Ongoing research on how diet influences cancer has produced new perspectives on what makes a healthy diet. You’re probably hearing the term “diet quality” more often as researchers and health professionals need new ways to study how nutrition supports health.
Years ago, research on diet’s influence on risk of diseases like cancer, heart disease and type 2 diabetes often focused on a few individual nutrients. For example, you probably heard a lot about specific vitamins or macronutrients such as fat and carbohydrates. In more recent years, research shows that the foods you eat and how they come together in an overall dietary pattern is likely more important than any single component of those foods. This is often referred to as the “food matrix,” where the whole food or whole diet matters more than any one nutrient in isolation.
With this angle in mind, researchers have new ways to study people’s diets, often with indexes that score diet quality. It has also changed how we talk about healthy eating as we focus more on what makes a healthy dietary pattern—and how different people can achieve it in different ways.
Let’s look at the American Institute for Cancer Research (AICR) Cancer Prevention Recommendations in the context of current research on diet quality.
Principle #1: Emphasize Plant Foods
Scoring systems have been developed to showcase how certain dietary patterns can help with disease prevention. They all focus on nutrient-rich plant foods (vegetables, fruits, whole grains, pulses like dried beans and lentils) as the largest part of the plate. Nuts and healthy oils provide most of the fat. Animal foods can fit, but in smaller amounts; and choices like red and processed meat, unhealthy fats and sweets are discouraged. A Mediterranean diet is one example of a dietary pattern that emphasizes plant foods.
AICR Recommendations provide a blueprint for a healthy, plant-focused dietary pattern by calling for a diet rich in whole grains, vegetables, fruits and beans. The goal of reaching at least 30 grams of dietary fiber each day can only be accomplished when plant-based foods are major elements in your eating choices throughout the day.
Principle #2: Quality of Plant Foods Matters
Dietary patterns that focus on plant foods promote the best overall health. The first studies using Plant-Based Diet Index scores awarded points for the balance of plant versus animal foods in the diet. The studies showed a lower risk of type 2 diabetes and heart disease in people following dietary patterns that included more plant foods.
Researchers then revised the system, creating a Healthy Plant-Based Diet Index that only adds points for plant foods that supply valuable nutrients and plant compounds and subtracts points for those with high levels of unhealthy fats and added sugars. These scores are even more strongly linked to health, including lower risk of some types of cancer.
Whole vs. ultra-processed plant foods: Plant foods that are highly processed do not contain as many beneficial nutrients as whole plant foods. Think about it like this: French fries started out as plants—they are made from potatoes and vegetable oil. The process of deep frying and adding salt changes their nutritional value. Flour and sugar also come from plants, but cake and cookies aren’t the foods that researchers are referring to when they recommend plant-based eating.
The plant foods you choose may also influence weight gain. One study followed a group of adults who did not originally have obesity. Those with higher scores for healthy plant-based foods were less likely to develop obesity. Yet those with higher scores on an index showing more unhealthy plant foods (with more refined grains and added sugars) were more likely to develop obesity.
AICR Recommendations focus on the nutritional quality of plant food choices. Choose nutrient-rich whole plant foods (vegetables, fruits, whole grains, beans, nuts) and limit sugar-sweetened drinks and ultra-processed foods that are high in added fats, starches or added sugars.
The AICR Recommendations go even further in promoting diet quality, since quality matters for plant foods and animal foods. The Healthy Plant-Based Diet Index system subtracts points equally for all animal foods. In contrast, AICR advises limiting consumption of red meat (like beef, lamb and pork) to no more than 12 to 18 ounces per week. Processed meat especially increases risk of colorectal cancer (and heart disease), so Recommendations call for limiting processed meat even more carefully. Yet poultry and fish don’t increase risk of cancer (or other chronic diseases), so there’s room for them in a healthy diet as long as plant foods remain the focus of the plate.
Principle #3: Choose the Path to Diet Quality that’s Right for You
There’s no single “best” diet for everyone. Diet quality pays off more and more over time, so it’s important to create a healthy dietary pattern that you can maintain. There’s always learning involved when you change habits, but my practical experience as a dietitian is consistent with research showing that most people are better able to stick with a diet that can fit their food preferences, cultural background, economic situation, lifestyle and health needs.
- Mediterranean-style diets protect health in many ways. But studies in Scandinavia (where food availability and cultural traditions differ from those in the Mediterranean) have been showing that traditional dietary patterns can be adapted to fit current recommendations for a healthy diet. And various forms of Asian-style dietary patterns also show lots of ways to focus on plant foods and limit red meat and sweets. Dietary patterns originating from cultures all around the world can fit the principles of diet quality.
- Mostly plant-based diets are consistently linked with better health. But a diet that includes only plant foods is simply one option for such a pattern. Don’t get confused by study headlines—one review found that nearly half of studies on “plant-based diets” included at least some kinds of animal foods in moderation.
- Diet quality doesn’t mean diet perfection. Studies showing that higher quality diets are linked with better health often compare people with the highest dietary scores to those with the lowest scores. Even more helpful, when studies analyze results across all diet quality scores, they usually show that each step up in diet quality is associated with a bit lower risk of chronic diseases.
AICR Recommendations meet this call for individual action and flexibility and go a few steps further for reducing cancer risk and promoting overall health. Diet quality is a vital part of a healthy lifestyle—but it’s not the only element.
AICR Recommendations also remind us to:
- Limit alcohol
- Maintain a weight that’s healthy for you
- Choose portions that are right for you
- By physically active as part of everyday life
Studies have used a scoring system to identify how closely people’s lifestyle habits come to the AICR Recommendations. The results? In general, we see a lower risk of cancer with each increase in score. Studies among people diagnosed with cancer are limited so far. But emerging evidence links higher scores with fewer deaths in several cancers, greater health-related quality of life and better overall health.
In other words, current research supports paying attention to overall diet quality and how your eating habits can promote health. The AICR Cancer Prevention Recommendations help you achieve better diet quality and highlight healthy eating as one part of a healthy lifestyle.
Looking for a plant-based diet? Start with AICR’s New American Plate for the big picture view of diet quality. And if you want some help to get closer to the blueprint provided by the Recommendations, take it step by step with the free online program, AICR’s Healthy10 Challenge.
This announcement was originally released on June 13, 2023, by the American Institute for Cancer Research. It is republished with permission.