<Reassessing Modern Lifestyles and Their Impact on Chronic Illness>
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Modern urbanization and technological advancements have led to significant scientific progress over the last few centuries. However, these developments have also contributed to a troubling increase in chronic non-communicable diseases (NCDs) such as allergies, diabetes, depression, metabolic syndrome, and heart disease, all of which are possibly linked to our contemporary lifestyles. Long before these health issues became widespread, microbiologist René J. Dubos (1901–1982) warned about the dangers of urban growth, biodiversity loss, and convenience-driven technological changes.
Dubos first gained recognition for discovering gramicidin, the first clinically tested antibiotic, in 1939. This breakthrough rekindled interest in Alexander Fleming’s penicillin and marked the beginning of the antibiotic era. Dubos later became a pioneer in what is now known as the developmental origins of health and disease (DOHaD). Ironically, his own discovery may have inadvertently supported the very trends he cautioned against. He expressed concerns about biodiversity, stating:
> “Man himself has emerged from a line of descent that began with microbial life, a line common to all plant and animal species… [he] depends not only on other humans and the physical world but also on other beings—animals, plants, microbes—that have evolved alongside him. Man will ultimately destroy himself if he thoughtlessly eliminates the organisms that are essential links in the intricate and fragile web of life of which he is a part.”
A study conducted in 2019 found that approximately one in four antibiotic prescriptions were unwarranted, based on outpatient data from 2016. Lead author Kao-Ping Chua, a researcher and pediatrician at the University of Michigan’s C.S. Mott Children’s Hospital, suggested that the real figure for unnecessary prescriptions could be even higher, as many prescriptions lacked proper diagnoses or were only deemed potentially appropriate.
While antibiotics can be life-saving when used wisely, their excessive and indiscriminate use poses several issues. The routine use of these drugs in livestock can lead to the rise of antibiotic-resistant bacteria, including methicillin-resistant Staphylococcus aureus (MRSA), harmful strains of Salmonella, and antibiotic-resistant E. coli, which can result in drug-resistant urinary tract infections in consumers.
The Importance of Gut Microbiota
Beyond the critical issue of life-threatening infections linked to antibiotic resistance, the overuse of antibiotics is also contributing to a significant decline in human gut microbiota diversity in Western societies. Events of gut microbial extinction driven by diet and antibiotics, particularly during early development, can have lasting health ramifications, increasing susceptibility to allergies, asthma, autoimmune diseases, and metabolic disorders later in life.
In addressing microbial extinction, it is crucial to avoid merely restoring our gut flora artificially while neglecting the underlying causes of microbial imbalance. Enthusiasm for microbial restoration therapies and pharmacological solutions must be balanced with ecological considerations. Likewise, public health initiatives focused on vaccination should not overlook vital factors such as nutrition, hygiene, and access to clean drinking water, all essential for enhancing immunity and preventing infectious diseases.
The Impact of Artificial Lighting
Our lifestyles, too, have significantly shifted due to changes in work and rest patterns. Historically, our ancestors were in sync with the sun, but today, we are surrounded by various artificial light sources from lamps, screens, and electronic devices, while our exposure to natural sunlight has markedly decreased.
Moreover, a significant percentage of Western populations—about 15–20%—now work at night in brightly lit environments. The introduction of electric lighting in the late 19th century was a remarkable technological advancement, yet it disrupted our natural circadian rhythms, which is linked to metabolic dysregulation, decreased insulin sensitivity, and increased obesity risk. On this topic, Dubos remarked:
> “Until the last century, man lived in darkness for long hours…modern man, in contrast, is exposed to bright light for 16 hours a day. Given that light rays can influence various hormonal activities and that many physiological functions are tied to circadian and seasonal cycles, it seems probable that this shift in lifestyle will have long-term consequences for humanity.”
Healthy circadian rhythms depend on the alignment of central and peripheral biological clocks. The primary circadian clock, situated in the suprachiasmatic nucleus, is influenced by light-dark cycles, while peripheral clocks in organs like the liver and pancreas rely on feeding and fasting patterns. Maintaining synchronization of these clocks is associated with numerous health benefits, including improved insulin sensitivity, enhanced sleep quality, and a lower risk of metabolic syndrome.
The availability of artificial light not only affects our sleep-wake cycles but also our eating habits, as many consume food after sunset. This seemingly benign behavior may have more detrimental health consequences than previously thought, as late-night eating can lead to circadian misalignment, microbial imbalances, and metabolic disease.
