 The brain parasite toxoplasma is responsible for considerable disease and death in the United States, the second leading cause of food-borne-related death in the United States after salmonella. It can invade through the placenta, so it can be especially devastating during pregnancy, leading to miscarriages or blindness or a developmental delay. It can impair cognitive function in adults, too, which explains why those who are infected appear to be at increased risk for getting to things like traffic accidents. Several lines of evidence indicate that chronic toxoinfections are likely associated with certain psychiatric disorders. It may even increase the risk of developing leukemia. Okay, okay, how do you prevent it? Well, the parasite can get into the muscles. So from food animals, people can get it through meat consumption. But in a non-food animal like a cat, you get infected through contact with feces. Thankfully, in cats, the danger of infection exists only when the animals actively shedding the parasite. They get it from eating infected rodents, and so cats that are kept indoors that don't hunt and are not fed raw meat shouldn't pose a threat. Though if feral cats are turning your local playground sandbox into a litter box, that could be a problem. As many as 6% of stray cats or those with outdoor access may be actively infected at any one time. They only shed the parasite for a few weeks, though, so if you adopt a cat at a shelter, it should be safe as long as they didn't just come in. Many women have heard about the cat connection, but may be less aware about the risk of foodborne infection. Only about 1 in 3 may be aware that toxoplasma may be found in raw or undercooked meat. Nevertheless, a high percentage of women indicate that they do try to practice good hygiene, such as washing their hands after handling raw meat, gardening, where cats may be pooping, or changing cat litter. What's the riskiest type of meat? Well, cattle are not considered important hosts for the parasite. It's more pigs in poultry, as well as sheep and goats. The prevalence of infection among factory-farmed pigs varies from 0 to over 90%, though, ironically, the likelihood of toxoplasma infection in organic meat may be higher because the animals have outdoor access. Who undercooks pork and poultry, though? Surprisingly, about 1 in 3 Americans may undercook meat across the board in terms of reaching necessary pathogen-killing temperatures, and a single slice of ham can end up with more than 1,000 parasites per slice. Current meat inspection at the slaughterhouse can't detect them. There are tests you can do, but there's no widespread testing. The risk from a single serving of meat, though, is really small. I mean, the average probability of infection per serving of lamb, for example, was estimated to be 1 in, like, 67,000. For the reason there are 16 times more number of cases attributed to pork, it's not because pigs are more affected. In the US, we just happen to eat a lot more pork chops than lamb chops. Is there anything we can do if we're one of the approximately 1 in 4 Americans already infected? Well, one of the problems with having these parasites in our brain is accelerated cognitive decline as we age. This study evaluated older adults every year for five years, and the executive function of those testing positive for toxoplasma seemed to drop quicker over time, as did a measure of their overall mental status. Another thing that's associated with cognitive decline is reduced folate availability, and the two may actually be related. As recent evidence suggests that toxoplasma may harvest folate directly from our nerve cells, sucking up folate from our brain. So beyond dopamine production, which is why we think toxo increases the risk of schizophrenia, the parasite may be sucking folate out of our brain, but enough to affect our cognitive functioning? Perhaps so. Here's a measure of cognitive function across a range of folate concentrations among those uninfected. It doesn't seem to matter whether they have lots of folate or little, they obviously have enough, either way. But those who are infected have worse scores at lower levels. Higher is worse in this test. The same thing with vitamin B12, so it's important to get enough B12 and folate. For B12, the official recommendations that all people aged 50 or over start taking a vitamin B12 supplement or eat vitamin B12 fortified foods every day and anyone on a plant-based diet should start taking that advice at any age, and folate is found concentrated in beans and greens. So following my Daily Dozen recommendations will get you more than enough, as, for example, a half cup of cooked lentils gets you half the way there, as does 3 quarters of a cup of cooked spinach.