 We all want to eat the kinds of foods that make us feel better and live longer, but there's so much conflicting information out there. So many nutrition opinions. Welcome to the Nutrition Facts podcast. I'm your host, Dr. Michael Greger. It's my job to give you the information you need to make the healthiest choices possible. Today, we're going to hear about dietary remedies that encourage mosquitoes and ticks to find a meal elsewhere. Are some people just more attractive to mosquitoes than others? Apparently so, as identical twins are most likely to be similarly tasty compared to fraternal twins who will only share 50% of their DNA, demonstrating an underlying genetic component that can be sniffed out by mosquitoes. Although it's not clear it's because some people smell better or other people just smell worse. We know pregnant women are twice as attractive to malaria mosquitoes and also that mosquitoes are attracted to sweat. Human sweat contains components that are attractive to anthropophilic, meaning human-loving mosquitoes. The unique composition of human sweat appears to explain its tantalizing effect, though sweat from some body parts are evidently more tantalizing than others. Skin emanations collected from armpits were less attractive compared to hands or feet. They think the difference may be caused by deodorant residues since in a subsequent experiment volunteers were asked to avoid using skin care products for five days and after that no differences were detected. The creepiest bit of research I found was this. The parasites that cause the mosquito-borne disease malaria, which kills hundreds of thousands of people a year, makes you more attractive to, you guessed it, the mosquitoes that transmit malaria. What better way for the parasites to hitch from person to person? Instead of leaving it up to chance, some parasites manipulate their hosts in elaborate ways. I've talked about how the toxoplasma brain parasite draws mice to the smell of cat urine to get into cat's brains. Or how about the rabies virus concentrating in the saliva while tapping into the Cujo rage circuit in the brain? There's even a parasite that needs to get from an ant to a bird, so it turns the ant's belly bright red to look like a ripe berry and makes the ant stick it up in the air to confuse the fruit-eating bird, just like malaria parasites making us particularly tasty to mosquitoes. Anything we can do to make ourselves less tasty? I've talked about the various mosquito repellents you can spray on your skin, both synthetic and natural mosquito repellents, but is there anything you can eat or drink to make you less of a target? When you search the scientific literature for diet and mosquitoes, a lot of articles pop up on diets for mosquitoes, like mosquito snack for that artificial blood meal replacement. Feeding mice, different diets makes a difference, but what about people? One of the most common anecdotes is that vitamin B-complex supplements protect against biting insects, other anecdotal remedies include the taking of garlic, marmite, veggie mite, brewer's yeast tablets, and alcohol, but you don't know until you put it to the test. How about a randomized, double-blind, but civil-controlled trial of garlic as a mosquito repellent? A belief in the ability of garlic to repel insects seems to be widespread, so researchers in Connecticut decided to see if it were true. They looked at the numbers of mosquitoes that did not feed on the subjects, the number of mosquito bites, the weights of the mosquitoes after feeding, and the amount of blood ingested all determined on people on and off garlic. And the data did not provide evidence of significant mosquito repellents. No surprise, given that even if you slather garlic oil on your skin within 30 minutes, mosquitoes don't seem to care. Eating garlic may, however, help against ticks, because military personnel can sometimes be at particularly high risk for tick bites and tick-borne diseases. The Swedish military conducted randomized, controlled, double-blind trials of garlic to prevent tick bites among marines. 50 swallowed the equivalent of about a clover day of garlic, and 50 took placebo pills. Then they all switched, and there was a significant reduction in tick bites when consuming garlic compared to placebo, cutting the risk of tick bites by about 20%. 20% is better than nothing, but treating your clothing with something like permethrin has been shown to be 100% effective against deer ticks, the vector of Lyme disease, and so that may be better than counting on garlic bread to save you. In our next story, what happens when mosquitoes put on beer goggles? An online survey of personal mosquito repellent strategies unearthed all sorts of strange stratagems from cutting a tomato in half and leaving it next to the bed to rubbing yourself with cigarette butts soaked in alcohol. You could also soak yourself in alcohol with a gin and tonic, cut down on sugar, cut out meat, or bananas. But what's funny is some say avoid bananas, some say eat bananas to stave off mosquitoes, and others say topically rub them on your skin. I don't even want to know about what else you might do with them. Eat bananas? Avoid bananas you don't know. Until you put it to the test, the impact of the consumption of bananas on attraction of a malaria mosquito to humans. Researchers in Wisconsin randomized subjects to eat grapes or bananas before testing what they then tasted like to mosquitoes, and the ingestion of bananas was strongly