In this article, I explain my traffic light system for ranking the relative healthfulness of Green Light vs. Yellow Light vs. Red Light foods.
Whenever I’m asked at a lecture whether a specific food is healthy or not, my reply is: “Compared to what?” For example, are eggs healthy? Compared to some breakfast sausage next to it? Yes. But compared to oatmeal? Not even close. Imagine having $2,000 in your daily calorie bank. How do you want to spend it? For the same number of calories, you can eat either one Big Mac, 50 strawberries, or half a wheelbarrow full of salad greens. Those don’t exactly fill the same culinary niche—if you want a burger, you want a burger—and I don’t expect quarts of strawberries to make it onto the Dollar Menu any time soon, but it’s an illustration of how mountainous a nutritional bang you can get for the same caloric buck.
Every time we put something in our mouth, it’s a lost opportunity to put something even healthier in our mouth. So, what are the best foods to eat and the best foods to avoid?
I like to think of it in a traffic light system, which I describe in my video Dining by Traffic Light: Green Is for Go, Red Is for Stop, to help quickly identify some of the healthiest options. Green means go, yellow means caution, and red means stop…and think before you put it into your mouth.
Ideally, on a day-to-day basis, green category foods (unprocessed plant foods) should be maximized, yellow foods (processed plant foods and unprocessed animal foods) minimized, and red category foods (ultra-processed plant foods and processed animal foods) avoided. As far as I can figure, the best available balance of evidence suggests the most healthful diet is one that maximizes the intake of fruits, vegetables, legumes (beans, split peas, chickpeas, and lentils), whole grains, nuts and seeds, mushrooms, and herbs and spices. Real food that grows out of the ground, from fields not factories. These are our most healthful choices. In general, the more whole plant foods and the fewer processed and animal foods, the better. So, I’m talking about more green-light foods and less yellow- and red-light foods. Similar to running red lights in the real world, you may be able to get away with it once and awhile, but I wouldn’t recommend making a habit out of it.
My traffic light model stresses two important concepts: Plant foods tend to be more healthful than animal foods, in terms of being packed with protective nutrients (such as phytonutrients, antioxidants, potassium, and fiber) and fewer disease-promoting factors (including saturated fat, cholesterol, trans fat, and sodium), and unprocessed foods tend to be more healthful than processed foods. Is that always true? No. Am I saying that all plant foods are better than all animal foods? No. In fact, the worst thing on store shelves has been partially hydrogenated vegetable shortening like Crisco, and that even has “vegetable” right in its name! Even some unprocessed plants, such as blue-green algae, can be toxic, and anyone who has ever had a bad case of poison ivy knows plants don’t always like to be messed with. In general, though, choose plant foods over animal foods, and unprocessed foods over processed.
What do I mean by processed? The classic example is the milling of grains from whole wheat to white flour. Isn’t it ironic that these grains are then called “refined,” a word that means improved or made more elegant? The elegance was not felt by the millions who died in the 19th century from beriberi, a vitamin B-deficiency disease that resulted from polishing rice from brown to white. White rice is now enriched with vitamins to compensate for the “refinement.” A Nobel Prize was awarded for the discovery of the cause of beriberi and its cure—rice bran, the brown part of rice. Beriberi can cause damage to the heart muscle, resulting in sudden death from heart failure. Surely, such a thing could never happen in modern times, right? An epidemic of heart disease that could be prevented and cured with a change in diet? For more on this, check out my videos on heart disease here.
Sometimes, processing can make foods more healthful. For example, tomato appears to be the one common juice that may actually be more healthful than the whole fruit. The processing of tomato products boosts the availability of its antioxidant red pigment by as much as five-fold. Similarly, the removal of fat from cacao beans to make cocoa powder improves the nutritional profile, since cocoa butter is one of the rare saturated plant fats, along with coconut and palm kernel oils, that may raise cholesterol.
So, for the purposes of the traffic light model, I like to think of “unprocessed” as nothing bad added and nothing good taken away. In the above example, tomato juice could be thought of as relatively unprocessed because even much of the fiber is retained. If salt is added, though, that would make it a processed food in my book and bump it out of the green-light zone. Similarly, I would consider chocolate as a processed food (since it has added sugar), but cocoa powder not.
The limited role I see for yellow-light foods in a healthy diet is to promote the consumption of green-light foods. Yellow-light foods can be the spoonful of sugar that makes the medicine go down. If the only way I can get a patient to eat oatmeal in the morning is to make it creamy with almond milk, then I tell them to add almond milk. The same could be said for red-light foods. If the only way you’re going to eat a big salad is to sprinkle on something like Bac-Os, then sprinkle away.
