How Much Water Should We Drink Every Day?

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More than 2000 years ago Hippocrates (460-377 BCE) said, "If we could give every individual the right amount of nourishment and exercise, not too little and not too much, we would have found the safest way to health." What does that mean when it comes to water? Water has been described as a neglected, unappreciated, and under-researched subject, and further complicating the issue, a lot of the papers extolling the need for proper hydration are funded by the bottled water industry.

It turns out the often quoted "drink at least eight glasses of water a day" dictum has little underpinning scientific evidence . Where did that idea come from? The recommendation was traced to a 1921 paper, in which the author measured his own pee and sweat and determined we lose about 3% of our body weight in water a day, or about 8 cups (see How Many Glasses of Water Should We Drink in a Day?). Consequently, for the longest time, water requirement guidelines for humanity were based on just one person.

There is evidence that not drinking enough may be associated with falls and fractures, heat stroke, heart disease, lung disorders, kidney disease, kidney stones, bladder and colon cancer, urinary tract infections, constipation, dry mouth, cavities, decreased immune function and cataract formation. The problem with many of these studies is that low water intake is associated with several unhealthy behaviors, such as low fruit and vegetable intake, more fast-food, less shopping at farmers markets. And who drinks lots of water? People who exercise a lot. No wonder they tend to have lower disease rates!

Only large and expensive randomized trials could settle these questions definitively. Given that water cannot be patented, such trials seem unlikely; who's going to pay for them? We're left with studies that find an association between disease and low water intake. But are people sick because they drink less, or are they drinking less because they're sick? There have been a few large prospective studies in which fluid intake is measured before disease develops. For example, a Harvard study of 48,000 men found that the risk of bladder cancer decreased by 7% for every extra daily cup of fluid we drink. Therefore, a high intake of water--like 8 cups a day--may reduce the risk of bladder cancer by about 50%, potentially saving thousands of lives.

The accompanying editorial commented that strategies to prevent the most prevalent cancers in the West are remarkably straightforward in principle. To prevent lung cancer, quit smoking; to prevent breast cancer, maintain your ideal body weight and exercise; and to prevent skin cancer, stay out of the sun. Now comes this seemingly simple way to reduce the risk of bladder cancer: drink more fluids.

Probably the best evidence we have for a cut off of water intake comes from the Adventist Health Study, in which 20,000 men and women were studied. About one-half were vegetarian, so they were also getting extra water by eating more fruits and vegetables. Those drinking 5 or more glasses of water a day had about half the risk of dying from heart disease compared to those who drank 2 or fewer glasses a day. Like the Harvard study, this protection was found after controlling for other factors such as diet and exercise. These data suggest that it was the water itself that was decreasing risk, perhaps by lowering blood viscosity (blood thickness).

Based on all the best evidence to date, authorities from Europe, the U.S. Institute of Medicine, and the World Health Organization recommend between 2.0 and 2.7 liters (8 to 11 cups) of water a day for women, and 2.5 to 3.7 liters (10 to 15 cups) a day for men. This includes water from all sources, not just beverages. We get about a liter from food and the water our body makes. So this translates into a recommendation for women to drink 4 to 7 cups of water a day and men 6 to 11 cups, assuming only moderate physical activity at moderate ambient temperatures.

We can also get water from all the other drinks we consume, including caffeinated drinks, with the exception of stronger alcoholic drinks like wines and spirits. Beer can leave you with more water than you started with, but wine actively dehydrates you. However, in the cancer and heart disease studies I mentioned above, the benefits were only found with increased water consumption, not other beverages.

I've previously touched on the cognitive benefits of proper hydration here: Does a Drink Of Water Make Children Smarter?

Surprised tea is hydrating? See my video Is Caffeinated Tea Dehydrating?

Surprised that the 8-a-day rested on such flimsy evidence? Unfortunately, so much of what we do in medicine has shaky underpinnings. That's the impetus behind the idea of evidence-based medicine (what a concept!). Ironically, this new movement may itself undermine some of the most effective treatments. See Evidence-Based Medicine or Evidence-Biased?

How else can we reduce our risk of bladder cancer? See Raw Broccoli and Bladder Cancer Survival.

What kind of water? I recommend tap water, which tends to be preferable from a chemical and microbial contamination standpoint. What about buying one of those fancy alkalizing machines? See Alkaline Water: a Scam?

It's so nice to have data on such a fundamental question. We have much to thank the Adventists for. You will see their studies cropping up frequently. See, for example, Plant-Based Diets and Diabetes, The Okinawa Diet: Living to 100, and Evidence-Based Eating.

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:

Image Credit: Sally Plank / Flickr. Image has been modified.

