The Real Science Behind What We Eat
Wu is an eighteen-year-old boy from China. He weighs 175 kg and has a BMI of 59. Unsurprisingly he has a whole host of medical problems, most of them caused by inflammation. His weight was not due to excessive calories. His food was the standard fare for Chinese teenagers of meat and noodles, and while he was eating slightly more than he should, it was not enough to make him 100 kg overweight. Wu was fortunate to find the clinic of Professor Zhao, a world expert on diet and gut bacteria, who examined his gut and discovered it had been colonized by Enterobacter, an aggressive bacteria that provokes inflammation. Professor Zhao put Wu on a diet that encouraged friendly bacteria growth in his gut. The diet was gluten free, free from meat, and high in fiber, comprising legumes, oats, peanuts, and Chinese herbs. After just nine weeks Wu lost 30 kg. After four months he lost 51 kg. After six months the Enterobacter bacteria was undetectable, Wu’s hunger vanished, and his inflammatory markers were normal. As an experiment Professor Zhao took Wu’s bacteria and implanted it into lean mice. Within one week the mice were fat, had diabetes, inflammation, and high blood lipid levels. The experiment was repeated by implanting different strains of gut bacteria from obese humans into lean mice, and in every case the lean mice became fat and unhealthy. To date, Professor Zhao has replicated Wu’s success with over 1,000 obese people.
What follows is the story of how good gut bacteria can restore health, prevent obesity, improve mental health, and help with a wide range of diseases that have inflammation at their root. The story is told by Professor Tim Spector of Kings College, London. Professor Spector is one of the world’s leading genetic epidemiologists and the author of over 500 peer-reviewed studies. He is also the world expert on twins, and it is his study of identical twins that allows him to determine the genetic and lifestyle influences upon health.
Professor Spector began to look at bacteria because he wanted to understand why two people, even two identical people, eating exactly the same food have different results. Some will get fat and ill, some will have heart disease, others will not. He took a large group of identical twins and overfed them by 1,000 calories a day with the same food. Their daily movement was closely monitored and controlled. At the end of the study all the twins had put on weight. This was expected. What floored Professor Spector’s team was that within the same set of identical twins the amount of weight gain was different. Vastly different. One twin put on as much as 14 kg, while the other put on as little as 3 kg. As the twins were identical this was not due to genes. In fact, Professor Spector estimated that genes only account for 60% of health problems. Genes alone do not explain why rates of obesity in Australia are rising faster than just about anywhere else. According to the medical journal the Lancet, 63% of adult Australians are now overweight. Or why Malaysia and the Gulf States have levels of diabetes approaching 50% of the population. Or why Egypt is faced with an unprecedented obesity crisis. Or why there are 1 billion obese people in China and India. And all of these people are at risk of inflammatory diseases ranging from dementia to heart disease. Genes alone do not explain why 50% of Aborigine males in Australia die before the age of forty-five. What Professor Tim Spector discovered is that two people eating the same diet have different illnesses due to gut bacteria and an interaction between genes and bacteria. Just as aggressive gut bacteria caused by poor diet made eighteen-year-old Wu obese, it also made the twins in his study obese. He and his fellow researchers also discovered that bad gut bacteria produces huge amounts of inflammation, which is at the root of almost every modern, major disease.
The human body contains around 100 trillion microbes made up of thousands of species that weigh 2 kg in our gut. Even a handful of dirt has more microbes than there are stars in the universe. While just one crumb of blue European cheese has millions of microbes. When babies are born they are exposed to billions of bacteria from the birth canal of the mother. Babies born by Caesarean section do not have the same exposure. These beneficial bacteria quickly populate the skin and mouth of the child without reaching the colon. However, for reasons that are still unknown, the bacteria transmitted from the mother’s breast milk are protected from stomach acid, and they quickly form a new colony in the stomach and colon. These bacteria divide every sixty minutes populating the newborn child with trillions of cells and hundreds of species during the first day and night. The fact that the colony establishes itself so quickly indicates that even twenty-four hours of breast feeding is beneficial. This transmission of bacteria from mother to child via breast milk was not known until the 1990s. As always there is a downside: the bacteria that colonize the baby are the same bacteria found in the mother’s gut. If the mother has unhealthy, aggressive, inflammatory bacteria due to poor diet, then it is these bacteria that colonize the child’s colon. It has been suggested that this transmission of unhealthy bacteria is responsible for rising obesity and inflammatory diseases among the very young.