Bac-Os are an example of what I refer to as an ultra-processed food, one that bears no redeeming nutritional qualities or resemblance to anything that grew out of the ground, and often has added badness. Bac-Os has added trans fats, salt, sugar, and even Red 40, a food dye that may cause thousands of thyroid cancers every year. As a red-light food, it should ideally be avoided, but if the alternative to your big spinach salad with something like Bac-Os is KFC, then it’s better to sprinkle on some Bac-Os. The same even goes for real bacon bits.
I realize some people have religious or ethical objections to even trivial amounts of animal products. Growing up Jewish next to the largest pig factory west of the Mississippi, I can relate to both sentiments. But, from a human health standpoint, when it comes to animal products and processed foods, it’s the overall diet that matters. For example, without hot sauce, my intake of dark green leafy vegetables would plummet. I could try making my own from scratch, of course, but for the time being, the “green” ends justify the “red” means.
On the same note, it’s really the day-to-day that matters most. It shouldn’t make a big difference what we eat on special occasions. Feel free to decorate your birthday cake with edible bacon-flavored candles (I’m not making those up!), though I guess from a food safety point of view, a raw cake batter Salmonella infection could leave you in dire straits. In general, though, it’s really your regular routine that determines your long-term health. Our body has a remarkable ability to recover from sporadic insults, as long as we’re not habitually poking it with a fork.
That’s why, from a medical standpoint, I don’t like the terms vegetarian and vegan, because they are defined by what you don’t eat. When I taught at Cornell, I had vegan students who appeared to be living off of french fries and beer. Vegan, perhaps, but not terribly health-promoting. That’s why I prefer the term whole food plant-based nutrition. In general, the dividing line between health-promoting foods and disease-promoting foods may be less plant-sourced versus animal-sourced foods, and more whole plant foods versus most everything else.
Every time we eat, we have an opportunity to enjoy something even healthier. I use a traffic light system when I look at food to quickly rank their relative healthfulness: green means go, yellow means caution, and red means stop and think before you put it into your mouth.
Green-light foods (unprocessed plant foods) should be maximized, yellow-light foods (processed plant foods and unprocessed animal foods) should be minimized, and we should avoid red-light foods (ultra-processed plant foods and processed animal foods).
The best available balance of evidence suggests the most healthful diet maximizes consumption of fruits, vegetables, legumes (beans, split peas, chickpeas, and lentils), whole grains, nuts and seeds, mushrooms, and herbs and spices.
Plant foods, which are typically more healthful than animal-based foods, are higher in protective nutrients, such as phytonutrients, antioxidants, potassium, and fiber, and lower in disease-promoting factors, including saturated fat, cholesterol, trans fat, and sodium. And, unprocessed foods tend to be more healthful than processed foods.
The classic example is a processed food is the milling of grains from whole wheat to white flour.
Processing doesn’t always lower the healthfulness of a food. For instance, tomato appears to be the one common juice that may be more healthful than the whole fruit because the processing of tomato products boosts the availability of its antioxidant red pigment by as much as five-fold.
In terms of my traffic light system, I think of “unprocessed” as nothing bad added and nothing good taken away.
There is a role for yellow-light foods, albeit a limited one—to promote the consumption of green-light foods. For example, if adding a yellow-light food to a green-light food is the only way you will eat it, then it’s worthwhile. Add almond milk to oatmeal, for example, if plain oatmeal isn’t creamy enough for you to eat it.
Ultra-processed foods have no redeeming nutritional qualities, don’t resemble anything that grew out of the ground, and often have added badness—e.g., Bac-Os, with their added trans fats, salt, sugar, and even Red 40, a food dye that may cause thousands of thyroid cancers every year. As a red-light food, it should ideally be avoided, but if the alternative to a spinach salad with Bac-Os is KFC, then sprinkle on some Bac-Os to avoid the even worse red-light meal.
Your regular routine determines your long-term health, so don’t place great significance on a special occasion meal here or there. Our body has a remarkable ability to recover from sporadic insults—just don’t constantly, habitually assault it with a fork.
I prefer the term “whole food, plant-based nutrition” to “vegetarian” or “vegan” because you can be veg*n without being health-promoting in your diet.
Generally speaking, the line in the same between health-promoting foods and disease-promoting foods may be less plant-sourced versus animal-sourced foods, and more whole plant foods versus most everything else.
This is one of those rare blogs I’ve done that’s not just straight peer-reviewed science. If you’re looking for more of this type of analysis, look no further than How Not to Die—more specifically, the whole second half of my book, which contains exactly that. Note that all of the recipes from its companion, The How Not to Die Cookbook, are comprised of 100 percent Green Light ingredients. How do you make something taste salty without salt? Sweet without sugar? Check out my cookbook and see—and then taste—for yourself! (All proceeds I receive from all my books are donated to charity.)
I explore another one of the tools I introduced in the book in my video Dr. Greger’s Daily Dozen Checklist.
Let me know if you like these more practical tips-type blogs, or if you’d rather I just stick to the science.
Michael Greger, M.D.
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