Kimchi: Salt and Spice and Everything Nice—or Not?

Kimchi, a pungent fermented cabbage, is a staple in the Korean diet and has gained popularity due to health claims about its anti-obesity, anti-cancer, anti-oxidative, and cholesterol-lowering effects (Park 2014). These potential benefits have been popularly attributed to lactic acid bacteria that undergo fermentation to produce compounds including vitamins, prebiotic factors, bacteriocins, and dietary fibers (Cheigh et al. 1994).

However, several studies (Nan et al. 2005) have raised questions regarding the risks associated with the frequent consumption of kimchi, particularly due to its high salt content. One study in South Korea estimated the average sodium content in 100 g of kimchi at approximately 830 mg, which translates to average intake of nearly 4,900 mg per day—more than twice the 2,000 mg recommended by the WHO/FAO (Park 2009). With such a high sodium content, kimchi has been linked to several diseases, mainly gastric cancer.

The World Cancer Research Fund found that there is probable evidence that both salt and salt-preserved foods are associated with an increased risk of stomach cancer (Ge et al. 2012, Umesawa et al. 2016). Moreover, countries with traditional diets that include substantial amounts of salty (rather than salt-preserved foods) also have high rates of stomach cancer (Kypridemos et al. 2017).

According to recent data on the global incidence of gastric cancer, Korea has an age-standardized rate (ASR) of 41.8., which is approximately three times the global ASR of 12.1 (GLOBOCAN 2012). Although the rates have slowly decreased since 1999 (Jung 2015), South Korea still has the highest prevalence of gastric cancer in the world.

Like most malignancies, the pathogenesis of gastric cancer is conventionally attributed to multiple vulnerabilities and insults, including genetics, smoking, alcohol, diet, hygiene, and Helicobacter pylori infection. The major risk factors traditionally associated with kimchi, specifically, are excessive levels of sodium as well as nitrate, which undergoes chemical reactions to form N-nitroso compounds, which are potent carcinogens (Song et al. 2015). However, nitrates occur endogenously; are seen naturally in fruit and vegetables and all animals, including humans; and are frequently used as additives in processed meats.

One case-control study claimed kimchi was a risk factor for gastric cancer solely due to a significantly higher consumption of kimchi reported by gastric cancer patients in comparison with the control group (Nan et al. 2005). Another paper proposed that high sodium intake alters the gastric mucosal barrier, increasing the possibility of exposure to N-nitroso compounds and causes inflammation to the gastric epithelium, promoting endogenous mutations (Wang 2009). But a prospective cohort study in the Netherlands followed a group of people for more than six years and reported that a higher intake of nitrate from foods did not correlate at all with an increased risk of gastric cancer (Van Loon et al. 1996).

Aside from the inconsistent results, the expected correlation between high salt intake and gastric cancer is not seen in the United States. According to 2007–2010 National Health and Nutrition Examination Surveys, the U.S. average intake of sodium per day is only slightly lower than Korea’s: 4,500 mg for males aged 19–50 and 3,000 mg for women of the same age group. What is intriguing, though, is that the incidence of gastric cancer is relatively low in the United States. Another important consideration is that while a national screening program has been implemented in Korea, there is no standard screening test for gastric cancer in the United States, possibly resulting in inaccurate data secondary to artifacts in reporting.

Adding to the interesting but confusing landscape painted by kimchi is the question of its red pepper content. Capsaicin is the principal pungent component in hot peppers, including red chili peppers. Conflicting epidemiologic data and basic research results suggest that capsaicin can act either as a carcinogen, co-carcinogen, or as a cancer preventive agent. Capsaicin is unique among naturally occurring irritant compounds because the initial neuronal excitation evoked is followed by a long-lasting refractory period during which the previously excited neurons are no longer responsive to a broad range of stimuli, a process that has been exploited for its therapeutic potential.

While kimchi’s high salt and hot pepper content may seem like risk factors for gastric cancer, the findings seem sufficiently divided and inconclusive to claim this association with any confidence. Further investigation is clearly mandated. In the meantime, it would seem that moderation in our habitual kimchi intake may be the best approach.

Roger Clemens, DrPH, CFS, Contributing Editor
Adjunct Professor, Univ. of Southern California School of Pharmacy, Los Angeles, Calif.
[email protected]

Angel Jung is a master’s degree candidate, global medicine, at the Univ. of Southern California School of Medicine ([email protected]).