American grocery store aisles are packed with a variety of processed foods and beverages. Crafted for the busy consumer with a small budget, these foods are a way of life for many Americans. However, eating a diet that is too high in these foods can increase the risk of many diseases, including cancer.
Some everyday items such as soda are cancer risks. Drinking alcohol increases the odds of getting liver cancer. Complex ingredients of processed foods that are loaded with preservatives are risk factors for digestive system cancers.
Fang Fang Zhang, Ph.D., a nutrition cancer epidemiologist at the Friedman School of Nutrition Science and Policy at Tufts University in Boston, studies the role of nutrition in preventing cancer. She has found that Americans are eating more healthily than they used to, but not enough to reduce the rates of diet-related cancers. She is working to understand what food policies are likely to encourage healthier eating and reduce cancer rates. This includes looking at policies that would help lower-income people, who generally have even less healthy diets.
How does food relate to cancer?
Often, what makes food a cancer risk is not the food itself but the way it is cooked or processed. For example, processed meats such as hot dogs and bacon are known to be a risk for cancers of the colon and rectum, parts of the digestive system. Natural and added materials in processed and red meats damage the cells lining the intestines and increase cancer risk. Refined grains and sugars added in foods, which together make up almost half the daily calorie intake of the average American,1 also indirectly raise the risk of cancer through obesity. On the other hand, eating a lot of fiber and nutrient-rich foods such as whole grains, dairy, fruits, and vegetables can reduce the risk of cancer, Zhang says.
Despite the relationship between processed meats and cancer, analysis by Zhang and her colleagues shows that Americans ate just as much processed meat in 2016 as they did in 1999.1 Nearly half of U.S. adults do not follow federal dietary guidelines. Other research has shown that only 1 in 3 women and 1 in 5 men eat the recommended amounts of fruits and vegetables.
Because Americans eat so poorly and poor diet is linked to cancer, Zhang did the math to figure out just how many cancer cases can be blamed on poor diet. She found that in 2015, about 80,000 cancer cases—more than 5 percent of cases in U.S. adults—were associated with poor diet.2 Obesity, which is often associated with a low-quality diet, also increases the risk for certain type of cancers, such as endometrial, esophageal, and kidney cancer. Other research has found that obesity-related cancers are predicted to rise in the future as obesity rates continue to rise, especially in younger people.
Added burden for economically disadvantaged people
Eating right is hard for everyone, but it can be particularly difficult for lower-income people. Cheap, processed foods are often less nutritious. “Access to affordable healthy foods is a challenge for many Americans, especially those living in low-income and minority neighborhoods and in rural areas,” Zhang said.
Food insecurity—not having reliable access to enough good, affordable food—and obesity are both linked to increased cancer burden for lower-income people.
The federal government’s Supplemental Nutrition Assistance Program (SNAP) combats food insecurity by helping tens of millions of low-income Americans afford food every year. Zhang’s team analyzed data on the diets of SNAP program beneficiaries from 1999 to 2014 and compared it with the diets of higher-income people. SNAP participants had poorer diets on average: they ate less fruit, vegetables, whole grains, legumes, nuts, and fish and were the highest consumers of soda and other beverages that are sweetened with sugar. Also, while higher-income people’s diets improved over the 15-year period, lower-income people’s diets did not change. Compared with higher-income people and income-eligible non-participants, SNAP participants did not reduce their consumption of processed meat and sugar. In the 15 years’ data that Zhang analyzed, shellfish and nuts were more common in the diets of higher-income people than in the diets of SNAP participants.3 Zhang also saw that low-income populations tended to adhere less to recommended dietary guidelines.
“The SNAP program’s aim is to reduce food insecurity, but food quality isn’t its focus area,” Zhang explained. She suggested that the SNAP program could be redesigned to focus on introducing healthier food options to reduce the disparity between SNAP participants and higher-income people.
Policies that could save lives
To encourage healthier eating, Zhang is studying how policies could change dietary habits. One of the policies she studies is the “soda tax”—a tax levied on beverages sweetened with excess sugars—intended to make them more expensive and therefore less attractive to consumers. Several places in the United States already have a soda tax. Zhang used computer-generated prediction programs to show that a national soda tax would prevent thousands of cancer deaths and save health care costs in the range of billions of dollars.4 The tax would especially help improve the health of low-income people, she says.
Processed meat is another target of Zhang’s evidence-based policy research. She has found that a 10 percent increase in tax on meat processing can prevent 77,000 colorectal and 12,500 stomach cancer cases over a period of 75 to 80 years. That would translate to savings of $2.7 billion on health care.5
Research and market experience have shown that warning labels on cigarette packs work as a deterrent to smoking. Zhang has studied the possibility of putting warning labels on food, too. She estimates that warning labels on packages of processed meat could prevent 85,400 colorectal and 15,000 stomach cancer cases over a 75- to 80-year period, saving the country $4.5 billion in health care spending.5
However, food taxation policies alone are not predicted to be the best way to reduce cancer in low-income populations. Zhang has also considered subsidy policies, which would make fruits and vegetables cheaper for low-income people, especially people participating in the SNAP program. Her analysis predicts that subsidizing healthy foods would reduce the number of cancer cases in low-income people.6
There would, of course, be costs to implementing all of the policies Zhang has studied, but her analysis shows that the costs would be overwhelmed by the benefits: significantly fewer cancer deaths and billions of dollars in health care savings.
“Eliminating health disparities among different segments of the U.S. population is an overarching goal for improving the nation’s health,” Zhang said. “Nutrition policies could be cost-effective strategies for reducing cancer burden and disparities.”
Page updated July 13, 2022