Decreased Cancer Risk for Vegetarians Who Eat Fish

Eating Fish

Story at-a-glance -

  • Vegetarians who ate fish at least once a month (pescovegetarians) had a 42 percent lower risk of colorectal cancer compared to non-vegetarians
  • Even when compared to vegetarians, the pescovegetarians had a 27 percent lower risk of colorectal cancer
  • Fish contains beneficial omega-3 fats that have anti-cancer activity

By Dr. Mercola

Colorectal cancer (colon and rectum cancers) is the third most-diagnosed cancer, the third leading cause of cancer-related deaths, in the US.1 It's widely known that your diet plays a major role in your risk of this disease, with processed meats being among the worst offenders and vegetables among the most protective.

So it's not surprising that a new study published in JAMA Internal Medicine found vegetarians had a 22 percent lower risk for all colorectal cancers, 19 percent lower risk for colon cancer, and 29 percent lower risk for rectal cancer compared to non-vegetarians.2

Vegetarians would, presumably, be eating more vegetables than the average American, although there are vast differences in quality of diet among vegetarians, too.

For instance, a person could eat primarily refined carbohydrates and still be considered vegetarian… and this type of diet would typically not lower your cancer risk but raise it.

Getting back to the featured study, however, it included Seventh-Day Adventist men and women, who typically avoid alcohol and tobacco and eat very little meat compared to the average American (an average of about two ounces a day).

Still, even cutting out that small amount of meat was protective… but not as protective as eating this…

Fish Eaters Cut Risk of Colorectal Cancer by 42 Percent

So-called "pescovegetarians," who ate fish at least once a month and other meats less than once a month, enjoyed the greatest cancer protection (a 42 percent reduction) compared to non-vegetarians.

Even when compared to vegetarians, the pescovegetarians had a 27 percent lower risk of colorectal cancer. Eating fish is likely protective because it contains beneficial omega-3 fats.

As nutritionist Lisa Drayer told CNN:3

"In addition to other dietary factors, fish may provide added protection from its high content omega-3 fatty acids. This is consistent with previous research that has found omega-3s have anti-cancer activity and that they may be helpful in the prevention and treatment of colorectal cancer."

Previous research has shown omega-3s to be protective against numerous types of cancer. For instance, in one study, the spread of cancer cells was blocked by omega-3 fats, suggesting that a diet rich in omega-3 fats could potentially inhibit cancer in men with early stage prostate cancer.4

A separate meta-analysis found that fish consumption was associated with a 63 percent reduction in prostate cancer-specific mortality.5

Meanwhile, omega-3 deficiency can cause or contribute to many serious health problems, both mental and physical, and may be a significant underlying factor of up to 96,000 premature deaths each year.6

Most People Benefit from Some Amount of Animal Protein

There is no debate that most people do not eat enough vegetables, let alone high-quality organic ones. So it makes perfect sense that individuals who consume more vegetables are likely to be healthier in many ways.

Most of us eat far too much protein and not enough vegetables, which likely accounts for most of the difference seen when comparing vegetarian to non-vegetarian diets.

But that does not justify excluding all animal products. I typically recommend avoiding strict vegetarian or vegan diets, because I believe most people benefit from at least some animal foods.

In addition to missing out on important animal-based omega-3 fats (plant-based omega-3s are not the same), those who abstain from animal protein are placing themselves at far greater risk of sulfur deficiency and its related health problems.

Research published in the journal Nutrition showed that people who eat a strictly plant-based diet may suffer from subclinical protein malnutrition,7 which means you're also likely not getting enough dietary sulfur.

Sulfur is derived almost exclusively from dietary protein, such as fish and high-quality (organic and/or grass-fed/pastured) beef and poultry. Meat and fish are considered "complete" as they contain all the sulfur-containing amino acids you need to produce new protein.

Sulfur also plays a vital role in the structure and biological activity of both proteins and enzymes. If you don't have sufficient amounts of sulfur in your body, this deficiency can cascade into a number of health problems, as it will affect bones, joints, connective tissues, metabolic processes, and more.

