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:

What to Eat to Boost Immunity

What we eat—or don’t eat—can affect our immune system. In my video Using the Produce Aisle to Boost Immune Function I profile a study conducted to determine the effect of the consumption of brightly colored vegetables on the immune system. For the first two weeks, the subjects ate basically no fruits and veggies. Then, they drank one and a half cups of tomato juice every day for two weeks, followed by two weeks of carrot juice, and then two weeks of spinach powder. Within just two weeks of a fruit- and veggie-deficient diet, immune function plummeted. However, just one and a half cups of tomato juice a day brought subjects back from the ashes. It didn’t take five servings a day—just one tall glass of tomato juice produced results. The carrot juice alone didn’t seem to help as well, however, nor did the powder equivalent of about one serving of spinach. This tells me two things: how remarkably we can affect our immune function with simple dietary decisions and, not all veggies are alike.

When this study was repeated looking at other immune markers, the tomato versus carrot appeared more evenly matched. There is one family of vegetables, however, that we definitely don’t want to miss out on. Inflammation and leaky gut can occur all because of an absence in our diet of AHR ligands—in other words, cruciferous vegetables, including cabbage, collards, cauliflower, kale, Brussels sprouts, and broccoli.

Do people who eat healthier actually get sick less? Those who eat more fruits and vegetables appear to have a lower risk of getting an upper respiratory tract infection like the common cold, whether they’re otherwise vegetarian or not. Even just one added apple a day may help keep the doctor away. The common cold is usually so innocuous, though, so why not test against something stronger?

Researchers have also looked at more serious respiratory infections like influenza. Studying the relationship between various risk factors and influenza-related hospitalizations in the United States, they found that a 5 percent increase in the prevalence of obesity was associated with a 6 percent increase in hospitalization rate. Physical inactivity had worse outcomes, resulting in a 7 percent increase in hospitalizations. Low fruit and vegetable consumption, however, had the most impact, increasing flu-related hospitalization rates by 8 percent.

The common cold isn’t always innocuous, though. For instance, a cold during the first trimester of pregnancy is associated with a number of birth defects, including anencephaly, one of the worst, which causes a fatal malformation of the brain. More recent data suggest that the cold-related fever is the real culprit, as anti-fever drugs appear able to prevent the possible birth defects caused by the common cold.

It’s best, of course, not to get sick in the first place. One thousand women and their diets were followed before and during pregnancy. It was found that “[w]omen who consume more fruits and vegetables have a moderate reduction in risk of [upper respiratory tract infection] during pregnancy, and this benefit appears to be derived from both fruits and vegetables instead of either alone.” Whole fruits and vegetables provide a natural balance of all sorts of things that may improve our immune function in a “complementary, combined or synergistic manner that could account for the protective effect observed from high consumption of both fruits and vegetables”—or maybe that’s the only way they got enough in their diet. The women who appeared protected in this study were eating nearly nine servings of fruits and vegetables a day, compared with only five servings of fruits or four of veggies. This suggests that the arbitrary five- or six-a-day minimum may be insufficient for effective immune function.

For example, in one famous study, elderly individuals were randomized into groups that ate either five servings of fruit and veggies a day or two servings a day. The five-a-day group showed an 80 percent improved antibody response to their pneumonia vaccination compared to the two-a-day group. Even though only about 30 percent (12 out of 40 people) of the five-a-day group reached their target levels of servings, they still did six times better than the two-a-day group. But maybe eight, nine, or ten servings a day would have worked even better.


Need a reminder about what those protective Ah receptors are? See The Broccoli Receptor: Our First Line of Defense and Counteracting the Effects of Dioxins Through Diet.

What’s the best way to prepare broccoli? Check out these videos:

In late pregnancy, however, women can overdo it. See Caution: Anti-Inflammatory Foods in the Third Trimester.

What else can we do to lower our risk of upper respiratory tract infections? See:

Also be sure to check out my video, Are Happier People Actually Healthier?, which compares people’s resistance to having the common cold virus dripped into their nostrils.

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: