Quinoa-Kale bowl

This delicious and filling entrée salad with south-of-the-border flavors is one of my favorite new dishes. It’s related to my Burrito Bowl, but calls for quinoa instead of rice, adds steamed kale, and is topped with a creamy, tangy, cilantro-lime dressing. Above: The romaine lettuce is on the bottom, with rows of goodies on top: kale, chopped red onion,...

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What to Eat to Protect Against Kidney Cancer

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58,000 Americans are diagnosed with kidney cancer every year, and 13,000 die. And the numbers have been going up. Approximately 4 percent of cases are hereditary, but what about the other 96 percent? The only accepted risk factor has been tobacco use, but cigarette smoking has been declining.

Nitrosamines are one of the most potent carcinogens in cigarette smoke. One hot dog has as many nitrosamines and nitrosamides as five cigarettes. And these carcinogens are also found in fresh meat as well: beef, chicken and pork. So even though smoking rates have dropped, perhaps the rise in kidney cancer over the last few decades may have something to do with meat consumption. But would kidney cancer just be related to the processed meats like bacon, sausage, hot dogs and cold cuts that have nitrate and nitrite additives, or fresh meat as well?

The NIH-AARP study featured in my video Can Diet Protect Against Kidney Cancer? is the largest prospective study on diet and health ever performed--about 500,000 followed for nine years. In addition to examining nitrate and nitrite intake from processed meat, they also looked at intake from other sources such as fresh meat, eggs and dairy. Nitrite from animal sources, not just processed meats, was associated with an increased risk of kidney cancer, and total intake of nitrate and nitrite from processed meat sources was also associated with kidney cancer risk. The researchers found no associations with nitrate or nitrite intake from plant sources, but nitrates from processed meat was associated with cancer.

When meat producers advertise their bacon or lunch meat as "uncured," this means no nitrites or nitrates added. But if you look at the small print you'll see something like, "except for celery juice." That's just a sneaky way to add nitrites. Processed meat producers ferment the nitrates in celery to create nitrites, then add it to the meat; a practice even the industry admits "may be viewed as incorrect at best or deceptive at worst."

But that same fermentation of nitrates to nitrites can happen thanks to bacteria on our tongue when we eat vegetables. So why are nitrates and nitrites from vegetables on our tongue harmless, but nitrates and nitrites from vegetables in meat linked to cancer? The actual carcinogens are not nitrites, but nitrosamines and nitrosamides. In our stomach, to turn nitrites into nitros-amines, and nitros-amides we need amines and amides, which are concentrated in animal products. And vitamin C and other antioxidants in plant foods block the formation of these carcinogens in our stomach. That's why we can safely benefit from the nitrates in vegetables without the cancer risk. In fact some of the highest nitrate vegetables like arugula, kale, and collards are associated with decreased risk of kidney cancer. The more plants, it appears, the better.

Plant-based diets and fiber-rich diets are recommended to prevent cancer directly, as well as chronic conditions associated with kidney cancer, such as obesity, high blood pressure and diabetes. It's similar to sodium intake and kidney cancer. Sodium intake increases kidney disease risk, but that's not just because sodium intake increases blood pressure. It appears the salt is associated with increased cancer risk even independently of hypertension. What about plant-based diets? Turns out the protective association remains even in people who are not obese and have normal blood pressure. So overall, plant-based and fiber-rich diets appear to do both: decrease cancer risk directly and indirectly.

I briefly address kidney health in Preventing Kidney Failure Through Diet and Treating Kidney Failure Through Diet, but have a whole series of more in-depth videos dealing with various kidney issues.

More on the fascinating nitrate/nitrite story in my 17-part series about improving athletic performance with nitrate-rich vegetables such as beets and arugula. Here are a few short highlights:

More on carcinogens caused by cooking meat in videos like:

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--2013: Uprooting the Leading Causes of Death, More Than an Apple a Day, 2014: From Table to Able: Combating Disabling Diseases with Food, 2015: Food as Medicine: Preventing and Treating the Most Dreaded Diseases with Diet, and my latest, 2016: How Not To Die: The Role of Diet in Preventing, Arresting, and Reversing Our Top 15 Killers.

Image Credit: RDSVS / Flickr

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Are Sprouted Lentils Healthier Than Canned Lentils?

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Beans, chickpeas, split peas and lentils are packed with nutrients and play a role in the prevention of chronic disease, but most can't be eaten raw. Some can be sprouted, though. Boiling is the most common cooking method, which is used for canned beans. Which is healthier, though, cooked or sprouted?

The easiest way to compare healthfulness is to measure nutrient levels--such as the anthocyanin pigments that make kidney beans so pretty--thought to account for some of beans' protective benefits against chronic disease. Sprouted beans have more of some anthocyanins, but less than others. We find this same pattern across the board with the other phenolic phytonutrients: sprouted beans have more of some, less of others. Because the positive effects of these compounds may be related to their antioxidant capacity, we can compare the overall antioxidant power of boiled versus sprouted beans. In that case, boiled appears to have a marginal edge.

Ideally, though, rather than merely comparing concentrations of phytochemicals, we'd measure physiological effects. For example, we might look at the effect of boiled versus sprouted beans against cancer cell growth. That's exactly what researchers did. In my video Cooked Beans or Sprouted Beans?, you can see the concentrations of bean extract needed to cut the breast cancer growth rate in half in a petri dish. Boiled beans do about 40 times better than raw beans--the same cancer growth inhibition at just a fraction of the concentration. Sprouted beans do about the same.

We can't eat most beans raw, but I wanted to include them to show you a fascinating phenomenon. No amount of raw bean extract appears to totally stop the growth of breast cancer cells, but just small amounts of cooked or sprouted beans can. We find the same thing with killing off cancer. No amount of raw bean extract can fully kill off breast cancer cells, but both boiled and sprouted beans can.

Similar results were found for melanoma cells, a type of malignant skin cancer. Processing the beans--either cooking or sprouting--boosted anticancer activity in vitro. However, against kidney cancer, raw and boiled worked, but sprouted didn't at all.

There has also been interest in brain protection. Given that elderly persons who report always eating legumes may be significantly less likely to experience cognitive decline, a group of Chinese researchers decided to compare the protective effects of boiled versus sprouted beans on astrocytes.

Astrocytes are the most abundant type of cell in our brain. They are star-shaped cells that keep our brain running smoothly. Should they become damaged, though, they may play an important role in the development of neurodegenerative disorders such as Lou Gehrig's disease, Alzheimer's, or Parkinson's. So if we're thinking clearly, we should thank our lucky stars.

To see if beans help protect astrocytes from damage, we'd have to first make sure bean extracts wouldn't cause any damage. Cooked beans don't seem to hurt cells at all, and sprouted beans seem to even help them grow a little. If we add an oxidative chemical to the cells, we can kill off about a quarter of them. However, if we add that chemical along with some boiled bean extract, the astrocytes were partially protected at higher doses. Sprouted bean extract didn't appear to offer significant benefit.

What's the takeaway? As far as I'm concerned, we should eat beans in whichever way will get us to eat the most of them.

I do love my lentil sprouts, one of the healthiest snacks on the planet (along with kale chips). I can grow my own in just 2 to 3 days. But using canned beans I can get similar nutrition in about 2 to 3 seconds.

Sprouting is so much fun, though! I've got a bunch of videos on broccoli sprouts, for example: Biggest Nutrition Bang for Your Buck.

But again, whichever way we like them we should eat them. Why? See:

Mostly I just used canned. See Canned Beans or Cooked Beans?

Other videos on practical prep tips include:

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 Uprooting the Leading Causes of Death, More Than an Apple a Day, From Table to Able, and Food as Medicine.

Image Credit: Veganbaking.net / Flickr

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What To Do if You Suspect Gluten Problems

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Symptoms of gluten sensitivity include irritable bowel type symptoms such as bloating, abdominal pain, and changes in bowel habits, as well as systemic manifestations such as brain fog, headache, fatigue, depression, joint and muscle aches, numbness in the extremities, skin rash, or anemia. I previously discussed why people who suspect they might be gluten sensitive should not go on a gluten-free diet. But if that's true, what should they do?