According to Dr. Stephanie Seneff, a senior scientist at MIT, areas where sulfur plays an important role include:

  • Your body's electron transport system, as part of iron/sulfur proteins in mitochondria, the energy factories of your cells
  • Vitamin-B thiamine (B1) and biotin conversion, which in turn are essential for converting carbohydrates into energy
  • Synthesizing important metabolic intermediates, such as glutathione
  • Proper insulin function. The insulin molecule consists of two amino acid chains connected to each other by sulfur bridges, without which the insulin cannot perform its biological activity
  • Detoxification

The Nutrition study also concluded that the low intake of sulfur amino acids by vegetarians and vegans explains the origin of hyperhomocysteinemia (high blood levels of homocysteine, which may lead to blood clots in your arteries -- i.e. heart attack and stroke) and the increased vulnerability of vegetarians to cardiovascular diseases.

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The Type of Meat You Eat Matters

Many studies have linked red meat and, especially, processed meats, to cancer, but most of these studies involved meat from concentrated animal feeding operations (CAFOs). I've often said that the difference between organic, pastured beef and that from animals raised in CAFOs is so great that you're really talking about two completely different animals.

In the grand scheme of all that is wrong with modern agriculture, the unnatural transition that turned cattle, which naturally eat only grass, into grain-eating ruminants is definitely toward the top of the list.

CAFO cows are fattened for slaughter in massive feedlots as quickly as possible (on average between 14 and 18 months) with the help of grains and growth-promoting drugs, including antibiotics.

The antibiotics and grains radically alter the bacterial balance and composition in the animal's gut. The natural diet for ruminant animals, such as cattle, is plain grass. When left to their own devices, cattle will not graze on corn or soybeans. Just as in humans, poor gut health in animals promotes disease. This radically altered diet also affects the nutritional composition of the meat.

For example, when raised on a grass-only diet, levels of conjugated linoleic acid (CLA) are three to five times higher in the meat compared to CAFO beef. CLA has been found to have a wide array of important health benefits, from fighting cancer to decreasing insulin resistance and improving body composition.

Grass-fed beef also tends to be leaner, and have higher levels of vitamins and minerals such as calcium, magnesium, and potassium. It also has a healthier ratio of omega-6 to omega-3 fats.

Unless labeled as grass-fed, virtually all the meat you buy in the grocery store is CAFO beef, and tests have revealed that nearly half of the meat sold in US stores is contaminated with pathogenic bacteria—including antibiotic-resistant strains. Grass-fed beef is not associated with this high frequency of contamination, and their living conditions have everything to do with this improved safety.

This doesn't only apply to beef, of course. It also applies to other animal foods as well, including dairy, eggs, and poultry, which should be organic and pasture-raised (or free-range certified), as well as fish, which should be wild-caught not farm-raised.

A Healthy Cancer-Preventive Diet…

Eating a healthy, balanced vegetarian diet is far better than eating a high-CAFO meat diet. But I believe most people would be wise to consider a more moderate plan, which, as I mentioned, includes at least some animal protein. To find out more about what I believe is a more ideal diet for most people, which will also help lower your risk of cancer, check out my nutrition plan. Here are the key points:

