Aside from skin problems, gut issues are also linked to many other health problems.

Distal acne causes: insulin resistance and oxidative stress

In the what causes acne section, we talked about how insulin resistance and oxidative stress can cause acne. Briefly,

• Insulin resistance means cells don’t respond adequately to the insulin hormone anymore. After eating carbohydrates, insulin levels increase much more in insulin resistant people than in people without insulin resistance. This causes many problems. Insulin directly stimulates skin cells (more sebum, more clogged pores) and makes them more sensitive to other hormones. Completing the one-two-three punch, insulin also stimulates the release of male sex hormones (androgens), which further cause acne.
• Oxidative stress depletes the body’s antioxidant reserves. This leaves fewer antioxidants to protect the skin from solar radiation, air pollution, or bacterial toxins, leading to oxidative damage to sebum that kicks off the entire acne formation process.

There’s strong evidence that links gut problems both to insulin resistance and oxidative stress.

Harmful bacteria contain a substance called lipopolysaccharides (LPS). One review describes it like this: “LPS are toxic compounds localized on the surface of bacterial cells as a part of the outer membrane”.

LPS triggers a similar response from the immune system than waving a red flag does to a bull. The immune system reacts to the LPS by releasing free radicals (oxidants) that kill the harmful bacteria. Unfortunately, free radicals aren’t precision weapons and always cause some collateral damage. Continuing with our bull analogy, the bull rush indeed destroys the offending red flag, along with a good portion of the china shop.

Constant immune activation, as a result of leakage of LPS into the bloodstream, leads to low-grade systemic inflammation. One of the consequences of which is insulin resistance. Another way to describe this is that you are constantly under mild infection that the immune system has to fight.

While in the bloodstream, LPS comes in contact with different insulin-sensitive tissues, such as muscle, liver, and fat tissues. Immune activation in these sites causes inflammation and damages the cellular machinery that responds to insulin, ultimately leading to insulin resistance. As a 2013 review on the topic states:

This degradation of tight junction junction [refers to intestinal permeability] leads to the leakage of bacterial products, such as LPS, and bacterial translocation, which have recently been described as key factors in both human and mice insulin resistance and inflammation.

Carvalho, B. M. & Saad, M. J. Influence of gut microbiota on subclinical inflammation and insulin resistance. Mediators Inflamm.2013, 986734 (2013). https://www.ncbi.nlm.nih.gov/pubmed/23840101

Just to give you an example, in a study published in the journal Diabetes, the researchers injected a small dose of LPS into the study participants. They found that following the injection insulin resistance increased by 46%. Alarmingly, many measures of inflammation increased by several ten-fold.

So in summary, increased intestinal permeability has been shown to affect some of the most important distal causes of acne: insulin resistance and systemic inflammation. Combined with the findings that gut problems are far, far more prevalent in people with skin issues, I firmly believe gut issues, along with female hormonal cycles, emerge as one of the most important factors in adult acne.

Stress, anxiety and depression

Based on recent discoveries, we suggest that gut microbiota are an important player in how the body influences the brain, contribute to normal healthy homeostasis, and influence risk of disease, including anxiety and mood disorders.

Foster, JA & Neufeld, K. Gut–brain axis: how the microbiome influences anxiety and depression. Trends in neurosciences (2013). https://www.ncbi.nlm.nih.gov/pubmed/23384445

The gut microbiota has also been linked to anxiety, depression, and stress sensitivity. Most of this data comes from animal and other preliminary studies, and I won’t delve into it in detail. I just want to point out the following:

• Studies have shown that an increase in harmful bacteria in the gut can cause anxiety and depression.
• Disturbances in the gut microbiota have been linked to higher stress sensitivity.
• Treatment with probiotics can reverse and mitigate the adverse effects of harmful bacteria on mood problems.
• A handful of studies has tested probiotics in depressed patients. While we can’t make any definite conclusions based on these studies, they do suggest probiotics can reduce depression.

How exactly this happens is still under study. Inflammation is one potential link. Depressed people show higher levels of systemic inflammation than people without depression. Leakage of LPS through the gut wall may be the cause of the inflammation. The gut bacteria have also been shown to produce various neurotransmitter chemicals. Changes in the levels of such chemicals could affect anxiety and depression.

Food sensitivities and allergic diseases

Many researchers believe that gut problems create conditions necessary for the development of food allergies and sensitivities. In other words, food allergies and sensitivities are far less likely to develop in people with a healthy gut.

One explanation is that intestinal permeability allows food proteins that would normally stay in the gut to pass into the bloodstream. The immune system attacks them as foreign, or non-self, proteins. This exposure can sensitize the immune system against these proteins and lead to food allergies and sensitivities.

That being said, scientists still don’t know whether intestinal permeability happens before food allergy or the other way around. Exposure to food allergens has been shown to cause intestinal permeability. It’s possible that the food allergy occurs first (perhaps as a result of increased intestinal permeability caused by stress) and a later exposure to the same foods causes further intestinal permeability and perpetuates the situation.

There’s also evidence to show healthy gut microbiota interacts with the immune system and prevents the development of food allergies. Consequently, microbiota disturbances can make one more susceptible to food allergies and sensitivities.

One case report from 2012 highlights a woman who developed drug and food allergies following dental work. Apparently, the antibiotics given during the dental procedure disrupted her gut microbiota and increased intestinal permeability, which then sensitized her towards gluten and the drugs used during the dental procedure. Following 6-months of wheat and gluten-free diet she was no longer sensitive to gluten.