How Much Water Should We Drink Every Day?

How Much Water Should We Drink Every Day?.jpeg

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 Best Way to Wash Fruit and Vegetables

The Best Way to Wash Fruit and Vegetables.jpeg

How might we reduce our exposure to pesticide residues on fruits and vegetables? What about staying away from imported produce? Well, it turns out domestic produce may be even worse, dispelling the notion that imported fruits and vegetables pose greater potential health risks to consumers.

Buying organic dramatically reduces dietary exposure to pesticides, but it does not eliminate the potential risk. Pesticide residues are detectable in about one in ten organic crop samples, due to cross-contamination from neighboring fields, the continued presence of very persistent pesticides like DDT in the soil, and accidental or fraudulent use.

By choosing organic, one hopes to shift exposures from a range of uncertain risk to more of a range of negligible risk, but even if all we had to eat were the most pesticide-laden of conventional produce, there is a clear consensus in the scientific community that the health benefits from consuming fruits and vegetables outweigh any potential risks from pesticide residues. And we can easily reduce whatever risk there is by rinsing our fruits and vegetables under running water.

There are, however, a plethora of products alleged by advertisers to reduce fruit and produce pesticide residues more effectively than water and touted to concerned consumers. For example, Procter & Gamble introduced a fruit and vegetable wash. As part of the introduction, T.G.I. Friday's jumped on board bragging on their menus that the cheese and bacon puddles they call potato skins were first washed with the new product. After all, it was proclaimed proven to be 98% more effective than water in removing pesticides.

So researchers put it to the test and it did no better than plain tap water.

Shortly thereafter Procter & Gamble discontinued the product, but numerous others took its place claiming their vegetable washes are three, four, five or even ten times more effective than water, to which a researcher replied, "That's mathematically impossible." If water removes 50%, you can't take off ten times more than 50%. They actually found water removed up to 80% of pesticide residues like the fungicide, Captan, for example. So, for veggie washes to brag they are three, four, five, ten times better than water is indeed mathematically questionable.

Other fruit and vegetable washes have since been put to the test. Researchers compared FIT Fruit & Vegetable Wash, Organiclean, Vegi-Clean, and dishwashing soap to just rinsing in plain tap water. 196 samples of lettuce, strawberries, and tomatoes were tested, and researchers found little or no difference between just rinsing with tap water compared to any of the veggie washes (or the dish soap). They all just seemed like a waste of money. The researchers concluded that just the mechanical action of rubbing the produce under tap water seemed to do it, and that using detergents or fruit and vegetable washes do not enhance the removal of pesticide residues from produce above that of just rinsing with tap water alone.

That may not be saying much, though. Captan appears to be the exception. When plain water was tried against a half dozen other pesticides, less than half the residues were removed.

Fingernail polish works better, but the goal is to end up with a less toxic, not a more toxic tomato.

We need a straightforward, plausible, and safe method for enhanced pesticide removal. Is there anything we can add to the water to boost its pesticide-stripping abilities? Check out my video, How to Make Your Own Fruit & Vegetable Wash.

If you soak potatoes in water, between about 2% to 13% of the pesticides are removed, but a 5% acetic acid solution removes up to 100%. What's that? Plain white vinegar. But 5% is full strength.

What about diluted vinegar? Diluted vinegar only seemed marginally better than tap water for removing pesticide residues. Using full strength vinegar would get expensive, though. Thankfully there's something cheaper that works even better: salt water.

A 10% salt solution appears to work as good or better than full-strength vinegar. To make a 10% salt solution you just have to mix up about one-part salt to nine-parts water (though make sure to rinse all of the salt off before eating!).

There's not much you can do for the pesticides in animal products, though. The top sources of some pesticides are fruits and vegetables; but for other pesticides, it's dairy, eggs, and meat because the chemicals build up in fat. What do you do about pesticides in animal products? Hard boiling eggs appears to destroy more pesticides that scrambling, but for the pesticides that build up in the fat in fish or chicken, cooking can sometimes increase pesticide levels that obviously can't just wash off. In fact, washing meat, poultry, or eggs is considered one of the top ten dangerous food safety mistakes.