The first thing is a formal evaluation for celiac disease, which currently involves blood tests and a small intestinal biopsy. If the evaluation is positive, then a gluten-free diet is necessary. If it's negative, it's best to try a healthier diet with more fruits, vegetables, whole grains and beans while avoiding processed junk. In the past, a gluten-free diet had many benefits over the traditional American diet because it required increasing fruit and vegetable intake--so no wonder people felt better eating gluten-free: no more unhealthy bread products, no more fast food restaurants. Now, there is just as much gluten-free junk out there.

If a healthy diet doesn't help, then the next step is to try ruling out other causes of chronic gastrointestinal distress. In a study of 84 people who claim gluten causes them adverse reactions (they're referred to in the literature as"PWAWGs," People Who Avoid Wheat and/or Gluten), highlighted in my video, How to Diagnose Gluten Intolerance, about a third didn't appear to have gluten sensitivity at all. Instead, they either had an overgrowth of bacteria in their small intestine, were fructose or lactose intolerant, or had a neuromuscular disorder like gastroparesis or pelvic floor dysfunction. Only if those are also ruled out, would I suggest people suffering from chronic suspicious symptoms try a gluten-free diet. If symptoms improve, stick with it and maybe re-challenge with gluten periodically.

Unlike the treatment for celiac disease, a gluten-free diet for gluten sensitivity is ideal not only to prevent serious complications from an autoimmune reaction, but to resolve symptoms and try to improve a patient's quality of life. However, a gluten-free diet itself can also reduce quality of life, so it's a matter of trying to continually strike the balance. For example, gluten-free foods can be expensive, averaging about triple the cost. Most people would benefit from buying an extra bunch of kale or blueberries instead.

No current data suggests that that general population should maintain a gluten-free lifestyle, but for those with celiac disease, a wheat allergy, or a sensitivity diagnosis, gluten-free diets can be a lifesaver.

For more on gluten, check out Is Gluten Sensitivity Real? and Gluten-Free Diets: Separating the Wheat from the Chat.

Some food strategies that may help with irritable bowel symptoms are covered in a few of my previous videos, such as Kiwifruit for Irritable Bowel Syndrome and Cayenne Pepper for Irritable Bowel Syndrome and Chronic Indigestion.

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 Uprooting the Leading Causes of Death, More Than an Apple a Day, From Table to Able, and Food as Medicine.

Image Credit: Jeremy Segrott/ Flickr

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How to Cook Broccoli

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When I used to teach medical students at Tufts, I gave a lecture about this amazing new therapeutic called "iloccor-B." I'd talk about all the new science, all the things it could do, its excellent safety profile. Just as they were all scrambling to buy stock in the company and prescribe it to all their patients, I'd do the big reveal. Apologizing for my "dyslexia," I would admit that I'd got it backwards. All this time I had been talking about broccoli.

The main active ingredient in broccoli is thought to be sulforaphane, which may protect our brains, protect our eyesight, protect our bodies against free radicals, boost our detoxification enzymes, and help prevent and treat cancer.

In my videos The Best Detox and Sometimes the Enzyme Myth is the Truth, I talked about how the formation of sulforaphane is like a chemical flare reaction, requiring the mixing of a precursor compound with an enzyme, which is destroyed by cooking. This may explain why we get dramatic suppression of cancer cell growth from raw broccoli, cauliflower and Brussels sprouts, but hardly anything from boiled, microwaved or steamed (except for microwaved broccoli, which actually retains some cancer fighting abilities). But who wants to eat raw Brussels sprouts?

There is a strategy to get the benefits of raw in cooked form. In raw broccoli, the sulforaphane precursor, called glucoraphanin, mixes with the enzyme (myrosinase) when you chew or chop it. If given enough time--such as when sitting in your upper stomach waiting to get digested--sulforaphane is born. The precursor and sulforaphane are resistant to heat and therefore cooking, but the enzyme is destroyed. No enzyme = no sulforaphane.

