This, in part, reflects a unique American belief that we can have control of all aspects of our lives. As a result, any adverse event may be linked to something “we did or potentially could have avoided.” Many patients desperately seek to understand the underlying cause of their cancer, in the hope that they can reverse or control this and improve their chances of survival. It is important to understand the “randomness” of mutational events that often initiate the cancer process and our inability to prevent all cancers. The message we get from the media and even the medical press is that we eventually will be able to explain every cancer that arises.
This is simply not true. And in many cases, “I thought I did everything right!” does not apply. We cannot necessarily identify any specific trigger or cause of many cancers. I believe the identification of tobacco and cancer risk and other less common exposure-related cancers, like asbestos, has in some ways fueled this confusion, as has the constant media attention to the “latest exciting findings” that link some exposure or dietary factor to cancer.
As I’ve previously discussed, the issue of height is a very important clue to many important issues surrounding risk. In recent months, the role of increasing height and cancer risk has been noted in the press. Despite this publicity, this is, not a new finding but has been extensively studied, and is well known among cancer epidemiologists (scientists who study the origins of disease in populations). In fact, height and cancer risk is associated with many “western cancers,” typical for modern life such as breast, colon, aggressive prostate, lung, uterine, and pancreatic cancers. Height is a clear contributor to our higher cancer rates, but it is crucial to explain exactly what this means. We cannot and would not want to change our height in hopes of changing cancer risk but importantly we can exploit an understanding of why this occurs to improve our health, lower our cancer risk, and markedly change cancer survival in the future! The following issues are helpful in understanding the height and cancer effect.
- While we think of height as being in our “genes,” both prenatal and postnatal factors such as good nutrition, freedom from serious childhood illnesses, and stress significantly increase the height we will attain as adults.
- Modern western populations (Europe, North America) have increased in height on an average of four inches in the last 100 years. Just visit a 200-year-old house. You need to duck as you pass from one room to another!
- We are learning that the origins of many chronic illnesses that occur in later adult life such as diabetes, heart disease, and cancer have their origins in the prenatal period and early childhood. I will address this in more detail in a later blog post.
- It is critical to recognize that height is not a “cause” but a side effect of early healthy and robust childhood growth and development — the very features that have provided our children with freedom from serious illness and high mortality rates common in earlier centuries and in underdeveloped areas of the world today. Remember, the reason historically that up to 50% of young children never survived to age 10 was due to such common ailments as infantile diarrhea and measles.
- The growth in average height is directly associated with an increasing number of cells in every tissue in our body, particularly in what are called “tissue stem cells,” which are produced early in life and allow the replenishment of cells as we grow and age.
- The current theory of cancer origins is that the earliest carcinogenic mutation occurs in the tissue stem cell. Thus, with more stem cells in every tissue, the probability of a critical mutation in any one of the cells is going to increase, leading to higher cancer risk over a lifetime. I call this “the lottery ticket effect,” or scientifically the “pre-initiation” phase of cancer.
- The paradox is that this late adult increase in cancer risk is far outweighed by the importance of early good nutrition and growth on overall survival of modern populations.
- As early childhood health and survival improves, there is a progressive increase in height. The positive side of greater height is both lower cardiovascular disease and reduced overall mortality in modern populations despite the increase in adult cancer risk. It is also noteworthy that height is a clear indicator of national economic well-being.
Now here’s where it gets a little complex, so stay with me if you want to fully understand the link between nutrition, life style, and cancer risk.
- An important clue to what influences the growth factor is early childhood is nutrition. This is likely a result of an adequate intake of calories, and micronutrients such as folic acid and other vitamins, particularly healthy dietary protein. One of the most closely linked components of diet to height is early childhood dairy intake, particularly milk. Some of you may be familiar with the China Study (TC Campbell) and the possible relationship of dairy protein, particularly casein, to adult cancer risk. What few people are aware of is the strong possibility that this relationship may be due to this important early childhood growth effect, rather than the effect of dairy intake later in life.
- What actually mediates this early nutritional effect is the insulin system. These dietary factors increase the levels of the hormone insulin, which is central to regulating carbohydrate and fat metabolism in the body. This occurs both prenatally and postnatally. Its relative, IGF-1 (insulin-like growth factor) enhances cell growth (proliferation), which leads to increased childhood growth. (IGF-1 is the protein similar to insulin in function and structure and is involved in mediating growth and development.)
So how can we exploit this understanding to change our risk and survival as adults? It’s actually simple and yet challenging. Let me first explain about insulin resistance, which is pretty self-explanatory. This is a condition in which cells fail to respond to the normal actions of the insulin. Although the body produces insulin, the cells in the body become resistant and are unable to use it as effectively.
The same hormonal factors, the insulin-IGF system, are central to the role of adult diet and lifestyle in changing cancer outcomes. When you couple the increase in the modern sedentary lifestyles with the abundant availability of cheap, calorie-dense foods consumed through late childhood and continuing into adulthood, we become not tall, but “long.” That is, we become heavier with an increasing burden of fat tissue called adipose. Couple this with inactivity and it leads to decreased muscle mass, resulting in “insulin resistance.” With sustained higher levels of these hormones, you have the same chronic stimulus to increased cell growth which fuels the probability of a critical mutation in any one of the cells and leads to higher cancer risk and “the lottery ticket effect” or the “pre-initiation” phase of cancer that I discussed earlier.
Unfortunately, when early precancerous cells (those random mutations again) are exposed to the chronic increase in insulin and IGF levels, it is a recipe for both higher cancer risk, and, importantly, more rapid growth and progression of existing cancers, shortening survival! Simple lifestyle changes can make a difference and this has become the central focus for many cancer specialists such as myself seeking to change long-term outcomes in the growing cancer survivor population.