Vegetarians and Cancer

Cancer rates are generally lower among vegetarians compared to meat eaters, but a new study suggests that this may not apply to all types of cancers.

The study included 32,403 meat eaters, 8,562 non-meat eaters who ate fish and 20,601 vegetarians. After an average of 12.2 years, 2,204 meat eaters (6.8 percent), 317 fish eaters (3.7 percent) and 829 vegetarians (4 percent) developed various types of cancer.

The findings, published in the British Journal of Cancer, suggest that the risk of developing stomach cancer, bladder cancer, non-Hodgkin's lymphoma and multiple myeloma may be cut by more than half in vegetarians.

The association was particularly strong for multiple myeloma, a type of bone marrow cancer. Vegetarians were 75 percent less likely to develop the disease than meat eaters. In addition, vegetarians and fish eaters were about one-third less likely to develop stomach cancer than meat eaters. Although the number of stomach cancer cases was small, earlier research suggests that processed meat may contribute to the disease.

In contrast, vegetarianism was not linked to a reduced risk of colon or rectal cancer. In fact, the incidence of these cancers was slightly higher among vegetarians than meat eaters. However, this risk was not statistically significant, meaning that the higher rate may be due to chance.

Additionally, the risk of cervical cancer was significantly higher among vegetarians than meat eaters. This increased risk was similar, although not statistically significant, among fish eaters compared to meat eaters. It has been suggested, but not scientifically proven, that dietary factors may contribute to the risk of infection with the human papillomavirus, which causes many cases of cervical cancer. The authors caution that these findings are based on only 50 cervical cancer cases and may be influenced by other factors, such as cervical cancer screening.

The authors conclude that more research is needed to fully understand the relationship between vegetarianism and cancer risk.

For more information about vegetarianism, please visit Natural Standard’s Health & Wellness database.

Comments

[Regina]

This is a fascinating article on the connection between vegetarianism and the risk of certain types of cancer. It's interesting that while vegetarians have lower risks of some types of cancer — stomach cancer, bladder cancer, non-Hodgkin's lymphoma and especially multiple myeloma — their risk of other type cancer types (for example, cervical cancer) is actually higher. A person would probably want to look at his or her other risk factors before deciding on specific dietary choices. In any case, additional research is needed. Personally, I am interested in learning more about this issue as further evidence is discovered.

[Annie]

This is really exciting news, and I would think it's very convincing evidence to at least get Americans to add more veggies and cut back on meat, even if they don't completely go vegetarian. (I'm assuming that you'd at least get some of the protective benefits this way?)

I looked up the vegetarianism monograph on www.NaturalStandard.com and found this under the Evidence heading: "In one review, it was concluded that lower mortality in British vegetarians was best explained by behaviors other than their non-consumption of meat." -- This makes me curious about whether the researchers in this study could screen out other lifestyle factors and practices such as smoking and physical activity levels?

[Adele]

I would have to agree with Annie that this may be a reason to for us to add veggies and decrease some of our meat intake to lessen our chances of developing various cancers. I would be interested to know what "meat-eater" means in this study. I eat meat, but not often/excessively, so I would want to know the quantity/frequency that is associated with the increased risks of the various cancers.

[tom]

I also wondered if the vegetarians' other lifestyle choices may be playing a role in their lower risk for some cancers. Some people adopt a vegetarian diet because of health reasons, so these people may naturally be inclined to follow other healthy practices, such as choosing healthy foods, exercising, etc. These other healthy practices could also be contributing to their lower cancer rates.

[Cathy]

In the study regarding vegetarians and cancer, I would also be interested to know how frequently the "meat-eaters" ate meat. There is a big difference between someone who occasionally eats it and someone who has a steak with every meal. I also wonder what kind of diets the vegetarians had. I know some vegetarians who are very health-conscious and who make excellent dietary choices by eating lots of beans, vegetables, fruits, tofu and nuts, but I also know some who don't eat meat, but who make very poor nutritional decisions, such as eating lots of chips/breads/sweets and processed foods. Technically, they are vegetarians, but the quality of their diet is vastly different from vegetarians who base their diet on quality, wholesome food.

[Mark]

Correlation does not necessarily mean causality. It is also important to keep in mind that even though the results are given as percentages, the meat eaters consisted of the largest group in the study, exceeding the vegetarian group by about 12,000 people. The larger the group, the higher was the percentage of participants that developed cancer during the time period. I don’t think that this is the best study from which to decide major dietary alterations, such as removing meat. However, I do think that it is always a good idea to eat more fruits and vegetables.

[Summer]

Although this is an interesting article suggesting a link between various cancers and diet, I would also like to know what each of the diets consisted of. As many of you mentioned, there are many different types of "meat-eaters" and "vegetarians." Lifestyle must have also played a large role in this study, unless all participants were "recommended" to do the same things (exercise, etc.). Before making my own conclusions regarding the diets and the associated risk of cancer, I'd like to find out these details of the study.

