Combating Air Pollution Effects with Food

There is a food that offers the best of both worlds—significantly improving our ability to detox carcinogens like diesel fumes and decreasing inflammation in our airways—all while improving our respiratory defenses against infections.

Outdoor air pollution may be the ninth leading cause of death and disability in the world, responsible for millions of deaths from lung cancer, emphysema, heart disease, stroke, and respiratory infection. In the United States, living in a polluted city was associated with 16, 27, and 28 percent increases in total, cardiovascular, and lung cancer deaths, compared to living in a city with cleaner air. As well, living in a city with polluted air may lead to up to a 75 percent increase in the risk of a heart attack. “Additionally, the possibility of dying in a traffic jam is two and a half times greater in a polluted city.” No one wants to be living in a traffic jam, but it’s better than dying in one.

In addition to causing deaths, air pollution is also the cause of a number of health problems. It may not only exacerbate asthma but also increase the risk of developing asthma in the first place. These pollutants may trigger liver disease and even increase the risk of diabetes. Indeed, “even when atmospheric pollutants are within legally established limits, they can be harmful to health.” So, what can we do about it?

Paper after paper have described all the terrible things air pollution can do to us, but “most…failed to mention public policy. Therefore, while science is making great strides in demonstrating the harmful effects of atmospheric pollution on human health, public authorities are not using these data” to reduce emissions, as such measures might inconvenience the population “and, therefore, might not be politically acceptable.” We need better vehicle inspections, efficient public transport, bus lanes, bicycle lanes, and even urban tolls to help clean up the air, but, while we’re waiting for all of that, is there anything we can do to protect ourselves?

As I discuss in my video Best Food to Counter the Effects of Air Pollution, our body naturally has detoxifying enzymes, not only in our liver, but also lining our airways. Studies show that people born with less effective detox enzymes have an exaggerated allergic response to diesel exhaust, suggesting that these enzymes actively combat the inflammation caused by pollutants in the air. A significant part of the population has these substandard forms of the enzyme, but, either way, what can we do to boost the activity of whichever detoxification enzymes we do have?

One of my previous videos Prolonged Liver Function Enhancement from Broccoli investigated how broccoli can dramatically boost the activity of the detox enzymes in our liver, but what about our lungs? Researchers fed some smokers a large stalk of broccoli every day for ten days to see if it would affect the level of inflammation within their bodies. Why smokers? Smoking is so inflammatory that you can have elevated C-reactive protein (CRP) levels for up to 30 years after quitting, and that inflammation can start almost immediately after you start smoking, so it’s critical to never start in the first place. If you do, though, you can cut your level of that inflammation biomarker CRP nearly in half after just ten days eating a lot of broccoli. Broccoli appears to cut inflammation in nonsmokers as well, which may explain in part why eating more than two cups of broccoli, cabbage, cauliflower, kale, or other cruciferous veggies a day is associated with a 20 percent reduced risk of dying, compared to eating a third of a cup a day or less, as you can see at 3:41 in my video.

What about air pollution? We know that the cruciferous compound “is the most potent known inducer” of our detox enzymes, so most of the research has been on its ability to fight cancer. But, for the first time, researchers tried to see if it could combat the pro-inflammatory impact of pollutants, such as diesel exhaust. They put some human lung lining cells in a petri dish, and, as you can see at 4:11 in my video, the number of detox enzymes produced after dripping on some broccoli goodness skyrocketed. Yes, but we don’t inhale broccoli or snort it. We eat it. Can it still get into our lungs and help? Yes. After two days of broccoli sprout consumption, researchers took some cells out of the subjects’ noses and found up to 100 times more detox enzyme expression compared to eating a non-cruciferous vegetable, alfalfa sprouts. If only we could squirt some diesel exhaust up people’s noses. That’s just what some UCLA researchers did, at an amount equal to daily rush hour exposure on a Los Angeles freeway. Within six hours, the number of inflammatory cells in their nose shot up and continued to rise. But, in the group who had been getting a broccoli sprout extract, the inflammation went down and stayed down, as you can see at 4:58 in my video

