Friday, October 08, 2010

LOL! Fish oil strongly linked to increased incidence of colon cancer

No, no no! Not the beloved fish oil!

Fish oil – long encouraged by doctors as a supplement to support heart and joint health, among other benefits – induced severe colitis and colon cancer in mice in research led by Michigan State University and published this month in the journal Cancer Research.

Jenifer Fenton, a food science and human nutrition researcher at MSU, led the research that supports establishing a dose limit for docosahexaenoic acid (DHA), one of the omega-3 fatty acids present in fish oil, particularly in people suffering from chronic conditions such as inflammatory bowel diseases.

"We found that mice developed deadly, late-stage colon cancer when given high doses of fish oil," she said. "More importantly, with the increased inflammation, it only took four weeks for the tumors to develop."

Specifically, the research team found an increase in the severity of the cancer and an aggressive progression of the cancer in not only the mice receiving the highest doses of DHA but those receiving lower doses as well. The mice used in the study were prone to inflammatory-like bowel disease; inflammation is an important risk factor for many types of cancers, including colon cancer.

"Our findings support a growing body of literature implicating harmful effects of high doses of fish oil consumption in relation to certain diseases," Fenton said. "Currently, there is a call by academics and the food industry to establish dietary guidelines for omega-3 consumption. This is primarily motivated by the fact that most Americans are deficient in omega-3 fatty acids, and there is substantial evidence supporting the beneficial effects of the consumption."

The findings were surprising, specifically because DHA has been shown to have some anti-inflammatory properties, according to Fenton: "We hypothesized that feeding fish oil enriched with DHA to mice would decrease the cancer risk; we actually found the opposite. These mice were less equipped to mount a successful immune response to bacteria that increased colon tumors."

Fenton cautions people may not need to avoid fish oil; what the research shows is needed are guidelines on dosing. With any nutrient, there is a "bell curve" effect. On the left of the curve are those deficient in a nutrient; on the right are those in excess.

She said people already receiving enough omega-3 fatty acids through their normal diet and foods have no need for added supplementation.

"With fish oil, we don't yet know how much is appropriate," said Fenton, also a researcher with the Michigan Agricultural Experiment Station. "There are many examples of taking supplements, nutrients or chemicals in excess that can promote cancer (for example, beta-carotene supplementation in smokers). Supplementation is most useful when the person taking them is deficient in that specific nutrient."

The research team's findings could have an important preventive health impact, specifically in light of the high rates of colon cancer in the United States. Individuals with inflammatory bowel disease have an increased risk of developing colon cancer, and when the cancer metastasizes it can be fatal.

The next step, Fenton said, is to test omega-3 fatty acid levels in people with inflammatory bowel disease. To that end, she is continuing to build relationships – via MSU's College of Osteopathic Medicine campus in Macomb County – with gastrointestinal specialists to develop a cohort of patients.

"To help develop guidelines, we need to see how these findings correlate to human populations," she said.


Some food trivia

Generally, cooler environments preserve food best – apart from tropical fruit. Banana skins, for example, have evolved to survive in warm conditions, because that is where they grow best. Anything below 13.3C damages the membranes, releasing enzymes which lead to skin blackening. To avoid a mushy banana, keep it away from the chiller.

It is not just fears for our health that keep food scientists busy. They are also involved in the aesthetics of the dinner table. Everybody loves that first frothy splash of champagne into a flute, but why, on pouring the second glass, does the fizz seem to be less fizzy?

Don't worry – it's not the alcohol playing tricks. A dry glass has thousands of tiny nucleation sites on its inside surface, caused by scratches, irregularities and even dust. Like all fizzy drinks, champagne is supersaturated with carbon dioxide, which is just itching to convert back into gas from its liquid form. When champagne meets one of these nucleation sites, its liquid is repelled, allowing the dissolved gas to form a bubble. This quickly grows and heads towards the surface, while another forms in its place. That is why trails of bubbles in champagne appear to emanate from the same point on the glass's inner surface.

A wet glass, therefore, provides fewer nucleation sites – hence, less fizz. In fact, glass manufacture has become so precise that producers have to ensure that the inner surface is rough enough to create bubbles by deliberately introducing imperfections. Otherwise, your champagne would look more like a chablis.

Such precision has also been applied to beer – in particular, to the discovery that the optimum number of sharp pointy bits on a bottle cap is 21. Go on, count them. Years of trial and error led to the internationally accepted German standard DIN 6099, which ensures that almost every bottle cap is the same. This is because 21 is the ideal number when you take into account the circumference of the cap, the likelihood of its metal splitting, and the chances of it sticking in the capping machine. So when you open your next bottle of lager, pay homage to those who bothered to find out, starting with William Painter, in 1892.

Of course, some researchers do care about the more serious stuff, driven by fear of the future and an ever-increasing population on a warming, land-impoverished planet. Sadly, New Scientist's correspondents concluded that there was no one foodstuff that could feed the world on its own – even the ingenious suggestion that we resort to cannibalism, to recycle the necessary nutrients, was vetoed on the grounds that it would be subject to diminishing returns.

However, they did come up with a menu that could feed a family of four for 365 days a year, using only eight square metres of land. Rotating crops (so that the soil didn't lose one nutrient more than any other) would be vital, as would ploughing back dead plant matter and maintaining a vegetarian diet. After that, you would need to grow crops that take up very little space and grow vertically rather than horizontally, if possible.

So, come 2100, we'll be existing on a diet of runner beans, mangetout, parsnips, potatoes, blackberries, sprouts, tomatoes and radishes. The adventurous among us will grow herbs, while the more wealthy may have a few hens wandering about providing eggs (and, more pertinently, providing their own fertiliser).

The only thing that could relieve the tedium of such a diet would be a few drinks – another pet topic of New Scientist readers. My book, Why Can't Elephants Jump?, covers such weighty questions as whether fizzy water weighs less than still, and why certain cocktail garnishes float while others sink.

Yet we have to admit that science alone can't provide all the answers. In particular, the question of why James Bond prefers his vodka martinis shaken rather than stirred taxed researchers for some time. Most connoisseurs now agree that a stirred martini is superior to Bond's shaken one. So why was a man of impeccable taste drinking the wrong kind?

Various theories bounced around the science foodie community. Was shaking better because aldehydes oxidised the vermouth in the Martini, in the way that red wine oxidises while it "breathes", as researchers in France surmised? Not so, said scientists in Ontario, who thought that shaking a Martini broke down hydrogen peroxide in the drink, thus altering its flavour. Or were spicules of ice from the shaking process clouding the Martini? Or did shaking the Martini "bruise" the vodka?

In the end, the answer was more prosaic. When Ian Fleming was writing his novels, shortly after the Second World War, grain was expensive, so a lot of vodka was made from potatoes. Potato vodkas are markedly more oily than the grain vodkas we are used to today. As a very enjoyable blind taste test in our offices confirmed, potato vodka shaken with ice dissipates the oil, making for a smoother drink. Bond, being a man of sophistication, would have known this. So it was that oily potatoes played their part in the birth of one of movieland's most famous catchphrases.

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