Researchers say the diet of many Americans is increasing their risk for developing a variety of cancers.

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Foods such as fish, fruit, and vegetables can help reduce a person’s risk for cancer. Getty Images

Americans still aren’t eating enough of the right foods and are consuming too much of the wrong ones.

And that’s increasing their risk for cancer.

A study published this week in the JNCI Cancer Spectrum reaffirmed that diet can play a significant role in whether people develop the disease and, like exercise and alcohol consumption, their eating habits are a lifestyle choice.

“I would hope that we would be aware that a large amount of new cancer cases is preventable,” said Dr. Fang Fang Zhang, the study’s lead author and an associate professor of epidemiology at Tufts University’s Friedman School of Nutrition Science and Policy in Boston.

“Diet is modifiable,” she told Healthline. “It’s difficult, of course, but if we can improve our intake of these dietary factors, many cancer cases can be prevented.”

Unlike earlier studies that have focused on cancer risks in individuals, this one ascertained the likelihood of the illness showing up in the adult U.S. population as a whole.

Zhang notes that more people in the United States die from cancer than anything else, except for heart disease.

Researchers analyzed national data on how much food in each of seven categories adults 20 years and older are eating.

It also looked at the incidence of different types of cancer in 2015.

The researchers then came up with estimates of how many of the cancer cases diagnosed each year can be attributed to diets featuring less than ideal amounts of whole grains, dairy products, fruits, vegetables, red and processed meats, and sugary drinks.

The study is part of a federally funded effort to come up with cost-effective ways of improving the nation’s health through diet.

What the researchers found is that poor diets accounted for about 80,110 of the cancer diagnoses in 2015.

Most of those cases — 84 percent — were the direct result of patients either not eating enough whole grains, dairy products, and produce or too much meat that’s considered carcinogenic and sugar-sweetened beverages.

Although scientists have long suspected a relationship between diet and cancer, in recent years an explosion of data has shown there’s a direct nexus, says Dr. Anton Bilchik, professor of surgery at the John Wayne Cancer Institute and chief of general surgery at Saint John’s Health Center in Santa Monica, California.

“We now have some real science that we really haven’t had before,” he told Healthline.

As an example, Bilchik notes that the number of new cases of colon cancer has skyrocketed among millennials, a trend thought to be the result of eating too much sugar and processed foods as well as having inadequate exercise.

High levels of sugar increase the production of insulin, a hormone that in turn is believed to stimulate the growth of cancer calls.

Bilchik was struck by this study’s focus on nutrition as a potential cancer-causing factor.

He notes that previous studies probing the origins of cancer typically have looked at a combination of risk factors — not just obesity, for example, but behaviors such as smoking and lack of exercise.

Zhang’s research, by contrast, zeroed in on diet, providing data showing that poor food choices alone can result in cancer regardless of whether a person has a nicotine habit or is sedentary.

“This study gives further evidence to the fact that diet is an important prevention. Diet stands on its own,” Bilchik said.

The remaining cases were ascribed to obesity, which itself is a significant risk factor for 13 types of cancer.

Researchers also found disparities among subgroups of the population.

Diet-related cancer risks were higher among men, middle-aged adults, and racial as well as ethnic minorities.

Drilling down further, they discovered that colon cancer was the most common type linked to subpar eating habits.

Other manifestations of the disease attributable to poor diet, listed in order of new cases, were:

  • cancer of the mouth, pharynx, and larynx
  • uterine cancer
  • breast cancer (postmenopausal)
  • kidney cancer
  • stomach cancer
  • liver cancer

Looking at which diets were most often associated with new cancer cases, scientists determined they were those that skimped on whole grains, such as oatmeal, brown rice, and bread containing whole-wheat flour.

The study’s authors noted that although Americans have been eating more whole-grain foods over the past 14 years, the one daily serving that they were averaging in 2013 to 2014 was still significantly less than the three servings per day the federal dietary guidelines recommend.

Other dietary missteps listed according to the cancer risk they posed from high to low were:

  • insufficient intake of dairy products
  • eating too much processed meat
  • not including enough vegetables and fruits in meals
  • overconsumption of red meat
  • drinking too many sugar-sweetened beverages

Adults currently eat less than half of the three daily servings of dairy foods endorsed in the 2015–2020 Dietary Guidelines for Americans.

And although the popularity of red meat is waning, this country’s love affair with processed meats has continued unabated for the past 15 years, the study reported.

Americans are eating about 1 ounce per day of this carcinogen on average — more than twice what the American Heart Association advises.

Researchers speculated that the public doesn’t recognize the dangers of processed meats or the health benefits of whole-grain foods.

They’re hoping their findings will turn that around by prompting the government to adopt policies, such as requiring warning labels on foods containing processed meats and restricting the quantities served in school and workplace cafeterias.

Acknowledging that poor diets can start early in life, the study also suggested that policymakers formulate cancer prevention strategies that young people can understand, require schools to limit the availability of sugary drinks, and serve meals that meet higher standards.

In the meantime, Bilchik says the study has sobering implications for those who consider themselves healthy despite what they eat.

“It really is sending a message that you can be physically active (and not) smoke, but if you’re eating poorly, you’re still putting yourself at risk of getting cancer,” he said.

Optimize your diet to reduce the chances of cancer by including servings from each of the following food groups. The number of recommended daily servings are for active women and most men:

  • Grains, especially whole grains (examples are foods containing wheat, corn, rice, or oats): 9 servings
  • Dairy products: 2 to 3 servings
  • Vegetables: 4 servings
  • Fruits: 3 servings
  • Low-fat meats, eggs, dry beans, nuts: 2 servings for a total of 6 ounces