By Shanna Ndong
In part one of this series on epigenetics (“Fundamentals”) we reviewed some general definitions and concepts and gave an overview of the topic. Epigenetics is the study of inherited changes in gene expression that, unlike mutations, are not caused by changes in the sequence of DNA. These are mechanisms that help to turn genes off and on, and include DNA methylation and acetylation, respectively.
Cancer is caused by an imbalance in the mechanisms that control cell reproduction. Loss of reproductive control in cancer cells can occur due to random gene mutations, exposure to high-risk environmental and lifestyle factors (e.g. poor diet, smoking, alcohol, obesity), or rare inherited cancer syndromes (e.g. BRCA mutations and increased risk for breast/ovarian cancers).
The loss of control of cell proliferation can be due to genetic mutations and epigenetic abnormalities. Epigenetic changes are potentially reversible and are targets for the development of future nutritional, drug, or dietary interventions to treat or prevent genetic conditions including cancer.
Nutrition can potentially affect epigenetic processes at multiple points in DNA methylation. Nutrients are the main source of methyl groups or act as coenzymes for methyl transfer and DNA synthesis. A number of phytochemicals found in plant foods and in dietary supplements alter epigenetic processes by interfering with the activities of methylation enzymes. I will review some of the foods that have been shown to have cancer preventative and therapeutic properties with epigenetic targets below.
Folate is one of the B vitamins and is obtained solely from food (green vegetables, beans, grains, and pasta). Folate regulates the biosynthesis, repair and methylation of DNA, whereas deficiencies in folate can initiate cancer due to disruptions of these processes. Low folate intake is reported to contribute to the development of several different cancers, including breast, cervix, ovary, brain, lung and colon.
Green Tea (EGCG)
EGCG, the major polyphenol in green tea, has been extensively studied as a potential demethylating agent. In cell culture and animal models of lung, colon, bladder, liver, prostate, breast and skin cancers, the most commonly observed anti-cancer mechanisms of EGCG include inhibition of proliferation and induction of programmed cell death.
Genistein is one of the many phytoestrogens contained in soybeans and is a demethylating agent. Several epidemiologic studies showed a relationship between a soy-rich diet and cancer prevention. These studies arose from observations that in Asian countries, such as Japan and China, where diets are high in soy products, the incidence of breast and prostate cancers is relatively lower. Furthermore, migration studies showed an increase in prostate and breast cancer incidence in Asians after immigration to the United States, suggesting that environmental factors and changes in lifestyle, particularly in dietary practices, affect these types of cancer.
Resveratrol is a polyphenol found in grapes, peanuts, and berries. It is concentrated in the skin of grapes, so the process of crushing and mashing grapes for winemaking results in high levels of resveratrol in wine. It has anti-cancer, anti-inflammatory, blood-sugar-lowering and other beneficial cardiovascular effects. It has been found to have anti-cancer activity against colon cancer in human clinical trials. Several studies using animal models for non-melanoma skin cancer, breast cancer, prostate cancer, liver cancer, pancreatic cancer, lung cancer, and stomach cancer all showed anti-tumor effects.
Members of the Brassicaceae family include broccoli, cauliflower, brussels sprouts, kale, and cabbage. They have anti-inflammatory properties and contain chemicals that stop cancer cell growth and stimulate programmed cell death. High rates of cruciferous vegetable consumption have been associated with lower risk for bladder cancer. Laboratory studies on human prostate, colon, and breast cancer cells have all shown positive anti-cancer effects of cruciferous vegetables and their metabolites.
Additional foods that have been shown to prevent cancer through epigenetic mechanisms are human breast milk, extra-virgin olive oil, garlic, selenium, curcumin (turmeric), and caffeic acid (thyme, sage).
It’s important to keep in mind that much of this research is in its infancy and many of these studies have been performed in the laboratory or on animals. In general, most of the foods listed are healthful and would be a great addition to your diet, but I suggest that you speak to your doctor before beginning any supplements as they may interact with medications you are already taking. Stay tuned for part three of this series called “Behavioral Epigenetics” where I review evidence that experiences can cause epigenetic changes, and psychological and behavioral tendencies are inherited.
By: Dr. Shanna Ndong