What do you call a person who doesn't like yogurt?

Uncultured.


Today is all about yogurt, probiotics, and the important role that our gut bacteria plays to govern our overall


physical and mental health.


Did you know that, at a cellular level, we are only 10% human? At a genetic level, more than 99% of our genetic information encodes for that of microbial species. It’s true! Microbiologists confirm that our microbial species outnumber our somatic cells 10 to 1 (1, 2). The microbiome is defined as the mosaic of microbial species that live in our gut, on our skin, and in our nasal cavities. Trillions of these microorganisms inhabit our body, and they play a multitude of roles in regulating our overall health. Further, the more variety of bacterial species one has, the more health benefits they reap.


Here is a list of just a few health benefits attributed to a healthy gut:



The Microbiome and Digestive Function


The majority of our microbial species are located in the gut, specifically in the large intestine. In the mammalian digestive process, there are a certain number of enzymes that work to break down larger compounds of carbohydrates, fats, and proteins into their building blocks. This allows for efficient absorption of their respective nutrients. For example, amylase is an enzyme that works to break down carbohydrates into simple sugars. Lipase is an enzyme that breaks down long triglycerides into monoglycerides and fatty acid chains. Pepsin is the main enzyme that works to break down large protein molecules into individual amino acids. Though there are specific enzymes that break down these macromolecules, they fall short in their digestive and absorptive processes without the help of bacterial species in the gut (2). The species of bacteria that most notably aid in digestion is that of Lactobacillus and Bifidobacteria. Lactobacillus is a bacteria that plays a key role in aiding the digestion of lactase (amongst other foods), which is the sugar found in dairy products to which many people are intolerant. Studies show that those who experienced lactose intolerance and supplemented with a Lactobacillus tablet experienced a significant reduction in symptoms (3). Biffidobacteria is a species that aids in the breakdown of fiber and many of the polyphenols (plant-derived micronutrients) that escape from the upper parts of the digestive tract (4). Without the presence of these two species, alongside many others, a laundry list of gastrointestinal symptoms and discomforts proceeds.



The Microbiome and Immune System Function


Did you know that a majority of the viruses that we encounter, from a head cold to the stomach flu, are actually ingested through the mouth and digested by our microbiome? This means that our bacterial species are one of the first lines of defense against parasitic and viral invaders. The objects we touch throughout the day like the steering wheel, doorknobs, and our cell phones have millions of pathogens and harmful bacterial species. This often goes unnoticed before we touch our mouth occasionally throughout the day. The feeling of being sick is actually the result of our body's immune response. This is often triggered by the gut microbiome acting with our other immune cells. The pathogens that we inevitably and mistakenly put in our mouths travel through the body to the gut and are broken down by bacterial cells, which then flag the foreign invaders and send out signals to immune cells (such as the T and B cells) which then target and neutralize the foreign invader. The lack of some species of bacteria is what leads us to illness and sometimes is the root cause of certain allergens, such as nut allergies (5).


The Gut's Influence on Our Susceptibility to Chronic Illness


When considering the impact that the gut microbiome has on the propensity for certain chronic illnesses such as type 2 diabetes, cardiovascular disease, and nonalcoholic fatty liver disease, it is important to pinpoint one frame of reference, and that is the relationship between the state of the microbiome and the presence—or lack thereof—of metabolic syndrome. Metabolic syndrome is a condition that involves a multitude of risk factors and symptoms that greatly influence someone’s susceptibility to things like diabetes and CVD. The risk factors include things like a large waist circumference, high blood pressure, low High Density Lipoprotein count (the good kind of cholesterol that is used for transport of essential cholesterol throughout the body), elevated triglyceride count, and elevated fasting glucose levels (meaning high levels of glucose even when you have not eaten in hours). When these conditions persist, it leads to the development of things like atherosclerosis and insulin resistance, which are the smoking guns of cardiovascular disease and type 2 diabetes.


A study performed by Emmanuelle Le Chatelier and colleagues examined the relationship between the gut microbiome flora profile (meaning the types and counts of different bacterial species that one houses) and the presence of certain parameters that pertain to metabolic syndrome. By taking fecal samples of 123 non-obese subjects and 169 clinically obese subjects, they determined that those with low “bacterial richness” or a microbial profile lacking diversity in its species show overall higher counts of adiposity (the fat we carry in our bodies used for energy storage), insulin resistance and dyslipidemia (meaning an overall abnormal level of cholesterol and triglycerides) (8). Other studies in mice and humans have highlighted the fact that not only is it incredibly vital to have a diverse microbial profile, but it also matters the exact type of microbial species one has, seeing as specific species are markedly correlated with certain health parameters. For example, in a study performed by Maria Carlota Dao et. al. in 2015, researchers observed that a large presence species called Akkermansia muciniphila was inversely correlated with things like resting blood glucose levels and waist-to-hip ratio. This means that those with higher amounts of this bacteria were at decreased risk for chronic illness (9). There are some studies, though many have been inconclusive, that have shown the possibility of allaying the accumulation of adipose in obese and metabolic syndrome patients by administering a fecal transplant from an individual with a diverse microbial profile (7).


