One Sweet Potato, Two Sweet Potato, YAM?!

Written by Melissa Hurley

Have you ever wondered, what is the difference in a sweet potato and a yam and all the different colors? And which one exactly is a yam?

Although orange-fleshed sweet potatoes have traditionally been referred to as yams in parts of the United States and Canada, they are not part of the same family and therefore they are not yams.

Sweet Potatoes – so many!

Diane/Garnet: red skin/orange flesh
Covington/Beauregard: orange skin/orange flesh
O’Henry/Golden Sweet: yellow skin/white flesh
Kotobuki/Murasaki: purple skin/white flesh
Stokes Purple: purple skin/purple flesh

True yams are cultivated in Africa, Asia, Latin America, the Caribbean and Oceania and not traditionally in the United States or Canada. The yam is a starchy, drier, edible root of the Dioscorea genus. It is rough and scaly and very low in beta carotene. They are related to lilies, and can be as small as a regular potato or ridiculously jumbo in size (some grow five feet long!). Yams have a cylindrical shape with blackish or brown, bark-like skin and white, purple or reddish flesh. True yams can be tough to find. They aren’t carried in many local grocery stores, so your best chances of finding them are in international and specialty markets.

Now you know. You’ve been probably eating sweet potatoes and calling them yams. Go forth and educate others. Keep it clear: sweet potatoes are not a type of yam and yams are not a type of sweet potato. They are both tuberous root vegetables that come from a flowering plant but they are not related and actually don’t even have a lot in common.

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What’s Up With the Bacteria In Your Gut?

PHOTOGRAPH BY DIXIE D. VEREEN, THE WASHINGTON POST, GETTY

We’ve known for decades that that the lush collection of bacteria that populate our guts plays a part in digestion. The famous after-effects of bean-eating—tactfully known in the 16th century as “windinesse”— are due to our resident microbes, chomping up an assortment of bean oligosaccharides (short chains of linked sugars) that our own enzymes can’t deal with, and generating in the process an unfortunate excess of bloating gas.

While gut bacteria play an essential (if not always socially tactful) role in human nutrition, a wealth of recent research now shows that they do far more. In fact, the key to whether we’re fat or thin, cheerful or depressed, healthy or chronically ill, may lie in the gut microbiome. Biologically, we’re the puppets of our bugs.

When it comes to gut bacteria, at least in the beginning, it’s all about mom. We start accumulating our resident bacteria at birth, following our unsterile passage through the birth canal; and we pick up even more through mother’s milk. Milk contains a population of complex carbohydrates that can only be digested by bacteria, specifically by Bifidobacterium infantis, a helpful bacterium that makes itself at home in the baby’s digestive tract and helps prevent infections. Milk, in other words, doesn’t just feed the baby; it also functions as a probiotic, providing infants with a growing population of beneficial microbes, and as a prebiotic—supplying those microbes with something to eat.

Generally, by the time kids turn three, following the introduction of solid foods and a lot of crawling around on the floor, their internal bacterial ecosystems are fully established. This means, inevitably, that they’ve come in contact with large numbers of fecal particles, which occupy a great deal more of the world than most of us care to think about. According to microbiologists, the environment is pretty much coated in poop.

Creepy though this may sound, it’s a good thing. Acquired bacteria provide us with enzymes and vitamins, such as vitamins B and K, help us battle infections, and manufacture neurochemicals essential for our mental health and well-being. An estimated 90 percent of the body’s serotonin, for example—a brain neurotransmitter that affects mood, sexual activity, appetite, sleep, memory, and learning— is made by gut bacteria.

Our personal bacteria also protect us from a wide range of ailments whose increasing prevalence, scientists now believe, may reflect that fact that something, bacteria-wise, is going seriously wrong. The modern rise in obesity, allergies, asthma, rheumatoid arthritis, Type I diabetes, multiple sclerosis, irritable bowel syndrome, cirrhosis of the liver, cardiovascular disease, and anxiety attacks – perhaps even autism – may be related to the bacterial populations in our guts.

The root of all evil here may be a leaky epithelium. The epithelium, the all-important lining of the digestive tract, ordinarily acts as a barrier between the teeming bacterial world of the gut and the rest of the body. Resident bacteria ordinarily keep epithelial cells healthy by providing them with short-chain fatty acids and other nutritive factors. In the absence of the appropriate nurturing bacteria, however, the starved epithelium breaks down, allowing bacteria and toxic bacterial byproducts to enter the bloodstream. This sends a signal to the immune system, alerting it to the presence of invaders, which can lead to persistent inflammation and eventually, a host of chronic diseases.

Helicobacter pylori. Image by The Science Picture Company, Alamy

In other words, many modern plagues may be occurring because our microbiomes aren’t what they used to be. In industrialized nations, overuse of antibiotics, a sanitized lifestyle, and a diet heavy in processed foods have all contributed to mass internal microbial die-off. The result is an impoverished Western microbiome. We’ve now got a far less diverse internal population of bacteria, and we’ve lost many helpful species altogether.