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The Two Most Active Ingredients of the Mediterranean Diet

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Olives and nuts are plant foods, and as such, are packed with antioxidants, raising the antioxidant level of our bloodstream resulting in lower fat oxidation and free radical DNA damage, but what's happening inside people's arteries?

Researchers measured the amount of atherosclerotic plaque in the neck arteries going to the brain in folks who for years were eating added nuts, added extra virgin olive oil or neither to their daily diets. In the control group, the plaque got worse, which is what happens when one continues to eat an artery-clogging diet, but there were no significant changes in the added extra virgin olive oil group, and the plaque in the added nut group appeared to get better. The nuts appeared to induce a regression of the disease, or at least a significant delay in the progression. The nut group was still suffering strokes, but only half as many, perhaps because the reduction in plaque height within the arteries on extra nuts was indicating a stabilization of the plaque, rendering them less likely to rupture. You can see these results in my video Which Parts of the Mediterranean Diet Extended Life?

Adding nuts to our diet may also improve endothelial function, boosting the ability of our arteries to dilate naturally by about 30 percent. If you look at the baseline adherence to Mediterranean diet principles and control for things like smoking and exercise, there were only two factors significantly associated with reduced heart attack and stroke risk: more vegetables and more nuts. No significant association with the olive oil, wine, fish or cutting back on soda and cookies. Among the individual components, only increased consumption of vegetables and nuts were related to reduced cardiovascular events.

On the one hand, cutting stroke risk in half just by eating a handful of nuts a day is pretty amazing, but those in the added nut group didn't appear to live any longer overall. This is in contrast to other studies that suggested that frequent nut consumption may extend life. For example, the Harvard health professionals studies, involving a whopping three million person-years of follow-up over decades, found nut consumption associated with fewer deaths from cancer, heart disease, respiratory disease and most importantly fewer deaths overall. This was confirmed by all the other big major prospective studies in a recent review.

So what's going on here with the study showing no longevity benefit from nuts? Did they just not wait long enough? Just because people were randomized to the nut group didn't mean they actually ate more nuts, and those randomized to the other groups didn't necessarily stay away.

If you re-analyze the data comparing the death rates of those who actually ate more nuts to those who actually didn't, nut consumption was indeed associated with significantly reduced risk of death. If you do the same kind of post hoc analysis with olive oil, even with the extra virgin, there is no benefit in terms of living longer. This is consistent with how Ancel Keys, the so-called Father of the Mediterranean diet, viewed olive oil. He thought of its benefit more as a way of just replacing animal fats; anything to get people to eat less lard and butter.

What is the best kind of nut? The greatest benefits were attributed to walnuts, particularly for preventing cancer deaths. Those eating more than three servings of walnuts a week appeared to cut their risk of dying from cancer in half.

Now it's just a matter of communicating the research to the public. All the major cancer groups emphasize a more plant-based diet, remarkably consistent with the World Health Organization guidelines for healthy eating. The far-reaching positive effects of a plant-based diet--including walnuts--may be the most critical message for the public.

Here are some of my previous videos on the Mediterranean diet:

Think the effects of adding a few nuts to one's daily diet are too good to believe? Check out my video Four Nuts Once a Month. For more on Walnuts and Artery Function check out the video, and for more on nuts and cancer prevention, see Which Nut Fights Cancer Better?

Nuts May Help Prevent Death and so may beans; see Increased Lifespan from Beans. What about Fruits and Longevity: How Many Minutes per Mouthful?

More on protecting ourselves from "brain attacks" in Preventing Strokes with Diet.

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:

Image Credit: garlandcannon / Flickr. This image has been modified.

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The Two Most Active Ingredients of the Mediterranean Diet

Which Parts of the Mediterranean Diet Extended Life.jpg

Olives and nuts are plant foods, and as such, are packed with antioxidants, raising the antioxidant level of our bloodstream resulting in lower fat oxidation and free radical DNA damage, but what's happening inside people's arteries?

Researchers measured the amount of atherosclerotic plaque in the neck arteries going to the brain in folks who for years were eating added nuts, added extra virgin olive oil or neither to their daily diets. In the control group, the plaque got worse, which is what happens when one continues to eat an artery-clogging diet, but there were no significant changes in the added extra virgin olive oil group, and the plaque in the added nut group appeared to get better. The nuts appeared to induce a regression of the disease, or at least a significant delay in the progression. The nut group was still suffering strokes, but only half as many, perhaps because the reduction in plaque height within the arteries on extra nuts was indicating a stabilization of the plaque, rendering them less likely to rupture. You can see these results in my video Which Parts of the Mediterranean Diet Extended Life?

