Hundreds of bacterial species call each of us "home." In sheer numbers, these microbes and their genes dwarf us. It turns out that we are only 10 percent human: for every human cell that is intrinsic to our body, there are about 10 resident microbes — including commensals (generally harmless freeloaders) and mutualists (favor traders) and, in only a tiny number of cases, pathogens. To the extent that we are bearers of genetic information, more than 99 percent of it is microbial. And it appears increasingly likely that this “second genome,” as it is sometimes called, exerts an influence on our health as great and possibly even greater than the genes we inherit from our parents. But while your inherited genes are more or less fixed, it may be possible to reshape, even cultivate, your second genome.

Justin Sonnenburg, a microbiologist at Stanford, suggests that we would do well to begin regarding the human body as “an elaborate vessel optimized for the growth and spread of our microbial inhabitants.” This humbling new way of thinking about the self has large implications for human and microbial health, which turn out to be inextricably linked. Disorders in our internal ecosystem — a loss of diversity, say, or a proliferation of the “wrong” kind of microbes — may predispose us to obesity and a whole range of chronic diseases, as well as some infections.

“Fecal transplants,” which involve installing a healthy person’s microbiota into a sick person’s gut, have been shown to effectively treat anantibiotic-resistant intestinal pathogen named C. difficile, which kills 14,000 Americans each year. (Researchers use the word “microbiota” to refer to all the microbes in a community and “microbiome” to refer to their collective genes.) We’ve known for a few years that obese mice transplanted with the intestinal community of lean mice lose weight and vice versa. (We don’t know why.) A similar experiment was performed recently on humans by researchers in the Netherlands: when the contents of a lean donor’s microbiota were transferred to the guts of male patients with metabolic syndrome, the researchers found striking improvements in the recipients’ sensitivity to insulin, an important marker for metabolic health. Somehow, the gut microbes were influencing the patients’ metabolisms.

Our resident microbes also appear to play a critical role in training and modulating our immune system, helping it to accurately distinguish between friend and foe and not go nuts on, well, nuts and all sorts of other potential allergens. Some researchers believe that the alarming increase in autoimmune diseases in the West may owe to a disruption in the ancient relationship between our bodies and their “old friends” — the microbial symbionts found within.

These claims sound extravagant, and in fact many microbiome researchers are careful not to make the mistake that scientists working on the human genome did a decade or so ago, when they promised they were on the trail of cures to many diseases. We’re still waiting. Yet whether any cures emerge from the exploration of the second genome, the implications of what has already been learned — for our sense of self, for our definition of health and for our attitude toward bacteria in general — are difficult to overstate. Human health should now “be thought of as a collective property of the human-associated microbiota,” as one group of researchers recently concluded in a landmark review articleon microbial ecology — that is, as a function of the community, not the individual.

Such a paradigm shift comes not a moment too soon, because as a civilization, we’ve just spent the better part of a century doing our unwitting best to wreck the human-associated microbiota with a multifronted war on bacteria and a diet notably detrimental to its well-being. Researchers now speak of an impoverished “Westernized microbiome” and ask whether the time has come to embark on a project of “restoration ecology” — not in the rain forest or on the prairie but right here at home, in the human gut.

Until about 2006, almost all studies on salt and health outcomes relied on the well-known fact that blood pressure can drop slightly when people eat less salt. From that, and from other studies linking blood pressure to risks of heart attacks and strokes, researchers created models showing how many lives could be saved if people ate less salt.

The United States dietary guidelines, based on the 2005 Institute of Medicine report, recommend that the general population aim for sodium levels of 1,500 to 2,300 milligrams a day because those levels will not raise blood pressure. The average sodium consumption in the United States, and around the world, is about 3,400 milligrams a day, according to the Institute of Medicine — an amount that has not changed in decades.

But more recently, researchers began looking at the actual consequences of various levels of salt consumption, as found in rates of heart attacks, strokes and death, not just blood pressure readings. Some of what they found was troubling.

One 2008 study the committee examined, for example, randomly assigned 232 Italian patients with aggressively treated moderate to severe congestive heart failure to consume either 2,760 or 1,840 milligrams of sodium a day, but otherwise to consume the same diet. Those consuming the lower level of sodium had more than three times the number of hospital readmissions — 30 as compared with 9 in the higher-salt group — and more than twice as many deaths — 15 as compared with 6 in the higher-salt group.

Another study, published in 2011, followed 28,800 subjects with high blood pressure ages 55 and older for 4.7 years and analyzed their sodium consumption by urinalysis. The researchers reported that the risks of heart attacks, strokes, congestive heart failure and death from heart disease increased significantly for those consuming more than 7,000 milligrams of sodium a day and for those consuming fewer than 3,000 milligrams of sodium a day.

