Not all microbes are bad. Some — especially yogurt’s — are downright nutritious and have changed the diets of prominent scientists.
Take Ilya Ilyich Mechnikov, the co-winner of the 1908 Nobel Prize for his work explaining how white blood cells fight disease. After years of studying intestinal bacteria, the Russian scientist blamed harmful microbes for senility — wrongly, as it turned out. Still, he prescribed yogurt as a natural remedy, and, just as today’s dieticians recommend eating trendy foods such as acai berries or wild salmon, Mechnikov turned the consumption of sour milk into a fad.
To make yogurt, consumers only need milk, a bacterial culture and a warm container to incubate the two overnight, allowing the bacteria to ferment the milk’s sugar into lactic acid. The weak acid is important; it makes the yogurt tart and curdles the milk proteins, giving yogurt its trademark custard-like texture.
Historically speaking, Mechnikov was late to the yogurt craze. Fermented milk had already showed up on Egyptian banquet tables and in Israeli, Turkish and Indian cooking. In the second century A.D., the famous physician Galen lauded yogurt for its soothing and purifying effects on the intestinal tract, according to David Kaiserman in The Book of Yogurt.
Once ingested, yogurt’s beneficial bacteria, called probiotics, flood the digestive tract, increasing microflora – the microbes in the gut that help fight diseases and break down foods, such as carbohydrates.
“It’s like seeding a lawn with new grass seed,” says Elizabeth Applegate, director of sports nutrition at University of California, Davis.
After reaching the intestines, probiotics help prevent disease. Lactobacillus strains bind to the linings of the small and large intestines, taking up space and preventing bad bacteria from attaching to the gut’s walls.
In a 2010 study, researchers studied 81 people with chronic liver disease, an illness that can lead to an imbalance of intestinal microflora. A group of 41 ate one cup of yogurt three times a day for two weeks, while a control group of 40 people did not eat any yogurt. At the end of the experiment, researchers found that the 41 participants had lower E. coli counts and a better intestinal flora balance compared to the control group, according to the journal Nursing Research.
Even better, probiotics can boost the immune system. A group of 33 women fed yogurt for four weeks improved their immune response, according to a 2006 study. In another experiment, mice fed yogurt and then infected with pneumonia recovered in seven days, compared to 21 days in the yogurt-free control group.
Apart from thwarting diseases, yogurt contains a host of nutrients: proteins, B vitamins and minerals such as calcium, magnesium, phosphorus, potassium and zinc. Interestingly, most lactose-intolerant people can eat yogurt because the microbes in it digest lactose (the sugar found in milk).
“Yogurt in general is a nutrient-dense food,” Applegate says. “It’s better than milk. It has a more concentrated dairy source.”
Dieters should take note. A survey of more than 120,000 Americans found that eating yogurt was associated with about a pound of weight loss in a four-year period, a group of Harvard University researchers reported in June. Another Harvard study found that a fatty acid found in dairy products, including yogurt, may substantially reduce the risk of Type 2 diabetes.
Though healthy, some yogurt has some unhealthy additions, such as sugar.
“I always tell people to get plain yogurt and add sweetener themselves,” Applegate says. “Then they can see how much they’re adding.”
She recommends using fruit and honey with low-fat yogurt. Applegate also warns that the bacteria cannot survive in extreme temperatures. Very few bacteria endure in frozen yogurt, and heating a dish above 120 degrees Fahrenheit is a bacteria death sentence.
Although advertised as a food that could extend and improve quality of life by scientists like Mechnikov and companies like Dannon (its 1977 commercial suggesting yogurt and longevity were correlated is credited with increasing sales), dieticians recommend eating it as a healthy snack, not as a miracle cure.
The observation that some yogurt eaters lived longer is a correlation, not causation, says Maudene Nelson, director of community outreach at the Columbia University Institute of Human Nutrition.
“Maybe some of the benefits that we attributed to yogurt were associated with a yogurt-based culture and not the yogurt itself,” she explains.
Still, yogurt makes for a delicious, healthy and immune-boosting snack.
“A yogurt is a really good safe food to carry around with you for a few hours without being worried about it,” says Nelson. “It’s tasty, assessable, affordable, portable, drinkable, eatable and it scores high on nutrition scales.”
And with that, Nelson went to check on the homemade yogurt fermenting in her kitchen.
“It’s so easy,” she says. “You could almost do it with one hand tied behind your back and one eye closed.” Here’s how you can make your own.