For more on organic foods, see:

The most important reason to wash produce is to reduce the risk of food-borne illness. Ironically, the food poisoning viruses may be found in the pesticides themselves. Check out my video Norovirus Food Poisoning from Pesticides.

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. This image has been modified.

Original Link

The Best Way to Wash Fruit and Vegetables

The Best Way to Wash Fruit and Vegetables.jpeg

How might we reduce our exposure to pesticide residues on fruits and vegetables? What about staying away from imported produce? Well, it turns out domestic produce may be even worse, dispelling the notion that imported fruits and vegetables pose greater potential health risks to consumers.

Buying organic dramatically reduces dietary exposure to pesticides, but it does not eliminate the potential risk. Pesticide residues are detectable in about one in ten organic crop samples, due to cross-contamination from neighboring fields, the continued presence of very persistent pesticides like DDT in the soil, and accidental or fraudulent use.

By choosing organic, one hopes to shift exposures from a range of uncertain risk to more of a range of negligible risk, but even if all we had to eat were the most pesticide-laden of conventional produce, there is a clear consensus in the scientific community that the health benefits from consuming fruits and vegetables outweigh any potential risks from pesticide residues. And we can easily reduce whatever risk there is by rinsing our fruits and vegetables under running water.

There are, however, a plethora of products alleged by advertisers to reduce fruit and produce pesticide residues more effectively than water and touted to concerned consumers. For example, Procter & Gamble introduced a fruit and vegetable wash. As part of the introduction, T.G.I. Friday's jumped on board bragging on their menus that the cheese and bacon puddles they call potato skins were first washed with the new product. After all, it was proclaimed proven to be 98% more effective than water in removing pesticides.

So researchers put it to the test and it did no better than plain tap water.

Shortly thereafter Procter & Gamble discontinued the product, but numerous others took its place claiming their vegetable washes are three, four, five or even ten times more effective than water, to which a researcher replied, "That's mathematically impossible." If water removes 50%, you can't take off ten times more than 50%. They actually found water removed up to 80% of pesticide residues like the fungicide, Captan, for example. So, for veggie washes to brag they are three, four, five, ten times better than water is indeed mathematically questionable.

Other fruit and vegetable washes have since been put to the test. Researchers compared FIT Fruit & Vegetable Wash, Organiclean, Vegi-Clean, and dishwashing soap to just rinsing in plain tap water. 196 samples of lettuce, strawberries, and tomatoes were tested, and researchers found little or no difference between just rinsing with tap water compared to any of the veggie washes (or the dish soap). They all just seemed like a waste of money. The researchers concluded that just the mechanical action of rubbing the produce under tap water seemed to do it, and that using detergents or fruit and vegetable washes do not enhance the removal of pesticide residues from produce above that of just rinsing with tap water alone.

That may not be saying much, though. Captan appears to be the exception. When plain water was tried against a half dozen other pesticides, less than half the residues were removed.

Fingernail polish works better, but the goal is to end up with a less toxic, not a more toxic tomato.

We need a straightforward, plausible, and safe method for enhanced pesticide removal. Is there anything we can add to the water to boost its pesticide-stripping abilities? Check out my video, How to Make Your Own Fruit & Vegetable Wash.

If you soak potatoes in water, between about 2% to 13% of the pesticides are removed, but a 5% acetic acid solution removes up to 100%. What's that? Plain white vinegar. But 5% is full strength.

What about diluted vinegar? Diluted vinegar only seemed marginally better than tap water for removing pesticide residues. Using full strength vinegar would get expensive, though. Thankfully there's something cheaper that works even better: salt water.

A 10% salt solution appears to work as good or better than full-strength vinegar. To make a 10% salt solution you just have to mix up about one-part salt to nine-parts water (though make sure to rinse all of the salt off before eating!).