That's why I described the "hack and hold" technique--if we chop the broccoli, Brussels sprouts, kale, collards, or cauliflower first and then wait 40 minutes, we can cook them all we want. The sulforaphane is already made; the enzyme has already done its job, so we don't need it anymore.

When most people make broccoli soup, for example, they're doing it wrong. Most people cook the broccoli first, then blend it. We now know it should be done the exact opposite way. Blend it first, wait, and then cook it.

What if we're using frozen broccoli, though? In my video, Second Strategy to Cooking Broccoli, you can see the amount of sulforaphane in someone's body after they eat broccoli soup made from fresh broccoli versus from frozen broccoli. The difference is dramatic. Commercially produced frozen broccoli lacks the ability to form sulforaphane because vegetables are blanched (flash-cooked) before they're frozen for the very purpose of deactivating enzymes. This prolongs shelf life in the frozen foods section, but the myrosinase is dead by the time you take it out of your freezer. It doesn't matter how much you chop it, or how long you wait, no sulforaphane is going to be made. This may be why fresh kale suppresses cancer cell growth up to ten times more than frozen.

The frozen broccoli is still packed with the precursor--remember that's heat resistant--and we could get lots of sulforaphane out of the frozen broccoli by adding some outside enzyme. Where do we get myrosinase enzyme from? Researchers just buy theirs from a chemical company. But we can just walk into any grocery store.

All cruciferous vegetables have this myrosinase. Mustard greens, a cruciferous vegetable, grow out of little mustard seeds, which we can buy ground up in the spice aisle as mustard powder. If we sprinkled some mustard powder on our cooked frozen broccoli, would it start churning out sulforaphane? We didn't know...until now.

Boiling broccoli prevents the formation of any significant levels of sulforaphane due to inactivation of the enzyme. However, researchers from the University of Reading found that the addition of powdered mustard seeds to the heat processed broccoli significantly increased the formation of sulforaphane. In the video I mentioned earlier, Second Strategy to Cooking Broccoli, you can see the amount of sulforaphane in boiled broccoli versus the amount after half a teaspoon or a teaspoon of mustard powder is added. Both a half teaspoon and a full teaspoon increase sulforaphane by the same amount, suggesting that we could use even use less mustard powder for the same effect. Therefore, although domestic cooking leads to the deactivation of myrosinase and stops sulforaphane formation, the addition of powdered mustard seeds to cooked cabbage-family vegetables provides a natural source of the enzyme such that it's practically like eating them raw.

So, if we forget to chop our greens in the morning for the day, or are using frozen, we can just sprinkle some mustard powder on top at the dinner table and we're all set. Daikon radish, horseradish, or wasabi--all cruciferous vegetables packed with the enzyme--work as well. Just a quarter teaspoon of Daikon radish root for seven cups of broccoli worked--just a tiny pinch can do it. Or you can add a small amount of fresh greens to your cooked greens, because the fresh greens have myrosinase enzyme that can go to work on the cooked greens.

I love kitchen chemistry--it totally revolutionized my daily greens prep. One of the first things I used to do in the morning is chop my greens for the day, so when lunch and supper rolls around they'd be good to go. But now with the mustard powder plan, I don't have to pre-chop.

This helps explain the results I presented in Raw Broccoli and Bladder Cancer Survival.

OK, but what's so great about this sulforaphane stuff? For a taste, see:

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 Uprooting the Leading Causes of Death, More Than an Apple a Day, From Table to Able, and Food as Medicine.

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Bile Binding Beets

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In my video Breast Cancer and Constipation, I discussed how fruits and veggies bind carcinogenic bile acids in our gut. Since bile acids are absorbed back into our systems, they may increase our risk of not only colon cancer but also other cancers as well. In light of this, researchers publishing in the journal, Nutrition Research, concluded that to "lower the risk of diet and lifestyle-related premature degenerative diseases and to advance human nutrition research, relative bile acid-binding potential of foods and fractions need to be evaluated."

They found that some vegetables bind bile acids better than others. We know that those eating more plant-based diets are at a lower risk of heart disease and cancer. This could partly be because of phytonutrients in plants that act as antioxidants and potent stimulators of natural detoxifying enzymes in our bodies. Veggies can also lower cholesterol and detoxify harmful metabolites, functions that can be predicted by their ability to bind bile acids.

