Toward a Diet That Prevents Cancer

New research says eating in accordance with the "Dietary Guidelines for Americans" correlates with lower risks of pancreatic cancer.

Only around one in five people who are diagnosed with pancreatic adenocarcinoma are offered the surgery to try and treat it. Usually by the time we find it, the disease is too advanced to try to remove. Even for those who do undergo the aggressive surgery, there is only a 25 percent chance that they will live five years.

So we're always looking for ways to prevent it. It's pretty well-established that smoking, obesity, and being sedentary increase our risk of pancreatic cancer. The relationship to diet is debated. People with lower levels of lycopene and selenium in their blood, for example, seem to be at higher risk — though we don't have evidence that we should be taking lycopene and selenium supplements. There's a lot of lycopene in fruit, and some studies tell us that eating more fruit and vegetables seems to be good, but that association hasn't held up in every study. Many blame the "Western" diet (high intake of fat and/or meat, particularly smoked or processed meats, refined grains, and sugars and lower intakes of fruits, vegetables, and whole grains) as a risk factor — especially because rates of pancreatic cancer are so, much higher in Western countries than many other parts of the world — though that variable also hasn't held up in prospective studies.

Pancreatic Cancer Rates

So it's good to see a solid study out this week in the Journal of the National Cancer Institute that says we seem to be on the right track diet-wise.
As you probably know, every five years since 1980 the U.S. government has issued new Dietary Guidelines for Americans. That once included acknowledging the now-infamous 1958 carb-based food pyramid. (But that was the 80s, when carbs were good.)The guidelines since are increasingly based in research and evidence. They'll continue to change as we learn more. They aren't specifically meant to protect us from cancer; just to get us as healthy as possible.
So Dr. Hannah Arem and a team at the National Institutes of Health wanted to see if we're on the right track. They calculated the Health Eating Indices (HEIs) of 537,218 people based on the guidelines (the 2005 version, which has since been lightly updated, in 2010), and then compared them to pancreatic cancer rates. 2,383 people ended up getting pancreatic cancer, but they were 15 percent less likely to get it if they had the highest HEIs as compared to the lowest. Arem's team controlled for other variables like diabetes and smoking.
According to Arem and colleagues, “[these] findings support the hypothesis that a high-quality diet may also play a role in reducing pancreatic cancer risk.”
Health Eating Index scoring
(USDA, 2005)

In accompanying commentary, Drs. Rachel Ballard-Barbash and Susan Krebs-Smith of the National Cancer Institute, along with Dr. Marian Neuhouser from the Hutchinson Cancer Research Center, seem on board with the study. They write, in long sentences, "Food based indices such as the HEI may provide a superior and more comprehensive analytic approach to characterizing our complex diets and their association with health outcomes compared with reductionist approaches focused on single foods or isolated nutrients."

(They're talking to you, lycopene!)

Arem made the same point in the original article: "There may be biologic interaction or synergy between different nutrients and/or dietary constituents/components that is not captured when assessing single foods or nutrients." So their conclusion is the bigger-picture "consuming a high-quality diet may reduce the risk of pancreatic cancer."

It's too bad we can't shake our fists at, or fill our totes with, one or two specific foods/nutrients. But with diet that's rarely the case, and at least now we can feel like we're doing something right (or wrong). Pancreatic cancer can be terrifying, so even if only as a conceptual step toward more progress and reassurance, this is not nothing.

Here is where we stand on defining "high-quality diet" as a country—the highlights of the 2010 guidelines:

• Increase vegetable and fruit intake.

• Eat a variety of vegetables, especially dark-green and red and orange vegetables and beans and peas.
• Consume at least half of all grains as whole grains. Increase whole-grain intake by replacing refined grains with whole grains.
• Increase intake of fat-free or low-fat milk and milk products, such as milk, yogurt, cheese, or fortified soy beverages.
• Choose a variety of protein foods, which include seafood, lean meat and poultry, eggs, beans and peas, soy products, and unsalted nuts and seeds.
• Increase the amount and variety of seafood consumed by choosing seafood in place of some meat and poultry.
• Replace protein foods that are higher in solid fats with choices that are lower in solid fats and calories and/or are sources of oils.
• Use oils to replace solid fats where possible.
• Choose foods that provide more potassium, dietary fiber, calcium, and vitamin D, which are nutrients of concern in American diets. These
foods include vegetables, fruits, whole grains, and milk and milk products.
Finally, since it's kind of become my beat, I will mention that there have been studies on coffee. That may be because Western countries do drink it in aggressively disproportionate amounts. Some studies did, unfortunately, find an elevated risk of pancreatic cancer with higher levels of coffee consumption. But, more importantly, a large analysis of the studies in aggregate last year (37 case-control and 17 cohort studies) did not find a statistically significant risk.
So the story remains, everything good in moderation. For now the same as it was three decades ago when the original Dietary Guidelines for Americans told us: "Food alone cannot make you healthy."