By Michael Greger M.D. FACLM on December 21, 2021

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. 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. .. These are our most healthful choices.

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.

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 (fake bacon pieces), 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.

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.