Think about the following scenario. A child is not breastfed, or is breastfed by a mother who has unhealthy bacteria. As a young child he is treated by his father and grandparents to sugary treats, Coke, and junk food. The food he eats at home is standard, modern Western or Asian food, high in bad fats and refined carbs. Then, by the time he approaches his teenage years, he is fat and various health conditions are starting to be seen. This is exactly what happened to Jason, whose story is increasingly common. Jason was just ten years old when he was admitted to hospital as his legs had swollen to twice their normal size. He had very high blood pressure, high cholesterol and triglycerides, Type 2 diabetes, and his liver was failing. He weighed 63 kg and had fatty liver disease. Aside from very rare cases it used to be unprecedented for children to have fatty liver disease, just as it used to be unprecedented for children to have Type 2 diabetes. Fatty liver disease is caused by high circulating levels of fats and sugars that overwhelm the liver, and is usually seen among adult alcoholics. Now, one in eight seventeen-year-old Australians have the early symptoms of non-alcoholic fatty liver disease due to a junk food diet, and 40% of adult Australians have the condition, even if they are unaware. The liver and fat cells of these children are in a constant state of inflammation and stress. If this is not addressed early in the disease then the two outcomes are a liver transplant or death.
It is now well known that junk food is bad for our health. What is often overlooked is its effect upon our gut bacteria. Junk food is made from four main ingredients: corn, wheat, soy, and meat, which constitute 80% of the volume of junk food. When walking around supermarkets we are lulled into thinking that we eat more varieties of food than ever before due to the amount of food on offer. This is an illusion. It is estimated that a modern Western diet has only twenty different types of food per week, and that the meals we eat are just variations on these twenty types of food. Our ancestors typically ate 150 varieties of food per week. That diversity of natural, wholesome food fed good bacteria and allowed it to colonize the colon. In contrast, the lack of variety from our modern junk diet destroys good bacteria and allows bad bacteria to flourish.
Witness the case of Tom. Tom is an aspiring twenty-one-year-old geneticist, who happens to be the son of Professor Tim Spector. As part of a university experiment, Tom agreed to eat only McDonald’s for ten days. By day eight his blood sugar levels were high, he had stopped sleeping, started sweating, and had put on 2 kg. However, the most significant change was in his gut. He lost fully 40% of his beneficial microbes and several hundreds of species in just ten days. The bacteria that remained were aggressive, promoted inflammation, and depleted his immune system. Similar results were observed at Harvard University in just three days after healthy volunteers were put on a ketogenic diet of meat, eggs, and processed cheese. The combination of a lack of variety coupled with high fat and high sugar is deadly for good gut bacteria, and it feeds inflammation. One of the emerging themes in the science of gut bacteria is that we need a diverse range of food to feed our bacteria. Adding bacteria to our diet is less successful. The problem with low carb diets is that they neglect the trillions of microbes in our guts that are constantly evolving and need feeding. In contrast, a varied diet made up of traditional foods transforms gut bacteria.
Junk food also contains transfats. Transfats are industrial oils from vegetable and seed oils. They are used in processed food, for frying, and margarine. If you eat fried food or cook with vegetable oils then you are eating transfats. The thing is there is no safe minimum amount for transfats, even a little is harmful, which is why Denmark has banned them and other European countries have restricted them. Just by getting 1% of your daily energy requirements from transfats, equivalent to 25 calories, is enough to increase lipid levels, and the risk of heart disease and cancer. Typically, people in the United States get 2% of their energy from transfats. The real danger though is for people from the Indian subcontinent. Currently, Pakistanis consume a giant 7% of their calories from transfats, mainly in the form of vegetable oil used for cooking. This disturbing figure explains the recent epidemic of heart disease, kidney disease, and cancer among people of Indo-Pak heritage.