  • Low amounts of high-quality (pastured or grass-fed) animal protein: A general recommendation is to limit animal protein to one gram of protein per kilogram of lean body mass, or one-half gram of protein per pound of lean body weight.
  • Extremely low amounts of refined grain carbohydrates: You need very little grains, if any. Even organic grains are best avoided to preserve optimal insulin and leptin signaling.
  • Extremely low amounts of processed sugar and fructose: A general guideline is to restrict your sugar/fructose consumption to 25 grams from all sources per day. If you are insulin or leptin resistant (if you are overweight, or have high blood pressure, diabetes, or heart disease, then you likely have insulin or leptin resistance), you'd be wise to keep your sugar/fructose to 15 grams per day, from all sources, until your condition has normalized.
  • High amounts of high-quality fats: As you cut out carbohydrates, you need to replace them with healthy fats. Most people probably need anywhere from 50 percent to 85 percent of their daily calories in the form of healthy fats, which include olives and olive oil, coconuts and coconut oil, butter made from raw grass-fed organic milk, organic raw nuts (especially macadamia nuts, which are low in protein and omega-6 fat), organic pastured eggs, and avocados. Omega-3 fats are also important, which can be found in wild-caught Alaskan salmon, sardines, anchovies, or a high-quality krill oil supplement.
  • Virtually unlimited amounts of vegetable carbohydrates: Making vegetable juice is a great way to boost the amount and variety of vegetables in your diet, but you'll also want to consume whole vegetables for added fiber.

One of the easiest ways to conform to these guidelines is to ditch processed foods and cook from scratch using whole, organic ingredients. I generally advise limiting processed foods to 10 percent of less of your total diet. As for whether or not to eat meat, I firmly believe that it plays a valuable role in optimal health, but quality and quantity are important considerations. Focusing on smaller portions of higher quality (pastured grass-fed and finished) meats will lead you in the right direction.

Other Important Considerations for Colorectal Cancer

In addition to choosing high-quality meats and eating them in limited amounts, you'll want to be careful with how you cook them. Heating proteins leads to the formation of unnatural peptides and amino acids, making them less digestible. Cooking food at temperatures over 180º Celsius (or 350º Fahrenheit) promotes the formation of several carcinogenic compounds, including aromatic hydrocarbon, benzopyrene, and heterocyclic amine (HCA).

In fact, research suggests that proteins, carbs, and fat cooked at very high temperatures can promote colon cancer. So you don't want to come home with a healthy grass-fed steak and then ruin it by charring it on the grill. Instead, eat your meat rare or consider cooking it using a gentle, low-heat method such as poaching or stewing. In addition, if you're interested in lowering your risk of colon cancer, consider:

  • Vitamin D: Vitamin D can significantly lower your risk of a variety of cancers, including bladder, colorectal, and breast cancer. Specifically, research has shown that a vitamin D level of more than 33 ng/mL was associated with a 50 percent lower risk of colorectal cancer.8 However, I recommend optimizing your vitamin D level to between 50 and 70 ng/ml year-round. Vitamin D from sun exposure or a high-quality tanning bed is the BEST way to optimize your vitamin D levels.
  • Magnesium: Higher intakes of dietary magnesium are associated with a lower risk of colorectal tumors. For every 100-mg increase in magnesium intake, the risk of colorectal tumor decreased by 13 percent, while the risk of colorectal cancer was lowered by 12 percent.9 Green leafy vegetables like spinach and Swiss chard are excellent sources of magnesium, as are some beans, nuts, and seeds, like almonds, pumpkin seeds, sunflower seeds, and sesame seeds. Avocados are also a good source. Surveys suggest, however, that many Americans are not getting enough magnesium from their diet alone, which is why in some cases a supplement may be necessary.
  • Oral Health: Pathogens in your mouth can enter your bloodstream to colonize other parts of your body. Two independent studies found a causal link between a common oral bacterium (F. nucleatum) and colorectal cancer.10 Maintaining good oral hygiene and eating a healthy diet to support oral health are very important.

Are You Looking for Healthy, Humanely Raised Meat, Dairy, and Eggs?

If you're a vegetarian or vegan who is considering adding some animal foods into your diet for health purposes, you're probably interested in supporting farmers who produce healthy pastured grass-fed meat, eggs, and dairy products using humane, environmentally friendly methods. You can do this not only by visiting the farm directly, if you have one nearby, but also by taking part in farmer's markets and community-supported agriculture programs, many of which offer grass-fed meats. The following organizations can also help you locate grass-fed beef and other farm-fresh foods in your local area, raised in a humane, sustainable manner.

Where to Buy Locally Grown Food