Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

How do you rate the quality of people’s diets? Well, what could be more nutrient dense than a vegetarian diet? Indeed, if you compare the diet quality of vegetarian diets compared with nonvegetarian diets, the more plant-based diets do tend to win out, and the higher diet quality in vegetarian diets may help explain better improvements in health outcomes. However, vegetarians appeared to have higher refined grain intake, eating more foods like white rice and white bread that have been stripped of much of their nutrition. So, just because you’re eating a vegetarian diet doesn’t mean you’re necessarily eating optimally healthy.

Those familiar with the science know the primary health importance of eating whole plant foods. So, how about a scoring system that just adds up how many cups of fruit, and vegetables, and whole grains, and beans or chickpeas or split peas or lentils, and how many ounces of nuts and seeds per 1,000 calories, with or without counting white potatoes. Well, just looking at the total intake of whole plant foods doesn’t mean you’re not also stuffing doughnuts in your face. So, you could imagine proportional intake measures, based on calories or weight, to determine the proportion of your diet that’s whole plant foods. In that case, you’d get docked points if you eat things like animal-derived foods—meat, dairy, or eggs—or added sugars and fats.

My favorite proportional intake measure is McCarty’s Phytochemical Index, which I profiled previously. I love it because of its sheer simplicity, defined as the percent of dietary calories derived from foods rich in phytochemicals. So, it’s a score from 0 to 100, the percentage of your calories that are derived from foods rich in phytochemicals, which are biologically-active substances naturally found in plants that may be contributing to many of the health benefits obtained from eating whole plant foods. I mean, monitoring phytochemical intake in the clinical setting could have great utility in assisting people with optimizing their dietary intake for optimal health and disease prevention. However, the quantification of phytochemicals in foods or tissue samples is impractical—expensive, laborious; but hey, this concept of a ‘phytochemical index’ (PI) score could be an alternative, simple method of monitoring phytochemical intake.

Theoretically, a whole food, plant-based or vegan diet that excluded refined grains, white potatoes, hard liquors, and added sugars and oils could achieve a perfect score of 100, whereas sadly, the most current American diets might be lucky to hit 20. Let’s see what’s going on. In 1998, our shopping baskets were filled with about 20 percent whole plant foods, and more recently that has actually shrunk.

Wouldn’t it be interesting if researchers used this index to try to correlate it with health outcomes. That’s exactly what they did. Look, we know that studies have demonstrated vegetarian diets have a protective association with weight and body mass index—five dozen studies have shown that vegetarians had significantly lower weight and BMI compared with non-vegetarians. And even more studies show that high intakes of fruits, vegetables, whole grains, and beans may be protective, regardless of meat consumption. So, researchers wanted to use an index that gave points for whole plant foods. They used a phytochemical index, and tracked people’s weight over a few years––which I profiled in my video, ”Calculate Your Healthy Eating Score”––on a scale of 0 to 100, simply reflecting what percentage of your diet is whole plant foods. And even though the healthiest eating tier only averaged a score of about 40, which meant the bulk of their diet was still made up of processed foods and animal products, just making whole plant foods a substantial portion of the diet may prevent weight gain and decrease body fat. So, it’s not all or nothing. Any steps we can make to increase our whole plant food intake may be beneficial.

A couple more studies have been performed since, and they all point in the same direction. About a third of the odds of abdominal obesity at higher healthy plant intake, and significantly lower odds of high triglycerides. So, the index may be a useful dietary target for weight loss, where there is less focus on calorie intake and more on increasing intake of these high-nutrient lower-calorie foods over time. The latest such study, published 2020, suggests the same is true for childhood obesity.

Even at the same weight, the same amount of belly fat, those eating plant-based have higher insulin sensitivity, meaning the insulin they make works better in their body, perhaps thanks to the compounds in plants that alleviate inflammation and quench free radicals. And indeed, things seemed to improve as people ate more and more plants.

No wonder researchers found 91 percent lower odds of prediabetes for people getting more than half their calories from healthy plant foods. Significantly lower odds of metabolic syndrome and high blood pressure. Only about half the odds of being diagnosed with hypertension over a three-year period among those eating more plants. Even mental health was impacted; about 80 percent less depression, 2/3 less anxiety, 70 percent less psychological distress.

What about the Dietary Phytochemical Index and benign breast diseases, such as fibrocystic diseases, ductal ectasia, fatty necrosis, and all sorts of benign tumors? The same thing was found. Seventy percent lower odds. OK, but what about breast cancer? A higher intake of healthy plant foods was indeed associated with lower risk of breast cancer, even after controlling for a long list of other factors. And not just by a little bit. Eating twice the proportion of plants compared to the standard American diet was linked to more than 90 percent lower odds of breast cancer.

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