Martin Blaser of the NYU School of Medicine, author of Missing Microbes: How the Overuse of Antibiotics Is Fueling Our Modern Plagues, uses as a prime example a corkscrew-shaped bacterium called Helicobacter pylori, known to be the causative agent of peptic ulcers, that thrives in the acid environment of the human stomach. At the beginning of the last century, nearly every stomach in the world harbored H. pylori; today just five percent of American children carry it. This sounds, initially, like a plus—who needs an ulcer?—but Blaser points out that H. pylori plays essential roles in mediating the metabolic and immune systems, and in regulating ghrelin, the hormone that tells the brain we’re hungry and stimulates appetite. In the absence of bacterial controls, too much ghrelin may egg us on to over-eat.

 

While microbiome research is still in its early days, one thing is clear: a diet of junk food doesn’t do our bacteria any good. In one much-publicized experiment, genetic epidemiology professor Tim Spector of King’s College in London convinced his adult son Tom to spend ten days on a dedicated fast-food diet of fries, burgers, chicken nuggets, and Coca-Cola. Tom started out with a gut population of 3,500 bacterial species; by the end of his fast-food binge, he’d lost a third of these.

So how to maintain a healthy microbiome? Scientists and medical doctors generally advise that the thriving commercial pre- and probiotic supplement industry be taken with a grain of salt. Such products to date are unregulated. And in any case, there’s not yet consensus on what constitutes a healthy microbiome.

There are, however, some general rules. Recommended for the good of the gut is a diet rich in probiotic fermented foods such as yogurt, sauerkraut, kimchi, and miso soup, and in fiber-rich prebiotic foods, such as whole grains, fruits, and vegetables. It’s also a good idea to avoid processed foods, which may feed you, but don’t provide much sustenance for your gut bacteria.

Exercise seems to benefit not just us, but our guts. One study, comparing rugby players to non-athletes, found that the rugby players had more diverse microbiomes, with higher proportions of at least 40 different bacterial species.

And, while antibiotics are certainly sometimes necessary, we should be cautious about overusing them. Studies show that that the gut microbiome can take up to a year to bounce back after a course of bacteria-blitzing antibiotics.

Finally, in the service of gut microbiome diversity, you might want to expand your environment. The more diverse bacteria you pick up, the better. So meet new people, pat the dog, dig in the garden, and play in the dirt. Bugs are good.

If you’re curious about the make-up of your check out American Gut, a citizen-science project in which participants can discover how their diet and lifestyle shape their microbiomes, and find out how theirs compares to others.

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Nuno Costa

This is the life story of a 7x Crossfit Games competitor and Affiliate champion.  My teammate, my colleague, and my friend Nuno Costa.

Bodybuilder with ONE ARM determined not to let condition hold him back

AN INSPIRATIONAL bodybuilder refuses to let his missing arm get in the way of his love of the gym. 

Fitness fanatic Max Okun, from Arizona, was born without one of his arms, but he won’t let that hold him back.

He said: “I was born missing my arm – I don’t care, that’s just the hand I was dealt in like so I’ve got on with it.”

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Paleo-diet debates evolve into something bigger

There is lots of debate about Paleo.  It just good to be educated about your diet.
Washington Post

The article kicked off not just a diet but also a movement. Appearing in the New England Journal of Medicine in January 1985, “Paleolithic Nutrition: A Consideration of Its Nature and Current Implications” argued that the human body is “genetically programmed” to run not on a modern diet but on the foods consumed by our Stone Age ancestors.

“The human genetic constitution has changed relatively little since the appearance of truly modern human beings, Homo sapiens sapiens, about 40,000 years ago,” S. Boyd Eaton and Melvin Konner wrote.

The authors reasoned that human bodies have been shaped more by our prolonged time as hunter-gatherers than by the brief span since the advent of farming. Meat, probably lots of it, as well as fruits and vegetables were in. The staples of agriculture — breads, cereals, milks and cheeses — were not.

Three decades later, that academic ripple is now a popular tidal wave. We have not just Paleo diets — the subject of multiple bestsellers — but also Paleo exercise, Paleo sleeping and Paleo toilets. They’re all based on the premise that our bodies are more suited for Paleo-era habits.

But even as the “cave man” diet rose to become the most-Googled diet in 2013 and 2014, evolutionary biologists, with much less fanfare, were using advanced DNA techniques, sometimes on ancient bones, to suggest that Eaton and Konner’s premise may be off the mark: In fact, it seems, we have evolved.

Over the past year alone, prominent scientific journals have published evidence of genetic shifts in humans over the past 10,000 years — apparently in response to mankind’s transition to agriculture.

Two relatively recent gene variants help humans survive with deficiencies characteristic of agricultural diets; another genetic shift appears to help fight the dental cavities that arose with farm-based staples; another changes the way humans digest fats; dozens of others help fight the diseases that came with living at higher densities.

Those new findings add to previously known adaptations to mankind’s changing diet. After the domestication of milking animals, many humans evolved to digest milk. Humans also appear to have developed better ways to digest the starches characteristic of agricultural diets.

