Fish Eaters and Vegetarians Have Less Cancer

by | Jul 15, 2009
Collards, Carrots and Lentils

Collards, Carrots and Lentils

There is much debate among nutrition scientists over whether meat eating is healthy. On one side there are the hardcore low-fat vegetarian advocates like Dr. Colin Campbell, author of The China Study, who believe all animal fat and protein is dangerous. On the other side are those who point to refined carbohydrates as the biggest threat to public health, citing studies that suggest meat alone is harmless or even helpful (for more information read Good Calories, Bad Calories, by Gary Taubes).

I tend to agree somewhat with both.

For heart disease, the evidence certainly seems to indicate that refined carbohydrates are the worst culprit. Though health advocates once pointed to saturated fat as the cause, this suggestion has not stood up to rigorous scientific testing. In fact, dietary fat (particularly from plants) seems to be protective against heart disease.

Refined carbohydrates are also the cause of type 2 diabetes and metabolic syndrome (a combination of insulin resistance, high blood pressure, heart disease and obesity), which is arguably the biggest health threat of our time.

For these reasons and many others, I avoid refined sugar and flour as much as possible in my daily life.

Heart disease and metabolic syndrome are not the only diseases that concern me, however. Cancer is another modern ailment that has been linked to diets high in both carbohydrates and meat. Though the studies are not perfectly consistent in showing harm or no harm regarding meat consumption and cancer, rarely does anything suggest meat eating is actually beneficial (though studies are almost always confounded because meat eaters also tend to eat the most sugar and refined grains).

Fish is another story entirely. Although fish is technically a meat, its properties are very different from land animals. For one thing, fish eating has consistently proven beneficial in scientific studies of heart disease and metabolic syndrome. It also seems to play a role in protecting the brain against degenerative diseases.

I am an avid fish eater and try to include seafood in my diet several times per week.

Until now, however, I have not read much about the role of fish in cancer. A new meta-analysis published in the British Journal of Cancer (part of the Nature publishing group) suggests that vegetarians have significantly less cancer than meat eaters, and that cancer rates are even lower in fish eaters.

The researchers analyzed data from two British studies of vegetarians from the early 80s and early 90s that includes over 60,000 individuals, mostly women but some men. The participants were followed until the end of 2006.

Incidence of malignant tumors was compiled for all the subjects and the relative risks were calculated. Vegetarians and fish eaters had significantly lower risk for stomach cancer, ovarian cancer, lymphatic and bone marrow cancers, and bladder cancer. Vegetarians had a higher risk of cervical cancer than meat eaters. Fish eaters had a lower risk of prostate cancer than meat eaters.

Overall vegetarians had 8% fewer cancers than meat eaters and fish eaters had 20% fewer.

Interestingly, no difference was found in breast cancer or colorectal cancer incidence, which have both been tied to meat consumption. The authors speculate that this study could be lacking in statistical power to observe a difference. However, the current data is inconsistent and no conclusions can be drawn.

While the results of this study are very compelling, there are several caveats that must be addressed. First, the number of cancers at individual sites were relatively few, meaning that findings may be exaggerated or due to chance. For me the most convincing numbers are of the overall cancer rates (the largest numbers and strongest statistics), but this leaves many questions about the causes of the different cancers.

Another issue is that vegetarians and fish eaters in the study tended to be younger and get more exercise than the meat eaters, so there may be important confounding factors that could influence the results. Likewise, studies that rely on self-reported dietary patterns have well-documented flaws (basically everyone believes they eat healthier than they really do).

It is not clear what is causing the differences in cancer incidence among vegetarians, fish eaters and meat eaters. Vegetables and fruits have been suspected of actively protecting against cancers, but so far the mechanisms are only speculative and not concrete. Recent studies have suggested vitamin D can be protective against certain cancers. Since some fish can be very high in vitamin D, this may explain some of the benefit seen in fish eaters.

The higher incidence of cervical cancer among vegetarians is also compelling and warrants further research.

Despite the flaws in this study it is mostly consistent with other research suggesting that an optimal diet is primarily fresh, unprocessed plants, some fish and little meat.

Moderation is usually the best policy.

What is your take on this study? How do you feel about health vs the ethics of fish consumption?

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14 Responses to “Fish Eaters and Vegetarians Have Less Cancer”

  1. Darya Pino says:

    Forgot to mention that How To Eat In Restaurants will continue next week.

  2. Thanks for the good summary and analysis. I’d heard of the study but hadn’t read it.

    I’d like to think that my current fish habit – two weekly servings of cold-water fatty fish – protects me from cancer. But I’m not a vegetarian who eats fish as in this study; I’m an omnivore who doesn’t eat as much red meat as the typical American.

    At the risk of sounding callous, I’ll state that I’m not much concerned about the ethics of fish consumption. It seems to me that fish is a lot less expensive than it was 20 years ago, so the fisheries may not be as threatened as I’ve read. [My teenage daughter won’t go trout fishing with me anymore, concerned that the hook causes the fish too much pain. She’s close to vegetarian.]

    • Darya Pino says:

      Thanks for chiming in, Steve. From reading the manuscript it seems the authors plan to use this study as a jumping off point to do more in depth research. I think everyone agrees it doesn’t really mean that much as a stand alone article.

  3. julie says:

    I mostly agree with you, but I think people who eat the most produce, whether omnivore or vegetarian, would be the healthiest. I don’t like much red meat, love fish, but don’t eat it often. I AM concerned about the ethics of fish, and also mercury and other heavy metals that bioaccumulate in the fat. I don’t think vegan is really healthy, and even worse, I know a fruititarian (fruits and grains), who’s currently having all kinds of gut problems, but doesn’t think they’re related to diet. I think a bit of meat on rare occasions is useful, just in case, for iron, zinc, other things that are more concentrated/digestible in meat. I think processed carbs have no nutritional use, but they’re hard to avoid, and likely benign if kept at low levels.