A group of USDA researchers studying this topic discovered three important things. First, they found an over five-fold variability in bile acid binding among various vegetables that had similar fiber content, suggesting that bile acid binding is not just related to total dietary fiber content (as previously thought), but instead some combination of unique phytonutrients yet to be determined.

Second, they discovered that steaming significantly improves the bile acid binding of collards, kale, mustard greens, broccoli, peppers, cabbage, beets, eggplant, asparagus, carrots, green beans, and cauliflower, suggesting that in this way steaming vegetables may be more healthful than those consumed raw.

Finally, they ranked multiple vegetables for bile binding ability. Which vegetables kicked the most bile butt? (in my video, Which Vegetable Binds Bile Best?, you can see a visual comparison of bile binding ability.) Turnips turned up last. Then came cabbage, cauliflower, bell peppers, spinach, asparagus and green beans. Mustard greens and broccoli were better. Eggplant, carrots and Brussels sprouts basically tie for the #5 slot. Then collards at #4. Kale got the bronze, okra the silver, and beets the gold. Kale, surprisingly, got beet.

The researchers concluded that inclusion of all these vegetables in our daily diets should be encouraged. When consumed regularly, they concluded, these vegetables may lower the risk of premature degenerative diseases and improve public health.

More raw versus cooked comparisons in

Beets also have a number of other remarkable properties. Check out my video series on Doping with Beet Juice as well as Hearts Shouldn't Skip a Beet, and Whole Beets vs. Juice for Improving Athletic Performance.

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 Uprooting the Leading Causes of Death, More Than an Apple a Day, From Table to Able, and Food as Medicine.

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Exercise as Medicine

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Physical inactivity has been called the biggest public health problem of the 21st century. Of course just because someone calls it that doesn't mean it's true, in fact physical inactivity ranks down at #5 in terms of risk factors for death, and #6 in terms of risk factors for disability. Diet is by far our greatest killer, followed by smoking.

But, there is irrefutable evidence of the "effectiveness of regular physical activity in the prevention of several chronic diseases--cardiovascular disease, diabetes, cancer, hypertension, obesity, depression, osteoporosis, and premature death"--helping to add years to our life, and above all, "life to our years." It truly may be survival of the fittest.

How much exercise do we need? In general, the answer is the more the better. Currently, "most health and fitness organizations advocate a minimum of a thousand calories of exercise a week," which is equivalent to walking an hour a day five days a week. Seven days a week, though, may be even better in terms of extending one's lifespan.

Exercise is so important that not walking an hour a day is considered a high risk behavior, alongside smoking, excess drinking, and being obese. Having any one of these effectively ages us three to five years in terms of risk of dying prematurely, though interestingly those who ate green vegetables on a daily basis did not appear to have that same bump in risk. Even if broccoli-eating couch potatoes live as long as walkers, there are a multitude of ancillary health benefits to physical activity that doctors are encouraged to prescribe it, to signal to the patient that "exercise is medicine."

Researchers at the London School, Harvard, and Stanford compared exercise to drug interventions in study highlighted in my video, Longer Life Within Walking Distance, and found that exercise often worked just as well as drugs for the treatment of heart disease, stroke, and diabetes. There's not a lot of money to fund exercise studies, so one option would be to require drug companies to compare any new drug to exercise. In cases where drug options provide only modest benefit, patients deserve to understand the relative impact that physical activity might have on their condition.

Exercise is just one of four lifestyle behaviors found to significantly extend our lifespan. See my video, Turning the Clock Back 14 Years.

Other longevity videos include:

More videos on exercise:

What about the stress it can put on our bodies? See:

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 Uprooting the Leading Causes of Death, More Than an Apple a Day, From Table to Able, and Food as Medicine.