There's not much you can do for the pesticides in animal products, though. The top sources of some pesticides are fruits and vegetables; but for other pesticides, it's dairy, eggs, and meat because the chemicals build up in fat. What do you do about pesticides in animal products? Hard boiling eggs appears to destroy more pesticides that scrambling, but for the pesticides that build up in the fat in fish or chicken, cooking can sometimes increase pesticide levels that obviously can't just wash off. In fact, washing meat, poultry, or eggs is considered one of the top ten dangerous food safety mistakes.

For more on organic foods, see:

The most important reason to wash produce is to reduce the risk of food-borne illness. Ironically, the food poisoning viruses may be found in the pesticides themselves. Check out my video Norovirus Food Poisoning from Pesticides.

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. This image has been modified.

Original Link

Deep Breathing Exercise for Nausea

Deep Breathing Exercise for Nausea.jpeg

One of the most common fears patients express when facing surgery is postoperative nausea, which can range from minor queasiness to protracted periods of vomiting. Feeling sick to one's stomach and throwing up after surgery is a common problem, affecting between a quarter and a half of those placed under general anesthesia, and more than half of those at high risk (women who don't smoke and have a history of motion sickness).

I've explored the science behind treating nausea with ginger (see Natural Nausea Remedy Recipe), but if you're too nauseous to eat, what do you do? Well, people are often sent home with anti-nausea rectal suppositories. Surveys, however, show that cultural and sexual attitudes may make a number of people sensitive to anything involving the rectum. Though the wording of the question researchers asked was, "are you happy to have a drug put in your back passage?" I can imagine many of the respondents thinking "well, maybe I wouldn't so much mind, but wouldn't exactly be happy about it," especially when you're feeling sick and throwing up.

For women who've had a C-section, they might not want to take drugs at all if they're breastfeeding, so researchers decided to put aromatherapy to the test. Research has shown that essential oils of both spearmint and peppermint are effective in reducing nausea and vomiting after chemotherapy, but this was after swallowing them.

Would just the smell of peppermint help with nausea? I explore this in my video Peppermint Aromatherapy for Nausea. Researchers had women take deep whiffs of peppermint extract (like you'd buy at a store) and it seemed to work. Eighty percent of the mint-sniffers felt better within just a few minutes, compared to no improvement in the placebo group who sniffed water with green food coloring, or the control group who didn't sniff anything.

The study was criticized for being small and for not using pure peppermint oil. Peppermint extract is peppermint oil plus alcohol. Maybe it was the smell of alcohol that made people better? And that's actually not too much of a stretch. In 1997, researchers reported a simple, innocuous, and inexpensive treatment for postoperative nausea and vomiting--the smell of isopropyl alcohol, which is what is found in those alcohol wipes, the little prep pads that nurses swab you with before shots. They found that they could just effectively tear one open and wave it under someone's nose and relieve nausea and vomiting in more than 80% of folks after surgery. It has been since shown to work as well as a leading anti-nausea drug, and may even work faster, cutting nausea in half within 10 to 15 minutes, rather than 20 or 25.

So was it the alcohol, the peppermint, or both? Researchers decided to put it to the test. They instructed patients to take three slow, deep breaths, smelling alcohol, peppermint, or nothing. The smell of peppermint cut nausea in half within five minutes, and so did the alcohol. But so did smelling nothing! So maybe it had nothing to do with the scent; maybe it was just the instruction to take slow, deep breaths. That would make it a really cost-effective intervention. Maybe it shouldn't be so surprising, given the proximity of the vomiting and breathing centers within the brain.

And indeed, controlled breathing was found effective with or without any scent. So next time you feel nauseous, inhale deeply through your nose to the count of three, hold your breath to the count of three, and exhale out the mouth to the count of three. Do that three times.

Ironically, the researchers continued to advocate using those nasty smelling alcohol pads even though they themselves showed they weren't any more effective than breathing alone. Why? Since isopropyl alcohol has a readily detectable odor, patients are more likely to think that their post-operation nausea and vomiting is being actively treated when they inhale alcohol vapors rather than just engaging in breathing exercises.


