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Adventure : Nutrition

What We've Learned from Fish Guts

It’s important for the human body to have a diverse set of bacteria in the gut; after all, low diversity is linked to many diseases. But mixing up your diet might not lead to a wider spectrum of microbes living in your midsection. 

According to researchers led by Dr. Daniel Bolnick of the University of Texas at Austin, the more diverse a fish’s diet, the less diverse the microbes in its gut. “We're still scratching our heads as to why,” Bolnick says. “We also don't really know yet whether this reduced microbial diversity is good or bad, though some diseases (colitis, for instance, and obesity) are associated with low microbial diversity.”

Studies have shown that diet and environment can affect the bacteria in the gut, but most studies have only looked at a single factor at a time, for instance the amount of fat in a person’s diet. Bolnick and his team wanted to go further to test how combinations of foods could affect bacteria in the gut. 

“Treating diet as a set of discrete and different options isn't realistic though,” he says. So they turned to two species of fish, the threespine stickleback and the Eurasian perch, and monitored their diets. The researchers thought the fish who ate a variety of foods would have more diverse gut bacteria than the fish who stuck to one type. It turned out the opposite was true. 

Fish and humans are very different, but they do share many of the same immune cells and genes in the gut lining. At the same time, our intestines are structured differently, and our diets are different. 

“It remains an open question whether the patterns identified in our study will also apply to humans,” Bolnick says.  He’s game to look into it, though. Bolnick plans to conduct diet experiments in humans to see if diverse diets lead to the same effect in humans. 

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Everything You Know About Breakfast Is Wrong

You’re wrong about breakfast. And so is everyone else. Despite years of hype, two new studies point to a startling conclusion: skipping breakfast doesn’t necessarily lead to weight gain. Nor does eating breakfast boost your metabolism, suppress appetite, or reduce overeating later in the day. But it still might be one of the most important meals of the day (more on that later).

“Our findings are a bit of a reality check,” said nutritionist Emily Dhurandhar, an assistant professor in the Department of Health Behavior at University of Alabama at Birmingham (UAB), lead author of one of the studies. “It’s a broader question we’re trying to answer. As a message interpreted by the general public, just recommending people eat breakfast is not sufficient.”

While years of observational research have shown associations between eating breakfast and being leaner, none of the studies reach the gold-standard level of evidence of showing causation—randomized controlled trials—to show that breakfast was indeed responsible for weight loss, says James O. Hill, a professor of pediatrics and medicine at the University of Colorado, Denver, and co-author on Dhurandhar’s study.

At last, gold-standard research on breakfast has arrived. And the findings subvert years of nutritional advice while highlighting one often underestimated and under-hyped benefit of the morning meal. Dhurandhar’s trial randomized 309 overweight or obese adults who were given healthy eating advice to two groups. One group ate breakfast and the other skipped. Both groups lost a little weight, but there was no greater weight loss in the breakfast eaters as compared to the skippers. The researchers are careful to note that the study was not a controlled feeding trial and the subjects were not told what to eat at breakfast.

Another smaller study, led by James Betts, a senior lecturer in nutrition from the University of Bath, randomized 33 lean adults to either eat or skip breakfast for six weeks. The study found no appreciable difference in metabolic or cardiovascular health markers. “It is commonly stated that breakfast kick-starts metabolism and/or reduces snacking, etc. We saw little or no evidence of these things,” Betts said.

Insofar as testing has gone, the evidence hasn’t boded well for breakfast. But it wasn’t all bad news, Betts said. His study was also one of the first to measure how a feeding pattern influenced physical activity levels throughout the day using combined heart rate and accelerometry (think: sophisticated wearable tech, not just pedometers).

Betts sums up the results: “Specifically, the breakfast group was much more physically active than the fasting group, with significant differences particularly noted during light-intensity activities during the morning.”

In this case, this was causal evidence (not just correlation) that breakfast gets people moving—good reason to keep enjoying the most important meal of the day.

Our near-sacred regard for “don’t skip breakfast” is one of the most fundamental but oversold nutritional guidelines, and as we’re now discovering, there are plenty of other flawed recommendations in the nutrition world. So the problem isn’t with breakfast. It’s with a failure of skepticism, says the study’s senior investigator whose previous work began the attack on the conventional thinking, David Allison, director of UAB’s Nutrition Obesity Research Center.

“This goes back to the idea that we need to be more skeptical—we as scientists, as journalists, we as public health officials,” Allison said. “These platitudes sound good. You tend to believe them, but some might not be true.”