Image Credit: Dominic Alves / Flickr

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Broccoli and Kale Taste Bitter

The golden age of nutrition bloomed in the twentieth century with discoveries of proteins, fats, carbohydrates, minerals, vitamins, and other plant (phyto)-derived chemicals required for human health. Accepted wisdom about these nutrients became, “if some is necessary, then more is better.” The search for ways to “supercharge nutrition” began with supplements: pills filled with isolated, concentrated substances, such as vitamins and minerals. Unfortunately, extensive research over the past century has consistently found that these expensive treatments offer few benefits and much harm to people. Consuming antioxidants, including beta-carotene and vitamin E, increases a person’s risk of suffering from earlier death, heart disease, and many forms of cancer. Jim Watson, co-discoverer of genetic DNA, wrote about the shortcomings of consuming too many micronutrients, even incriminating so-called superfoods with “Blueberries best be eaten because they taste good, not because their consumption will lead to less cancer.” Besides taking pill-like supplements, the micronutrient content of a person’s diet can be enhanced by choosing foods with the highest concentrations of these substances. Colorful vegetables, especially those from the cruciferous genus, which include cabbage, collard greens, broccoli, cauliflower, kale, Brussels sprouts, turnips, and mustards, are known for their high nutrient density. Some of their disease-preventing properties come packaged with bitter tasting chemicals that the plants produce. Bad Taste for Good Reason The July 2015 issue of Scientific American provided a scientifically supported argument for why many people dislike eating vegetables. The bitter tastes are from the noxious chemicals produced by plants. The authors explain, “The health benefits of fruits and vegetables are an inadvertent offshoot of eons-long wars waged by plants against critters, mostly insects, that are intent on eating them.” In small amounts these phyto-chemicals seem to be beneficial to humans; stimulating our immune/disease-fighting systems to ward off cancers, diabetes, and heart disease. So far, except for a few allergies, consuming “typical portion sizes” of cruciferous plants is found to be safe in humans. Even concerns about plant-derived goitrogens, substances that suppress thyroid function, are largely rumor, with very few actual cases reported. But do consider that in her grand scheme, Mother Nature rarely makes mistakes: bad tastes suggest toxicity, and this may be especially important with higher consumptions. Greens and Malnutrition Many people seeking a micronutrient-dense diet struggle to attain nutritional balance. A diet based on foods that are especially high in micronutrients, mainly non-starchy vegetables, is naturally very low in calories. People who eat this way find it a challenge to feel full, even after consuming uncomfortably large volumes of food. Consider that to meet daily energy needs of 1500 calories, 11 pounds of kale, for example, must be swallowed every 24 hours. (Cooked cabbage requires 14 pounds and broccoli 10 pounds for 1500 calories, whereas potatoes are 4 pounds and rice is 3 pounds of food.) Compounding this energy insufficiency (by relying too heavily on these green vegetables) is the overload of certain nutrients, like protein. Our daily nutritional protein requirement is no more than 5% of our total calories; the liver and kidneys will dispose of any excesses. Metabolic burdens placed on these organs by consuming excess protein include the loss of calcium from the body and the accumulation of nitrogenous waste products in the body. In terms of excess, cabbage provides 4 times, kale 5 times, and broccoli 7 times more protein than is required. These superfoods can also be contaminated with poisonous heavy metals. Kale, cabbage, broccoli, cauliflower, and collard greens are “hyper-accumulators” of thallium and cesium. Headlines about “arsenic in rice” must be shared with news that nickel, lead, cadmium, aluminum, and arsenic are commonly found in both organically and commercially produced greens. A Starch-based Diet Is Healthful and Sustainable A diet made up mostly of starchy vegetables and grains provides the abundant energy and balanced nutrition humans require. (As most readers of the McDougall philosophy already know:) All large populations of trim, healthy, athletic-competing, war-fighting people throughout verifiable human history have obtained the bulk of their calories from high-carbohydrate foods (starches). Examples of thriving populations include the Japanese, Chinese, and other Asians, who eat sweet potatoes, buckwheat, and/or rice; Incas in South America who eat potatoes; Mayans and Aztecs in Central America who eat corn; and Egyptians in the Middle East who eat wheat. A diet of mostly nutrient-dense superfoods is unrealistic for both humans and the Planet. The financial cost difference between choosing calories from starchy and non-starchy sources is budget-breaking. The raw ingredients for a 1000-calorie meal plan based on beans, corn, potatoes, and/or rice is about 20 cents (US dollars).  A “1000-calorie meal plan” as broccoli or kale is about 3 dollars. (People typically eat 1500 to 3000 calories daily.) In the global sense, calories from non-starchy vegetables are also too difficult and expensive to grow. Broccoli and kale could not feed seven billion people, either directly or through livestock. Furthermore, these green vegetables are highly perishable, failing again to provide a reliable and sustainable food source for humankind. Starches, like beans, corn, potatoes, and rice are high-yield, inexpensive to produce, and can be stored for decades for later use. Thus, these conventional foods, not greens, are the bulk of the natural human diet. Dieters should not forgo bread and potatoes for platefuls of kale, nor should they force down Brussels sprouts rather than enjoy rice and beans. Make micronutrient-dense “green vegetables” side dishes rather than main dishes, as they provide color and flavor, and their various repugnant chemicals boost our defenses against common diseases.

