Recently, there’s been a great deal of coverage about the obesity epidemic in media outlets right across the globe. As a scientist I welcome the spotlight being turned on this issue, as the work I do shows strong evidence that being overweight or obese increases the risk of 10 cancers. What isn’t as well known, however, is that there is another aspect of a person’s size that's also linked to cancer: height. World Cancer Research Fund International’s analysis of worldwide research reveals that taller people are at an increased risk of 6 cancers. For our Continuous Update Project we analyse global evidence on the link between diet, weight, physical activity and cancer. This analysis reveals strong evidence that the taller you are, the more at risk you are of developing ovarian, prostate, pancreatic, colorectal, pre and post-menopausal breast, and - in the report we are publishing today - kidney cancer.
Specifically, for every extra 5 cm in height the increased risk of the six cancers is as follows:
- Kidney (10% increased risk)
- Pre- and post-menopausal breast cancer (9% and 11% increased risk respectively)
- Ovarian (8% increased risk)
- Pancreatic (7% increased risk)
- Colorectal (5% increased risk)
- Prostate (4% increased risk)
Unlike being overweight or obese, though, once you have reached your final height it’s impossible to do anything about it. So why am I discussing it? Well, the increased risk seen in taller people for different cancers and in different populations suggests that a basic common mechanism - possibly acting in early life - might be involved. So while you cannot change someone’s final height once they’ve reached it, how tall someone grows can be influenced by the way they are nurtured and fed in the womb, and throughout the rest of their childhood and adolescent growth and development phase.
Adult height is a marker that represents a growth process
The most important thing to remember is that it is not a person’s height itself - ie. the distance from your head to your feet - that increases your risk of cancer. Instead, it is the process that your body has undergone to make you tall, that is linked to cancer. In other words, a person’s final adult height is a visual representation of the growth process that someone’s body has undergone from conception through to adulthood. This process is influenced not only by their genes, but also by modifiable developmental factors (eg. growth factors such as insulin, insulin-like growth factor, growth hormone, and sex hormones such as oestrogens) in the womb, and during childhood and adolescence. So height should be thought of only as a marker, or indicator, of the whole series of events and experiences from conception to adulthood - and it is identifying what aspect or aspects of this process inﬂuences cancer risk that is important.
What determines a person’s height?
We know that people grow to their maximum height around the age of 20, and that how tall a person grows is influenced in part by their genes as well as the nutritional quality and quantity of the food they receive in their growth and development phase. The inﬂuence of the environment on height is evident by the increase in the height of populations in many countries at the beginning of the 19th century, reﬂecting improvements in hygiene and nutrition during that period.
We also know that the growth of infants can be accelerated by feeding high protein formula, which in turn leads to taller adults. In addition, children who are heavier for their height (mainly due to fat) tend to grow faster and become taller (and fatter). These children also reach developmental milestones earlier. In high-income countries – where people tend to be relatively tall and obesity rates also tend to be high - the age at which girls see their first period has fallen steadily over the last few decades from about 15 to under 11 years. All these processes are directly or indirectly the result of nutrition during development, and altered hormone levels (either hormones related to growth or to sex hormones). These hormones influence both the visible structure of people (such as their height) and the growth and behaviour of cells within the body, so it seems likely that these are at least part of the reason that taller people are at higher risk of these six cancers.
Research & policy implications
It is important to note that being tall is not all bad news. In fact, being taller appears to be beneficial when it comes to some other diseases. Babies that are born large (within the normal range), and taller people, have a lower risk of diabetes, strokes and heart attacks as adults, compared with shorter people. This is why it is so important to conduct further research that helps identify the processes that lead to these different adult health risks. If we can identify optimal growth patterns, that minimise the risk of all these chronic diseases, and the best feeding practices to promote them, we can give better advice to young women and parents both in developed and developing countries.
This could also be of great importance, for instance, to policymakers who are responsible for developing the standards against which children’s growth is assessed worldwide.
The hope is that research into hormones and other growth factors that influence height, will provide a better understanding of the association between height and cancer. Knowing how the growth process influences the risk of these cancers (but not others) and reduces the risk of other conditions could help support the development of policies to improve health throughout the life course around the world.