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Potential 50% higher risk of gastric cancer associated with intake of pickled vegetables/foods and perhaps stronger associations in Korea and China
- Thread starter ginfreely
- Start date
Abstract
Background: Ecological and experimental studies have suggested an increased risk of gastric cancer in relation to consumption of pickled vegetables in East Asia.Methods: We conducted a meta-analysis of epidemiologic observational studies to evaluate the existing evidence. Searching PubMed, Vip Chinese Periodical, and China National Knowledge Infrastructure databases, we found a total of 60 studies, 50 case–control, and 10 prospective. We compared gastric cancer risk in pickled vegetable/food users versus nonusers (11 studies) or versus those in the lowest reported category of use (49 studies). Pooled results were computed with random-effects models.
Results: Among case–control studies, 30 showed significant increased risk and one showed significant decreased risk. Among prospective studies, two showed a significant increased risk but none showed a significant decreased risk. The OR (95% CI) was 1.52 (1.37–1.68) for the overall association, 1.56 (1.39–1.75) for case–control, and 1.32 (1.10–1.59) for cohort studies. The OR (95% CI) was 1.89 (1.29–2.77) in Korean, 1.86 (1.61–2.15) in Chinese, and 1.16 (1.04–1.29) in Japanese studies, and 1.14 (0.96–1.35) in studies from other countries. There was high heterogeneity in overall and subgroup analyses. There was little evidence for publication bias.
Conclusion: Our results suggest a potential 50% higher risk of gastric cancer associated with intake of pickled vegetables/foods and perhaps stronger associations in Korea and China.
Impact: The results of this study may offer ways to reduce the risk of gastric cancer in highly populated areas with high incidence of gastric cancer. Cancer Epidemiol Biomarkers Prev; 21(6); 905–15. ©2012 AACR.
Introduction
Despite a remarkable decline in its incidence and mortality in many nations, gastric cancer remains the fourth most common malignancy and the second leading cause of cancer death in both sexes worldwide (1, 2). Distribution of gastric cancer incidence shows remarkable heterogeneity across the world. Of the nearly 1 million estimated new annual cases, approximately half occur in Eastern Asia (1).Known risk factors of gastric cancer, most notably Helicobacter pylori (3), account for only a proportion of all cases, and do not completely explain the heterogeneity in its distribution. Only a small proportion of people who carry H. pylori in their stomachs develop gastric cancer (4), suggesting that other factors, such as eating pickled food, may be responsible in cocarcinogenesis.
Ecological studies have shown higher risks of esophageal and gastric cancers in areas with high consumption of pickled food (5, 6). In high-risk areas of China, pickled food, particularly pickled vegetables, were eaten daily for 9 to 12 months a year and constituted an important part of the family diet (5). The traditional way of preparing pickled vegetables, packing moist vegetables in a jar for a few weeks or months, allows fermentation and growth of fungi and yeasts (5, 7) and can potentially yield carcinogenic compounds such as N-nitroso compounds and mycotoxins (5, 8, 9). Indeed, a number of experimental and in vitro studies have shown mutagenicity and carcinogenicity of pickled vegetables (5, 10, 11).
Whereas ecological studies and mechanistic studies have provided support for a role of pickled food in gastric carcinogenesis, the results of epidemiologic case–control and cohort studies have not been consistent. Hence, in 1991, the Working Group of the International Agency for Research on Cancer (IARC) classified traditional Asian pickled vegetables as possibly carcinogenic to humans (7). The Working Group found limited evidence in humans and inadequate evidence in experimental animals for carcinogenicity of pickled vegetables. Since then, however, a large number of additional studies have investigated the association of pickled vegetables/foods with different cancers, including stomach cancer. In this systematic review and meta-analysis, we examine and present results of epidemiologic studies that have investigated the association of pickled vegetable/food consumption with risk of stomach cancer.