associated with an increase in the number of mosquito contacts for hours after eating a banana, translating to about 11 extra contacts after one hour and seven contacts after two hours. Meanwhile, the ingestion of grapes had no effect. Interestingly, it didn't seem to matter how many bananas you eat at once as eating three bananas didn't appear to make people any tastier than eating one. Bottom line, after years of repeat experiments, they concluded that ingestion of bananas, but not grapes, resulted in a significantly higher attraction in mosquitoes for hours after ingestion on average, though some people did appear to be immune to the banana effect. What about that gin and tonic? Some have suggested alcohol will keep the bugs away. Others suggest we might suffer more mosquito bites after ingesting liquor. Well, there's only one way to find out. Drink some beer and put your arm in a box with some mosquitoes. The title of the study gives it away. Alcohol ingestion stimulates mosquito attraction. About 40% of mosquitoes landed on their arms before drinking a bottle of beer, compared to about 50% afterwards. And it didn't appear to have anything to do with changes in sweat production or skin temperature after the booze. It might just be something you start exuding after you drink. And so it's also not just because you got bit a bunch of times because you like blacked out in an alley or something. The researchers concluded that since the percent of mosquitoes landing on volunteers significantly increased after beer ingestion, drinking alcohol stimulates mosquito attraction. But it could just be drinking beer, not necessarily all alcohol. And they only tested one species of mosquito, the one that transmits diseases like dengue, zika, and yellow fever. What about gauging human attractiveness to malaria mosquitoes? Before and after volunteers consumed either beer, using 25 volunteers and a total of 2,500 mosquitoes, or water as a control with 18 volunteers and only about 1,800 mosquitoes. And water consumption had no effect, but beer consumption increased the attractiveness of the volunteers. It's like the mosquitoes put on beer goggles. Beer consumption increases human attractiveness. To date, bananas and beer are the only dietary components that have been shown to increase mosquito attraction. OK, but we want to repel mosquitoes, not attract them. What about testing B vitamins as a home remedy against mosquitoes? B vitamins are often recommended in the popular media. As a systemic repellent against mosquitoes, especially on the web, the first studies date back over a half century. They gave people doses of vitamins B1 and B6, yet in a series of subsequent tests, the mosquitoes probed avidly and bit promptly. They only tested the vitamins on four people, but the vitamins appeared so useless they didn't think it worth repeating the experiments and view the obvious lack of repellency of these vitamins. We believe, the researchers wrote, that we have disproved the notions that vitamins take an orally act as mosquito repellents, but they only tested vitamins B1 and B6. What about B2, B3, B5, B9, B12? You don't know until you put it to the test. Vitamin B complex supplements are not effective as repellents, but these studies were limited by the use of very few human subjects, only one species of mosquito, and a limited number of B vitamins. So researchers decided to put it to rest, once and for all, B1, B2, B3, B5, B6, B7, also known as biotin, B9, B12. They also just tried a megadose of thiamine, B1, which is rumored to be the most effective B, and nothing. No effective vitamin B supplementation, any of them. I mean, it'd be nice to have an effective oral insect repellent. Unfortunately, vitamin B1 has been proved to be ineffective, and this includes so-called mosquito repellent patches that supposedly deliver B1 through the skin. No protection provided whatsoever. Bottom line, vitamin B1, also known as thiamine, is not a systemic mosquito repellent in men. They also tried smearing it on people's skin with failure. After failure, you start feeling bad for the volunteers, seated in a room with their shirts off, then they just released 100 suckers into the room. Up to 96 bites per minute, just think how bad it would have been if they had had some bananas and beer. We would love it if you could share with us your stories about reinventing your health through evidence-based nutrition. Go to nutritionfacts.org slash testimonials, which may be able to share it on social media to help inspire others. If you'd like to see any graphs, charts, graphics, images or studies mentioned here, go to the Nutrition Facts podcast landing page. There you'll find all the detailed information you need, plus links to all the sources we cite for each of these topics. My last two books were How to Survive a Pandemic and My How Not to Diet Cookbook. Get ready this year for the launch of How Not to Age, and of course all the proceeds for the sales of all my books goes directly to charity. NutritionFacts.org is a non-profit science-based public service. We can sign up for free daily updates on the latest in nutrition research with bite-sized videos and articles uploaded nearly every day. Everything on the website is free. There are no ads, no corporate sponsorship, no kickbacks, it's strictly non-commercial, not selling anything. I just put it up as a public service as a labor of love as a tribute to my grandmother, whose own life was saved with evidence-based nutrition.