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.

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Preserving Male Reproductive Health With Diet

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In 1992 a controversial paper was published suggesting sperm counts have been dropping around the world over the last 50 years. However, this remains a matter of debate. It's notoriously difficult to determine sperm counts in the general population for obvious reasons. If you just go ask men for samples, less than 1 in 3 tend to agree to participate.

Finally though, a study of tens of thousands of men studied over a 17-year period was published. It indeed found a significant decline in sperm concentration, about a 30 percent drop, as well as a drop in the percentage of normal looking sperm. Most sperms looked normal in the 90's, but more recently that has dropped to less than half. This may constitute a serious public health warning.

Semen quality may actually be related to life expectancy. In a study of more than 40,000 men visiting a sperm lab during a 40-year period, they found a decrease in mortality was associated with an increase in semen quality, suggesting that semen quality may therefore be a fundamental biomarker of overall male health. Even when defective sperm are capable of fertilizing an egg, creating a child with abnormal sperm may have serious implications for that child's future health.

What role may diet play? I profiled a first-of-its-kind Harvard study suggesting that a small increase in saturated fat intake was associated with a substantially lower sperm count, but not all fat was bad. Higher intakes of omega-3's were associated with a more favorable sperm shape. This may help explain why researchers at UCLA were able to improve sperm vitality, movement, and shape by giving men about 18 walnuts a day for 12 weeks. Walnuts have more than just omega 3's, though. They also contain other important micronutrients. In a study of men aged 22 through 80, older men who ate diets containing lots of antioxidants and nutrients such as vitamin C had the genetic integrity of sperm of much younger men.

The antioxidants we eat not only end up in our semen, but are concentrated there. The amount of vitamin C ends up nearly ten times more concentrated in men's testicles than the rest of their bodies. Why? Because sperm are highly susceptible to damage induced by free radicals, and accumulating evidence suggests that this oxidative stress plays an important role in male infertility. So, more fruits and vegetables and perhaps less meat and dairy, but the Harvard data were considered preliminary. They studied fewer than 100 men, but it was the best we had... until now.

A much larger follow-up study, highlighted in my video, The Role of Diet in Declining Sperm Counts, found that the higher the saturated fat intake the lower the sperm count, up to a 65 percent reduction. These findings are of potentially great public interest because changes in diet over the past decades may be part of the explanation for the recently reported high frequency of subnormal human sperm counts. In any case, the current findings suggest that adapting dietary intake toward eating less saturated fat may be beneficial for both general and reproductive health.

Why is high dietary intake of saturated fat associated with reduced semen quality? What's the connection? Sex steroid hormones in meat, eggs, and dairy may help explain the link between saturated fat intake and declining sperm counts. That's the subject of my video, Dairy Estrogen and Male Fertility.

More on male infertility in my videos Fukushima and Radioactivity in Seafood and Male Fertility and Diet.

Diet also has a role to play in sexual dysfunction:

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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Which Nut Suppresses Cancer Cell Growth the Most?

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People who eat nuts in their adolescence may have a better chance of fighting off breast cancer later in life, according to data from the Harvard Nurse's Study. A follow-up study involving the daughters of the nurses corroborated the findings. Those eating more peanut butter, nuts, beans, lentils, soybeans, or corn were found to have just a fraction of the risk for fibrocystic breast disease, which places one at higher risk of cancer. The protective effects were found to be strongest for those most at risk, such as those with a family history of breast cancer.

Another study out of the British Journal of Cancer found that even two handfuls of nuts a week may protect against pancreatic cancer, one of our most fatal malignancies.

Nuts are described as "nutritionally precious," which may explain some of the mechanisms by which nut components induce cancer cell death and inhibit cancer growth and spread in vitro. But which nuts work the best? In my video #1 Anticancer Vegetable, we learned that two classes of vegetables--the broccoli family vegetables and the garlic family vegetables--most effectively suppressed breast cancer cell growth. In Which Fruit Fights Cancer Better?, cranberries and lemons took the title.

What about nuts? In terms of antioxidant content, walnuts and pecans steal the show. Twenty-five walnuts have the antioxidant equivalent of eight grams of vitamin C (the vitamin C found in a hundred oranges).