Consuming carbohydrates late in the day may lead to elevated blood sugar levels because melatonin, which is released at night, inhibits insulin secretion from the pancreas. This is an evolutionary adaptation aimed at preventing blood sugar drops during the night when food was typically scarce. Conversely, consuming a larger share of daily calories early in the day aligns better with circadian rhythms and offers metabolic advantages, as glucose tolerance and diet-induced thermogenesis tend to be higher in the morning.
Circadian misalignment also disrupts gut microbiota, which display daily variations linked to food timing, fasting duration, and light exposure. A 2018 study on mice revealed that constant exposure to artificial light, as opposed to a 12-hour light cycle, led to an increased presence of Ruminococcus torques, a bacterium associated with gut barrier dysfunction, and a decreased presence of Lactobacillus johnsonii, known for maintaining intestinal health. These findings suggest a potential mechanism by which disrupted circadian rhythms can harm the gastrointestinal lining and lead to further health issues.
The Dangers of Reduced Sun Exposure
The increased reliance on artificial lighting has coincided with a decline in natural sunlight exposure, leading to various physiological issues. Before the Industrial Revolution, most people worked outdoors, but now the majority in developed nations are confined to indoor jobs. Since World War II, innovations such as cars, televisions, and computers have encouraged indoor activities over outdoor engagement.
For millennia before these technological changes, human skin pigmentation adapted to balance the benefits and risks of sun exposure in different climates. Dark skin likely provided protection against sunburn and folate deficiency, while lighter skin facilitated adequate vitamin D synthesis in areas with lower ultraviolet radiation.
However, the modern lifestyle has resulted in erratic sunlight exposure patterns, particularly for lighter-skinned individuals in tropical regions. The increase in skin cancer cases is often attributed to this mismatch between skin type and geographical location. Dermatologist Richard Weller from the University of Edinburgh explains:
> “Homo sapiens have existed for 200,000 years. Until the industrial revolution, we lived outdoors. How did we manage during the Neolithic Era without sunscreen? Actually, we did just fine. It’s counterintuitive that dermatologists warn, ‘Don’t go outside, you might die.’”
Approximately one billion people globally are estimated to suffer from vitamin D deficiency or insufficiency. Insufficient sun exposure and the resultant vitamin D deficiency elevate risks for numerous health issues, including hypertension, heart disease, metabolic syndrome, diabetes, obesity, Alzheimer's, multiple sclerosis, rheumatoid arthritis, psoriasis, non-alcoholic fatty liver disease, macular degeneration, and myopia, as well as increased susceptibility to colorectal, breast, prostate, and pancreatic cancers.
In 2016, Pelle Lindqvist from Sweden’s Karolinska Institute published findings from a two-decade study of nearly 30,000 Swedish women, revealing a startling conclusion:
> “Nonsmokers who avoided sun exposure had a life expectancy comparable to that of smokers in the highest sun exposure group, indicating that sun avoidance poses a death risk similar to smoking.”
Currently, the only identified risk related to the necessary non-burning sun exposure to maintain serum vitamin D levels of 30 ng/mL is a potential increased risk of non-melanoma skin cancers, such as basal and squamous cell carcinomas, which are rarely fatal. Additionally, sun exposure is linked to better outcomes and survival rates in malignant melanoma. Weller suggests:
> “The risk factor for melanoma seems to be intermittent sunshine and sunburn, especially in youth. However, evidence shows that long-term sun exposure is associated with a lower incidence of melanoma.”
The advantages of sunlight extend well beyond adequate vitamin D levels. Sun exposure stimulates the release of vital compounds in the body, including serotonin, endorphins, and melatonin. Furthermore, sunlight prompts the skin to produce nitric oxide, which dilates blood vessels and reduces blood pressure, providing cardiovascular protection and antihypertensive effects. A 2014 study indicated that the benefits of ultraviolet radiation in suppressing obesity and metabolic syndrome symptoms were independent of vitamin D.
Moreover, both UVA and UVB rays can aid in preventing autoimmune diseases by enhancing cytokine activity and boosting the function of regulatory T cells that eliminate self-reactive T cells. Additionally, calcitonin gene-related peptide (CGRP) is released in response to both UVA and UVB light, inhibiting mast cell degranulation, which may explain sunlight's effectiveness in treating skin conditions like psoriasis.
Given the overwhelming evidence highlighting the health advantages of diet and lifestyle adjustments, we should seize the opportunity to enhance our well-being through the simplest means available. Ultimately, we should strive to maintain circadian alignment, which may involve adopting a restricted feeding window, sticking to regular sleep schedules, and enjoying appropriate sun exposure. We may discover that the best medicine lies in the habits we can control, should we choose to adjust our behaviors and embrace the sunlight.
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