Exercising leads to a vast array of direct and indirect biochemical changes in the body that may explain its anti-cancer benefits, finds a recent review of the science. The study, published in the British Journal of Sports Medicine, highlights the effect of exercise on potential cancer pathways, ranging from the immune system to weight management.
The study offers a greater understanding of how exercise lowers the risk of developing cancer. AICR research shows that exercise reduces the risk for breast, colorectal and endometrial cancers. Emerging studies also suggest it can help improve cancer survival.
For the review, three scientists evaluated the 168 papers that investigated biological changes occurring after physical activity. The studies included both lab and human trials. They divided the mechanisms of actions into direct and indirect changes.
Some of the direct effects of exercise, in no particular order, include:
- Changes to cell-growth regulators, such as insulin-like growth factor (IGF-1): IGF-1 and its related proteins can activate signaling pathways that lead to the inhibition of apoptosis, cell growth and angiogenesis. Exercise appears to lower IGF-1.
- Increasing proteins involved in DNA repair: Exercise appears to influence the expression of inherited genes without modifying the gene – a process known as epigenetics. Genes particularly sensitive to exercise included those involved in supporting DNA repair, such as the genes BRCA1 and BRCA2.
- Improved immunity: For moderate exercise, particularly with regular training, most long-term studies suggest exercise improves immune function in all age groups. Its benefits appear especially relevant to the elderly and other populations whose immune function may be reduced.
- Reducing chronic inflammation: Exercise is known to increase the activity of immune cells, including types of white blood cells called Natural Killer and T cells. This leads to the body producing fewer anti-inflammatory cells, which can reduce chronic inflammation.
Indirect effects, in no particular order include:
- Weight loss and management: Exercise can play a role in weight loss, and that can reduce excess fat cells, which increase the risk of many cancers. Exercise and eating a healthy diet can also help with weight control and lowering total cholesterol. Some studies have suggested that high levels of cholesterol in the blood are associated with increased risk of cancer.
- Increased vitamin D and sunlight: These are both higher among regular exercisers. While sun damage clearly increase cancer risk, regular “sensible” sun exposure has an anticancer effect by maintaining adequate vitamin D levels, the authors state.
As the study notes, there is an overlap between the direct and indirect effects of exercise, especially from weight reduction. There are likely many other pathways by which being active leads to anti-cancer effects. Research is ongoing as to which of these mechanisms has the strongest effects on certain cancers and for certain individuals.
Source: Thomas RJ, Kenfield SA, Jimenez A. Exercise-induced biochemical changes and their potential influence on cancer: a scientific review. Br J Sports Med. Published Online First: December 19, 2016.