But how do they do against cancer? In the video, Which Nut Fights Cancer Better?, you can see a graph of human cancer cell proliferation versus increasing concentrations of the ten most common nuts eaten in the United States. If you drip water on these cancer cells as a control, nothing happens. Hazelnuts, pistachios and Brazil nuts don't do much better. Pine nuts, cashews and macadamias start pulling away from the pack. Almonds appear twice as protective, halving cancer cell growth at only half the dose as pine nuts, cashews, and macadamias. Walnuts, pecans, and peanuts come out as the clear winners, causing a dramatic drop in cancer proliferation at just tiny doses.

More nuttiness:

-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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Where Do You Get Your Fiber?

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Vegetarians and vegans are all too familiar with the question: Where do you get your protein?

Well, we can finally put to rest the question of whether vegetarians get enough protein thanks to a large study that compared the nutrient profiles of about 30,000 non-vegetarians to 20,000 vegetarians and about 5,000 vegans, 5,000 flexitarians (vegetarian most of the time), and 5,000 pescetarians (no meat except fish). The average requirement is 42 grams of protein a day. As you can see in the graph in the video, Do Vegetarians Get Enough Protein, meat eaters get way more than they need, and so does everyone else. Vegetarians and vegans average 70% more protein than the recommendation every day.

It's surprising that there's so much fuss about protein in this country when less than 3% of adults don't make the cut, presumably because they're on extreme calorie-restricted diets and aren't eating enough food period. But 97% of Americans get enough protein.

There is a nutrient, though, for which 97% of Americans are deficient. That nutrient is fiber.

Less than 3% of Americans get even the recommended minimum adequate intake of fiber. That's something we really have to work on.

On average, we get only about 15 grams a day. The minimum daily requirement is 31.5, so we get less than half the minimum. Men are particularly deficient. If we break down intake by age and gender, after studying the diets of 12,761 Americans, the percent of men between ages 14 and 50 getting the minimum adequate intake is zero. (The only nutrient Americans may be more deficient in than fiber is potassium. See 98% of American Diets Potassium Deficient.)

This deficit is stunning in that dietary fiber has been protectively associated in population studies with the risk of diabetes, metabolic syndrome, cardiovascular disease, obesity, and various cancers as well high cholesterol, blood pressure, and blood sugars. Therefore, it is not surprising that fiber is listed as a nutrient of concern reported by the Dietary Guidelines Advisory Committee. Protein is not.

One problem is that most people have no idea what's in their food; more than half of Americans think steak is a significant fiber source. By definition, fiber is only found in plants. There is no fiber in meat, dairy or eggs, and little or no fiber in junk food. Therein lies the problem. Americans should be eating more beans, vegetables, fruits, and whole grains--but how are they doing?

96% of Americans don't eat the minimum recommended daily amount of beans, 96% don't eat the measly minimum for greens, and 99% don't get enough whole grains. Nearly the entire U.S. population fails to eat enough whole plant foods.

Even semi-vegetarians make the fiber minimum, though. Those eating completely plant-based diets triple the average American intake. When closing the fiber gap, you'll want to do it gradually though, no more than about five extra grams a day each week until you can work your way up. But it's worth it. "Plant-derived diets tend to contribute significantly less fat, saturated fat, cholesterol, and food-borne pathogens, while at the same time offering more fiber, folate, vitamin C, and phytochemicals, all essential factors for disease prevention, optimal health, and well being." And the more whole plant foods the better. If we compare the nutritional quality of vegan versus vegetarian, semi-vegetarian, pesco-vegetarian and omnivorous diets, traditional healthy diet indexing systems consistently indicate that the most plant-based diet is the healthiest one.

For more on how S.A.D. the Standard American Diet is, see Nation's Diet in Crisis.

Americans eating meat-free diets average higher intakes of nearly every nutrient. See my video Nutrient-Dense Approach to Weight Management.

Isn't animal protein higher quality protein though? See my videos:

For more on protein, see: Plant Protein Preferable and Prostate Cancer Survival: The A/V Ratio.

