10 Most Important Studies On Human Health

If you want to be healthy, you need to stop outsourcing your health to others.

You need to take responsibility for your own body and mind. 

If you don’t know where to start, the following 10 scientific studies helped me to understand the foundation of good human health. 

  1. Sunlight study

Title: Avoidance of sun exposure as a risk factor for major causes of death: a competing risk analysis of the Melanoma in Southern Sweden cohort

In one of the most enlightening studies on human health, researchers followed 30,000 Swedish women over 20 years and discovered that non-smokers who avoided the sun had a life expectancy similar to smokers who got the most sun.

The 2016 study authors write that avoiding the sun “is a risk factor for death of a similar magnitude as smoking.” 

There was a 2X increased risk of death among sun-avoiders compared with the highest sun exposure group.

The benefits of sun exposure have long been known. In the early 1900’s, light therapy, also known as phototherapy, was a popular medical treatment for all sorts of disorders including diabetes, gout, chronic ulcers, and wounds.

Modern research has found that sunlight cues special areas in the retina, triggering the release of serotonin. This is why one of the main treatments for seasonal depression is a box that mimics natural sunlight.

Yes, skin cancer is associated with too much sunlight exposure. However, other cancers could result from too little. 

Living at higher latitudes (less sun) increases the risk of dying from Hodgkin lymphoma, as well as breast, ovarian, colon, pancreatic, prostate, and other cancers, when compared with those living at lower latitudes (more sun).

Even in those who do get skin cancer, continued high sun exposure is linked with increased survival rates, according to this 2005 study

Plus, there are ways to mitigate against the skin cancer risks of ultraviolet radiation, like avoiding excessive exposure and burning, slowly increasing exposure, eating a healthy diet, etc. 

Scientists are now calling for health guidelines regarding sun exposure to be revised, saying that insufficient sun exposure has become a real public health problem.

They’re right. 

  1. Insulin resistance study 

Title: Insulin Resistance as a Predictor of Age-Related Diseases 

In perhaps the most important study on chronic disease, researchers evaluated the relationship between insulin resistance and the development of hypertension, coronary heart disease, stroke, cancer, and type 2 diabetes – all common diseases of aging.

Insulin resistance is when the body’s cells stop responding to insulin, a hormone that helps sugar get into cells for energy. This causes sugar to build up in the blood and can lead to diabetes.

The research involved 208 healthy individuals between 1988 and 1995. The participants were divided into three groups based on their baseline insulin resistance levels, and the events in these groups were compared.

The findings of the study revealed that clinical events, such as hypertension, type 2 diabetes, cancer, coronary heart disease or stroke occurred in 37 individuals out of the total 208 evaluated (18%). 

Notably, 28 out of the 40 clinical events (70%) were observed in the group with the highest level of insulin resistance, while the remaining 12 events occurred in the group with an intermediate degree of insulin resistance. 

What’s most interesting about this study is that there were no clinical events in the most insulin-sensitive group. 

These results identified insulin resistance as an independent predictor of all clinical events.

To improve insulin resistance is pretty simple: avoid frequent high doses of sugar and carbohydrates. 

  1. Muscle study

Title: Muscle Mass Index As a Predictor of Longevity in Older Adults

In this study, researchers looked at over 3,500 people who were at least 55 years old over the years 1988-1994. They wanted to understand how muscle mass relates to the risk of dying from any cause. 

To do this, they measured muscle mass using a special method and calculated a muscle mass index. 

They found that people with more muscle mass had a lower risk of dying – of anything. 

They also accounted for factors like obesity and other important things that could affect the results.

Simply put, the more muscle mass you have as you age, the less risk you have of dying. 

And it turns out that just one hour of resistance exercise each week is enough to see a decrease in all-cause mortality risk.   

Furthermore, this review discusses the underappreciated role of muscle metabolism in health and disease. 

It explains how altered muscle metabolism plays a key role in the genesis and prevention of many common diseases, and how maintaining and building muscle mass is important in the prevention and management of chronic diseases, including heart disease, cancer, and sarcopenia.

The researcher also advises increasing protein intake to optimise muscle strength and metabolism, improving overall health.

  1. Meat study 

Title: The evolution of the human trophic level during the Pleistocene

The trophic level of an organism is the position it occupies in a food web, and this study from 2021 found that humans were apex predators that mostly ate meat for two million years. 

To determine whether Stone Age humans were specialised carnivores or generalist omnivores, the researchers analysed genetics, metabolism, physiology, morphology and archaeology of tool development.

“It is hard to convince a devout vegetarian that his/her ancestors were not vegetarians, and people tend to confuse personal beliefs with scientific reality. Our study is both multidisciplinary and interdisciplinary,” said Prof. Ran Barkai, one of the researchers.

He continues: “We propose a picture that is unprecedented in its inclusiveness and breadth, which clearly shows that humans were initially apex predators, who specialized in hunting large animals. 

“As Darwin discovered, the adaptation of species to obtaining and digesting their food is the main source of evolutionary changes, and thus the claim that humans were apex predators throughout most of their development may provide a broad basis for fundamental insights on the biological and cultural evolution of humans.”

  1. Saturated fat study

Title: Saturated fat: villain and bogeyman in the development of cardiovascular disease? 

Between 2010 and 2021, scientists searched PubMed, Google scholar, and Scopus for articles published on the association between saturated fat consumption and cardiovascular disease risk and outcomes.

The conclusion of the study reads: “Findings from the studies reviewed in this paper indicate that the consumption of SFA [saturated fat consumption] is not significantly associated with CVD [cardiovascular disease] risk, events, or mortality. 

“Based on the scientific evidence, there is no scientific ground to demonize SFA as a cause of CVD. SFA naturally occurring in nutrient-dense foods can be safely included in the diet.”

  1. Artificial light at night study

Title: Evaluating the Association between Artificial Light-at-Night Exposure and Breast and Prostate Cancer Risk in Spain (MCC-Spain Study)

This study used images taken by astronauts aboard the International Space Station to evaluate outdoor lighting in Spanish cities Madrid and Barcelona.

It found that participants exposed to higher levels of blue light had a 1.5 and 2-fold higher risk of developing breast and prostate cancer, respectively.

It is known that artificial light at night disrupts the circadian rhythm, decreases melatonin production, and is linked to insulin resistance and diabetes.

Digital screens emit large amounts of melatonin-blocking blue light

  1. Rat park study 

Title: Rat Park

Rat Park was a series of studies on drug addiction conducted in the late 1970s by Canadian psychologist Bruce K. Alexander.

In the experiments, two groups of rats were given a choice between sweetened morphine water and plain water.

Rats in small cages (isolated, unstimulating) preferred the morphine water, while rats in Rat Park (other rats, lots of space, stimulating) preferred plain water.

The results showed that living conditions of the rats (including social interactions, sex and freedom to exercise and play) influenced their preference for morphine.

  1. Mushroom study 

Title: Association of mushroom consumption with all-cause and cause-specific mortality among American adults

A study from 2021 found that adults who ate mushrooms had a lower risk of premature death, regardless of their demographics, lifestyle choices and other dietary factors. 

The study analysed the diets of more than 15,000 U.S. adults and found that individuals who consumed mushrooms had lower risk of death by all causes compared with those who did not eat mushrooms. 

The researchers also observed a dose-response relationship between higher mushroom consumption and lower risk of all-cause mortality, meaning the more mushrooms the subjects ate, the less chance they had of dying.

Mushroom consumption also decreases risk of depression and cancer

  1. Cholesterol study

Title: Lack of an association or an inverse association between low-density-lipoprotein cholesterol and mortality in the elderly: a systematic review 

The cholesterol hypothesis, which states that cholesterol, particularly LDL-C, is inherently harmful, is questioned by the findings of this review of 19 previous studies (total of 68,094 elderly participants).

It found that the higher the cholesterol, the longer one lives. Some studies even suggest a potential protective role of high cholesterol against infections and atherosclerosis,

  1. Grounding study

Title: The effects of grounding (earthing) on inflammation, the immune response, wound healing, and prevention and treatment of chronic inflammatory and autoimmune diseases

This review discusses the evidence for the beneficial effects of grounding – being in direct skin contact with the earth, also known as ‘earthing’. 

The research suggests that grounding produces measurable differences in white blood cell concentrations, cytokines, and other molecules involved in the inflammatory response.

Grounding also appears to speed wound healing, reduce blood viscosity, improve sleep, normalise cortisol rhythms, reduce pain and stress levels, and shift the autonomic nervous system towards parasympathetic activation.

It is thought that connecting the body to the Earth allows free electrons to have antioxidant effects, preventing “collateral damage” and reducing inflammation.