HOME > Doctor’s Health Advice > Adulthood Cancers — A Lifestyle-related Disease

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  • Yuzo Endo, M.D., Ph.D.
  • Masahito Hitosugi, M.D., Ph.D.
  • John E. Lewis, Ph.D.

Doctor’s Health Advice

Doctor’s Health Advice

Pathologist’s advice on how to combat cancer


Adulthood Cancers — A Lifestyle-related Disease

Conquering externally-caused diseases, but fighting internally caused diseases

Today, most diseases that are identified as having external causes such as bacteria and viruses can be largely controlled. However, internally-caused diseases, or “disease from within,” such as lifestyle-related diseases, allergies, and autoimmune diseases (which are all closely related to body constitution) have started to afflict humans. In fact, adulthood cancer belongs to the category of lifestyle-related diseases. The idea of cancer as a lifestyle-related disease might come as a complete surprise to many people.
Cancer is a lifestyle-related disease because its prevention is linked to the concept of protecting the human body as a whole, which is what I aim to do in my medical practice. In simplified terms, cancer is a DNA-related disease. Cancer develops when a parent cell divides into two daughter cells, which divides into four cells, eight cells, and so on, dividing limitlessly. In other words, cancer originates from DNA defects in a parent cell.

Defects in chromosomal DNA accumulate over a decade or more, resulting in cancer

A pathologist makes the diagnosis of cancer by examining cell samples under a microscope. The appearance of the cells change, and this indicates the various stages of the cells, ranging from normal to cancerous stages. The earlier stages are sometimes referred to as atypical cells or pre-cancerous change. That is to say, cancer cells do not develop suddenly. All diseases have a latency period, and likewise, many adulthood cancers have a latency period that is ten or more years long.

What happens during this latency period? Minor damages occur daily to the DNA of cells in various parts of the body. The body has a mechanism that tries to repair these damages. However, if too many damages accumulate in the DNA, and if they cause defects in genes that regulate cell division or cell death, cells gradually become abnormal.

For example, if a person has a job that involves being exposed to the sun for long periods, precancerous changes develop in their skin cells, and these slowly develop into cancer. Ultraviolet rays in sunlight damage the DNA of skin cells. When cells are destroyed by UV, a fatty acid called arachidonic acid, an inflammation-causing substance that originally exists in the cell membrane, causes inflammation. White blood cells appear at the sites of inflammation and produce “bad” oxygen species (reactive oxygen species), which not only kills bacteria and other pathogens, but also begins to damage the DNA of the body’s own cells. Similar series of events are occurring all the time, in all parts of the body. The development of cancer signifies that such events had been continuously occurring for a decade or more.

Considering how cancers in adults develop after a long latency period, it should come as no surprise if the number of cancer patients increases as the population ages. People who are aged 50 years old and above are generally considered more “cancer-prone”. Is this an accurate conclusion? Thorough research suggests that this conclusion may not be necessarily true.

Stomach cancer and cervical cancers are tending to decline

Looking at adulthood cancers as a whole, mortality rates have continued to rise in recent years. In fact, one in three people die from cancer in Japan. However, a closer examination of the different adulthood cancers reveals that while the mortality rates of some cancers are continuing to rise, certain cancers have declining or stagnant mortality rates. Thus, it would be inaccurate to conclude that death rates of all cancers are rising.

Among the cancers on the decline, stomach cancer in the elderly has shown the largest decline. Both the mortality rate and incidence of stomach cancer have been declining worldwide. During the first half of the 20th century, the most common cause of death from cancer for American men was stomach cancer. In response, the US National Cancer Institute’s main research focus in the 1940s was the eradication of stomach cancer. Cancer death rates naturally declined in the United States, and the rate of this decline has been particularly prominent after the 1960s.

During the 1960s, Japan, Chile, and Finland were among countries with a high stomach cancer mortality rate. However, mortality rates started declining after the 1960s, particularly in Finland. Although Japanese people were previously thought to have some genetic predisposition to developing stomach cancer, no genes associated with stomach cancer have been found in the Japanese to date.

The dissemination of screening programs for cancer is considered to be one of the contributing factors in the reduction of stomach cancer mortality. However, stomach cancer mortality also tended to decline in countries in which cancer screening programs were not commonplace. Diet is also considered as a contributing factor. Topics such as food preservatives, chronic gastritis caused by pyloric bacteria, restrictions in salt intake, intake of fresh vegetables, and vitamin C have received much attention. Much information on stomach cancer has been accumulated to date, and it is perhaps not an overstatement to say that medical professionals now have almost all the knowledge required to eradicate stomach cancer in the elderly.

Cervical cancer is the second fastest declining cancer after stomach cancer. Cervical cancer is triggered by chronic inflammation of vagina caused by viral infection or sexual intercourse. The decline in cervical cancer mortality has been mediated by screening programs, sex and hygiene education, and by habits such as keeping the vagina clean.

Searching for factors that trigger the onset of cancer and devising preventive measures

Though lung cancer mortality has been increasing in many countries around the world, including Japan, it has tended to decrease in men in the USA and UK. It is interesting to note that lung cancer is not a cancer that has been feared throughout history. Up until the beginning of the 20th century, when tobacco cigarettes began to be mass produced and sold, lung cancer was a very rare type of cancer. Following the period in which shredded tobacco was popular came the period of cigarette smoking, which rapidly increased tobacco tar inhalation and triggered an increase in the incidence of lung cancer. Anti-smoking campaigns in the USA and UK have been reducing lung cancer mortality in men. However, mortality is still tending to rise in women. The male smoking rate in the USA is approximately 25% while Japan’s male smoking rate still lingers at around 50%.

Colon cancer, breast cancer, and prostate cancer are among cancers whose incidences have been rising. These cancers have been strongly associated with the increase in consumption of Western-style foods. In fact, we have already come to understand many of the causes of adulthood cancer through a careful study of these cancers. The causes can be directly linked to people’s lifestyles, in areas such as diet and daily habits.

Analysis of these causes will allow us to devise preventive measures against cancer. As the saying goes, know thy self, and know thy enemy; if we can achieve this, we may be able to extend the latency period of cancer limitlessly, which practically means that we will no longer have cancer. An ounce of prevention is worth a pound of cure; it is imperative that we find measures to prevent this lifestyle-related disease.


Yuzo Endo, M.D., Ph.D.

Yuzo Endo, M.D., Ph.D.
Hamamatsu University School of Medicine

1969.9: Graduated from Medical School, University of Tokyo Consultant pathologist in Hamamatsu University, Medical School, and Fujimoto General Hospital. Medical Consultant in conventional and integrative medicine.

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