And for a few on fiber:

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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Eliminate Most of Your Chronic Disease Risk in Four Steps

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In 1903, Thomas Edison predicted that the doctor of the future will give no medicine, but instead "instruct his patient in the care of the human frame in diet and in the cause and prevention of disease." A hundred and one years later, the American College of Lifestyle Medicine was born. Lifestyle docs like myself still prescribe meds when necessary, but, based on the understanding that the leading causes of disability and death in the United States are caused mostly by lifestyle, our emphasis is particularly on what we put in our mouths: food and cigarettes. An "impressive number of studies have shown that lifestyle is the root cause of what ails us." The good news is that by changing our lifestyle we can dramatically improve our health.

You have the power.

We've known for a long time that for most of the leading causes of death our genes account for at most 10 to 20% of risk, given that rates of killers like heart disease and major cancers differ up to a 100-fold among various populations, and that when people migrate from low- to high-risk countries, their disease rates almost always change to those of the new environment. For example, at least 70% of strokes and colon cancer are avoidable, as are over 80% of coronary heart disease and over 90% of type 2 diabetes. So maybe it's "time we stop blaming our genes and focus on the 70% that is under our control." That may be the real solution to the health care crisis.

It doesn't take much. Adhering to just four simple healthy lifestyle factors can have a strong impact on the prevention of chronic diseases: not smoking, not being obese, exercising half an hour a day, and eating healthier (more fruits, veggies, whole grains, less processed foods and meat). Four simple things cut our risk of developing a chronic disease by 78%. 95% of diabetes risk out the window, 80% of heart attack risk, gone. Half of stroke risk, a third of cancer risk, simply gone. Think of what that means in terms of the numbers. As it stands now, each year a million Americans experience their first heart attack or stroke, a million get diabetes, a million get cancer.

Do we actually get to live longer, too? The CDC followed about 8,000 Americans 20 years or older for about six years. They found that three cardinal lifestyle behaviors exerted an enormous impact on mortality. People who do not smoke, consume a healthy diet, and engage in sufficient physical activity can substantially reduce their risk for early death. By "not smoking" they just meant not currently smoking; by "healthy diet" they just meant in the top 40% in terms of complying with the rather wimpy federal dietary guidelines; and by being "physically active" they just meant averaging about 21 minutes a day or more of at least moderate exercise. Those that managed at least one of the three had a 40% lower risk of dying. Those that hit two out of three cut their chances of dying by more than half. Those that scored all three threw 82% of their chances of dying in those six years out the window.

What does that mean in terms of how much longer we get to live? A similar study on health behaviors and survival, highlighted in my video, Turning the Clock Back 14 Years, didn't just take people's word for how healthfully they were eating, they measured the level of vitamin C in people's blood, a biomarker for how many plants they were eating, and the drop in mortality risk in those nailing all healthy behaviors was equivalent to being 14 years younger.

I discuss the role diet may play in preventing the 15 leading causes of death in my 2012 annual review video Uprooting the Leading Causes of Death.

How does your diet compare? Calculate Your Healthy Eating Score.

I go into depth into the exercise component in my video Longer Life Within Walking Distance.

For more on slowing the aging process, see my videos:

And more on my chosen clinical specialty, lifestyle medicine, in:

In health,
Michael Greger, M.D.

PS: If you haven't yet, you can subscribe to my videos for free by clicking here and watch my full 2012 - 2015 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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Why Deep Fried Foods May Cause Cancer

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In the latest study on dietary patterns and breast cancer risk among women, healthier eating was associated with eliminating three-quarters of the odds of breast cancer, whereas less healthy eating was associated with up to nearly eight times the odds. Included in the unhealthy eating pattern was the consumption of deep-fried foods, which have previously been linked to breast cancer, pancreatic cancer, lung cancer, oral and throat cancers, esophageal cancer, and cancer of the voicebox. No deep fried foods? What's a Southern belle to do? Instead of deep fried foods, how about the traditional Southern diet, characterized by high intakes of cooked greens, beans, legumes, cabbage, sweet potatoes and cornbread, which may reduce the risk of invasive breast cancer significantly.