Adding nuts to our diet may also improve endothelial function, boosting the ability of our arteries to dilate naturally by about 30 percent. If you look at the baseline adherence to Mediterranean diet principles and control for things like smoking and exercise, there were only two factors significantly associated with reduced heart attack and stroke risk: more vegetables and more nuts. No significant association with the olive oil, wine, fish or cutting back on soda and cookies. Among the individual components, only increased consumption of vegetables and nuts were related to reduced cardiovascular events.

On the one hand, cutting stroke risk in half just by eating a handful of nuts a day is pretty amazing, but those in the added nut group didn't appear to live any longer overall. This is in contrast to other studies that suggested that frequent nut consumption may extend life. For example, the Harvard health professionals studies, involving a whopping three million person-years of follow-up over decades, found nut consumption associated with fewer deaths from cancer, heart disease, respiratory disease and most importantly fewer deaths overall. This was confirmed by all the other big major prospective studies in a recent review.

So what's going on here with the study showing no longevity benefit from nuts? Did they just not wait long enough? Just because people were randomized to the nut group didn't mean they actually ate more nuts, and those randomized to the other groups didn't necessarily stay away.

If you re-analyze the data comparing the death rates of those who actually ate more nuts to those who actually didn't, nut consumption was indeed associated with significantly reduced risk of death. If you do the same kind of post hoc analysis with olive oil, even with the extra virgin, there is no benefit in terms of living longer. This is consistent with how Ancel Keys, the so-called Father of the Mediterranean diet, viewed olive oil. He thought of its benefit more as a way of just replacing animal fats; anything to get people to eat less lard and butter.

What is the best kind of nut? The greatest benefits were attributed to walnuts, particularly for preventing cancer deaths. Those eating more than three servings of walnuts a week appeared to cut their risk of dying from cancer in half.

Now it's just a matter of communicating the research to the public. All the major cancer groups emphasize a more plant-based diet, remarkably consistent with the World Health Organization guidelines for healthy eating. The far-reaching positive effects of a plant-based diet--including walnuts--may be the most critical message for the public.

Here are some of my previous videos on the Mediterranean diet:

Think the effects of adding a few nuts to one's daily diet are too good to believe? Check out my video Four Nuts Once a Month. For more on Walnuts and Artery Function check out the video, and for more on nuts and cancer prevention, see Which Nut Fights Cancer Better?

Nuts May Help Prevent Death and so may beans; see Increased Lifespan from Beans. What about Fruits and Longevity: How Many Minutes per Mouthful?

More on protecting ourselves from "brain attacks" in Preventing Strokes with Diet.

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:

Image Credit: garlandcannon / Flickr. This image has been modified.

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Do You Meet the Simple Seven?

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In public health school, you learn there are three levels of preventive medicine. Primary prevention would be like trying to prevent someone at risk for heart disease from getting his or her first heart attack. Secondary prevention is when you already have the disease and are trying to prevent your second heart attack, and tertiary prevention is like cardiac rehab, where you're just trying to reduce the complication rates. A fourth level was suggested in 2000, quaternary prevention, trying to reduce the damage from all the drugs and surgery from the first three levels. But people seem to forget about a fifth concept, introduced by the World Health Organization back in 1978, termed primordial prevention, which is being embraced by the American Heart Association's 2020 strategic impact goals.

Primordial prevention was conceived as a strategy to prevent whole societies from experiencing epidemics of the risk factors. The corresponding strategy at the individual level is to prevent the development of risk factors. Instead of trying to prevent someone with high cholesterol from getting a heart attack, why not prevent them from getting high cholesterol in the first place?

So the American Heart Association came up with the simple seven, featured in my video, How Many Meet the Simple Seven?. These health behaviors or factors include not smoking, not being overweight, being "very active" (defined as walking at least 22 minutes a day), eating a few fruits and veggies, having below average cholesterol, normal blood pressure, and normal blood sugars.

Their goal was to reduce heart disease deaths by 20% by 2020. Why so modest an aim? An improvement of 25% was deemed "unrealistic," and 15% was considered insufficient, so they decided on 20. If 90% of risk can be thrown out the window by engaging in simple lifestyle modifications, why is just 25% considered unrealistic? To understand, one must realize just how bad our diets have gotten.

The most common reason patients give for not complying with a cholesterol-lowering diet may be the presumption that they're already eating healthy and so don't need to change. But if you look at the status of cardiovascular health in U.S. adults, only about 1% of Americans have a bare minimum of healthy eating behaviors, such as five-a-day fruits and veggies, eating beans, whole grains, drinking less than three cans of soda a week, etc. What percentage of Americans hit all seven of the simple seven? 14,000 men and women were surveyed, and most had two or three, but hardly any had all seven simple health components. Just how low a prevalence was having seven out of seven? Only about 1 out of 2,000 Americans had all seen factors intact. And the one they were missing the most was diet.