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Foods for Glaucoma

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Glaucoma is the second leading cause of legal blindness in white women, and the number one cause of blindness in African-American women. In a study I profile in the video Greens vs. Glaucoma, researchers chose a population of African-American women to study the effects of fruit and vegetable consumption on glaucoma risk because they were specifically interested in studying the effect of foods with the highest concentration of those eye-protecting phytonutrients like zeaxanthin. Zeaxanthin is found primarily in plants such as kale and collard greens. (It is also found in eggs--find out how much in Egg Industry Blind Spot). However, we'd be lucky if we could find one in ten white people eating even a single serving of these dark green leafy vegetables a month, whereas nearly nine out of ten African-American women in the study consumed this amount.

What did the researchers find? Well, as I've stressed over the years, all fruits and vegetables are not the same (see for example, How to Reach the Antioxidant "RDA"). Whether the participants hardly ever ate bananas or had one or more every day didn't seem to matter much in terms of the risk of glaucoma. However, eating only a couple oranges every week was associated with dramatically lower risk. Orange juice was not associated with a lower risk, though, even if drunk every day. A similar finding was found for peaches: fresh peaches seemed to help, but canned peaches didn't.

Similarly the intake of vegetables in general as a catch-all term didn't seem to matter. For example, whether subjects ate a green salad twice a week, once a week, or zero times a week didn't seem to matter when it came to reducing glaucoma risk, but most people's salads are pretty pitiful. It was a different story for kale and collard greens: just two or three servings a month was associated with half the risk of glaucoma compared to once a month or less.

It may be especially important for white people to consume kale and collard greens. The lighter our eye color, the more greens we need to eat. Blue eyes let 100 times more light through, so people with blue or gray eyes appear significantly more vulnerable to damage compared to brown or black. Green and hazel fall somewhere in the middle.

This is interesting: carrots appeared to be less protective in black women compared to white women. They suggest it could be a difference in food preparation methods. Perhaps the African-American subjects tended to eat carrots raw, limiting the absorption of certain nutrients, while they chopped and prepared their collard greens with oil, making the nutrients more bioavailable because the absorption of carotenoid phytonutrients depends on the presence of fat. This is why I encourage people to eat nuts or seeds with the greens--such as a little tahini sauce or something.

Why not just take a zeaxanthin pill? We don't know what exactly it is in these wonderful foods that's working their wonders, so it's probably better to just eat our greens rather than supplements. In fact, people that take calcium or iron supplements may even be doubling, quadrupling, or septupling their odds of glaucoma. It's better to get most of our nutrients from produce, not pills.

I wish there were more studies on under-represented populations. I've covered a few, such as Preventing Breast Cancer By Any Greens Necessary, but I am constantly on the lookout for more.

My other videos on glaucoma include Prevent Glaucoma and See 27 Miles Farther and Dietary Treatment of Glaucoma. For more on eye health check out my video, Dietary Prevention of Age-Related Macular Degeneration.

-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 Uprooting the Leading Causes of Death, More Than an Apple a Day, and From Table to Able.