What about the consumption of deep-fried foods and risk of prostate cancer? Researchers at the Fred Hutchinson Cancer Research Center and the University of Washington found that eating French fries, fried chicken, fried fish, and doughnuts was associated with about a third greater odds of prostate cancer. After stratifying for tumor aggressiveness, they found slightly stronger associations with more aggressive disease, suggesting that regular intake of deep-fried foods may contribute to the progression of prostate cancer as well.

What in deep fried foods is so bad for us? Just heating oil that hot can generate potentially carcinogenic compounds, and then known carcinogens such as heterocyclic amines and polycyclic aromatic hydrocarbons form when the muscles of chickens and fish are cooked at that temperature. Deep-fried plants, on the other hand, can form acrylamide.

I did a video about acrylamide back in 2008, suggesting it's a probable human carcinogen (See Acrylamide in French Fries). Since then, studies have suggested pregnant women may want to cut back on French fries to protect the growth of their baby's body and brain. Based on a study (highlighted in my video, Cancer Risk from French Fries) feeding people a little bag of potato chips every day for a month, it now seems acrylamide may also cause inflammation as well, which could explain its purported role in cancer progression.

Acrylamide intake has been associated with endometrial cancer, ovarian cancer, lung cancer, kidney cancer, and esophageal cancer. How much cancer risk are we talking about? Taiwanese researchers examined lifetime cancer risk and French fry consumption. The researchers picked on French fries because they comprise by far the greatest percentage contribution of acrylamide to the diets of children. They estimated that, at most, one or two boys and girls out of every ten thousand would develop cancer eating French fries that they would otherwise not have developed if they hadn't eaten French fries. So it's not as bad as eating something like fried fish, or fried chicken, but how much is that saying?

The level of cancer risk in both boys and girls associated with French fries depends on how long and hot they're fried. In Europe, the food industry swore that they'd self-regulate and control fry times to decrease acrylamide levels, but we've yet to see any subsequent change in acrylamide levels in French fries.

Researchers continue to urge that the cooking temperature should be as low as possible and the cooking time should be as short as possible, "while still maintaining a tasty quality" of course. We wouldn't want to reduce cancer risk too much--they might not taste as good!

Blanching the potatoes first reduces acrylamide formation, but potato chip companies complain that, not only would it muck with the flavor, but it would reduce the nutritional properties by leaching away some of the vitamin C. But if we're relying on potato chips to get our vitamin C, acrylamide is probably the least of our worries.

More on heterocyclic amines:

There are some things we can do to counteract the effects of these carcinogens, though:

I touch on polycyclic aromatic hydrocarbons in Meat Fumes: Dietary Secondhand Smoke and Is Liquid Smoke Flavoring Carcinogenic?
Certain fats may play a role in breast cancer survival as well: Breast Cancer Survival, Butterfat, and Chicken and Breast Cancer Survival and Trans Fat.

-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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Treating Asthma With Plants vs. Pills

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In my video Treating Asthma With Fruits and Vegetables, I highlighted a landmark study on manipulating antioxidant intake in asthma. The study found that just a few extra fruits and vegetables a day can powerfully reduce asthma exacerbation rates. If the antioxidants in the plants are ameliorating asthma, then why can't we take antioxidant pills instead? Because antioxidant pills don't appear to work.

Studies using antioxidant supplements on respiratory or allergic diseases have mostly shown no beneficial effects. This discrepancy between data relating to fruit and vegetable intake compared with those using antioxidant supplements may indicate the importance of the whole food, rather than individual components. For example, in the Harvard Nurse's Health Study, women who got the most vitamin E from their diet appeared to be at half the risk for asthma, (which may help explain why nut consumption is associated with significantly lower rates of wheezing), but vitamin E supplements did not appear to help.

Men who eat a lot of apples appear to have superior lung function, as do kids who eat fresh fruit every day, as measured by FEV1 (basically how much air you can forcibly blow out in one second). The more fruit, salad, and green vegetables kids ate, the greater their lung function appeared.