Since the dose in those studies is equivalent to the consumption of one or two cups of broccoli, their study “demonstrates the potential preventive and therapeutic potential of broccoli or broccoli sprouts,” but if broccoli is so powerful at suppressing this inflammatory immune response, might it interfere with normal immune function? After all, the battle with viruses like influenza can happen in the nose. So what happens when some flu viruses are dripped into the nostrils of broccoli-sprout eaters compared with people consuming non-cruciferous alfalfa sprouts? After eating broccoli sprouts, we get the best of both worlds—less inflammation and an improved immune response. As you can see at 5:55 in my video, after eating alfalfa sprouts, there is a viral spike in their nose. After eating a package of broccoli sprouts every day, however, our body is able to keep the virus in check, potentially offering “a safe, low-cost strategy for reducing influenza risk among smokers and other at risk populations.”

So, better immune function, yet less inflammation, potentially reducing the impact of pollution on allergic disease and asthma, at least for an “enthusiastic broccoli consumer.” But what about cancer and detoxifying air pollutants throughout the rest of our body? We didn’t know, until now. Off to China, where “levels of outdoor air pollution…are among the highest in the world.” By day one, those getting broccoli sprouts were able to get rid of 60 percent more benzene from their bodies. “The key finding…was the observed rapid and highly durable elevation of the detoxification of… a known human carcinogen.” Now, this was using broccoli sprouts, which are highly concentrated, equivalent to about five cups of broccoli a day, so we don’t know how well more modest doses would work. But if they do, eating broccoli could “provide a frugal means to attenuate…the long-term health risks” of air pollution. More on air pollution here.

I’ve been reading about the terrible effects of air pollution for a long time and I am thrilled there’s something we can do other than uprooting our families and moving out to the countryside.


For more on cruciferocity, see my videos Lung Cancer Metastases and Broccoli and Breast Cancer Survival Vegetable.

There’s a secret to maximizing broccoli’s benefits. See Flashback Friday:Second Strategy to Cooking Broccoli.

For more on Cooking Greens: How to Cook Greens and Best Way to Cook Vegetables.

What about broccoli sprout pills? See Broccoli: Sprouts vs. Supplements.

Speaking of respiratory inflammation, what about dietary approaches to asthma? Learn more:

There are sources of indoor pollution, too. See Throw Household Products Off the Scent.

There is one way what we eat can directly impact air pollution, beyond just personal protection. Check out Flashback Friday: Diet and Climate Change: Cooking Up a Storm.

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:

We Have Specific Fruit and Vegetable Receptors

According to a recent survey, the number of Americans adults who say they are eating ‘pretty much whatever they want’ is at an all-time high,” which unfortunately includes “too few fruits and vegetables,” as well as “too little variety.” Half of all fruit servings are taken up by just six foods: orange juice, bananas, apple juice, apples, grapes, and watermelons. Only five foods—iceberg lettuce, frozen potatoes, fresh potatoes, potato chips, and canned tomatoes—make up half of all vegetable servings. We’re not only eating too few fruits and veggies. We’re also missing out on the healthiest fruits, which are berries, and the healthiest vegetables, which are dark green leafies. The fruit and vegetable palette for our palate is sadly lacking.

Why does dietary diversity matter? As I discuss in my video Specific Receptors for Specific Fruits and Vegetables, different foods may affect different problems. Cabbage, cauliflower, broccoli, and Brussels sprouts are associated with lower risk of colon cancer in the middle and right side of our body, whereas risk of colon cancer further down on the left side of our body appears to be better lowered by carrots, pumpkins, and apples. So, “different F/V [fruits and vegetables] may confer different risks for cancer” of different parts of even the same organ.

Variety is the spice of life—and may prolong it. “Independent from quantity of consumption, variety in fruit and vegetable consumption may decrease lung cancer risk,” meaning if two people eat the same number of fruits and vegetables, the one eating a greater variety may be at lower risk.