Unfortunately unhealthy behaviors extend into the medical profession. Just like smoking doctors are less likely to tell their patients to stop smoking, and couch potato docs are less likely to push exercise, or things like more fruits and vegetables; we need to role-model healthy behavior. This greatly enhances our credibility and effectiveness. Gone are the days of traditional authority when the fat physician, dropping cigarette ash down his gravy-stained vest, could credibly prescribe a change in behavior.

So What Diet Should Physicians Recommend? Watch the video!

Lifestyle medicine, the use of diet and lifestyle changes to prevent and treat disease, cannot only be cheaper and safer, but also more effective. See, for example:

I've previously noted just how sad the Standard American Diet is in Nation's Diet in Crisis. See how you compare: Calculate Your Healthy Eating Score.

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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How Much Added Sugar is Too Much?

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In 1776, at the time of the American Revolution, Americans consumed about four pounds of sugar per person each year. By 1850, this had risen to 20 pounds, and by 1994 to 120 pounds. Now we're closer to 160 (See How Much Added Sugar is Too Much?). Half of table sugar is fructose, taking up about 10 percent of our diet. This is not from eating apples, but rather the fact that we're each guzzling the equivalent of 16-ounce soft drink every day; that's about 50 gallons a year.

Even researchers paid by the likes of the Dr. Pepper Snapple Group and The Coca Cola Company acknowledge that sugar is empty calories, containing "no essential micronutrients, and therefore if we're trying to reduce calorie intake, reducing sugar consumption is obviously the place to start." Concern has been raised, though, that sugar calories may be worst than just empty.

A growing body of scientific evidence suggests that "the fructose added to foods and beverages in the form of table sugar and high fructose corn syrup in large enough amounts can trigger processes that lead to liver toxicity and other chronic diseases."

Fructose hones in like a laser beam on the liver, and like alcohol, fructose can increase the fat in the liver. The increase in non-alcoholic fatty liver disease is one of the most remarkable medical developments over the past three decades--the emergence of fatty liver inflammation as a public health problem here and around the globe.

These may not be messages that the sugar industry or beverage makers want to hear. In response, the director-general of the industry front group, the World Sugar Research Organization, replied, "Overconsumption of anything is harmful, including water and air." Yes, he compared the overconsumption of sugar to breathing too much.

Under American Heart Association's new sugar guidelines, most American women should consume no more than 100 calories per day from added sugars, and most American men should eat or drink no more than 150. That means one can of soda could take us over the top for the day. The new draft guidelines from the World Health Organization suggests we could benefit from restricting added sugars to under 5 percent of calories. That's about six spoonfuls of added sugar. I don't know why they don't just recommend zero as optimal, but you can get a sense of how radical their proposal is given that we consume an average of 12-18 spoonfuls a day right now.

This underscores why a whole foods, plant-based diet is preferable to a plant-based diet that includes processed junk.

I've touched on the harm of refined sugars before in:

For healthful alternatives in baking, see The Healthiest Sweetener, and for beverages, Erythritol May Be a Sweet Antioxidant.

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: Adam Engelhart / Flickr

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No More Than a Quart a Day of Hibiscus Tea

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Over the counter antacids are probably the most important source for human aluminum exposure in terms of dose. For example, Maalox, taken as directed, can exceed the daily safety limit more than 100-fold, and nowhere on the label does it say to not take it with acidic beverages such as fruit juice. Washing an antacid down with orange juice can increase aluminum absorption 8-fold, and citric acid-the acid found naturally concentrated in lemon and limes--is even worse.

Just as sour fruits can enhance the absorption of iron (a good thing), the same mechanism they may enhance the absorption of aluminum (a bad thing). This raises the question of what happens when one adds lemon juice to tea? Previously, I concluded that the amount of aluminum in tea is not a problem for most people because it's not very absorbable (See Is There Too Much Aluminum in Tea?). What if we add lemon? Researchers publishing in the journal Food and Chemical Toxicology found no difference between tea with lemon, tea without lemon, or no tea at all in terms of the amount of aluminum in the bloodstream, suggesting that tea drinking does not significantly contribute to aluminum getting inside the body.

The researchers used black tea, green tea, white tea, oolong tea, but what about the "red zinger" herbal tea, hibiscus? The reason hibiscus tea is called "sour tea" is because it has natural acids in it like citric acid. Might these acids boost the absorption of any hibiscus's aluminum? While a greater percentage of aluminum gets from the hibiscus into the tea water than from the other teas, there's less aluminum overall.