[Savira]

I think the most important thing that regulates cancer formation is our DNA. If it's genetically linked, I will say that, even though I am a vegetarian, I will have a greater chance of developing cancer. Another factor could be that the vegetables may have a lot of pesticides or germs that may change/mutate our DNA so that we develop tumorous cells. It's very interesting how human body is such a complex thing. One thing that we can do is wash the vegetables with vinegar and water so the majority of pesticides/bacteria will be gone.

[Helen]

I agree with the author that the cervical cancer incidence may be caused by other factors, such as how often the women aware of the cervical cancer screening or the person's accessibility to healthcare or getting medications. Also, maybe not all vegetarians eat the same food. I'd like to see more evidence for the link between cancer and vegetarian before making any conclusions.

[Albert]

I agree. It seems that someone’s individual risk of cancer is very genetically linked. Although every type of cancer is different, a strong family history tends to be the strongest predictor for many cancers. However, since we also know that our risk for cancer can be affected by our environment, taking precautions is always a good idea. Perhaps even increasing the amount of organic and free range foods we eat would be a good measure to take as well.

[Tom]

While I think that this study is very interesting and causes us all to take a closer look at our diets’, there may be too many confounders in the study to draw any definite conclusions. For example, if one of the meat-eaters in the study smoked and ended up getting lung cancer, that result cannot be attributed to the meat-eating. There are already proven causes of some cancers: smoking and lung cancer, human papillomavirus and cervical cancer, alcohol and liver cancer, etc. While I do believe that diet may play a role in the development of cancer, it will not trump any of the other proven causes of cancer.

[Jess]

Vegetables should be an important part of diet, no matter what. Major risk factors for cancer are age, daily environmental exposures, certain chemicals and pesticides, diet, heredity and history of cancers. Based on risk factors in general, following a vegetarian diet may lead to a lower risk of cancer development. This study was done in UK, and it cannot be generalized to U.S. population, as we tend to have different lifestyles and food intake. Randomized controlled trial (RCTs) will be needed to determine the association between cancer and vegetarian diet vs. meat diet.

[k]

This article reiterates the importance of eating a well-balanced diet that includes vegetables and meat. Eating healthily has gotten harder with so many fast-food places and busy lifestyles. But, I think articles like this one help people in their effort to eat healthier. I am interested in knowing if other risk factors, such as family history, exercise, access to healthcare were considered in this study. All these factors play a role in developing cancer, so I would like to see a study that compares various risk factors and diet.

[bbm]

I can't say that I'm surprised by the results of this study. Cancer can be caused by any number of dietary, lifestyle, or environmental factors. The difference between eating natural products versus processed animal products makes sense. In theory, anything foreign you put in your body could trigger a cancerous cell to develop, so I wonder if there would be a difference between organic and non-organic vegetable eaters regardless of meat consumption. I did think it was strange that colon cancer did not have a significant difference between the two groups.

Historically nutritionists have said that vegetables aid in digestion and some meats, especially pork, are harder to digest. You would think something that moves through the digestive tract quickly and efficiently wouldn’t cause any local harm. I hope to see further studies examining specific foods and specific types of cancer. One day we will be able to specially design diets for patients depending on their risk factors for diseases, including cancers.

[Cassandra]

It is possible that the study may be confounded by the patients recall. How exactly were the dietary intakes measured? Were the patients more likely to report consuming a certain type of diet (vegetarian, meat-eater, fish-eater) because they knew they were being studied and possibly judged on their intake? If so, the data may be subject to bias. Although it is not practical, monitoring dietary intake would ensure what patients were actually eating is reported accurately and any links to cancer would be more credible.

[YJL]

This study is interesting, but we need further information about what meat-eaters eat and how much they eat, as well as what vegetarians are eating. From this study, we can probably conclude that there's an interesting pattern about types of eating habits and frequency of cancer, but there are many confounding factors that need to be considered, such as family history, current diseases, etc. I would also assume vegetarians are usually more health conscious and exercise more. I wouldn't attribute being vegetarian to a reduce risk of certain cancers at this point.

[Barry]

This is an interesting find on the correlation between cervical cancer and vegetarians. Like the study suggests, more research is needed to identify the mechanism behind this. Maybe the cohort of subjects they studied were more sexually active or maybe HPV is more prevalent in the area that they studied. I don’t understand how eliminating meats from your diet would make you more susceptible to HPV. This would be a really interesting area of research in the future.

[TY]

The human body survives because of its ability to maintain balance. Even with our body’s amazing ability to keep this balance, it is our responsibility to keep it from working too hard. Diet is one thing that has been overlooked since we began supplementing high-sugar juice boxes with three days worth of vitamins.

Because we obtain our recommended daily allowances from whatever we eat, the importance of a healthy, balanced diet has become less of a thought.

Cholesterol is extremely important to our development, but of course, too much cholesterol is dangerous. We are not animals that have diets that consist strictly of vegetables, but often times vegetables are left out of our daily intake because we find our daily requirements of vitamins and minerals in non-fruit and vegetable sources. The relationship between diet and cancer is only in the beginning stages of development. Further studies need to isolate what it is that causes this, but it is certainly thought provoking.

[Sandra]

Sweet! (=