) (diet), (
) (pickled food), (
) (pickled vegetable), (
) (pickled vegetable), (
) (pickled vegetable), (
) (pickled vegetable), (
) (pickled vegetable), (
) (digestive tract), (
) (stomach or gastric), (
) (cancer or carcinoma), and (
) (tumor). Using this approach, we identified 124 articles from the PubMed database and 195 from the Chinese databases. Two of the authors (F. Islami and J.-S. Ren) reviewed the publications in English language. Chinese publications were reviewed by one of the authors (J.-S. Ren).
We examined the abstracts of the selected articles and retrieved and reviewed the full text of possibly eligible articles. Furthermore, bibliographies of the relevant original and review articles were searched manually. Only case–control and cohort studies that provided risk estimates or crude numbers of cases and controls for the exposure of interest were included. Studies that reported results for cancer of the stomach in combination with other cancers were excluded. When results from an individual study were available in several publications, we used the most informative article, for example, results were reported for a higher number of participants or were adjusted for main confounding factors. For case–control studies, we limited our inclusion to those that used control subjects who did not have other upper gastrointestinal cancers. One study (12) was excluded because study subjects were atomic bomb survivors in Japan, a group heavily exposed to γ radiation, an important risk factor for gastric cancer among the exposed individuals (13). Therefore, the risk associated with other factors could be difficult to disentangle. Using these approaches, 60 full-text articles were included in this meta-analysis (14–73). A summary of the study selection process is presented in Fig. 1.
Materials and Methods
Selection of studies
To identify publications in English or Chinese languages on the association of pickled vegetable/food consumption and risk of gastric cancer, we conducted a comprehensive search of the PubMed, Vip Chinese Periodical, and China National Knowledge Infrastructure databases. All results were updated on January 18, 2012. The following terms were used to search text words in the PubMed database: (stomach OR gastric) AND (cancer OR carcinoma OR adenocarcinoma OR neoplasm OR neoplasia OR neoplastic) AND (pickle OR pickled OR moldy OR fermented). Combinations of the following terms were used to search the Chinese databases: (
We examined the abstracts of the selected articles and retrieved and reviewed the full text of possibly eligible articles. Furthermore, bibliographies of the relevant original and review articles were searched manually. Only case–control and cohort studies that provided risk estimates or crude numbers of cases and controls for the exposure of interest were included. Studies that reported results for cancer of the stomach in combination with other cancers were excluded. When results from an individual study were available in several publications, we used the most informative article, for example, results were reported for a higher number of participants or were adjusted for main confounding factors. For case–control studies, we limited our inclusion to those that used control subjects who did not have other upper gastrointestinal cancers. One study (12) was excluded because study subjects were atomic bomb survivors in Japan, a group heavily exposed to γ radiation, an important risk factor for gastric cancer among the exposed individuals (13). Therefore, the risk associated with other factors could be difficult to disentangle. Using these approaches, 60 full-text articles were included in this meta-analysis (14–73). A summary of the study selection process is presented in Fig. 1.
Results
Summary characteristics of the 60 studies that were included in this analysis are presented in Table 1. There were 50 case–control and 10 prospective studies. The majority of studies (n = 49) were from Eastern Asia, including 29 studies from mainland China, 13 from Japan, 6 from Korea, and one study from Taiwan. Twenty studies were retrieved from Chinese literature. The total number of cases in case–control and cohort studies was 16,448. The number of controls in case–control studies was 87,622.
Table 2 shows the results of overall and subgroup analyses. For the overall association, the OR (95% CI) was 1.52 (1.37–1.68). The I2 statistic was 80% (P < 0.001), suggesting high heterogeneity. A forest plot and Begg funnel plot for overall association are shown in Figs. 2 and 3, respectively. Of the 50 case–control studies, 44 showed increased risk (30 being statistically significant) and 6 showed decreased risk (1 being statistically significant) of gastric cancer associated with use of pickled vegetables/foods. Among the 10 prospective studies, 9 showed increased risk (2 being statistically significant) and 1 showed decreased risk (not statistically significant). The distribution of the dots on the Begg funnel was fairly symmetric, and P for bias in Egger weighted regression method was 0.40, suggesting little evidence for publication bias.
