Bugs for our bugs? Edible insects and the microbiome
You’ve likely heard some of the recent buzz around edible insects. But most Americans still think of insects primarily as pests, vectors of disease, or perhaps pollinators. For billions of people across the globe, however, insects are also an important part of the diet. While the idea of eating insects—termed entomophagy—may seem peculiar in the West, it has been practiced by humans throughout history; more than 2,100 edible species have been documented to-date, from grasshoppers, to beetles, to cicadas, to wasps.1 There is a wide array of ways to cook and process edible insects; they are flavorful, diverse, and occupy a meaningful space in traditional food culture for millions. Furthermore, insects can serve as nutritious feed for livestock, poultry, and aquaculture. They have been touted for their desirable environmental and nutritional characteristics compared to conventional meat products.
The vast majority of insects consumed today are harvested from the wild, but there is potential for insect cultivation, sometimes called minilivestock farming, to increase production of and consequently access to insect foods year-round for consumers in contexts where insect eating is already prevalent as well as where it is just gaining steam. There are ample opportunities for minilivestock to benefit both people and the planet, but substantive questions regarding their viability and utility as both food and feed in the future remain. I have been personally fascinated by this topic for the past 6 years, recognizing the need for outside-the-box thinking to help us meet our global food security challenges in the face of climate change.
- Their environmental impact is estimated to be significantly lower than traditional livestock,2–4 as they need less land, water, and feed to survive and thrive,4 and emit fewer greenhouse gases (GHGs).3 Their high feed-conversion efficiency,2 relatively short lifespans, ectothermic thermoregulation, and large edible body mass percentage5 contribute to overall sustainability and desirability.
- Production of 1 kg live mass gain in crickets requires about eight time less feed than 1 kg mass gain in beef, for example.2,6
- Most edible insects do not produce methane,7 and overall, total GHG emissions from several common edible insects are lower by a factor of about 100 than pigs or beef cattle.3
- Some insects are adept recyclers that can be cultivated using organic side streams, agricultural byproducts, manure, or rotting food—thereby recycling and adding value to otherwise inedible biomass.8
Edible insects are also nutrient dense and high in crude protein,9–11 containing between 40 and 75% by dry weight on average12—even more than of dried beef.13 Most offer all essential amino acids for human nutrition2 and are rich in polyunsaturated fatty acids.14 Insects are typically good sources of minerals, including potassium, calcium, magnesium, phosphorous, iron, and zinc.12,15–17 Some are also high in B vitamins, such as biotin, riboflavin, pantothenic acid, and folate.12,16 You should note that the nutritional value of insects varies greatly by species, life stage, and feed; plus, we don’t know much about nutrient bioavailability.
Interestingly, and unlike other animal products, insects contain meaningful levels of dietary fiber. Not surprisingly, dietary fiber intake contributes to gut microbiome health by increasing microbial diversity,18,19 and high fiber intake has been associated with a reduced risk of some cancers20 and heart disease.21,22 Most of the fiber in insects, which accounts for about 10% of dry weight,11 is found in the insect exoskeleton (made of chitin). Chitin, a modified polysaccharide, is abundant in nature and its more soluble derivatives have been evaluated for potential health-promoting properties, such as an ability to modulate serum cholesterol with implications for heart disease,23 controlling lipid absorption,24 and exhibiting prebiotic effects.25 Little is known about the fate of insect chitin in human digestion, however. It is possible, but as of yet unverified, that insect fibers could modulate gut microbiota by serving as a prebiotics, those non-digestible food items that promote the growth of beneficial gut bacteria (probiotics).
To date, no comprehensive clinical studies have investigated the impact of insect consumption on the human microbiome. Hence, my colleague Dr. Tiffany Weir from the Department of Food Science and Human Nutrition at Colorado State University (CSU) and I set out to investigate just this. We wanted to determine if edible crickets offer any beneficial properties beyond their nutrition composition, potentially related to their fiber content. (I say beyond nutrition because fiber is not technically a nutrient since it is not digested by humans directly, but passes through undigested or is broken down by the microbes in our gut.) Dr. Weir and I are both very interested in the microbiome, given the crucial role it plays in both mental and physical health. As an undergraduate student at CSU, I worked as a laboratory assistant for Dr. Weir. Now, many years later, as a postdoctoral researcher at the University of Wisconsin-Madison, I am grateful for the opportunity to collaborate with Dr. Weir on this project.