The Gut-Brain Axis and its Affect on Mood Disorders


A research area of rising interest as it pertains to the gut and human health has to do with the microbiome’s influence on mood disorders. Recent studies have shown a general relationship between an imbalance in the distribution of microbial species and the onset of things like depression, dementia, and even autism. The same dysbiosis is also noted in cases on obesity, allergies, irritable bowel syndrome/disease, and psychiatric disorders. The concept of the gut-brain axis describes the bidirectional signaling pathway between the gut microbiome and the brain, and the influence that they impose on each other (6). Much of the research on this topic points to the gut’s inflammatory response and how that affects the brain. The occurrence of inflammation in any area of the body is your body’s immune response to any sort of danger it encounters. Inflammation refers to the accumulation of certain molecules, most widely known as “pro-inflammatory cytokines” and “pro-inflammatory endotoxins”, which are basically just signaling molecules released by cells to let other cells know that it is threatened or in danger. These threats are things like pathogens, damaged cells, toxic compounds, or irritation. When the gut microbiome is put under conditions of stress or danger, it sends out these inflammatory molecules to signal to the rest of the body that an immune response needs to proceed. This is a beneficial pathway that allows for prolonged immunity to many pathogens and viruses we encounter every day. However, excess inflammation in the body (meaning too many inflammatory cytokines) can happen when we experience a shift or imbalance in our microflora (the species in our gut) and/or when certain bacterial species to escape the gut and travel through the bloodstream to other areas of the body, otherwise known as “leaky gut”. This dysbiosis leads to many detriments in our health, one of them being the onset of symptoms of mood disorders due to the accumulation of inflammatory cytokines in the brain (10). Though many species of our gut release pro-inflammatory molecules, there are other bacterial species that target, down regulate, and prevent the accumulation of these molecules, called anti-inflammatory cytokines. By widening the diversity of our microflora, we are able to maintain a proper immune response while also keeping excess inflammation at bay, potentially protecting ourselves from certain mood and personality disorders.


The microbiome plays many more roles than just this! Just like the gut-brain axis, the GI tract has a direct relationship with other organs in the body such as the gonads and the thyroid. We will likely dive deep into these gut axes in later discussions!


To put it simply, our microbial species have a hand in almost every system of the body, and they influence many different health parameters like or propensity of chronic illness and even the onset of certain mood disorders. Therefore, it is incredibly vital to consume foods rich in probiotic species on a regular basis in order to ensure that we have a rich bacterial profile. Foods that are rich in probiotics are items like yogurt and various fermented foods, such as sauerkraut and kimchi. Research suggests eating one serving of fermented food results in a significant improvement in microbial diversity.



Did you know you can actually make yogurt for yourself? The method may seem a bit counterintuitive…The starting ingredient? Yogurt! That’s right. In order to cultivate a large portion of yogurt, you have to begin with a small sample of the cultures and allow for them to compound on each other to create more yogurt. Basically, you need yogurt to make yogurt. Below is the ingredients and instructions to make homemade yogurt and granola.


Enjoy!!



Homemade Yogurt


Ingredients (Makes about 4 cups)

  • 4 cups of whole milk

  • 3 tablespoons plain yogurt (purchased or homemade)

  • 1 teaspoon vanilla

Special Equipment

  • Thermometer to use for taking the temperature of the milk

  • Cheesecloth for straining

Method

  1. Make sure that all utensils and work spaces are sterile--we are working with bacteria, after all!

  2. Preheat the oven to a very low setting--most recommend 110 degrees F.

  3. Prepare a large bowl with ice to use in later steps.

  4. Add the milk to a heavy, large pot. Adjust the thermometer so that it does not touch the bottom of the pot but is adequately positioned in the milk. Heat the milk over medium high heat until it reaches 180 degrees F or boils. Stir the milk occasionally to prevent a skin from forming and making sure the milk doesn't scald or boil over.

  5. Remove the milk from the heat and place it in the ice bath. Allow it to cool to 110-115 degrees F. Stir the milk occasionally.

  6. In a small bowl, combine about 1 cup of warm milk with the yogurt starter and stir to combine. Add the vanilla and stir to combine. Add the yogurt-milk mixture to the remaining warm milk and stir completely incorporated. Do not stir vigorously. Add the vanilla and stir to combine, but again, do not stir vigorously.

  7. Pour or ladle the mixture into an oven-safe dish and wrap a warm towel around the bottom and side of the dish. Cover the dish with aluminum foil. Place the yogurt in the warm oven, and leave them in the oven for 6 hours.

  8. Top with your favorite granola, honey, and/or fruit for added benefits and flavor!


References


1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4425030/

2. https://www.nih.gov/news-events/news-releases/nih-human-microbiome-project-defines-normal-bacterial-makeup-body

3. https://pubmed.ncbi.nlm.nih.gov/27207411/

4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3145055/

5. https://pubmed.ncbi.nlm.nih.gov/28092661/

6. https://pubmed.ncbi.nlm.nih.gov/27647198/

7. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6682904/

8. https://pubmed.ncbi.nlm.nih.gov/23985870/

9. https://pubmed.ncbi.nlm.nih.gov/26100928/

10. https://pubmed.ncbi.nlm.nih.gov/29134359/

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