Not all fat is bad. Junk food and transfats certainly kill off good bacteria and increase inflammation, yet other types of fat encourage the growth of good bacteria. Traditional cheese maintains gut bacteria even after people have taken antibiotics. It is full of yeasts, microbes, and fungi, and has been shown to be protective against high blood lipid levels. These microbes in cheese are strong enough to survive stomach acid and can change the balance of our gut bacteria in just one day. Unfortunately, this is the very type of cheese that is banned in the United States. Allowed in its place is the sterile, processed, dead cheese that does not nourish our microbes. This doesn’t mean that unlimited amounts of traditional cheese, such as brie and stilton, can be eaten, just because cheese is good for us. The French have it about right in consuming no more than 30 grams at a time.
Yogurt is another food that affects gut microbes but in an unexpected way. The bacteria in yogurt does not survive in the colon. Even when microbes from yogurt reach the stomach or colon they do not affect the composition of bacteria in the gut. Yet behind the scenes the bacteria in yogurt have a remarkable effect. They ramp up the activity of genes that control the breakdown of carbohydrates and attack inflammation. From the gut the microbes in yogurt act on key centers in the brain, as the network of nerves in the gut sends signals to the brain that influence mood. Through this mechanism the microbes in yogurt increases serotonin in the gut and brain, removing anxiety, stress, and depression.
Another key fat is found in olive oil. In 2013 a study comparing the risk of heart disease in an olive oil rich diet to a low-fat diet had to be stopped on ethical grounds. The low-fat group were having 30% more heart attacks than the people consuming olive oil, making it unethical for the study to continue. We know that the polyphenols in olive oil switch off genes that cause inflammation in blood vessels, and that 80% of nutrients in olive oil make it to the colon where they feed good bacteria. This feeding frenzy produces antioxidants that signal the body to lower lipid levels, boost the immune system, reverse plaque build-up, and prevent bad microbes from flourishing. Unsalted nuts have a similar effect.
Remember earlier we said that 50% of Australian Aborigine men die before the age of forty-five. This is due to the adoption of a Western lifestyle to which Aborigines are ill-suited. Researchers took a group of Aborigine men back to the bush in northwestern Australia. They lived off a high-protein, low-fat, lowish-carb diet made up of kangaroos, yams, birds, insects, vegetables, and honey. After just seven weeks their weight, blood sugar, lipids, and triglycerides all normalized. They didn’t get the beneficial effects of cheese, yogurt, or olive oil, but they did eat the food that most suited their particular microbes and genes.
It is not just food that impacts our gut bacteria. One of the strongest predictors of gut bacteria health is the amount of exercise a person does. Exercise produces the fatty acid butyrate, which improves the immune system and makes more good microbes. The more athletic a person is the healthier their gut bacteria will be. Fasting also radically improves the diversity of our gut microbes. It is a myth originally promoted by cereal companies that breakfast is essential. The Greeks, Romans, Persians, and early Jews only had one big meal a day. One third of people in Mediterranean countries continue to skip breakfast. And breakfast was not widespread in Anglo-Saxon countries until the eighteenth century. The norm was two meals a day. An extended period of time overnight and the next morning is known to benefit gut bacteria. Only when a person eats their first meal after 1:00 p.m. does their metabolism start to slow. Two days a week fasting is also beneficial upon gut bacterial heath, with the proviso that a rich diversity of traditional foods are eaten the rest of the week.
The most dangerous myth is that we all respond to the same food in the same way. Different people will flourish on different food depending on their ethnicity, their genes, and where they currently live. The good news is that healthy gut microbes can be regenerated within as little as one week, without supplementing bacteria. The first step is to do no harm by removing all junk food, processed food, sugars, and especially transfats. Then the microbes need the right food upon which to feed. Microbes love food rich in polyphenols and high in nondigestible fiber. Microbes thrive on a varied diet that does not omit whole macronutrients such as carbohydrate, and which comprises food that our ancestors ate. This varied, fiber, plant, and polyphenol rich diet, with quality fish, dairy or meat, coupled to exercise and fasting makes our microbes and health thrive.