There are physiological consequences of consuming little sodium, said Dr. Michael H. Alderman, a dietary sodium expert at Albert Einstein College of Medicine who was not a member of the committee. As sodium levels plunge, triglyceride levels increase, insulin resistance increases, and the activity of the sympathetic nervous system increases. Each of these factors can increase the risk of heart disease.

“Those are all bad things,” Dr. Alderman said. “A health effect can’t be predicted by looking at one physiological consequence. There has to be a net effect.”

Medical and public health experts responded to the new assessment of the evidence with elation or concern, depending on where they stand in the salt debates.

“What they have done is earth-shattering,” Dr. Alderman said. “They have changed the paradigm of this issue. Until now it was all about blood pressure. Now they say it is more complicated.” The report, he predicted, “will have a big impact.”

Recycling used materials can take a more traditional aspect, for economic reasons for instance. When she returned to Switzerland after working for ten years in Africa, architect Barbara Buser from Basel architectural firm In Situ, rebelled against the huge amounts of perfectly good construction materials thatwere being wasted.

“It’s possible to build entire houses using recycled materials, their used aspect even adds charm to the structure.” Buser knows that in Switzerland this is still a niche market, tied to economic aspects more than innovation.

Only a few architects use this second-hand exchange or use recyclable objects. This is not because of legislation, because the same fire safety and security rules apply to new and used material, explains Thomas Muller from the Swiss Association of Engineers and Architects. On the contrary, recycling is encouraged in Switzerland through specific construction standards.

According to Muller, the reluctance of architects to work with reclaimed objects is the main reason why they are not used more widely. For architects, recycled materials causes artistic limitations, especially in the case of visible elements. And even though clients want to be alternative and innovative, are often hesitant of taking the actual step of building their homes with old materials.

The city of Tucson receives more rainfall than it uses annually, yet the city still imports the great majority of their municipal water via the Colorado River. Where does all that rainfall go? This short video touches upon ideas for harvesting rainwater in the city instead of sending it to the sewers.

In many parts of the world, women traditionally have an important role in providing food for the community and for their families. They cultivate the soil, look after the seeds of traditional plants, and safeguard recipes of the local cuisine. Yet the situation of women farmers is too often a story of a denial of the fundamental and inalienable right to feed themselves. 

We tend to forget that the future of many developing countries is in the hands of women. According to FAO, if women farmers had access to the same opportunities and resources as their male counterparts, their productivity would rise significantly and the food security of millions of people would be improved. Our job is to support them, put their demands for rights at the center of debates on development, campaigns and actions of political pressure from civil society.

        Traditional fermentation of raw milk into cheese, creme fraiche, yogurt, lassi and other dairy products is a form of natural preservation with many health benefits. The identities of the micro-organisms that generate medicinal molecules in raw milk dairy products are often known. Lactic acid bacteria are examples of important fermenters. They enrich milk with vitamins and also make small proteins called bacteriocins—antibiotics that work by perforating bacterial cell membranes. One bacteriocin, lacticin 3147, destroys the diarrhea-inducing germ Clostridium difficile. Other important fermenters include strains of Lactobacillus, Propionibacterium, Bifidobacterium, and Enterococcus. These fermenters serve double duty synthesizing conjugated linoleic acid, an anti-clotting and anti-cancer agent. (Curiously, aged cheeses contain less of this acid than cheeses with a short ripening period.)

           Moreover, bacteria that could have a hand in improved fermentation are being revealed all the time. One such strain is Lactobacillus helveticus BGRA43 which breaks apart key proteins as it ferments milk such that it imbues the milk with anti-microbial, anti-hypertensive, and immunomodulatory properties.

           But in most cases, the enrichment of health-promoting substances was an unintended, and until recently, an unnoticed, side effect of making tasty foodstuffs that last. It isn’t always clear whether the chemicals involved survive digestion in the human gut and go on to do good things around the body. This point needs examining before fermentation science can be used to design healthier dairy products in the future.

Many studies rely on people’s recollection of what they ate. But in this study, funded mainly by the Spanish government, the researchers actually checked people’s consumption of olive oil and nuts with lab tests.

The researchers didn’t set any limits on calories or give targets for exercise, but the results were still astounding.

The study was stopped early (after a median follow-up of 4.8 years) because the benefits from the Mediterranean diet were readily apparent. Overall, the people consuming the diets rich in olive oil (at least 1/4 cup per day!) or nuts had about a 30 percent lower risk of having a heart attack, stroke or dying from a cardiovascular cause when compared to those on a low-fat diet.