Researchers are "cautious about concluding which nutrient might be responsible." There's vitamin C in fruits, salads, and green vegetables, but there are lots of other antioxidants, such as "vitamin P," a term used to describe polyphenol phytonutrients found in grapes, flax seeds, beans, berries, broccoli, apples, citrus, herbs, tea, and soy. Polyphenol phytonutrients can directly bind to allergenic proteins and render them hypoallergenic, allowing them to slip under our body's radar. If this first line of defense fails, polyphenols can also inhibit the activation of the allergic response and prevent the ensuing inflammation, and so may not only work for prevention, but for treatment as well.

Most of the available evidence is weak, though, in terms of using supplements containing isolated phytonutrients to treat allergic diseases. We could just give people fruits and vegetables to eat, but then we couldn't perform a double-blind study to see if they work better than placebo. Some researchers decided to use pills containing plant food extracts. Plant extracts are kind of a middle ground. They are better than isolated plant chemicals, but are not as complete as whole foods. Still, since we can put whole foods in a capsule, we can compare the extracts to fake sugar pills that look and feel the same to see if they have an effect.

The first trial involved giving people extracts of apple skins. I've talked about the Japan's big cedar allergy problem before (See Alkylphenol Endocrine Disruptors and Allergies), so apple extract pills were given every day for a few months starting right before pollen season started. The results were pretty disappointing. They found maybe a little less sneezing, but the extract didn't seem to help their stuffy noses or itchy eyes.

What about a tomato extract? A randomized, double-blind, placebo-controlled eight-week trial was performed on perennial allergic rhinitis, this time not for seasonal pollen, but for year-round allergies to things like dust-mites. There are lots of drugs out there, but you may have to take them every day year-round, so how about some tomato pills instead? After oral administration of tomato extract for eight weeks, there was a significant improvement of total nasal symptom scores, combined sneezing, runny nose and nasal obstruction, with no apparent adverse effects.

Would whole tomatoes work even better? If only researchers would design an experiment directly comparing phytonutrient supplements to actual fruits and vegetables head-to-head against asthma, but such a study had never been done... until now. The same amazing study, highlighted in my video, Treating Asthma with Plants vs. Supplements?, that compared the seven-fruit-and-vegetables-a-day diet to the three-fruit-and-vegetables-a-day diet, after completion of its first phase, commenced a parallel, randomized, controlled supplementation trial with capsules of tomato extract, which boosted the power of five tomatoes in one little pill, and the study subjects were given three pills a day.

Who did better, the group that ate seven servings of actual fruits and vegetables a day, or the group that ate three servings a day but also took 15 supposed serving equivalents in pill form? The pills didn't help at all. Improvements in lung function and asthma control were evident only after increased fruit and vegetable intake, which suggests that whole-food interventions are most effective. Both the supplements and increased fruit and vegetable intake were effective methods for increasing carotenoid concentrations in the bloodstream, but who cares? Clinical improvements--getting better from disease--were evident only as a result of an increase in plant, not pill, consumption. The results provide further evidence that whole-food approaches should be used to achieve maximum efficacy of antioxidant interventions.

And if this is what a few more plants can do, what might a whole diet composed of plants accomplish? See Treating Asthma and Eczema with Plant-Based Diets.

I also dealt with preventing asthma in the first place: Preventing Asthma With Fruits and Vegetables.

The theme of whole foods being more efficacious than supplements seems to come up over and over again. See for example:

More on "vitamin P" in How to Slow Brain Aging by Two Years.

The anti-inflammatory effects of nuts may explain the Harvard Nurse's Health Study finding: Fighting Inflammation in a Nut Shell.

-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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How Fruits and Vegetables Can Prevent Asthma

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Asthma is the most common chronic disease in children and the prevalence is increasing around the world. Despite this, most research dollars are spent on adult chronic disease. "One might ask," a group of researchers posited "whether this is because our politicians and senior administrators feel themselves to be more likely to suffer from the latter, and thus ignore allergic diseases as they mostly impact children and young adults" - who don't vote.