The real question is whether the aluminum then gets from the tea water into our bodies. We don't have that data, so to be on the safe side we should assume the worst: that hibiscus tea aluminum, unlike green and black tea aluminum, is completely absorbable. In that case, based on this data and the World Health Organization weekly safety limit, we may not want to drink more than 15 cups of hibiscus tea a day, (based on someone who's about 150 pounds). If you have a 75 pound 10-year-old, a half-gallon a day may theoretically be too much. Recent, more extensive testing highlighted in my video, How Much Hibiscus Tea is Too Much?, suggests that levels may reach level twice as high. Therefore, to be safe, no more than about two quarts a day for adults, or one quart a day for kids or pregnant women. Hibiscus tea should be completely avoided by infants under six months--who should only be getting breast milk--as well as kids with kidney failure, who can't efficiently excrete it.

There is also a concern about the impressive manganese level in hibiscus tea. Manganese is an essential trace mineral, a vital component of some of our most important antioxidant enzymes, but we probably only need about two to five milligrams a day. Four cups of hibiscus tea can have as much as 17 milligrams, with an average of about ten. Is that a problem?

One study from the University of Wisconsin found that women given 15 milligrams of manganese a day for four months, saw, if anything, an improvement in their anti-inflammatory, anti-oxidant enzyme activity. Another study using 20 milligrams a day similarly showed no adverse short-term effects, and importantly showed that the retention of dietary manganese is regulated. Our bodies aren't stupid; if we take in too much manganese, we decrease the absorption and increases the excretion. Even though tea drinkers may get ten times the manganese load (10 or 20 milligrams a day) the levels in their blood are essentially identical. There is little evidence that dietary manganese poses a risk.

These studies were conducted with regular tea, though, so we don't know about the absorption from hibiscus. To err on the side of caution we should probably not routinely exceed the reference dose of ten milligrams per day, or about a quart a day for adults and a half-quart for a 75 pound child.

I've actually changed my consumption. Given the benefits of the stuff, I was using it as a substitute for drinking water, drinking around two quarts a day. I was also blending the hibiscus petals in, not throwing them away, effectively doubling the aluminum content, and increasing manganese concentrations by about 30%. So given this data I've cut back to no more than a quart of filtered hibiscus tea a day.

Lemon can actually boost the antioxidant content of green and white tea. See Green Tea vs. White. For a comparison of their cancer-fighting effects in vitro, Antimutagenic Activity of Green Versus White Tea.

Before that I covered another potential downside of sour tea consumption in Protecting Teeth From Hibiscus Tea, and before that a reason we should all consider drinking it in: Hibiscus Tea vs. Plant-Based Diets for Hypertension.

For more on the iron absorption effect, see my video Risks Associated with Iron Supplements.

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: mararie / Flickr

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Aluminum Levels in Tea

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While aluminum is the third most abundant element on Earth, it may not be good for our brain, something we learned studying foundry workers exposed to particularly high levels. Although the role of aluminum in the development of brain diseases like Alzheimer's is controversial, to be prudent, steps should probably be taken to lessen our exposure to this metal.

There are a number of aluminum-containing drugs on the market (like antacids, which have the highest levels), though aluminum compounds are also added to processed foods such as anti-caking agents in pancake mix, melting agents in American cheese, meat binders, gravy thickeners, rising agents in some baking powders and dye-binders in candy. Therefore, it's better to stick to unprocessed, natural foods. Also, if you cook those natural foods in an aluminum pot, a significant amount of aluminum can leach into the food (compared to cooking in stainless steel).

When researchers tried the same experiment with tea, they got a few milligrams of aluminum regardless of what type of pot they used, suggesting that aluminum was in the tea itself. Indeed, back in the 1950's researchers noticed that tea plants tended to suck up aluminum from the soil. But it's the dose that makes the poison. According to the World Health Organization, the provisional tolerable weekly intake--our best guess at a safety limit for aluminum--is two mg per healthy kilogram of body weight per week, which is nearly a milligram per pound. Someone who weighs around 150 pounds probably shouldn't ingest more than around 20 mg of aluminum per day.

Up to a fifth of aluminum intake may come from beverages, so what we drink probably shouldn't contribute more than about four mg a day, the amount found in about five cups of green, black, or oolong tea. So should we not drink more than five cups of tea a day?

It's not what you eat or drink, it's what you absorb. If we just measured how much aluminum was in tea, it would seem as though a couple cups could double aluminum intake for the day. But if we measure the level of aluminum in people's bodies after they drink tea, it doesn't go up. This suggests that the bioavailability of aluminum in tea is low, possibly because most of the extractable aluminum in brewed tea is strongly bound to large phytonutrients that are not easily absorbed, so the aluminum just passes right through us without actually getting into our bodies. Probably more than 90 percent of the aluminum in tea is bound up.