It’s not just cancer risk. In a study of thousands of men and women, a greater quantity of vegetables and a greater variety may independently be beneficial for reducing the risk of type 2 diabetes. Even after removing the effects of quantity, “each different additional two item per week increase in variety of F&V [fruit and vegetable] intake was associated with an 8% reduction in the incidence of T2D [type 2 diabetes].” Why? Well, it “may be attributable to individual or combined effects of the many different bioactive phytochemicals contained in F&V. Thus, consumption of a wide variety of F&V will increase the likelihood of consuming” more of them.

“All the vegetables may offer protection…against chronic diseases,” but “[e]ach vegetable group contains a unique combination and amount of these [phytonutrients], which distinguishes them from other groups and vegetables within their own group.” Indeed, because “each vegetable contains a unique combination of phytonutriceuticals (vitamins, minerals, dietary fiber and phytochemicals), a great diversity of vegetables should be eaten…to get all the health benefits.”

Does it matter, though, if we get alpha-carotene or beta-carotene? Isn’t an antioxidant an antioxidant? No. “It has been shown that phytochemicals bind to specific receptors and proteins” in our bodies. For example, our body appears to have a green tea receptor—that is, a receptor for EGCG, which is a key component of green tea. There are binding proteins for the phytonutrients in grapes, onions, and capers. In my video The Broccoli Receptor: Our First Line of Defense, I talk about the broccoli receptor, for instance. Recently, a cell surface receptor was identified for a nutrient concentrated in apple peels. Importantly, these target proteins are considered indispensable for these plants foods to do what they do, but they can only do it if we actually eat them.

Just like it’s better to eat a whole orange than simply take a vitamin C pill, because, otherwise, we’d miss out on all the other wonderful things in oranges that aren’t in the pill, by just eating an apple, we’re also missing out on all the wonderful things in oranges. When it comes to the unique phytonutrient profile of each fruit and vegetable, it truly is like comparing apples to oranges.


This is one of the reasons I developed my Daily Dozen checklist of foods to incorporate into one’s routine. Download the free iPhone and Android apps, and be sure to watch my video Dr. Greger’s Daily Dozen Checklist.

I discuss how produce variety—not just quality and quantity—may be important in Apples and Oranges: Dietary Diversity and Garden Variety Anti-Inflammation, so I hope you’ll check them out. You can also learn more about why combining certain foods together may be more beneficial than eating them separately in Food Synergy.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

Plant vs. Animal Food Purines for Preventing Gout

More than 2,000 years ago, “Hippocrates described gout as a disease of kings primarily because it was the wealthy who could afford the ‘rich’ foods, which seemed to precipitate gouty attacks.” Today, however, we can all eat like kings and acquire some diseases of royalty ourselves. That’s why I produced my video Preventing Gout Attacks with Diet.

Gout is caused by needle-sharp crystals of uric acid in our joints. Uric acid comes from the breakdown of purines, which are the breakdown product of genetic material—DNA, the foundation of all life. So, “there is no such thing as a purine-free diet, but foods do vary in their purine content.” It was long thought that people with gout just needed to stay away from all high-purine foods, whether from animals, like organ meats, or plants, like beans, but this strategy proved ineffective. Yes, all uric acid comes from the breakdown of purines, so limiting meat makes sense, but plant sources “have largely been exonerated.”

“The association of gout with alcohol intake and increased dietary purine consumption had been known since ancient times, but there were no prospective trial data” to back it up until fairly recently. The Harvard Health Professionals Follow-Up Study, which followed about 50,000 men for a dozen years, found that alcohol intake was “strongly associated with an increased risk of gout.” In terms of food, they found “an increased risk of gout with higher meat consumption or seafood consumption,” but not with higher consumption of purine-rich plant foods. Perhaps this is because the purines in plants are less bioavailable? So, though it had been suggested that gout sufferers should moderate purine-rich animal and plant foods, their “results suggest that this type of dietary restriction may be applicable to purines of animal origin but not to purine-rich vegetables.”

Although it was not surprising that meat, including seafood, had significant associations with the incidence of gout, this lack of effect of purine-rich plant foods was new. There don’t appear to be any long-term studies showing purine-rich plant foods increase risk, though there are still some guidelines continuing to disseminate those outdated recommendations.