Discussion
The combined result from all studies showed an approximately 50% increase in risk of gastric cancer in those who consumed pickled vegetables/foods versus those who did not consume pickled vegetables/foods or those who used it minimally (lowest consumption category).There are reasons to conclude that the results might be biased or confounded, and not causal. Mainly, subgroups of studies that had stronger designs showed smaller increases in risk, and these small increases in risk could still be due to bias and confounding. Case–control studies, which showed stronger associations, may be subject to interviewer bias, recall bias, and other methodologic problems (75). Cohort studies, which have been argued to generate more valid results, particularly in nutritional studies (75), showed less strong associations. Among case–control studies, those that used population-based controls or adjusted for potential confounders showed smaller increases in risk.
There are also reasons to believe that the increased risk is causal. The large majority of the studies (53 of 60) showed point estimates that were above one and only 7 were below one. All subgroup analyses showed statistically significant increased risk. The results are consistent with ecological studies (5, 6), animal studies (5), and laboratory findings (5, 10, 11) pointing toward a possible role of pickled vegetable/food in alimentary tract carcinogenesis. The results are also supported by findings from a recent meta-analysis that showed a doubling of esophageal cancer risk with consumption of pickled vegetables (74). A study from China—not included in this meta-analysis because results were reported for a combination of gastric (501 cases) and esophageal (250 cases) cancers—also showed a 3-fold increase in risk of those cancers associated with pickled food consumption (76). Although point estimates in our meta-analysis did not indicate strong associations, nutritional studies are highly subject to measurement errors that bias results toward null. Therefore, the unbiased relative risks might be substantially higher than those observed in individual studies. In particular, it has been argued (74) that some studies conducted in high-risk areas of China that have shown null results [e.g., the study by Tran and colleagues (73)] may suffer from misclassification.
We conducted multiple subgroup analyses to test the robustness of the results and to explore the reasons for heterogeneity. As discussed earlier, all subgroup analyses showed a statistically significant increased risk. Part of the heterogeneity was due to study design; studies adjusted for confounders showed smaller increases in risk. Except for studies from Japan, the results within each geographic region remained heterogeneous. For example, Chinese studies showed an I2 index of 78%.
We studied the possibility of publication bias using funnel plots and Egger weighted regression method. Neither method provided substantial evidence for publication bias.
Another recent meta-analysis of this same subject included 14 Japanese and Korean studies has reported an overall 28% (95% CI, 6%–53%) increase in risk of gastric cancer associated with high intake of pickled vegetables (77). Although both studies have shown an increased risk, our study included a much larger number of studies, and included studies from several others parts of the world, most notably China. In our analysis, we observed higher relative risks in studies conducted in Korea and China than those conducted in Japan and other countries. This difference between regions may be due to the variant ingredients, processing, or consumption habits. For example, in Korea, pickled food (kimchi) is more popular and consumed in greater amount than other countries. Major types of pickled vegetables used in Japan are salted products, such as shinzuke-takana (with 3 or 4% salt) and furuzuke-takana (with approximately 10% salt), and nonsalted products, such as Sunki, which is prepared without salt but undergoes lactic acid fermentation (7). The average daily per capita consumption of various salt-fermented vegetables in Japan (37 g/d) is substantially lower than of kimchi used by Koreans (200–300 g/d; ref. 7). In some areas of China, pickled vegetables were eaten daily for 9 to 12 months a year and were an integral part of the diet in some families (5), traditionally prepared by keeping tightly packed moist vegetables in a jar packing for a few weeks or months, allowing fermentation and growth of fungi and yeasts (5, 7). On the other hand, in the United States and northern Europe, vinegar is the most commonly used preservative in the manufacture of cucumber pickles (7).
Pickled food intake could increase gastric cancer risk due to their nitrate and nitrite content, which can react to form gastric carcinogens, N-nitroso compounds (78). Other factors may also increase gastric cancer risk. For example, extra salt is consumed with intake of pickled food, and high salt intake may increase the risk of gastric cancer (71). Moreover, increased intake of pickled food may reduce consumption of fresh vegetables, which may again lead to increased risk of gastric cancer.
