by Taraneh Soleymani, MD
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“The American Institute for Cancer Research (AICR) reports that only half of all Americans are aware of the link between obesity and cancer.”
Most people know that obesity and excess weight increase the risk for certain health conditions, such as type 2 diabetes, heart disease, hypertension and high cholesterol, but they are less aware of the increase in risk of developing cancer.
While the exact links between obesity and cancer are not fully known, research studies have proposed several possibilities:
- Cancer is a disease caused by uncontrolled growth of cells which can take place in any part of the body. Obesity is often associated with increased insulin (a hormone which regulates metabolism) and insulin-like growth factor-1 (a hormone which increases cell growth and slows cell death) levels in blood, and they can result in overstimulation of cells to grow and potential cancer cell development.
- Fat cells produce hormones that can stimulate or inhibit cell growth. There is an increase in fat cell size and quantity in individuals with obesity versus more lean individuals. In obesity, the fat cells produce more leptin, which stimulates cell growth, and less adiponectin that slows cell growth. Collectively, they increase the risk for cancer cell formation (for all cancer types).
- In obesity, there is an increase in the number of immune cells in the extra adipose tissue. These immune cells release inflammatory substances that can result in a chronic inflammatory state that is associated with increased cancer risk.
- After menopause, a woman’s ovaries stop producing estrogen, and the primary source of estrogen is the woman’s body fat. A woman with a higher body fat during the post- menopausal years would be expected to have a higher level of estrogen. Excess estrogen is associated with increased risk for post-menopausal breast cancer and uterus cancer.
The American Institute for Cancer research (AICR) reports that 38 percent of breast cancers, 50 percent of colon and rectal cancers, 69 percent of throat cancers, 24 percent of kidney cancers and 19 percent of pancreatic cancers can be prevented by maintaining a healthy weight, balanced diet and by increasing physical activity.
10 Recommendations for Cancer Prevention
1. Maintain a healthy weight and waist circumference
Aim for a healthy BMI between 18.5-25 kg/m2. The location where excess fat is stored in the body can influence cancer risk. Excess fat around the midsection, or “belly-fat,” increases the risk of certain cancers, such as colon, pancreas, uterus and post-menopausal breast cancer. It will also increase the risk for heart disease and type 2 diabetes. Waist circumference should not go above 35 inches in women and 40 inches in men.
2. Increase physical activity
We live in an environment where it has been made easy to follow a lifestyle with less movement: watching television, working on a computer, driving to work etc. Physical inactivity has multiple harmful effects. It increases the risk of colon and breast cancer, type 2 diabetes, heart attack, stroke and cognitive decline. Any amount of physical activity is better than none, so start slow, and build to a goal of 30 minutes of moderate physical activity (any exercise that increases your heart rate and makes you breath harder) every day. Physical activity also helps you maintain a healthy weight.
Juice with added sugar, soda and sweet tea are examples of sugar-sweetened beverages. They are easy to drink and make it easy to increase our total daily calorie intake. They have minimal to no nutritional value, high carbohydrate content and do not make us feel full. A healthy alternative is water or zero-calorie drinks like unsweetened tea.
Eating a plant-based diet that includes fruit, vegetables, whole grains, nuts and legumes has several benefits. This diet has a higher content of fiber that is healthy for the intestines and improves its ability to digest the foods you eat. Fiber helps with weight management. A plant-based diet also provides vitamins and minerals in their natural form that are necessary for normal body functions, and the antioxidants (molecules that help delay and prevent cell damage) present in fruits and vegetables help protect the body cells from cancer-causing substances. The goal is to fill two-thirds of the plate with plant-based food items as often as possible.
5. Limit red meat and avoid processed meat as much as possible
There is a strong link between red meat (i.e. beef, lamb, pork) and colon and rectal cancers. The heme iron, which gives red meat its color, can damage the cells lining the colon. Eating up to 18 oz. of red meat per week is safe.
However for every 1.7 oz. above this limit, the risk of cancer will increase by 15 percent. Eighteen ounces of meat is a little more than one pound of meat you can eat safely per week, and meat is typically recommended to be served in a three ounce portion – about the size of a deck of playing cards.
Meat that has been preserved by salting, smoking or curing contains chemicals that can damage cells in the body. Any amount of processed meat will increase cancer risk.
6. Limit alcohol consumption
Studies have shown that alcohol can increase the risk of several cancers, such as mouth, throat, vocal chord, breast cancer and colon or rectal cancer in men. It is recommended that alcohol be limited to one drink for women and two drinks for men per day.
- 12 oz. of beer (1 regular sized can) (5 percent alcohol content)
- 5 oz. of wine (about 1⁄4 of a large glass and 1⁄2 of a smaller glass) (12 percent alcohol content)
- 1.5 oz. (1 shot glass) of 80-proof liquor such as vodka (40 percent alcohol content)
High salt consumption has been associated with increased risk for stomach and throat cancer as it can damage their lining. Processed meat has a high content of salt, especially when it is salt-cured or salt-pickled. Other processed food such as cereal, pizza, chips, canned soups, frozen meals and flavored noodles can increase salt intake above the recommended 2400 mg per day (about 1 teaspoon).
- Reduce intake to less than 2300 mg per day, and
- Further reduce intake to 1500 mg per day for Adults ages 51+, African Americans ages 2+ and people ages 2+ with high blood pressure, diabetes or chronic kidney disease.
Supplements should not be used to protect against cancer. It is best to get the nutrients we need from our diet in their natural form. Also it is important to keep in mind that very high doses of vitamin and mineral supplements has been associated with increased cancer risk. Supplements are recommended for the following groups: women of childbearing age, pregnant and nursing women, children between the ages of 6 months and 5-years-old, seniors and bariatric patients.
It is recommended that mothers breast-feed exclusively for 6 months and then add other liquid and food to their baby’s diet. Breast-feeding is good for the mother and the baby. It protects the mother against breast cancer by reducing the cancer producing hormones in the body, and it protects the child from becoming affected by excess weight or obesity.
AICR recommends that cancer patients follow the nine cancer prevention strategies stated in this article.
Our overall cancer risk is affected by our lifestyle over the span of our life. It is never too early or late to start cancer prevention, and most importantly, making small every day changes that are sustainable today can help lower the cancer risk throughout our lifetime.
Taraneh Soleymani, MD, is an assistant professor in the Department of Nutrition Sciences and Medicine at the University of Alabama at Birmingham (UAB), and the medical director of EatRight by UAB, a comprehensive weight management program. Dr. Soleymani is also the co-director of UAB’s Weight-loss Medicine Center, and the director of nutrition consultation services at Birmingham VA Medical Center. She is board certified in internal medicine with fellowship training in clinical nutrition and obesity management, and her clinical expertise includes patient tailored comprehensive medical management of obesity and inpatient nutrition management for the critically ill.