The perpetuation of pro-breakfast bias could be said to come in part by lobbying and funding of research by food companies keen on selling breakfast cereals and packaged breakfast foods. But diet myths are also often spread through shoddy reporting and writing. And they frequently come from public figures at the intersection of health and pop-culture. Take this line from the polarizing celebrity surgeon Dr. Oz. His site reads, “The fact is, when you’re trying to lose body fat, you can’t skip breakfast…” and “Boost your metabolic rate by 25%.”

Don’t trust Dr. Oz? How about this line from the Mayo Clinic’s site, “In fact, skipping breakfast actually increases your risk of obesity” or this quote from a researcher on Yahoo! Health, “Skipping breakfast may lead to one or more risk factors, including obesity, high blood pressure, high cholesterol and diabetes, which may in turn lead to a heart attack over time.”

Not only is the Internet rife with this kind of language, but so too is the scientific literature, Allison points out. And it’s not always in research that has received food industry funding, he says. There’s what he calls “white hat bias” largely found in observational or short-term trials that also suggest breakfast produces beneficial effects on metabolism and satiety. But, once again, these types of studies cannot demonstrate causation. These limitations are rarely addressed in the research or in the media hype. Plus, not all breakfasts should be considered equal; the timing and nutritional content (think: sugary cereal versus eggs) are both key.

“It’s tempting to assume that if something shows promise in a short-term study, or if it has some aspect on insulin or fat metabolism, that we can extrapolate from these. But I think that it’s important that we test these things,” Dhurandhar said.

If there’s one underlying message these researchers are giving, it’s just this: beware oft-repeated diet advice not rooted in evidence. Additional vague platitudes that perhaps deserve equal attention are “eat everything in moderation” and “eat only when you’re hungry.”

As made clear with the rigorously designed tests on breakfast, our presumptions don’t always hold true. But breakfast now has one new thing going for it: increasing physical activity.

“Whether or not you have breakfast can dictate how much activity you engage in, which directly impacts energy balance but also holds implications for health via the independent benefits of living a more active lifestyle,” Betts said.

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Sunscreen On a Plate

Summer may seem like the best season for your skin. But under that well-tanned surface, the sun is actually wreaking havoc on your cells.

“When you leave lettuce in the sun too long, it wilts and turns brown because the light is causing oxidative damage. This is similar to your skin exposed to sunlight,” says Elizabeth Johnson, Ph.D., who researches antioxidants at Tufts University. On your skin, the damage manifests in the short term as a red-hot sunburn, but long-term, it can cause cancer.

And while sunscreen helps prevent the light from penetrating, what comes to the rescue once free radicals have taken over? The hero has to come from your plate in the form of antioxidants—like vitamin C, E and beta-carotene—which block free radicals from causing more damage. “Antioxidants float through your blood and amass in tissues, including the skin,” she says. This means when the sun damages your cells, antioxidants are already on the front line to battle damage.

Plus phytochemicals—a nutrient group that includes antioxidants—may ramp up your body’s natural protection systems against cancer-causing damage, adds Karen Collins, registered dietitian, Nutrition Advisor to the American Institute for Cancer Research. In fact, a 2010 study from Tel Aviv University found that participants who follow diet rich in antioxidants and omega-3 fatty acids, like that in the Mediterranean region where melanoma rates are extremely low, have lower incidences of skin cancer.

One of the best foods for protection? Tomatoes. A new British study found that people who ate ¼ cup of tomato paste—which offers high levels of the nutrient lycopene—for two weeks saw less oxidative damage. And a 2012 UK study found women who eat a tomato-heavy diet have 33 percent more protection against UV exposure than those who skip the fruit.

But since nutrients all have different functions and interactions, it’s important to eat all colors of the rainbow. “Many phytochemicals manifest as pigments, so eating fruits and vegetables of all colors guarantees that you’re diversifying your nutrient intake and better fortifying your skin,” says Johnson.

The best skin protectors include dark leafy greens, beta-carotene-rich carrots and cantaloupe, and polyphenol-packed berries and citrus fruit. And skip supplements in favor of whole foods. Most phytochemicals are bioactive, meaning they’re most effective coming from whole foods, and the high doses of most supplements can be harmful to your health.

Protection doesn’t occur overnight, Collins adds. In fact, most studies supporting nutrition’s benefit on sunburns or cancer prevention don’t see results until participants have been eating the food for at least 8 weeks, she adds.

Most importantly, there is no better protection against developing skin cancer than limiting your exposure to UV light, Collins adds. And, while a nutrient-rich diet can help fortify your cells, slathering on sunscreen as well will give your skin the best chances to stay healthy.

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