We studied the possibility of publication bias using funnel plots and Egger weighted regression method. Neither method provided substantial evidence for publication bias.
Another recent meta-analysis of this same subject included 14 Japanese and Korean studies has reported an overall 28% (95% CI, 6%–53%) increase in risk of gastric cancer associated with high intake of pickled vegetables (77). Although both studies have shown an increased risk, our study included a much larger number of studies, and included studies from several others parts of the world, most notably China. In our analysis, we observed higher relative risks in studies conducted in Korea and China than those conducted in Japan and other countries. This difference between regions may be due to the variant ingredients, processing, or consumption habits. For example, in Korea, pickled food (kimchi) is more popular and consumed in greater amount than other countries. Major types of pickled vegetables used in Japan are salted products, such as shinzuke-takana (with 3 or 4% salt) and furuzuke-takana (with approximately 10% salt), and nonsalted products, such as Sunki, which is prepared without salt but undergoes lactic acid fermentation (7). The average daily per capita consumption of various salt-fermented vegetables in Japan (37 g/d) is substantially lower than of kimchi used by Koreans (200–300 g/d; ref. 7). In some areas of China, pickled vegetables were eaten daily for 9 to 12 months a year and were an integral part of the diet in some families (5), traditionally prepared by keeping tightly packed moist vegetables in a jar packing for a few weeks or months, allowing fermentation and growth of fungi and yeasts (5, 7). On the other hand, in the United States and northern Europe, vinegar is the most commonly used preservative in the manufacture of cucumber pickles (7).
Pickled food intake could increase gastric cancer risk due to their nitrate and nitrite content, which can react to form gastric carcinogens, N-nitroso compounds (78). Other factors may also increase gastric cancer risk. For example, extra salt is consumed with intake of pickled food, and high salt intake may increase the risk of gastric cancer (71). Moreover, increased intake of pickled food may reduce consumption of fresh vegetables, which may again lead to increased risk of gastric cancer.
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This meta-analysis has several strengths. We searched both English and Chinese literature and included a large number of studies. We also conducted several preplanned subgroup analyses. However, because all studies included in the meta-analysis had observational design, the results may be confounded or distorted by biases affecting observational studies.
In summary, our results suggest a potential 50% higher risk of gastric cancer associated with intake of pickled vegetables/foods and perhaps stronger associations in China and Korea. Results should be interpreted considering limitations of observational studies and in the light of analysis of dose–response effect, laboratory and animal studies, and perhaps human studies of other gastrointestinal tract organs.
In summary, our results suggest a potential 50% higher risk of gastric cancer associated with intake of pickled vegetables/foods and perhaps stronger associations in China and Korea. Results should be interpreted considering limitations of observational studies and in the light of analysis of dose–response effect, laboratory and animal studies, and perhaps human studies of other gastrointestinal tract organs.
Combinations of the following terms were used to search the Chinese databases: () (diet), () (pickled food), () (pickled vegetable), () (pickled vegetable), () (pickled vegetable), () (pickled vegetable), () (pickled vegetable),
The pickled word meaning in this scientific paper is the same as fermented. Just look at the word search they used for their meta analysis can tell:
Combinations of the following terms were used to search the Chinese databases: (
) (diet), (
) (pickled food), (
) (pickled vegetable), (
) (pickled vegetable), (
) (pickled vegetable), (
) (pickled vegetable), (
) (pickled vegetable),
All these are the same as kimchi and sauerkraut all using salt for fermentation. You can trust the Angmoh YouTubers and eat more sauerkraut but Angmoh got good genes not so prone to stomach cancer while East Asians obviously not the same. And the latter is a fact proven from China to korea to Japan all the high stomach cancer incidence areas eat alot of fermented vegetables.