One study out of Singapore, highlighted in my video, Is There Too Much Aluminum in Tea? did show a large spike in aluminum excretion through the urine after drinking tea compared to water. The only way for something to get from our mouth to our bladder is to first be absorbed into our bloodstream. But the researchers weren't comparing the same quantity of tea to water. They had the study subject chug down about eight and a half cups of tea, or drink water at their leisure. Therefore, the tea drinkers peed a lot more, so the aluminum content cup-for-cup was no different for tea versus water. This suggests that gross aluminum absorption from tea is unlikely and that only a little aluminum is potentially available for absorption.

So although as few as four cups of tea could provide 100 percent of our daily aluminum limit, the percentage available for absorption in the intestine may be less than 10 percent. It is therefore unlikely that moderate amounts of tea drinking can have any harmful effects--for people with normal aluminum excretion. Tea may not, however, be a good beverage for children with kidney failure, since they can't get rid of aluminum as efficiently. For most people, though, tea shouldn't be a problem.

On a special note, if you drink tea out of a can, buy undented cans. The aluminum in dented cans can leach into the liquid, boosting aluminum levels by a factor of eight while sitting on store shelves for a year.

What about the levels and absorbability of the aluminum in my other favorite type of tea? Find out in my video, How Much Hibiscus Tea is Too Much?

The tea plant also sucks up fluoride. So much so that heavy tea drinking can stain the teeth of children. See my video Childhood Tea Drinking May Increase Fluorosis Risk.

Why should we go out of our way to drink tea? See:

Is Caffeinated Tea Dehydrating? Find out by watching the video!

For more on metals in our food supply, 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: Toshiyuki IMAI / Flickr

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Plant-Based Diets for Hypertension

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Recently, researchers from Taiwan pitted the herbal tea hibiscus against obesity. They gave hibiscus to overweight individuals and reported that subjects showing reduced body weight. However, after 12 weeks on hibiscus subjects only lost about three pounds, only one and a half pounds over placebo. Hibiscus is clearly no magic fix for obesity.

The purported cholesterol-lowering property of hibiscus tea looked a bit more promising. Some older studies suggested as much as an 8% reduction from drinking two cups a day for a month. When all the studies are put together, though, the results are pretty much a wash. This may be because only about 50% of people respond at all to drinking the equivalent of between two to five cups a day, though those that do may get a respectable 12% drop. That's nothing like the 30% one can get within weeks of eating a healthy, plant-based diet, though.

Hibiscus may really shine in treating high blood pressure, a disease affecting a billion people and killing millions. Up until 2010, there wasn't sufficient high quality research to support the use of hibiscus tea to treat hypertension, but there are now randomized double-blind, placebo-controlled studies where hibiscus tea is compared to artificially colored and flavored water that looks and tastes like hibiscus tea, and the tea lowers blood pressure significantly better.

We're still not sure how it works, but hibiscus appears to boost nitric oxide production, which could help our arteries relax and dilate better. Regardless, an updated review acknowledged that the daily consumption of hibiscus tea may indeed significantly lower blood pressures in people with hypertension.

How does hibiscus compare to other blood pressure interventions? The premier clinical trial when it comes to comprehensive lifestyle modification for blood pressure control is the PREMIER Clinical Trial. Realizing that nine out of ten Americans are going to develop hypertension, researchers from John Hopkins randomized 800 men and women with high blood pressure into one of three groups. One was the control group, the so-called "advice only group," where patients were just told to lose weight, cut down on salt, increase exercise and eat healthier. In the two behavioral intervention groups the researchers got serious. Eighteen face-to-face sessions, groups meetings, food diaries, physical activity records, and calorie and sodium intake monitoring. One intervention group just concentrated on exercise; the other included exercise and diet. Researchers pushed the DASH diet, which is high in fruits and vegetables and low in full-fat dairy products and meat. In six months subjects achieved a 4.3 point drop in systolic blood pressure, compared to the control, slightly better than the lifestyle intervention without the diet.

A few points might not sound like a lot--that's like someone going from a blood pressure of 150 over 90 to a blood pressure of 146 over 90--but on a population scale a five point drop in the total number could result in 14% fewer stroke deaths, 9% fewer fatal heart attacks, and 7% fewer deaths every year overall.

A cup of hibiscus tea with each meal didn't just lower blood pressure by three, four, or five points, but by seven points, from an average of 129 down to 122. In fact, tested head-to-head against a leading blood-pressure drug, Captopril, two cups of strong hibiscus tea every morning (five tea bags for the two cups) was as effective in lowering blood pressure as a starting dose of 25mg of captopril taken twice a day.

So hibiscus tea is as good as drugs, without side-effects, and better than diet and exercise? Well, the lifestyle interventions in the PREMIER study were pretty wimpy. As public health experts noted, the PREMIER study was only asking for 30 minutes of exercise a day, whereas the World Health Organization recommends a minimum of an hour a day.