Not only has the intake of purine-rich plants not been associated with high uric acid levels, but the vegetables gout sufferers are specifically told to stay away from—mushrooms, peas, beans, lentils, and cauliflower—were actually found to be protective. This may be because foods rich in fiber, folate, and vitamin C appear to protect against uric acid buildup and gout. “Fiber,” for example, “has been recognized as having a potential role in binding uric acid in the gut for excretion.”

Lack of association between purine-rich vegetables and urate could be due to the co-packaging of these “beneficial plant components (such as vitamin C, dietary fiber or some phytochemicals), which may have masked an effect of purine on [uric acid]. Vegetable intake, regardless of purine content, may also be protective as it may increase [uric acid] excretion.”

By changing the pH of our urine, we can change uric acid clearance. Eating an alkaline diet, which was a vegetarian diet in the case of the study I profile in my video, was found “effective for removing uric acid from the body.” Those eating the alkaline diet excreted significantly more uric acid than those eating the acidic diet. As such, uric acid levels in the blood of those eating the acid-forming diet rose within days.

So, one would assume uric acid levels are lower in vegetarians, and, indeed, those eating vegetarian diets long-term were found to have significantly lower levels in their blood. To prove cause and effect, though, you need to do an interventional trial, where you take people, change their diets, and see what happens. Researchers took ten guys to study the build-up of uric acid in their kidneys, kept them on a standard Western diet for five days, and measured their relative supersaturation for uric acid. Then, they tried a vegetarian diet for five days. The result? Within days, the intake of the vegetarian diet led to a 93 percent decline in the risk of uric acid crystallization.

You can do it the other way, too: Take a bunch of people with gout, feed them a big meal of meat, and see if you can trigger an attack. Seven patients were put in a hospital, “stabilized on a low-purine diet and then challenged with a meat-laden dinner.” In response, their uric acid levels shot up, and they started getting gout attacks. Then they added alcohol, and their uric acid levels shot up even further. In all, the researchers were able to trigger gout attacks in six out of the seven patients with just single meals.

Now, some meats have less purines than others. For those who aren’t squeamish, inches-long superworms, for example, have particularly low purine levels.

Not all animal foods increase gout risk, though. Low-fat dairy products were found to be protective. Given that, we would predict vegans to be at a disadvantage, which is indeed what was found, though all groups tested—meat eaters, fish eaters, vegetarians, and vegans—were within the normal range of around 3.5 to 7.

Should gout patients add milk to their diets? Well, although drinking the equivalent of ten cups of skim milk at a time appears to have an acute lowering effect on uric acid levels, in the long term over months, at the equivalent of two cups a day, there was not a statistically significant lowering effect. Gout patients were given skim milk powder for three months, and it did not appear to help. Though soymilk has also been associated with a lower risk of uric acid buildup, there are no interventional trials to back that up.

The bottom line is that we now have good research on how to reduce risk of gout “without the use of drug treatments through modification of diet.” That’s important, because allopurinol is the “drug of choice.” It’s considered generally safe, but what does it mean when doctors talk about a relatively safe drug? Well, about “2% of patients develop hypersensitivity reactions, which can sometimes be severe and fatal with a mortality rate of ~20%”—and that’s the safe drug. The other leading drug, colchicine, has “no clear-cut distinction between nontoxic, toxic, and lethal doses.”


A better choice is through diet, and these videos show you how sweet that diet choice can be:

And, for alkalinizing your urine, see How to Treat Kidney Stones with Diet and Testing Your Diet with Pee and Purple Cabbage.

Uric acid is double-edged sword, as both high and low levels are associated with increased mortality. If our uric acid levels are too high, we can get gout; if they’re too low, it may increase our risk of neurodegenerative diseases such as Alzheimer’s and Parkinson’s. This is presumed to be because uric acid acts as a powerful brain antioxidant. See my videos Miocene Meteorites and Uric Acid and Parkinson’s Disease and the Uric Acid Sweet Spot for more on this.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations: