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Can Modern Lifestyles Cause Chronic Disease?

Antibiotic exposure, artificial lighting, and eating around the clock may all play a role

By Nita JainPublished 2 years ago 8 min read
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Can Modern Lifestyles Cause Chronic Disease?
Photo by Anh Nguyen on Unsplash

Global urbanization and modern civilization have been responsible for countless scientific and technological achievements over the past couple centuries. But these advances have also been accompanied by a more disturbing trend - the rise in chronic non-communicable diseases (NCDs), such as allergies, diabetes, depression, metabolic syndrome, and cardiovascular disease, which are likely at least partly fueled by our modern lifestyles. Decades before such chronic medical conditions reached epidemic proportions, a microbiologist named René J. Dubos (1901–1982) had already begun cautioning against impending urbanization, loss of biodiversity, and technological shifts borne out of convenience rather than necessity.

Dubos initially gained fame after discovering the first clinically tested antibiotic, gramicidin, in 1939. His discovery revived interest in Alexander Fleming's discovery of penicillin and launched the era of antibiotics. Dubos would go on to pioneer the field that is now known as the developmental origins of health and disease (DOHaD). Ironically, Dubos' discovery may have galvanized the very forces he warned against. In his discussions on biodiversity, Dubos intoned:

"Man himself has emerged from a line descent that began with microbial life, a line common to all plant and animal species…[he] is dependent not only on other human beings and on the physical world but also on other creatures - animals, plants, microbes - that have evolved together with him. Man will ultimately destroy himself if he thoughtlessly eliminates the organisms that constitute essential links in the complex and delicate web of life of which he is a part."

A 2019 study discovered that as many as one in four antibiotic prescriptions were not medically justified, according to data on outpatient antibiotic prescription fills from 2016. Lead author Kao-Ping Chua, a researcher and pediatrician an University of Michigan C.S. Mott Children's Hospital, commented that the actual percentage of unnecessary prescriptions may be much higher than the numbers suggest, as many additional prescriptions were either not associated with a documented diagnosis or only considered potentially appropriate.

While antibiotics hold the potential to save lives when used judiciously, the unrestricted use of these drugs can be problematic in a number of ways. Indiscriminate antibiotic use for the purposes of fattening livestock has a number of harmful downstream effects, such as the spread of antibiotic-resistant microorganisms including methicillin-resistant Staphylococcus aureus (MRSA), pathogenic species of Salmonella, and antibiotic-resistant E. coli strains, the last of which can contribute to the development of drug-resistant urinary tract infections in consumers.

Honor Thy Gut Symbionts

Apart from the well-documented issue of life-threatening infections associated with the development of antibiotic resistance, over-prescription of antibiotics is also contributing to a substantial loss of human gut microbiota biodiversity in Westernized societies. Diet- and antibiotic-driven gut microbial extinction events, especially during early development, can have long-term health consequences and predispose individuals to allergies, asthma, autoimmunity, and metabolic disorders later in life.

However, when seeking solutions to our modern microbial extinctions, we must take care not to simply artificially restore our microbes while the mechanisms that first led to dysbiotic shifts remain in place. Enthusiasm for microbial restoration therapies and other pharmacological interventions should be checked by a comparable consideration of ecological solutions. Similarly, public health programs targeting vaccination should not neglect proper nutrition, hygiene, and access to clean drinking water as other crucial factors necessary for host immunity and prevention of infectious diseases.

Burning the Midnight Oil

In addition to pharmacological agents, lifestyle changes have also had dramatic impacts on our patterns of activity and rest. Our ancestors rose and set with the sun. We are presently exposed to numerous sources of bright light from lamps and light fixtures, television and computer screens, and other light-emitting devices while our daytime exposure to sunlight has considerably diminished.

Additionally, 15–20 percent of western populations regularly work at night in illuminated surroundings. The advent of light bulbs and artificial lighting at the end of the 19th century was undoubtedly a technological wonder but also contributed to disruption of natural circadian rhythms, which is associated with metabolic dysregulation, reduced insulin sensitivity, and risk of obesity. On light, Dubos wrote:

"Until the last century, man lived in the dark for long hours…modern man, in contrast, is exposed to bright light for 16 hours a day. In view of the fact that light rays can affect several hormonal activities, and that many, if not most, physiological functions are linked to circadian and seasonal cycles, it seems possible that this change in the ways of life will have long-range consequences for the human species."

Robust circadian rhythms are established by the alignment of the central and peripheral clocks. The central circadian clock, located in the suprachiasmatic nucleus, is dictated by light-dark cycles while the peripheral clocks in tissues such as the liver, muscle, and pancreas are governed by feeding and fasting patterns. Synchronizing these clocks is associated with various health benefits, including improved insulin sensitivity, better sleep quality, and reduced risk of metabolic syndrome.

The availability of artificial lighting not only impacts our sleep-wake cycle but our feeding-fasting cycles as well, as most of us commonly consume food after sundown. This seemingly innocuous habit might have more insidious health effects than initially realized, as late-night eating drives circadian misalignment, microbial dysbiosis, and the development of metabolic disease.

Carbohydrate consumption, in particular, after sundown can lead to hyperglycemia since melatonin inhibits insulin secretion by the pancreas, an evolutionary adaptation designed to prevent blood sugar from crashing in the middle of the night when food was typically scarce. Conversely, consumption of a larger proportion of our daily energy requirements early in the day promotes circadian alignment and produces metabolic benefits since glucose tolerance and diet-induced thermogenesis are higher in the morning than in the evening.

Circadian misalignment also affects our microbial inhabitants, as the gut microbiota display diurnal variations related to timing of food consumption, overnight fast duration, and frequency of light exposure. A 2018 study conducted in a mice model discovered that, in contrast to 12 hours of artificial light exposure per day, constant exposure to artificial light resulted in an increased abundance of Ruminococcus torques, a bacterial species associated with gut barrier degradation, and a decreased abundance of Lactobacillus johnsonii, a species known maintain the integrity of the intestinal epithelial layer. These findings may provide a possible mechanism by which disruption of normal circadian rhythms can damage the gastrointestinal lining and lead to other subsequent effects.

Ain't No Sunshine

Increased exposure to artificial lighting in modern times has also typically been accompanied by reduced exposure to solar ultraviolet radiation, which is in turn associated with a number of physiological consequences. Until the Industrial Revolution, our ancestors mainly held outdoor occupations whereas the majority of the population in developed countries now works indoors. Since the Second World War, developments such as automobiles, television, computers, video games, and other technological devices promoted indoor activities over outdoor pursuits.

In the millennia before these technological advancements, the skin pigment of a population reflected the ideal balance between the positive and deleterious effects of sun exposure in a given climate. Darker skin is hypothesized to protect against sunburn and possibly folate deficiency while lighter skin is thought to allow sufficient biosynthesis of vitamin D and other compounds in areas with less ambient ultraviolet radiation.

However, lifestyle changes and the migration of light skinned people to tropical climates have resulted in a more intermittent pattern of sunlight exposure. The recent rise in skin cancer is often considered a result of evolutionary mismatch between skin type and geography. Richard Weller, a dermatologist at the University of Edinburgh, explains,

"Homo sapiens have been around for 200,000 years. Until the industrial revolution, we lived outside. How did we get through the Neolithic Era without sunscreen? Actually, perfectly well. What's counterintuitive is that dermatologists run around saying, 'Don't go outside, you might die.'"

An estimated one billion people worldwide suffer vitamin D deficiency or insufficiency. Inadequate amounts of non-burning sun exposure and resulting vitamin D deficiency carry increased risks of all-cause mortality, hypertension, cardiovascular disease, metabolic syndrome, diabetes, obesity, Alzheimer's disease, multiple sclerosis, rheumatoid arthritis, psoriasis, non-alcoholic fatty liver disease, macular degeneration, and myopia as well as increased risks of colorectal, breast, prostate, and pancreatic cancers.

In 2016, Pelle Lindqvist, a senior research fellow at Sweden's Karolinska Institute, published the results of a 20-year study he conducted in which he followed the sunbathing habits of nearly 30,000 women in Sweden and made a startling discovery:

"Nonsmokers who avoided sun exposure had a life expectancy similar to smokers in the highest sun exposure group, indicating that avoidance of sun exposure is a risk factor for death of a similar magnitude as smoking."

So far, the only identified risk associated with the amount of non-burning sun exposure required to achieve serum vitamin D levels of 30 ng/mL is a possible increased risk of non-melanoma skin cancers such as basal and squamous cell carcinomas, which are almost never fatal. Moreover, sun exposure is associated with a relatively favorable prognosis and increased survival rate in malignant melanoma. According to Weller,

"The risk factor for melanoma appears to be intermittent sunshine and sunburn, especially when you're young. But there's evidence that long-term sun exposure associates with less melanoma."

The benefits of sun exposure extend far beyond those conferred by adequate levels of vitamin D. Sunlight also triggers the release of various other important compounds in the body, including serotonin, endorphins, and melatonin. Additionally, sun exposure induces skin to release nitric oxide, which dilates blood vessels and lowers blood pressure, into systemic circulation to exert cardioprotective and antihypertensive effects. A 2014 study found that nitric oxide-mediated effects of ultraviolet radiation suppressed obesity and symptoms of metabolic syndrome independently of vitamin D.

Furthermore, exposure to both UVA and UVB radiation can help prevent autoimmune disease through upregulation of cytokines (TNF-α and IL-10) and increased activity of regulatory T cells that remove self-reactive T cells. Calcitonin gene-related peptide (CGRP) is also released in response to both UVA and UVB light and inhibits mast cell degranulation, which may explain sunlight's efficacy in treating skin disorders such as psoriasis.

With the preponderance of evidence suggesting numerous health benefits associated with diet and lifestyle changes, we would be remiss not to take advantage of the opportunity to improve our health using the simplest of means. Ultimately, we as humans should strive to cultivate a reasonable adherence to the maintenance of circadian alignment as much as possible, which may include the use of a restricted feeding window, regular sleeping schedules, and sensible sun exposure. We may come to find that the best medicine is that over which we have the most autonomy, our personal habits, if we are only willing to modify our behaviors and step into the sunlight.

wellness
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About the Creator

Nita Jain

Researcher, podcaster, scicommer | nitajain.substack.com

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