Raw food is rich in bacteria, not nutrients

The raw food crazies are making themselves sick.

There's a thing called the Raw Food Movement that has been growing in popularity in recent years. Proponents argue that it's far healthier than our usual (human) diet of cooked foods, claiming that cooking removes many of the natural enzymes that make food nutritious. They also believe that cooking creates harmful toxins.

What's really happening, though, is that raw foodies are putting themselves at risk of serious bacterial infections. Just last week, we learned that a salmonella outbreak tied to raw food has sickened people in 15 states so far. The CDC reports that the outbreak is linked to Garden of Life's RAW Meal Organic Shakes, which come in chocolate, vanilla, and vanilla chai flavors. The FDA issued a recall and warned that "persons infected with Salmonella often experience fever, diarrhea (which may be bloody), nausea, vomiting and abdominal pain."

According to the CDC, no one has died from any of these Salmonella infections, although 4 people have been hospitalized.

It's not clear why raw food is so trendy, other than the obsession of some people with everything "natural."

Natural or not, cooking is one of mankind's greatest inventions. It allows us to spend far less time eating, because cooked food is much easier to chew and digest. We extract more nutrients from cooked food–not fewer, despite what the raw foodies claim. Chimpanzees, our closest relative, spend up to 50% of their waking hours eating, because they subsist entirely on raw food. A 2011 study by Chris Organ and colleagues at Harvard University pointed out that

"The ancestors of modern humans who invented food processing (including cooking) gained critical advantages in survival and fitness through increased caloric intake."

Cooking our food has another huge advantage as well: it kills harmful bacteria and viruses. The current Salmonella outbreak could easily have been avoided if people had simply cooked their food instead of consuming raw shakes.

Raw foodies, though, seem to live in Opposite Land, where food science gets turned on its head. The website RawFoodLife.com claims that

"Science now proves that cooking not only destroys nutrition and enzymes but chemically changes foods from the substances needed for health into acid-forming toxins, free-radicals and poisons that destroy our health!"

Er, no. Science proves nothing of the sort (nor does that website provide any citations to scientific articles to back up its claim). As Christopher Wanjek explained ten years ago at LiveScience,

"plant enzymes, which raw dieters wish to preserve, are largely mashed up with other proteins and rendered useless by acids in the stomach. Not cooking them doesn't save them from this fate. Anyway, the plant enzymes were for the plants ... they are not needed for human digestion. Human digestive enzymes are used for human digestion."

Raw foodies also love raw milk, another dangerous trend, which has sickened thousands of people in the U.S. over the past decade. That topic deserves another column all to itself, but for now, suffice it to say that one of the greatest scientists of the 19th century, Louis Pasteur, discovered that heating milk briefly can kill a host of dangerous pathogens. Pasteurization, which is named for him, has been rightly credited with saving millions of lives. A few years ago, the Royal Society named pasteurized milk the 2nd greatest invention in the history of food (after refrigeration).

Obviously some foods, fruits in particular, are generally eaten raw, and fruits are indeed very healthy. But don't be fooled into thinking that cooking somehow makes food bad for you: it doesn't. Cooked food is easier to digest, more nutritious, and to most of us, pretty darned tasty.

Fish really is brain food

Everyone has heard that eating fish is good for the brain. This notion goes back at least a century; the famous humorist and novelist P.G. Wodehouse often mentioned it in his books. In one scene, after Jeeves (the butler) describes a clever scheme to escape a ticklish problem, Bertie Wooster reacts:

I stared at the the man.
'How many tins of sardines did you eat, Jeeves?'
'None, sir. I am not fond of sardines.'
'You mean, you thought of this great, this ripe, this amazing scheme entirely without the impetus given to the brain by fish?'
'Yes, sir.' [From Very Good, Jeeves, (c) 1930 by P.G. Wodehouse]

A century ago, the evidence that fish is brain food was virtually nonexistent. Researchers have been looking at this question ever since, and the evidence has been mixed. Even if fish is good for the brain, the mercury content in some fish might have the opposite effect.

A new study that appeared last week in JAMA answers this question: fish is indeed good for the brain. More precisely, eating fish regularly was associated with a reduced risk of Alzheimer's disease. This benefit occurred despite the fact that people who ate more fish did have higher levels of mercury in the brain. Apparently, the levels of mercury were too low to cause harm, and the benefits of eating fish easily outweighed any risks.

The new study, by Martha Clare Morris and colleagues at Rush Medical Center in Chicago, looked at 554 Chicago residents, all part of a long-term aging study, who died over a ten-year period. The scientists conducted autopsies to look directly in the brain for physiological changes such as neuritic plaques, which are signs of Alzheimer's or other disease. They used questionnaire data, which they collected for everyone in the study, to measure how much fish people had been eating–an imperfect way to measure eating habits, but it's often the only realistic way to gather this information.

Here's what they found: people who ate seafood at least once per week had lower levels of three different physiological signs of Alzheimer's, but only in people with a genetic marker known as APOE ε4, which itself carries an increased risk of Alzheimer's. (None of the people in the study had dementia when they first enrolled, starting in 1997.) Somehow, then, eating fish seems to counteract the effects of this harmful genetic mutation.

Bad news for fish oil supplement makers: the study found that "fish oil supplementation had no statistically significant correlation with any neuropathologic marker." In other words, people who took supplements got no benefit. You just have to eat fish.

This isn't the first study to show a positive benefit to brain health from eating fish. The authors cite 13 previous studies that reported "protective relations between seafood consumption and n-3 fatty acids with cognitive decline and incident dementia." The JAMA study is the first to include mercury levels, brain changes associated with Alzheimer's, and diet all in the same study. It's reassuring to learn that despite the increased mercury caused (probably) by eating more fish, the overall effect is beneficial.

The authors also pointed out that as we age, our brains lose DHA, a critical lipid in the brain, and that therefore "fish consumption may be more beneficial with older age." The FDA already recommends that pregnant women and young children eat more fish for its nutritional benefits. Now there's evidence that older people should eat fish regularly too.

So it seems that Wodehouse's character Bertie Wooster might have been right: fish really is brain food.