An enormous study about asthma and allergies in childhood, highlighted in my video, Preventing Asthma with Fruits and Vegetables, was published that includes more than a million children in nearly a hundred countries, making it the most comprehensive survey of asthma and allergies ever undertaken. The researchers found striking worldwide variations in the prevalence and severity of asthma, allergies, and eczema--a 20 to 60-fold difference in prevalence of symptoms of asthma, allergic runny nose, and atopic eczema around the world. The large variability suggests a crucial role of local characteristics that are determining the differences in prevalence between one place and another.

What kind of environmental factors? Why does the prevalence of itchy eyes and runny noses range anywhere from 1% in India, for example, and up to 45% of kids elsewhere? There were some associations with regional air pollution and smoking rates, but the most significant associations were with diet. Adolescents showed a consistent pattern of decreases in symptoms of wheeze (current and severe), allergic rhinoconjunctivitis, and atopic eczema with increases in per capita consumption of plant foods. The more their calories and protein came from plant sources, the less allergies they tended to have.

In general, there seems to be an association between an increase in asthma prevalence and a decrease in consumption of fresh fruits, green vegetables, and other dietary sources of antioxidants, helping to explain why the prevalence of asthma and respiratory symptoms are lower in populations with high intake of foods of plant origin. High intakes of fat and sodium, and low intakes of fiber and carbohydrates, are linked with asthma, while traditional and vegetarian diets are associated with lower rates. For example, if we look closer within India, in a study of more than 100,000 people, "those who consumed meat (daily or occasionally) were more likely to report asthma than those who were strictly vegetarian." This also meant avoiding eggs.

Eggs have been associated (along with soft drink consumption) with increased risk of respiratory symptoms and asthma in schoolchildren. On the other hand, consumptions of soy foods and fruits were associated with reduced risk of respiratory symptoms. In fact, removing eggs and dairy from the diet may improve lung function in asthmatic children in as little as eight weeks. Therefore, it may be a combination of eating fewer animal foods and more plants.

High vegetable intake, for example, has been found protective in children, potentially cutting the odds of allergic asthma in half. And fruit has also shown a consistent protective association for current and severe wheeze and runny nose in adolescents, and for current and severe asthma, allergies, and eczema in children.

Why is this? I've talked about the endocrine-disrupting industrial pollutants (see Dietary Sources of Alkylphenol Endocrine Disruptors) building up in the meat supply that may increase the risk of allergic disease, but the increase in asthma may be a combination of both a more toxic environment and a more susceptible population. One review notes that, "The dietary changes which have occurred over recent years may have led to a reduction in these natural antioxidant defenses, resulting in a shift of the antioxidant status of the whole population and leading to increased susceptibility to oxidant attack and airway inflammation."

In adults, for example, the risk of airway hyper-reactivity may increase seven-fold among those with the lowest intake of vitamin C from plant foods, while those with the lowest intake of saturated fats may have a 10-fold protection, presumably because of saturated fat's role in triggering inflammation.

The protective effect of plant-based food may also be mediated through effects on intestinal microflora. It turns out that differences in the indigenous intestinal flora might affect the development and priming of the immune system in early childhood. Kids with allergies, for example, tend to be less likely to harbor lactobacilli, the good bacteria that's found in fermented foods, and naturally on many fruits and vegetables. Lactobacillus probiotics may actually help with childhood asthma, which may help explain why children raised on largely organic vegetarian diets may have a lower prevalence of allergic reactions. Infants raised this way tend to have more good lactobacilli in their guts compared to controls, though they were also more likely to have been born naturally, breastfed longer, and not been given antibiotics, so we can't really tell if it's the diet until we put it to the test (See Treating Asthma with Fruits and Vegetables).

More on preventing allergic diseases can be found in my videos Preventing Childhood Allergies and Preventing Allergies in Adulthood.

More on protecting lung function with fruits and vegetables can be found in Preventing COPD With Diet.

Surprised probiotics can affect immune function? Check out my video Preventing the Common Cold with Probiotics? And if you think that is wild, wait until you see Gut Feelings: Probiotics and Mental Health.

What might be in plants that's so beneficial? See Anti-inflammatory Antioxidants.

