 If you expose pregnant crickets to a predatory wolf spider, her babies will hatch exhibiting increased anti-predator behavior, and as a consequence, improved survival from wolf spider attack. The mother cricket appeared to be able to forewarn her babies about the threat when they were still inside her so they would be pre-adapted to their external environment. This even happens in plants. If you grow two genetically identical plants, one in the sun, one in the shade, the sun-grown plant will produce seeds that grow better in the sun, and the shaded plant will grow seeds better, growing better in the shade, even though they're genetically identical. So what we're dealing with is epigenetics, external factors changing gene expression. Vole pups born in the winter come out growing thicker coats. Vole mothers are able to communicate the season to their babies in utero and tell them to put a coat on even before they're born, and people are no different. You know how different people have different temperature tolerances, resulting in battles of the bedroom. Do you turn the AC on or off, open the windows? It's not just genetics. Whether you're born in the tropics or in a cold environment determines how many active sweat glands you have in your skin. But what does this have to do with diet? Can what a pregnant woman eats permanently alter the biology of their children in terms of what genes are turned on or off throughout life, or what they don't eat? What happened to the children born during the 1945 Dutch famine imposed by the Nazis? Higher rates of obesity 50 years later. The baby's DNA gene expression reprogrammed before birth to expect to be born into a world of famine, to conserve calories at all costs. But when the war ended, this propensity to store fat became a disadvantage. What pregnant women eat and don't eat doesn't just help determine the birth weight of the child, but the future adult weight of the child. For example, maternal protein intake during pregnancy may play a role in the obesity epidemic, but not just protein in general, protein from animal sources, primarily meat products consumed during pregnancy may increase the risk of their children growing up overweight. Originally, they thought it might be the IGF-1, a growth hormone boosted by animal product consumption that may increase the production of fatty tissue. But weight gain was tied more to meat than dairy. Every daily portion of meat intake during the third trimester resulted in about an extra percent of body fat mass in their children by their 16th birthday, potentially increasing their risk of becoming obese later in life, independent of how many calories they ate or how much they exercised. But no such link was found with cow's milk intake, which would presumably boost IGF-1 levels just as high. So maybe instead it's the obesogens in meat, chemicals that stimulate the growth of fatty tissue. Emerging evidence demonstrates that environmental factors can predispose exposed individuals to gain weight irrespective of diet and exercise. After all, even our infants are fatter. You can't blame that on diet and exercise. Animals, too. And not just our pampered pets, even rats in labs and subways. The likelihood of 24 different animal populations from 8 different species, all showing a positive trend in weight over the last few decades, by chance is less than 1 in a million. So it appears there's something else going on, like obesogenic chemicals. One such candidate is polycyclic aromatic hydrocarbons, found in cigarettes spewing out of exhaust pipes and in grilled meat. This nationwide study of thousands found that the more children are exposed, the fatter they tended to be. They could measure the levels of these chemicals right out of their urine, and it can start in the womb. Prenatal exposure to these chemicals may cause increased fat mass gain during childhood and a higher risk of childhood obesity. If these pollutants sound familiar, I've covered them before in relation to increasing breast cancer risk in the Long Island Breast Cancer Study. So maybe they're not just obesogens, but carcinogens as well, perhaps explaining the 47% increase in breast cancer risk among older women in relation to a lifetime average of grilled and smoked foods. If you look at one of the most common of these toxins, smokers get about half from food and half from cigarettes. But for non-smokers, 99% comes from diet. The highest levels are found in meat, with pork apparently worse than beef, but as you can see, even dark green leafies like kale can get contaminated by pollutants in the air. So don't forage your dandelion greens next to the highway and make sure to wash your greens under running water. Now these are fat-soluble pollutants, so need lots of fat to be absorbed, so even heavily contaminated plant-based sources may be safer unless you pour lots of oil on your food, in which case the toxins would presumably become as readily absorbed as the toxins in meat. The good news is that they don't build up in your body. If you expose people to barbecued chicken at time zero here, you can see they get a big spike in these chemicals, like up to a hundred-fold increase, but your body can get rid of it within about 20 hours. The problem, of course, is that people who eat these kinds of foods every day may be constantly exposing themselves, which may not only affect their health and their children's health, but maybe even their grandchildren's health. Being pregnant during the Dutch famine didn't just lead to an increase in diseases among their kids, but even, apparently, their grandkids. So what a pregnant woman eats now may affect future generations. The issue of generation-spanning effects of poor conditions during pregnancy may help shed some light on the explosive epidemics of diabetes, obesity, cardiovascular disease associated with this transition towards Western lifestyles.