The pickled word meaning in this scientific paper is the same as fermented. Just look at the word search they used for their meta analysis can tell:
Combinations of the following terms were used to search the Chinese databases: (
) (diet), (
) (pickled food), (
) (pickled vegetable), (
) (pickled vegetable), (
) (pickled vegetable), (
) (pickled vegetable), (
) (pickled vegetable),
All these are the same as kimchi and sauerkraut all using salt for fermentation. You can trust the Angmoh YouTubers and eat more sauerkraut but Angmoh got good genes not so prone to stomach cancer while East Asians obviously not the same. And the latter is a fact proven from China to korea to Japan all the high stomach cancer incidence areas eat alot of fermented vegetables.
The pickled word meaning in this scientific paper is the same as fermented. Just look at the word search they used for their meta analysis can tell:
Combinations of the following terms were used to search the Chinese databases: (
) (diet), (
) (pickled food), (
) (pickled vegetable), (
) (pickled vegetable), (
) (pickled vegetable), (
) (pickled vegetable), (
) (pickled vegetable),
All these are the same as kimchi and sauerkraut all using salt for fermentation. You can trust the Angmoh YouTubers and eat more sauerkraut but Angmoh got good genes not so prone to stomach cancer while East Asians obviously not the same. And the latter is a fact proven from China to korea to Japan all the high stomach cancer incidence areas eat alot of fermented vegetables.
https://www.thehealthyhomeeconomist.com/the-crucial-difference-between-pickled-and-fermented/
The Crucial Difference Between Pickled and Fermented
by Sarah Pope / Affiliate Links ✔Table of Contents[Show]
The often overlooked differences between pickled and fermented foods. They are not necessarily the same nor do they offer the same benefits to health.
There seems to be a bit of confusion going around about fermented foods and the difference between what you make in your kitchen and the pickled versions that are available on the supermarket shelf. For example, in one of my video lessons, I demonstrate how to make sauerkraut in the traditional manner.
After the shredded cabbage ferments on the kitchen counter for a few days, it is then refrigerated or kept in a cool cellar where the sauerkraut remains naturally preserved for extended periods of time.
How does this homemade pickled cabbage compare to the pickled cabbage in a jar in the supermarket? What about pickled cucumbers or pickled garlic, also popular commercial choices?
Pickled vs Fermented Foods
Alex Lewin, author of Real Food Fermentation explains that the confusion comes from the overlap in definition. In a nutshell, not all fermented foods are pickled and not all pickles are fermented.In other words, foods that are pickled are those that have been preserved in an acidic medium. In the case of various types of supermarket pickles on the shelf, the pickling comes from vinegar.
These vegetables, however, are not fermented (even though vinegar itself is the product of fermentation) and hence do not offer the probiotic and enzymatic value of homemade fermented vegetables.
Vegetables that you ferment in your kitchen using a starter, salt, and some filtered water create their own self-preserving, acidic liquid that is a by-product of the fermentation process. This lactic acid is incredibly beneficial to digestion when consumed along with the fermented vegetables or even when sipped alone as anyone on the GAPS Intro Diet has discovered (cabbage juice anyone?). In other words, homemade fermented veggies are both fermented and pickled.
Alcoholic Fermentation
What about alcoholic fermentation?In the case of wine and unpasteurized beers, fermentation occurs as the result of certain yeasts converting sugars into alcohol but there is no pickling that takes place despite the common expression that a person who has had too much to drink is “pickled”.
4 Benefits of Culturing without Heat or Pressure
Home fermentation of vegetables preserves without the use of any pressure or heat unlike supermarket versions of the same foods. It allows the ubiquitous and beneficial lactobacilli present on the surface of all living things – yes, even your own skin – to proliferate creating lactic acid which not only pickles and preserves the vegetables, but also promotes the health of those that consume it in the following ways:- Enhances the vitamin content of the food.
- Preserves and sometimes enhances the enzyme content of the food.
- Improves nutrient bio-availability in the body.
- Improves the digestibility of the food and even cooked foods that are consumed along with it!
Avoid Shelf Stable Pickled Foods
So don’t be fooled by unhealthy supermarket pickled versions of homemade fermented foods.These modern foods are the product of high heat and pressure which destroys nutrients and does not in any way enhance health.
The one exception to this rule is the various fermented foods in the refrigerator section of many health food stores. These products are actually fermented and pickled. The only drawback is that these gourmet items are rather expensive compared to the pennies per ounce it costs to make them yourself.
