Gut microbiota plays a very important role in human health. The intake of microbes in the diet can affect the composition of intestinal microbes. When microbes are lacking in food, intestinal microbes will also It can lead to abnormal development of the body’s immune system and an increased risk of chronic diseases, affecting health.
Diet is the main source of gut bacteria. To change the gut microbiota, we first need to quantify the level of active microorganisms we consume daily from diet, food and probiotic supplements .
Scientists from the University of California and other institutions have completed the first large-scale food assessment, revealing how many living microorganisms the American population can consume each day.
First, the researchers assigned an estimated range of viable microbes per gram for each food in the database and created food categories with low, moderate, and high levels of viable microbes. The specific way of setting the number of viable bacteria is: low (Lo; 107CFU/g) level of viable microorganisms.
Fermented foods that are not processed to remove or inactivate microorganisms often contain >10^7 CFU/gram, with microbial cell counts ranging from 10^6 on raw, unpeeled fruits and vegetables to 10^8 CFU/g.
These cell numbers are comparable to those that are commercially sterile or pasteurized and contain very low levels of viable microorganisms (
Sandwiches containing processed American cheese are classified as Lo. Sandwiches with cheese and other main ingredients (such as steak) are likewise classified in the Lo category. Cheddar and regular cheese sandwiches are marked as Med to account for the weight of the bread and other potential condiments such as mayonnaise.
Using data from the NHANES from 2001-2018, which included nearly 75,000 children and adults, scientists found: 52%, 20%, and 59% of children/teens, and 61%, respectively %, 26% and 67% of adults, respectively, ate moderate, high or moderate microbial-containing foods. The per capita intakes of these foods were 69, 16 and 85 g/d for children/adolescents and 106, 21 and 127 g/d for adults, respectively. During the 9-cycle/18-year study period, the proportion of subjects consuming live microorganisms and total per capita intake increased significantly (0.9-3.1 g/d per cycle for children and 1.4 g/d per cycle for adults) across categories.
However, the researchers say that the microbes quantified in this study are not necessarily probiotics, but microbes that are carried in the food itself, and probiotics are only available when a certain amount of live bacteria is ingested. There are clear health benefits, however, unlike live food-associated microbes, bacteria in food generally do not qualify as probiotics.
Researchers analyzed dietary microbes contained in fermented and undercooked foods consumed by the body. It is of great interest to assess the daily intake of microorganisms in modern society, and this is the first step in scientifically evaluating the mechanism by which dietary microorganisms affect human health.
The next step will be an in-depth study to determine the association of live dietary microbes with health endpoints collected in the NHANES database.
This study shows that the levels of U.S. children, adolescents and adults consuming foods containing live microorganisms during the survey period were the highest in the earliest (2001-2002) and most recent (2017-2018) surveys The steady increase between cycles is only the first step, and further studies are needed to investigate the association between live microbes in food and specific health outcomes or biomarkers in the body.
Some categories of foods that contain microorganisms:
Processed foods (milk; prepared meats; pork, poultry, and seafood dishes; sauces and gravies) that are typically heat-treated are considered to have very low levels of microorganisms and are assigned to Lo.
Similarly, raw meat, pork, poultry, and seafood are considered cooked before consumption and are also assigned to Lo (with the exception of a few foods that are prescribed raw).
Uncooked mixed salads, such as tuna, macaroni and beef salads and sushi, are considered to consist primarily of low CFU/g ingredients and are assigned to Lo. Fresh fruits and vegetables that are peeled before consumption are assigned the Lo category.
The top 2 foods assigned to Med consisted of fresh vegetables and fruits: 41% and 39%, respectively.
Fresh juices, such as fruit smoothies, are allocated to Med. Beverages, Condiments and Sauces> 10% of the food offering.
Some fermented foods such as miso and sauerkraut are assigned to Med.
Yogurt and other cultured milks are assigned to Hi unless present as an ingredient in other foods.
Codes that contain a lot of fermented foods (like yogurt or sour cream) are assigned to Hi.
Most cheeses are assigned to Hi, with the exception of long-aged cheeses (eg, Parmesan), pizza-type cheeses that are usually heated before serving, and American (processed) cheeses, which are a Pasteurized products.
Cheese-containing sandwiches (unless made or heated with American cheese) are assigned to Hi.
Foods that contain cheese as a secondary ingredient are assigned either Lo or Med, depending on their relative amounts in the food.
Original credit:
Maria L Marco, Robert Hutkins, Colin Hill, et al. A Classification System for Defining and Estimating Dietary Intake of Live Microbes in US Adults and Children, The Journal of Nutrition (2022). DOI : 10.1093/jn/nxac074