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Our Immune System Uses Plants To Activate Gut Protection

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It might seem that our skin is the first line of defense between our insides and the outside world, but our greatest interface with our environment is actually through the lining of our intestines, which covers thousands of square feet. And all that separates our gut from the outer world is a single layer of cells, 50 millionth of a meter thick - less than the thickness of a sheet of paper.

Compare that to our skin. In the video, The Broccoli Receptor: Our First Line of Defense, you can see a layer of skin, dozens of protective cells thick, to keep the outside world outside of our bodies. Why don't we have multiple layers in our gut wall? Because we need to absorb stuff from food into our body. It's a good idea for our skin to be waterproof, so we don't start leaking, but the lining of our gut has to allow for the absorption of fluids and nutrients.

With such a thin, fragile layer between our sterile core and outer chaos, we better have quite a defense system in place. Indeed, that's where "intraepithelial lymphocytes" come in.

Intraepithelial lymphocytes serve two functions: they condition and repair that thin barrier, and they provide a front-line defense against intestinal pathogens. These critical cells are covered with Ah receptors. Ah receptors are like locks, and for decades researchers have been searching for a natural key to fit in these locks to activate those receptors and sustain our immunity. We recently discovered a key: broccoli.

Cruciferous vegetables--broccoli, kale, cauliflower, cabbage, Brussels sprouts--contain a phytonutrient that is transformed by our stomach acid into the key that fits into the Ah receptor, stimulating our intraepithelial lymphocytes. In other words, broccoli leads to the activation of our immune foot soldiers.

In an editorial about Ah receptors and diet, researcher Lora V. Hooper from the Howard Hughes Medical Institute noted, "From childhood we learn that vegetables are good for us, and most of us eat our veggies without giving much thought to the evidence behind this accepted wisdom or to the mechanisms underlying the purported health-boosting properties of a vegetable-rich diet." But now we know that "specific dietary compounds found at high levels in cruciferous vegetables such as broccoli, cauliflower, and cabbage are essential for sustaining intestinal immune function." Green vegetables are in fact required to maintain a large population of those protective intraepithelial lymphocytes.

Maybe that's why vegetable intake is associated with lower risk of inflammatory bowel diseases such as ulcerative colitis, whereas the more meaty Western diet is associated with higher risk of inflammatory bowel diseases. This may be because the activating receptors on our intestinal immune cells are basically sensors of plant-derived phytochemicals.

This raises a broader question: Why did our immune system evolve this requirement for broccoli and other plant foods? Well, when do we need to boost our intestinal defenses the most? When we eat! That's when we may be ingesting pathogens. Linking heightened intestinal immune activation to food intake could serve to bolster immunity precisely when it is needed. At the same time, this would allow energy to be conserved in times of food scarcity, since maintaining these defenses takes considerable amounts of energy. Why remain at red alert 24 hours a day when we eat only a couple of times a day? We evolved for millions of years eating mostly weeds--wild plants, dark green leafy vegetables (or as they were known back then, leaves). By using veggies as a signal to upkeep our immune system, our bodies may be bolstering our immune defenses when we most need them. Thus, the old recommendation to "eat your veggies" has a strong molecular basis. (Did we really evolve eating that many plant foods? See my video Paleolithic Lessons).

This discovery has been all exciting for the drug companies who are looking into Ah receptor active pharmaceuticals. "However," as one research team at Cambridge concluded, "rather than developing additional anti-inflammatory drugs, changing diets which are currently highly processed and low in vegetable content, may be a more cost effective way towards health and well-being."

As remarkable as this story is, it is just the tip of the cruciferous iceberg! See, for example:

How else can we protect our immune function? Exercise (Preserving Immune Function In Athletes With Nutritional Yeast) and sleep (Sleep & Immunity)!

Given the variety and flexibility of most mammalian diets, a specific dependence on cruciferous vegetables for optimal intestinal immune function would seem overly restrictive, no? I address that in my video, Counteracting the Effects of Dioxins

-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 Uprooting the Leading Causes of Death, More Than an Apple a Day, and From Table to Able.

Images thank to Nomadic Lass / Flickr.

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