If home fermentation is a kitchen goal that you are ready to tackle, there are plenty of fermented foods recipes on this blog to help get you started on this fun journey! If you prefer trying fermented beverages first, the provided link will take you to over two dozen recipes to consider.
Didn’t i already say those so called China pickled vegetables in the scientific paper 腌菜 酸菜 酱菜 咸菜 泡菜 and German sauerkraut Korean kimchi Japan miso etc are all fermented using salt not vinegar. So they are not pickled using vinegar and no difference at all and not pickled but fermented according to strict definition of pickled. Read properly.https://www.thehealthyhomeeconomist.com/the-crucial-difference-between-pickled-and-fermented/
The Crucial Difference Between Pickled and Fermented
by Sarah Pope / Affiliate Links ✔
Table of Contents[Show]
The often overlooked differences between pickled and fermented foods. They are not necessarily the same nor do they offer the same benefits to health.
There seems to be a bit of confusion going around about fermented foods and the difference between what you make in your kitchen and the pickled versions that are available on the supermarket shelf. For example, in one of my video lessons, I demonstrate how to make sauerkraut in the traditional manner.
After the shredded cabbage ferments on the kitchen counter for a few days, it is then refrigerated or kept in a cool cellar where the sauerkraut remains naturally preserved for extended periods of time.
How does this homemade pickled cabbage compare to the pickled cabbage in a jar in the supermarket? What about pickled cucumbers or pickled garlic, also popular commercial choices?
Pickled vs Fermented Foods
Alex Lewin, author of Real Food Fermentation explains that the confusion comes from the overlap in definition. In a nutshell, not all fermented foods are pickled and not all pickles are fermented.
In other words, foods that are pickled are those that have been preserved in an acidic medium. In the case of various types of supermarket pickles on the shelf, the pickling comes from vinegar.
These vegetables, however, are not fermented (even though vinegar itself is the product of fermentation) and hence do not offer the probiotic and enzymatic value of homemade fermented vegetables.
Vegetables that you ferment in your kitchen using a starter, salt, and some filtered water create their own self-preserving, acidic liquid that is a by-product of the fermentation process. This lactic acid is incredibly beneficial to digestion when consumed along with the fermented vegetables or even when sipped alone as anyone on the GAPS Intro Diet has discovered (cabbage juice anyone?). In other words, homemade fermented veggies are both fermented and pickled.
Alcoholic Fermentation
What about alcoholic fermentation?
In the case of wine and unpasteurized beers, fermentation occurs as the result of certain yeasts converting sugars into alcohol but there is no pickling that takes place despite the common expression that a person who has had too much to drink is “pickled”.
4 Benefits of Culturing without Heat or Pressure
Home fermentation of vegetables preserves without the use of any pressure or heat unlike supermarket versions of the same foods. It allows the ubiquitous and beneficial lactobacilli present on the surface of all living things – yes, even your own skin – to proliferate creating lactic acid which not only pickles and preserves the vegetables, but also promotes the health of those that consume it in the following ways:
- Enhances the vitamin content of the food.
- Preserves and sometimes enhances the enzyme content of the food.
- Improves nutrient bio-availability in the body.
- Improves the digestibility of the food and even cooked foods that are consumed along with it!
Avoid Shelf Stable Pickled Foods
So don’t be fooled by unhealthy supermarket pickled versions of homemade fermented foods.
These modern foods are the product of high heat and pressure which destroys nutrients and does not in any way enhance health.
The one exception to this rule is the various fermented foods in the refrigerator section of many health food stores. These products are actually fermented and pickled. The only drawback is that these gourmet items are rather expensive compared to the pennies per ounce it costs to make them yourself.
If home fermentation is a kitchen goal that you are ready to tackle, there are plenty of fermented foods recipes on this blog to help get you started on this fun journey! If you prefer trying fermented beverages first, the provided link will take you to over two dozen recipes to consider.
Ya they should ban it indeed but it’s called great culture, hard to admit something wrong and hard to ban.
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