To investigate our questions linked to entomophagy, we developed a human dietary intervention study, which we implemented in Fort Collins, Colorado with healthy (and gullible?) volunteers from the area. The purpose of the study was threefold. We wanted to confirm that cricket consumption was safe and tolerable. (Considering people eat crickets around the world, we expected this to be true, but wanted to verify it clinically.) We also wanted to see if eating edible crickets influenced human health directly by changing lipid metabolism or markers of inflammation. Lastly, we were interested in assessing if insect fibers, such as chitin – the primary component of the exoskeleton – could serve as prebiotics.
We set up a double-blind, randomized, crossover clinical trial to evaluate what effects consuming 25 g of whole cricket powder per day had on gut microbiota composition, while also assessing safety and tolerability. A total of 20 healthy adults participated in the six-week dietary intervention. Participants were randomized into two study arms and consumed either cricket-containing or control breakfast foods for 14 days, followed by a washout period and assignment to the opposite treatment. The breakfast foods included a chocolate malt smoothie and a pumpkin spice muffin. The cricket treatment breakfast included cricket powder purchased from a commercial minilivestock farm in Canada (Entomo Farms). Blood and stool samples were collected at baseline and after each treatment period to assess changes in blood chemistry, liver function, and shifts in microbiota.
Results from our clinical trial demonstrated that cricket consumption was safe and tolerable at the study dose. All participants completed the trial. Additionally, we learned that there may be some benefits to gut health from eating crickets. We observed that cricket consumption was associated with a slight increase in the liver enzyme alkaline phosphatase, and this result along with our observation that there was a slight decrease in circulating pro-inflammatory cytokine TNF-alpha with cricket consumption, is suggestive of an improvement in intestinal homeostasis (presence of a healthy gut mucosal barrier that maintains equilibrium and segregates microbiota and host immune cells). Eating crickets may improve gut health and reduce systemic inflammation; however, more research is needed to understand these effects and underlying mechanisms. We also observed several changes in the abundance of specific microbial taxa after eating cricket powder, including a prebiotic effect. Specifically, after eating crickets, we measured a significant increase in the abundance of one good bacterial species, the probiotic Bifidobacterium animalis (about a 5.7 log fold change). B. animalis has been studied extensively and is known to inhibit pathogens, improve gastrointestinal function, and protect against diarrhea and food borne pathogens. An increase in its abundance over the long-term could have a positive impact on human health.
I want to be careful not to overstate the strength of these results; this was a very small pilot study—the very first of its kind! More than anything, our results suggest that we need more research on the topic to understand potential health benefits and risks of eating crickets and other edible insects for the 2 billion people that current eat insects and the countless others that may be interested. Additional research on the environmental and health impacts of edible insects is certainly warranted. The University of Wisconsin and CSU aim to continue this work by looking more closely at potential benefits of insect fiber, the ability of insect chitin to serve as a sole carbohydrate source for probiotic bacteria, and the bioavailability of insect nutrients. You can read the details of this study in our paper, which was published in Scientific Reports last summer.26
To conclude, please allow me to point out the obvious: you’re probably saying to yourself, “this is all fine for people that eat insects, but how might it affect me?” You likely don’t eat insects if you live in the United States, and you’ve got plenty to eat already. But insects represent a food of both historical and contemporary importance for humans, and they will likely play an increasingly notable role in the future. Minilivestock may serve as key ingredients in animal feed and even make their way onto western plates thanks to their diversity in flavor and environmental benefits. Of course this will take time, but Mexican spiced grasshoppers (chapulines) are already being sold at the Seattle Mariners baseball games, and cricket-laden tortilla chips can be bought at mainstream supermarkets. Change is on the menu.
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