“It drives me crazy when Paleo-diet people say that we’ve stopped evolving — we haven’t,” said Anne C. Stone, a professor of human evolution at Arizona State University who has shown that genes related to starch digestion appear to have changed in number, apparently in response to farming. “Our diets have changed radically in the last 10,000 years, and, in response, we have changed, too.”

Although all this new evidence challenges the Paleo-diet argument, it doesn’t necessarily disprove it. And Eaton and Konner, for their part, maintain that their central hypothesis — that there is a mismatch between our bodies and our diets — remains sound.

Pace of research picks up

Yes, Konner said in an interview, there is more research that humans have evolved recently.

“There’s evidence that there’s been a lot more selection and genetic change in the last five to 10 thousand years than previously thought,” he said. “This is a challenge to the Paleo-diet claims — including mine and Boyd Eaton’s over the years.”

“But,” he said, “I don’t think it’s much of one.”

For one thing, he and Eaton say, the newly discovered genetic differences between Paleolithic hunter-gatherers and modern humans are not very numerous. Although there may be some ways in which humans have adapted to agricultural diets, those are far outnumbered by the ways in which human bodies remain suited for the Paleo era.

And even if one concedes that there has been significant genetic change over the past 10,000 years, Konner said, those changes would only catch us up to human diets from 10,000 years ago. But our diets have changed radically over the last 300 years alone — we consume less fiber, more refined grains, etc. — and evolutionary forces cannot have altered our bodies so quickly over that time.

“The bulk of the chronic degenerative disease in our population is due to dietary changes in the last few centuries; they’re not necessarily related to the shift from hunter-gatherers to agriculture,” Konner said. “The biggest culprit with the current epidemic of diabetes, a looming problem worldwide, is refined carbohydrates. There’s no way humans could have adapted to that because they haven’t been around long enough.”

The outcome of the debate rests for now on the ongoing research, which has accelerated markedly in recent years.

When Eaton and Konner wrote their article, the human genome had not been fully sequenced, and it was far more difficult to detect evidence of recent human evolution.

Take, for example, the discovery that humans gained the ability to digest milk — lactose tolerance — as they began to domesticate milking animals.

First, scientists had to discover that lactose tolerance is an inherited trait. This came about after scientists noticed similarities within families. Once that was established, scientists were forced to look for clues from geography and anthropology. What they found is that in populations where cattle had been long domesticated, most people could digest milk easily; in populations without domesticated milking animals, most could not.

“This trait seems to be common or extremely common only in populations which have established the custom of having milk regularly in their diet after weaning,” Stanford University geneticist Luigi Luca Cavalli-Sforza wrote in 1972. “It is rare or absent in others.”

Eaton and Konner acknowledged this dietary adaptation in their 1985 paper but said that “very few other examples are known.”

Signs of adaptation

After that, however, the pace of evolution research accelerated rapidly, especially with the ability to sequence the entire human genome. It allowed researchers, for example, to compare the DNA of populations with different diets — new and old — and look for signs of adaptation.

Stone and her colleagues, for instance, were interested in the varying abilities of people to handle diets loaded with starch. After the transition to agriculture, which brought steady supplies of wheat, corn, rice, barley and other crops, the ability to digest starches probably became more useful. Did human bodies adapt?

To answer that question, the researchers compared the DNA of peoples with high-starch diets and with the DNA of remote peoples who had low-starch diets.

The high-starch groups included European Americans, Japanese and Tanzania’s Hadza people, hunter-gatherers who rely on starch-rich roots. The low-starch groups were African pygmies, some African cattle farmers and a Russian ethnic group known as the Yakut.

DNA analysis showed that individuals from the high-starch groups were roughly twice as likely as the others to have inherited many extra copies of the AMY1 gene. The saliva of people with more copies of this gene tends to have more amylase, an enzyme that allows them to better digest starch.

More recently, another advance gave scientists a direct way of comparing contemporary humans to our Paleolithic ancestors by recovering DNA from ancient bones.

In a paper that appeared in December in the journal Nature, scientists looked at DNA recovered from the bones of more than 200 ancient Eurasian humans. The samples ranged from about 2,000 to 8,000 years old, a span that covers hunter-gatherers as well as early farmers.

The scientists noted thousands of distinct places in the DNA where there were changes that didn’t seem random but that instead appeared to be adaptation to environment.

From those thousands of places, the scientists highlighted 12 places where the signs of selection were clustered. One of those clusters related to the digestion of milk — a DNA change that confirmed previous findings. Another related to how humans digest fatty acids. Two others may have a link to celiac disease. Others were related to skin color, which got lighter as humans moved northward from Africa, and disease resistance.

“Europeans of 4,000 years ago were different in important respects from Europeans today, despite having overall similar ancestry,” the authors concluded.

Those findings, like the others, challenge the Paleo idea that humans have not changed. What remains unanswered, though, is how much change there has been.

“My overall opinion of this is that we don’t really know,” said Iain Mathieson, a Harvard University Medical School researcher and a co-author of the Nature paper. “We do know there are some specific changes in humans. But they are relatively small in number. To me, it’s an open question. It’s a hypothesis.”

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