Diet-wise, the lower the animal fat intake, and the more plant sources of protein the PREMIER participants were eating, the better the diet appeared to work. This may explain why vegetarian diets appear to work even better, and the more plant-based, the lower the prevalence of hypertension.

On the DASH diet, subjects cut down on meat, but were still eating it every day, so would qualify as nonvegetarians in the Adventist 2 study (highlighted in my video Hibiscus Tea vs. Plant-Based Diets for Hypertension) which looked at 89,000 Californians. It found that those who only ate meat on a weekly basis had 23% lower rates of high blood pressure. Those who cut out all meat except fish had 38% lower rates. Those eating no meat at all, vegetarians, have less than half the rate. The vegans--cutting out all animal protein and fat--appeared to have thrown three quarters of their risk for this major killer out the window.

One sees the same kind of step-wise drop in diabetes rates as one's diet gets more and more plant-based, and a drop in excess body weight, such that only those eating completely plant-based diets in the Adventist 2 study fell into the ideal weight category. Could that be why those eating plant-based have such great blood pressure? Maybe it's just because they're so skinny. I've previously shown how those eating plant-based just have a fraction of the diabetes risk even at the same weight. but what about hypertension?

The average American has what's called prehypertension, which means the top number of our blood pressure is between 120 and 139. We don't have hypertension yet, which starts at 140, but we may be well on our way. Compare that to the blood pressure of those eating whole food plant-based diets. In one study, those eating plant-based didn't have blood pressures three points lower, four points lower, or even seen points lower, but 28 points lower. However, the group eating the standard American diet was, on average, overweight with a BMI over 26, still better than most Americans, while the vegans were a trim 21--that's 36 pounds lighter.

Maybe the only reason those eating meat, eggs, dairy, and processed junk had such higher blood pressure was because they were overweight. Maybe the diet per se had nothing to do with it?

To solve that riddle we would have to find a group still eating the standard American diet, but as slim as vegans. To find a group that trim, researchers had to use long-distance endurance athletes, who ate the same crappy American diet, but ran an average of 48 miles per week for 21 years. Anyone who runs almost two marathons a week for 20 years can be as slim as a vegan--no matter what they eat!

How did the endurance runners compare to the couch potato vegans? It appears that if we run an average of about a thousand miles every year our blood pressures can rival some couch potato vegans. That doesn't mean we can't do both, but it may be easier to just eat plants.


Those who've been following my work for years have seen how my videos have evolved. In the past, the hibiscus results may have been the whole article or video. But thanks to everyone's support, I've been able to delegate the logistics to staff and concentrate more on the content creation. This allows me to do deeper dives into the literature to put new findings into better context. The posts are a bit longer, but hopefully they're more useful--let me know what you think!

For such a leading killer, hypertension has not gotten the coverage it deserves on NutritionFacts.org. Here's a few videos, with more to come:

So should we all be drinking hibiscus tea every day? This is the first of a four part series on the latest on hibiscus. Stay tuned for the next three:

For another comparison of those running marathons and those eating plants, see: Arteries of Vegans vs. Runners

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: Amy / Flickr

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Antibiotic-Resistant "Superbugs" in Meat

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As a rule, "high-ranking public-health officials try to avoid apocalyptic descriptors. So it's worrying to hear those like the Director of the CDC warn of a coming health 'nightmare' and a 'catastrophic threat.'" A number of prominent publications recently warned of the threat of antibiotic resistance. The CDC estimates that at a minimum, more than two million people are sickened every year with antibiotic-resistant infections in the United States, with at least 23,000 dying as a result (See MRSA Superbugs in Meat).

We may be at the dawn of a post-antibiotic era. Achievements in modern medicine that we today take for granted, such as surgery and the treatment of preterm babies, would not be possible without access to effective treatment for bacterial infections. For example, without antibiotics, the rate of postoperative infection after a procedure like a hip replacement would be 40-50% and about one in three of those patients would die. So the so-called worst case scenarios where resistant infections could cost $50 billion a year might still be an underestimate. "From cradle to grave, antibiotics have become pivotal in safeguarding the overall health of human societies."

So the dire phrasing from head officials may be warranted. There are now infections like carbapenem-resistant enterobacter that are resistant to nearly all antibiotics, even to so-called drugs of last resort. Worryingly, some of these last resort drugs are being used extensively in animal agriculture.

According to the World Health Organization, more antibiotics are fed to farmed animals than are used to treat disease in human patients. Doctors overprescribe antibiotics, but huge amounts of antibiotics are used in fish farming and other intensive animal agriculture, up to four times the amount used in human medicine. Why? "Suboptimum growth to slaughter weight caused by unsanitary conditions can be compensated with the addition of antibiotics to feed." Instead of relieving any stressful overcrowded unhygienic conditions, it may be cheaper to just dose the animals with drugs.

