2) increasing duration of consumption; (3) increasing frequency of consumption; and (4) cooking the fish by steaming it rather than grilling, frying, or boiling it. Significant associations were also observed for consumption of salted shrimp paste during childhood (increased risk) and consumption of carrots (reduced risk). The three dietary effects (consumption of salted fish, salted shrimp paste, and carrots) were found to be independent of each other. None of the nondietary factors studied were found to be significantly associated with nasopharyngeal cancer risk.
Dietary, total body, and intracellular potassium-to-sodium ratios and their influence on cancer Cancer Detection and Prevention, 1990;14(5)
One of the greatest alterations in the human diet, a change which has taken place only within the past few millennia, is the huge increase in the intake of sodium resulting from the use of salt in the preparation and preservation of food. At the same time, man's intake of potassium has decreased. As a result, the dietary potassium/sodium ratio has been reduced by a factor of about 20 from Paleolithic times to the present. Based on a comparison of first world people with the Yanomamo Indians in South America (who do not consume salt directly but who do grow and eat potassium-rich cooking bananas), this factor may be even higher (on the order of 100 to 200). Human beings originally were adapted to retain sodium (from a sodium-poor diet) and to excrete potassium (from a potassium-rich diet) and they are not well suited to today's high-sodium, low-potassium diet. This factor has contributed to increased rates of a number of diseases, among them cancer. The relationship between the potassium/sodium ratio and cancer development--first uncovered by epidemiologic studies--has been confirmed by various means, including dietary studies, gerontological studies, animal studies, studies of the relationships between hyper- and hypokalemic diseases and cancer, and studies of the cellular changes of this ratio induced by carcinogenic and anticarcinogenic compounds. The authors conclude that the recommended dietary potassium/sodium ratio should be well above one, preferably five or higher, and that the cellular potassium/sodium ratio should be above 10.