What might be in animal products that is harmful to lung function? There are endocrine-disrupting industrial pollutants that build up in the food chain that may be playing a role. See my video Alkylphenol Endocrine Disruptors and Allergies. Also there's an inflammatory omega-6 fatty acid found predominantly in chicken and eggs that may contribute to inflammation as well. See Inflammatory Remarks About Arachidonic Acid.

Choosing fragrance-free personal care products may also help reduce airway reactivity: Throw Household Products Off the Scent.

I compare the efficacy of plants to pills (Treating Asthma With Plants vs. Supplements?) and explore the role an entire diet filled with plants might play in Treating Asthma and Eczema With Plant-Based Diets.

-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.

Image Credit: EdTech Stanford University School of Medicine / Flickr

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Slowing Cognitive Decline with Berries

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A plant-based diet is thought to have played a significant role in human evolution and the consumption of whole plant foods and even just extracts have repeatedly been associated with a decreased risk of aging related diseases. And by healthy aging I'm not talking preventing wrinkles, what about protecting our brain? "Two of the most dreaded consequences of dementia with aging are problems moving around and difficulty remembering things. Dementia robs older adults of their independence, control, and identity."

Fruits and vegetables help reduce the risk of other chronic diseases, so might they work for brain diseases as well?

There has been a proliferation of recent interest in plant polyphenols as agents in the treatment of dementia. There are 4,000 different kinds of polyphenols found ubiquitously in foods of plant origin, but berries are packed with them, possessing powerful antioxidant and anti-inflammatory properties. There's a subset of polyphenols called anthocyanidins, which are found in blue and purple pigmented fruits and berries. These polyphenols are uniquely and specifically capable of "both crossing the blood-brain barrier and localizing in brain regions involved in learning and memory." And that's precisely where we need them.

The brain takes up less than 2% of body weight but may burn up to 50% of the body's fuel, creating a potential firestorm of free radicals. Maybe these brain-seeking phytonutrients in berries could fight oxidation and inflammation, and even increase blood flow? This raised a thought-provoking idea. Maybe a "nutritional intervention with blueberries may be effective in forestalling or even reversing the neurological changes associated with aging?" It would be a decade before the first human trial was conducted, but it worked! "Blueberry supplementation improves memory in older adults," suggesting that "consistent supplementation with blueberries may offer an approach to forestall or mitigate brain degeneration with age."

What other blue or purple foods can we try? Concord grape juice was also tested and had a similar benefit, suggesting that supplementation with purple grape juice may enhance cognitive function for older adults with early memory decline. Why use juice and not whole concord grapes? Because then you couldn't design a placebo that looked and tasted exactly the same to rule out the very real and powerful placebo effect. And also because the study was funded by the Welch's grape juice company.

This effect was confirmed in a follow-up study, showing for the first time an increase in neural activation in parts of the brain associated with memory using functional MRI scans. But this brain scan study was tiny: just four people in each group. And same problem in the blueberry study: it had only nine people in it.

Why haven't large population-based studies been done? Because we haven't had good databases on where these phytonutrients are found. We know how much vitamin C is in a blueberry, but not how much anthocyanidin--until now. The Harvard Nurses' Health Study, highlighted in my video, How to Slow Brain Aging by Two Years, followed the cognitive function of more than 16,000 women for years, and found that "long-term consumption of berries was related to significantly slower rates of cognitive decline, even after careful consideration of confounding socioeconomic status" (that is, even after taking into account the fact that rich people eat more berries). The Harvard Nurses' Health Study was the first population-based evidence that greater intakes of blueberries and strawberries were highly associated with slower rates of cognitive decline, and not just by a little bit. "The magnitude of associations were equivalent to the cognitive differences that one might observe in women up to two and a half years apart in age." In other words, women with higher intake of berries appeared to have delayed cognitive aging by as much as two and a half years.

Why shouldn't we just take some anthocyanidin supplement? Because there hasn't been a single study that found any kind of cognitive benefit by just giving single phytonutrients. In fact, the opposite is true. "Whole blueberries appear to be more effective than individual components, showing that the whole is greater than the sum of its parts." These findings have potentially substantial public health implications, as increasing berry intake represents a fairly simple dietary modification to test in older adults for maintaining our brain function.

What other ways could we improve our memory and cognitive function?

