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A high-fat diet may increase the risk of colon cancer by causing lasting changes in intestinal stem cells, according to early research from scientists at Arizona State University. The study, published in Stem Cell Reports, found that mice fed a Western-style high-fat diet for about six months developed more intestinal stem cells, and these cells grew faster than those in mice fed a low-fat diet. The researchers also found changes in the DNA of these stem cells that could help explain their increased growth and survival.
The findings of the study are important because intestinal stem cells help maintain and repair the lining of the gut, but they can also be a starting point for some tumours. In mice that were genetically more likely to develop intestinal cancer, a high-fat diet was linked to more and larger tumours. However, the research is still at an early stage and was conducted in mice. Hence, it does not prove that eating a high-fat diet causes colon cancer in humans. The researchers say that the study could offer a possible explanation for how long-term dietary patterns could influence cancer risk.
How Can A High-Fat Diet Affect Intestinal Stem Cells?
The researchers fed mice a Western-style diet in which a large proportion of calories came from fat. They then compared them with mice that consumed a low-fat diet. After about six months, mice on the high-fat diet had more intestinal stem cells and the cells were dividing more rapidly. This is important because stem cells constantly produce new cells to replace those lost from the intestinal lining. Miyeko Mana, PhD, senior author of the study and assistant professor in the School of Life Sciences at Arizona State University, explained that intestinal stem cells are also among the cell types where tumours can begin.
When there are more actively dividing stem cells, there may be more opportunities for a cell carrying a cancer-related mutation to expand and contribute to early tumour formation.
High-Fat Diet Caused Changes That Lasted After The Diet Changed
One of the significant findings was that some changes did not disappear immediately after the mice stopped eating the high-fat diet. The researchers switched the mice from a high-fat diet to a low-fat diet and found that the behaviour of their intestinal stem cells returned towards normal. However, some changes in the DNA and its organisation remained.
After four weeks, around 18% of the changes were still present. When the mice were later exposed to the high-fat diet again, their intestinal stem cells responded more quickly and strongly than those of mice that had not previously consumed the high-fat diet.
Mana said the research suggests that the past diet may leave a kind of molecular memory in intestinal stem cells. "What changed was how the DNA was packaged and which regions were accessible to the machinery that turns genes on," she explained. Some of these changes remained even after stem cell activity had returned to normal.
Mice On A High-Fat Diet Developed More Tumours
The researchers also studied mice that were genetically predisposed to intestinal cancer. These animals developed more and larger tumours when they were given the high-fat diet.
The effect was also seen when the mice were exposed to the diet again after a period on a low-fat diet. Tumours grew larger in mice that had previously consumed the high-fat diet compared with those experiencing it for the first time. According to the researchers, these findings suggest that high-fat diets may create lasting changes in intestinal stem cells that make them more responsive to future exposure and potentially more vulnerable to cancer-promoting changes.
Does This Mean A High-Fat Diet Causes Colon Cancer In People?
Not yet, the biggest limitation is that the study was conducted in mice. Human diets, genetics, metabolism and other lifestyle factors are much more complicated.
The diet used in the study was also extremely high in fat, with about 60% of calories coming from fat, primarily from lard. This is important because different types of dietary fat can have different effects on health.
The study also mainly examined intestinal stem cells rather than directly studying human colon tissue. Therefore, the findings cannot currently be used to say that eating fatty foods will directly cause colon cancer.
The findings do not mean that people should completely avoid dietary fat. The body needs fat for several important functions, and foods containing unsaturated fats can be part of a healthy diet. The bigger concern is a diet consistently high in saturated fats, processed meats, fried foods and highly processed foods, particularly when it is also low in fibre. A diet rich in vegetables, fruits, whole grains and legumes can provide fibre and other nutrients associated with better colorectal health.
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