Kimchi: Friend or Foe?

I love kimchi, and this year during Spring Festival I went to South Korea to try the real deal. But when I got there my friend living in Seoul informed me that kimchi is (a) not vegan and (b) may be linked to stomach cancer. What!?

我非常喜欢吃韩国泡菜。今年春节时，我去了韩国品尝这道佳肴。但是到了那儿之后，一位首尔的朋友却对我说，(1) 泡菜不是素食食品，(2) 可能导致胃癌。什么情况！？

Kimchi has been previously rated one the world’s top 5 healthiest foods. Originally meant to keep people well nourished during long Korean winters, it contains high levels of vitamin C, calcium, and iron. Since kimchi is fermented it contains plentiful friendly bacterial strains, so it’s a good alternative to dairy-based probiotics like yogurt.

韩国泡菜最近被评为了世界五佳健康食品之一。泡菜原来是为了让韩国人在漫长的冬日里保持平衡的营养的，它富含维生素C、钙质和铁。由于泡菜是经过发酵制得的，它还含有许多对人体有益的微生物，所以泡菜是酸奶以外的另一种富含益生菌的食品。

Kimchi and Additives 泡菜与添加剂

Back in California a friend taught me to make kimchi by combining cabbage, garlic, ginger, chili peppers, and salt in a jar.   Apparently most varieties served in restaurants use the fish sauce or shrimp instead of salt, albeit in small amounts.  I can’t really taste the difference between the two recipes.

回到加州后，另一个朋友教了我用圆白菜、洋葱、姜、辣椒和盐等原料在罐子里自己制作泡菜。目前大多数餐馆里的泡菜都是用鱼酱或虾酱来替代盐，尽管用量很少。我其实不太能尝出这两种做法的区别。

More concerning is the presence of additives in some types of commercially prepared kimchi. Korea has blocked imported kimchi from China over safety concerns about artificial sweeteners and banned colorings ¹ and Japan invented fake processed food kimchi. They used citric acid to replace the flavor produced by the fermentation process, which shortens production time but of course eliminates the probiotic benefits. ² For kimchi fans like me, the best option is probably making it at home (very easy), or finding restaurants that prepare it fresh.

更让人担忧的是韩国泡菜中的食品添加剂。出于食品安全考虑，韩国已经停止了从中国进口泡菜，因为中国生产的泡菜中含有甜味剂和禁用的色素¹。日本也生产过伪劣的泡菜，他们用柠檬酸来产生发酵过程的香味，这样可以缩短生产时间，但同时益生菌的效果会明显降低²。因此，对于像我这样的泡菜发烧友来说，最好的选择或许就是在家自己制作（非常简单），或者寻找提供新鲜泡菜的餐馆。

Kimchi DIY

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Kimchi and Cancer 泡菜与癌症

More recently, some studies have drawn links between high stomach cancer rates in South Korea and kimchi, citing kimchi as a risk factor.  As with most nutritional studies, the relationship is complex.   Let’s break it down:

Note: If your eyes start to glaze over, skip to end for conclusions

近来，一些研究表明韩国泡菜与胃癌的高发病率有关，并把泡菜列为一个危险因素。而考虑到营养学的研究，这一关系变得更加复杂。下面我们就来分析一下：

注：如果你看到这儿已经开始两眼无神了，那就直接到最后去看结论吧！

Gastric (stomach) cancer is most prevalent type of cancer in Korea ³.  Koreans also have a far higher rate of stomach cancer than Korean Americans, suggesting that environmental rather than genetic factors are at play. ⁴

According to the World Institute of Kimchi, Koreans eat 50-100 g/d of kimchi in the summer and 150-200 g/d per day in the winter, accounting for 12.5% of total daily food intake. Kimchi contain relatively high levels of nitrates, a known precursor to carcinogenic compounds ^{5 6}

胃癌是韩国发病率最高的一种癌症³，韩国本地人的胃癌发病率也比美籍韩国人还高很多。这说明环境因素比遗传因素对发病率的影响更大⁴。

根据世界泡菜学会提供的数据，每个韩国人夏天平均每天吃50-100 g泡菜，而在冬天每天要吃150-200 g，占每日进食量的12.5%。而泡菜中含有较多硝酸盐，这是一种已知的致癌化合物^{5 6}。

However, it’s unlikely the nitrates in plant foods are actually harmful.  One study done in Mexico City showed that it was the total level of nitrites or nitrates/nitrities from animal sources that increased risk, while total intake nitrates or nitrites/nitrates from fruits and vegetables decreased risk. ⁷ In another study done in Korea, it wasn’t absolute nitrate intake but a higher ratio of nitrate to antioxidant and vitamin intake (i.e. fruit and vegetable) that was posed a risk for gastric cancer. ⁸

然而，植物食品中含有的硝酸盐可能对人类并没有危害。一项在墨西哥城的研究表明，真正产生危害的是动物产品中的亚硝酸盐总量或者硝酸盐与亚硝酸盐的比例，而植物或水果中的这些物质反而会降低患病风险⁷。另一项在韩国的研究也表明，单独的硝酸盐并不会增加危险，而是摄入食物中过高的硝酸盐对抗氧化剂和维生素（如蔬菜、水果）的比例会增加胃癌的发病率⁸。

The one study that analyzed kimchi and reported high levels of N-nitroso (the carcinogenic compound) found this after the kimchi was mixed with nitrites in “simulated human stomach conditions.” This at best is an imperfect proxy for how much N-nitroso is truly formed in the body after eating kimchi ⁹.