What other near-miraculous properties of berries are there?

I add them to my morning smoothie: A Better Breakfast.

-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.

Image Credit: Angelo Desantis / Flickr

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The Reason We Need More Antioxidants

NF-Nov27 The Reason We Need More Antioxidants (And Why We're Not Getting Them).jpg

Glucose is the primary fuel of the human body. We consume glucose and breathe in oxygen to make the energy needed to power our bodies. Plants then take the water and carbon dioxide we breathe out to make oxygen and organic compounds like glucose--and the circle of life continues. The word carbohydrate means, basically, hydrated carbon, which is what plants use to make carbs and all that's left after we burn them for energy in our muscles and brain.

This process of oxidizing glucose to make energy is messy, though, and generates free radicals. Chugging sugar water increases the level of oxidation in our bloodstreams over the next few hours as our bodies metabolize the glucose. (Digestion isn't the only physiological source of free radicals--exercise is too. See Preventing Exercise-Induced Oxidative Stress With Watercress). Why would we evolve to have a negative reaction to our primary fuel? Because over the millions of years we evolved, there was no such thing as sugar water--all sugars and starches came pre-packaged with protective compounds: antioxidants. In nature, sugar always comes with phytonutrients.

If we drink the same amount of sugar in the form of orange juice, we don't get that spike in oxidation, because the sugar in fruit comes prepackaged with antioxidants. We can't just drink vitamin C enriched sugar water either, because it's not the vitamin C in the OJ but the citrus phytonutrients like hesperetin and naringenin that beat back the oxidation. And it's always better to eat the whole fruit than drink the juice (See Best Fruit Juice and Apple Juice May Be Worse Than Sugar Water). If those citrus phytonutrients sounded familiar to you, it's because I mentioned them before in videos like Keeping Your Hands Warm With Citrus and Reducing Muscle Fatigue With Citrus.

If we don't eat phytonutrient-rich plant foods with each meal, then for hours after we eat, our bodies are tipped out of balance into a pro-oxidative state, which can set us up for oxidant stress diseases. That's why we need to ideally eat antioxidant rich foods with every meal.

In the video, Minimum "Recommended Daily Allowance" of Antioxidants, we can see the levels of oxidized fat in our blood one, two, and three hours after sugar water ingestion, and the corresponding drop in vitamin E levels in our blood as our body's antioxidant stores are being used up. If we don't eat phytonutrient-rich foods with our meals, our body has to dip into its backup supply of antioxidants. We can't get away with that for long. So while ideally we should stuff our faces with as many phytonutrient-rich foods as we can.

In the very least we should eat enough antioxidants to counter the oxidation of digestion. We don't want to slide backwards every day and end up with less antioxidants in our bodies than we woke up with.

A chart in the video, Minimum "Recommended Daily Allowance" of Antioxidants, shows the amount of antioxidants we need every day, depending on how much we eat, just to counter the oxidation of digestion. Men in the U.S. average about 2500 calories a day and so should be getting at least 11,000 antioxidant units a day. Women eat about 1800 calories and so should get at least 8,000 units just to stay solvent. However, the average American doesn't even get half the minimum-no wonder oxidant stress related diseases abound. We're getting so few antioxidants in our diet that we can't even keep up with the free radicals created by merely digesting our meals. We are a nation in chronic oxidative debt.

Developed societies eat a lot of food but not enough plants, which could result in exaggerated and prolonged metabolic, oxidative, and immune imbalance. This presents opportunity for biological insult that over time could supersede our defense and repair systems, and manifest in cellular dysfunction, disease, and ultimately death.

Is there a refined sweetener that doesn't cause free radical formation? Yes: Erythritol May Be a Sweet Antioxidant.

What's the best way of reaching our daily minimum of 8,000-11,000 antioxidant units a day? That's covered in my video How to Reach the Antioxidant "RDA".

Background on the role free radicals play in aging and disease can be found in my video Mitochondrial Theory of Aging. Antioxidant-rich diets can even change gene expression: Plant-Based Diets and Cellular Stress Defenses.

-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.

Image Credit: Benson Kua / Flickr

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