In this way, factory farms are driving the growth of antibiotic-resistant organisms that cause human diseases. "This may help bolster the industry's bottom line, but in the process, bacteria are developing antimicrobial resistance, which affects human health."

In the United States, the FDA reports that 80% of antimicrobial drugs in the United States are used in food animals, mainly to promote growth in this kind of high-density production. This can select for antibiotic-resistant bacteria like methicillin-resistant Staph aureus, or MRSA, considered a serious threat in the United States.

These industrial pig operations may provide optimal conditions for the introduction and transmission of MRSA. U.S. pork producers are currently permitted to use 29 antibiotic drugs in feed--all without a prescription. Antiobitics are currently added to about 90% of pigs starter feeds.

When animals receive unnecessary antibiotics, bacteria can be come resistant to the drugs, then travel on meat to the store, and end up causing hard-to-treat illnesses in people.

MRSA present in retail raw meat may serve as a possible source of bacterial infections of food preparers in the food industry and the hands of consumers in the home. Once MRSA gets into our homes on meat, it can transfer to our cutting boards, knives, and onto our skin at a rate similar to the rate of transmission from touching an infected patient contaminated with MRSA. Washing of hands after touching raw pork is advised.

I know I've already covered this topic before, but it never fails to shock me that the meat industry can get away with something so forcefully and universally condemned by the public health community. What other industrial sector could get away with putting people at such risk? It speaks to the combined might of the livestock industry and the pharmaceutical industry in holding sway over our democratic process, no matter what the human health consequences.

If you've missed my other MRSA videos, check out:

And for more on this critical issue in general:

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: Jellaluna / Flickr

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How Learning to Cook Can Save Your Life

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The eating habits of modern Americans have been described as, "eating breakfast in their cars, lunch at their desks and chicken from a bucket." Within the last few decades, Americans are eating out more and more, and cooking fewer meals at home, which are typically healthier. Home-cooled meals tend to contain less saturated fat, cholesterol, and sodium, and more fiber. Therefore, the benefits to preparing healthy food at home may include the prevention of chronic disease. Just because food is prepared at home doesn't mean it's healthy, though. Microwaving a frozen pizza isn't exactly home cooking.

One of the problems is many people no longer know how to cook. For example, one study reported that 25% of the men in the study had absolutely no cooking skills whatsoever. Another study in the UK compared the nutritional content of meals created by television chefs to TV dinners, and both were then compared to the nutritional guidelines published by the World Health Organization. The researchers looked at a hundred of each, and not a single one complied with the nutrition standards. And the TV chef recipes were even less healthy than the TV dinners!

Many people don't know how to make healthy food taste good. This is not a new problem; an editorial in the Journal of the American Medical Association bemoaned the same issue back in 1913. In the United States, "vegetables are frequently boiled in a way which deprives them of their characteristic odor and their toothsomeness. 'Villainous and idiotic' are the only adjectives that can describe our methods of cooking vegetables."

Researchers in Taiwan recently found that in a group of elderly Taiwanese people, those who cooked their own food were not only healthier, but also lived longer. In a ten year study, highlighted in my video, Cooking to Live Longer, those who cooked most frequently had only 59% of the mortality risk. This took into account the exercise people got grocery shopping, physical function, and chewing ability. So why did they live longer? Those that cooked typically ate a more nutritious diet with a higher consumption of vegetables.

The effect on mortality was much more evident in women than in men. It turns out that "men were, with doubtful justification, more positive about the nutritional value of convenience foods compared with women." Women who cooked made better food choices in general.

As one author noted in the book Something from the Oven, over the last century:

"we began the long process of turning over to the food industry many of the decisions about what we eat...Today our staggering rates of obesity and diabetes are testimony to the faith we put in corporations to feed us well. But the food industry is a business, not a parent; it doesn't care what we eat as long as we're willing to pay for it. Home cooking these days has far more than sentimental value; it's a survival skill."

With the onslaught of health information out there, access to simple, healthy recipes has never been easier. While cooking at home requires more effort, energy, and cleaning, the results, health aside, are often more rewarding. Learning to cook is a simple art, and with the right amount of patience and delicious ingredients, it can help us take back control of our own lives.

Check out your local public library for cookbooks--I've been amazed at the selection in all of the cities I've lived. Or for those for which books are just so 20th century, the online Rouxbe Cooking School holds healthy cooking classes.

More on fast food:

Some other unsavory bits about the food industry:

I think this is the only other mention of celebrity chefs I have:
Paula Deen: diabetes drug spokesperson

-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.

Picture by Moyan Brenn on Flickr

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