那项研究泡菜并且发现其中含有大量亚硝西维因（致癌化合物）的研究，是在泡菜混合了亚硝酸盐之后的“人类胃肠受激状态”下检测出来的。所以，在研究食用泡菜后身体中实际产生多少亚硝西维因上，这项研究不能算是一个具有说服力的实验⁹。

Another element of kimchi that may contribute is high salt levels. In addition to the high prevalence of gastric cancer, Koreans have some of the highest 24-hr sodium excretion levels (a proxy for sodium intake) in the world ¹⁰  A study examining the role of dietary factors in Korea and stomach cancer concluded that a high salt diet was correlated with stomach cancer. ¹¹  In 2003, another study found that high intakes of salt-fermented fish and kimchi were associated with gastric cancer. The same study reported that patients with both heliobacter pylori infection and high salty preference had a 10 fold higher risk of early gastric cancer risk compared to those with no infection and a low-salty preference. ¹²

泡菜中，另一种容易引起疾病的是大量的盐。韩国人除了胃癌发病率高以外，钠盐的分泌量（也可看作钠盐摄入）在世界上也是最多的¹⁰。一项针对饮食因素与韩国人胃癌发病率的研究表明，高盐摄入与胃癌发病是相关的¹¹。2003年的另一项研究，证明进食大量的盐类腌制产品——如鱼类和泡菜——和胃癌发病也是相关的。这项研究还证明，幽门杆菌的感染者、高盐饮食习惯的人跟不感染该菌，并且没有高盐饮食习惯的人相比，早期胃癌的发病率高出10倍¹²。

So what does it all mean?

In sum, I think if you stick to low-salt kimchi, there’s not much of a risk.  If you are truly worried about gastric cancer, get tested for H. Pylori infection, reduce your salt intake, eat more fresh fruits and vegetables, and reduce known animal sources of nitrites and nitrates in your diet, such as processed meats.

综上所述，我认为如果你一直吃的都是低盐泡菜，那并不会有太高的风险。如果你真的非常担忧是否会患胃癌，可以查一查幽门杆菌的感染情况。日常生活中，要降低盐类的摄入，多吃新鲜的蔬菜水果，并且要降低饮食中诸如加工过的肉制品等动物来源的硝酸盐和亚硝酸盐含量。

So where did the hype come from?  In 2005 a study entitled “Kimchi and Soybean Pastes are risk factors for Gastric Cancer” came out in the World of Gastroenterology, in which they concluded that the heavy kimchi eaters have a ~50% higher risk of gastric cancer.  ¹³ (Note: This was a case-control study, so they were comparing people who already had gastric cancer with another group of statistically age-gender similar people without gastric cancer.  Of the people with gastric cancer, 60% reported eating lots of kimchi in the previous year, 40% reported eating not that much kimchi in the previous year.  In the controls, this number was split 50/50 between high and low kimchi.  This is how they concluded that there was a 50% higher risk of gastric cancer associated with “high kimchi” eating. Check out this link on the odds ratio if you want to know how they came up with this number).

既然这样，那些谣传都是从哪里来的呢？2005年，一项名为“泡菜与豆瓣酱是胃癌的风险因子”的研究发表在《世界肠胃病学杂志》上，其中作者总结到，高量进食泡菜的人比普通人群胃癌发病率高50%¹³。（注：这是一项案例对照的研究，也就是研究者们比较了两个人群：一部分已经患有胃癌，另一部分与其年龄与性别相似，但不患有胃癌。在身患胃癌的人群中，60%在之前几年饮食了大量泡菜，40%在前些年吃泡菜并不多。在对照组中，大量和少量泡菜摄入的人群比例各占50%，他们便由此总结出“大量进食泡菜”会使胃癌发病率增加50%。如果你想知道怎样得出的这个数字，请查阅此处有关优势比的链接）。

Naturally, after reading the title and results you would assume that kimchi and soybean paste = bad.  But the study doesn’t mention other potential risk factors like processed meat consumption or H. pylori infection.  Moreover, they also concede that the high salt level in kimchi and soybean paste may be one factor accounting for the relationship. In the future, I think a study that includes high and low salt kimchi varieties, animal nitrates and nitrites, and ratio of these foods with fresh fruits and vegetables would be illuminating on this topic.

因此，在阅读这篇文章的标题和结论之后，我们会自然而然地认为，泡菜和豆瓣酱都是有害的。然而这个研究中并没有提到其他危险因素，诸如加工肉制品的食用量以及幽门杆菌的感染等。再者，这篇文章中也已经承认了泡菜和豆瓣酱中高盐含量是造成这一关系的因素之一。因此，我希望在今后的研究中，能够把泡菜中盐类含量的多少、动物制品中的硝酸盐和亚硝酸盐含量、以及这些食品与水果蔬菜的比例添加到研究主题里。

As with most nutrition research, the interpretation generally focuses myopically on one food item. But the categorization of one food or another as a “risk factor” is really a distraction from the main picture. Forget about kimchi: stop smoking, start exercising, sleep well, eat fresh fruits and vegetables, and ignore the latest nutrition headlines.

绝大多数营养学的研究，基本上都只关注一种食品。但是单独的一类食品就能成为某种疾病的“危险因素”，实在有点把大家的视线拉偏了。到此为止，我们还是忘记泡菜的事吧——停止吸烟、锻炼身体、按时睡觉、多吃新鲜蔬果，不要再管那些最新的营养学的研究啦！

翻译者：谭骁

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