    • Darya Pino says:

      Thanks for you thoughts Julie. I agree with you completely. I try to make sure that if I do eat processed carbs they are some of the most delicious foods money can by. Then at least it’s worth it 🙂

  4. Hanlie says:

    I eat very little animal produce or refined carbohydrates. My intake is mostly fruit and vegetables, legumes and whole grains. When I eat animal produce, I prefer it to be fish.

    I am very concerned about the ethical side of fish-eating though (which is a bit of a problem, since my husband makes our living from fish). Fish stocks are definitely dwindling and increased consumption could cause a lot of problems. Furthermore, most wild fish these days are caught for the purpose of feeding farmed fish, which are starting to exhibit some of the same problems that factory farming has – pollution, disease, high pesticide and antibiotics use, etc. Then of course there are those pesky PCB and mercury residues that are so prevalent in larger fish.

    So, I would say, keep the animal food consumption low, and opt for sustainable fish species that are low in the food chain and not farmed. Your best friends when it comes to good health are fruit and vegetables!

    • Darya Pino says:

      Great points Hanile! I’d like to add that the main fish I eat are anchovies, sardines and canned Alaskan salmon. Otherwise I buy my fish from responsible places like Bi-Rite market and sometimes Whole Foods (where I’m careful). If I’m eating fresh fish though, it’s usually at a swanky SF restaurant 🙂

  5. ps says:

    I wonder if it’s meat itself that is bad or if it’s the meat that comes out of our industrialized agricultural system that is bad. So, if they did that study on people who only ate free range, organic meat their whole lives versus people who eat the regular supermarket stuff, who would have the higher incidence of cancer? It’s probably an impossible study to complete, but I’d be curious.

    I only eat meat when I go out to eat which is about once a week. Otherwise I’m all about the legumes. This was originally motivated by the fact that I was too poor to buy meat for a while, but I stuck with it because I became more adept at cooking vegetarian food than non-veg. It’s good to know that it’s keeping me healthier as well!

    • Darya Pino says:

      Great point ps! I think there is probably a difference between high quality meat and feedlot meat. There is also the issue of food combinations. For instance, most people I know willing to eat feedlot meat also eat a lot of processed carbs and fewer vegetables. It would be very difficult to design an experiment to test the hypothesis that meat alone increases cancer risk in the background of a healthy diet. My guess is that it probably doesn’t, at least in modest quantities.

  6. Matt Shook says:

    Sounds fishy. 😉

    Kidding aside, I think it’s a telling study…even with many “confounding factors.” I would want to know what the “vegetarian diet” consisted of as I know a few vegetarians who have horrific diets. I guess I’d like the study to be more specific…but I imagine that could be a logistical nightmare with such a fine scope.

    Health vs. the ethics of fish consumption ? Now that’s a great question…the article did a great job illustrating the pros and cons of eating fish. My take on eating fish is the same as eating animals…if someone wants to eat them they should raise/catch/hunt/kill them yourself. The dynamic completely changes when profits (not the eating flesh itself) are the motivating factor. I have no qualms killing my broccoli, spinach, and strawberries… 😉

    • Darya Pino says:

      Thanks for bringing up the issue of the “junk food vegetarians.” There is actually plenty of evidence that healthy meat eaters are healthier than people who eat pasta all day.

      As I mentioned in a comment above, from reading the manuscript it seems the authors of the study intend this to be a jumping off point for further research and think it does not mean much as a stand alone study.

      I agree with you in theory on your ethics argument, mainly because I think it is important for people to realize the full cost of what they are eating, including life. It is a little impractical, however. I have no problem killing things myself, I am a neuroscientist after all. But as much as I would like to spend all day fishing, someone has got to run Summer Tomato 😉

  7. I find myself “reacting” many different ways to articles like this. I’ve been “observing” people eating my whole life, always intrigued by health, food, fads, trends, weight loss, weight gain etc. etc.

    I’ve been vegetarian and back again. I think most of these “do not eat meat” studies are flawed, because the measurement is about how much meat and not about what kind of meat, and what other things are eaten. I eat meat in moderation, but I eat produce in abundance. Many meat eaters don’t eat enough produce. Vegetarians (I’m a former, recovered) often start to see themself as living a spiritually superior life. It’s not always good for the “attitude.” Our food supply is so varied (here in America), that other factors have to looked at. Food supply, what the animals eat, gmo’s, environmental factors, prescription drugs, eating at home vs. restaurant, eating out of a box, what part of the country, how much produce…

    There are a million questions to be asked, because it’s not so simple that we can put people into three boxes, meat eaters, fish eaters, vegetarians. It’s not simple like that.

    I am not the person who rolls my eyes at good health, organic food, etc., but I fully believe that meat (and saturated fat) have gotten a bad rap for the wrong reasons.

    P.S. I like your articles and that you make people think.

    • Darya Pino says:

      Thanks for your thoughtful reply, Angela.

      I agree with you 100% and as I discussed in some of the above comments, this study is only a jumping off point and means relatively little on its own.

      Eating is very complicated and, as you point out, the source of food is turning out to be a much more important factor than the technical composition of food. In the mean time it sounds like most Summer Tomato readers have a pretty health, moderate approach to meat and a love of veggies!

  8. fei says:

    i concur. moderation is the best policy. and eat both (veg and fish) ! =D

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