What do you think of still using the alcohol pads even though they were shown to offer no additional benefit? I have a whole video on such questions: The Lie That Heals: Should Doctors Give Placebos?

For those who can swallow, I offer more about powdered ginger in my video Dangerous Advice From Health Food Store Employees.

There's more on aromatherapy here:

What about actually eating the peppermint?

Of course, the best way to avoid postsurgical nausea is to try to avoid surgery in the first place. Those that eat healthy may be less likely to go under the knife. See Say No to Drugs by Saying Yes to More Plants.

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. This image has been modified.

Original Link

Deep Breathing Exercise for Nausea

Deep Breathing Exercise for Nausea.jpeg

One of the most common fears patients express when facing surgery is postoperative nausea, which can range from minor queasiness to protracted periods of vomiting. Feeling sick to one's stomach and throwing up after surgery is a common problem, affecting between a quarter and a half of those placed under general anesthesia, and more than half of those at high risk (women who don't smoke and have a history of motion sickness).

I've explored the science behind treating nausea with ginger (see Natural Nausea Remedy Recipe), but if you're too nauseous to eat, what do you do? Well, people are often sent home with anti-nausea rectal suppositories. Surveys, however, show that cultural and sexual attitudes may make a number of people sensitive to anything involving the rectum. Though the wording of the question researchers asked was, "are you happy to have a drug put in your back passage?" I can imagine many of the respondents thinking "well, maybe I wouldn't so much mind, but wouldn't exactly be happy about it," especially when you're feeling sick and throwing up.

For women who've had a C-section, they might not want to take drugs at all if they're breastfeeding, so researchers decided to put aromatherapy to the test. Research has shown that essential oils of both spearmint and peppermint are effective in reducing nausea and vomiting after chemotherapy, but this was after swallowing them.

Would just the smell of peppermint help with nausea? I explore this in my video Peppermint Aromatherapy for Nausea. Researchers had women take deep whiffs of peppermint extract (like you'd buy at a store) and it seemed to work. Eighty percent of the mint-sniffers felt better within just a few minutes, compared to no improvement in the placebo group who sniffed water with green food coloring, or the control group who didn't sniff anything.

The study was criticized for being small and for not using pure peppermint oil. Peppermint extract is peppermint oil plus alcohol. Maybe it was the smell of alcohol that made people better? And that's actually not too much of a stretch. In 1997, researchers reported a simple, innocuous, and inexpensive treatment for postoperative nausea and vomiting--the smell of isopropyl alcohol, which is what is found in those alcohol wipes, the little prep pads that nurses swab you with before shots. They found that they could just effectively tear one open and wave it under someone's nose and relieve nausea and vomiting in more than 80% of folks after surgery. It has been since shown to work as well as a leading anti-nausea drug, and may even work faster, cutting nausea in half within 10 to 15 minutes, rather than 20 or 25.

So was it the alcohol, the peppermint, or both? Researchers decided to put it to the test. They instructed patients to take three slow, deep breaths, smelling alcohol, peppermint, or nothing. The smell of peppermint cut nausea in half within five minutes, and so did the alcohol. But so did smelling nothing! So maybe it had nothing to do with the scent; maybe it was just the instruction to take slow, deep breaths. That would make it a really cost-effective intervention. Maybe it shouldn't be so surprising, given the proximity of the vomiting and breathing centers within the brain.

And indeed, controlled breathing was found effective with or without any scent. So next time you feel nauseous, inhale deeply through your nose to the count of three, hold your breath to the count of three, and exhale out the mouth to the count of three. Do that three times.

Ironically, the researchers continued to advocate using those nasty smelling alcohol pads even though they themselves showed they weren't any more effective than breathing alone. Why? Since isopropyl alcohol has a readily detectable odor, patients are more likely to think that their post-operation nausea and vomiting is being actively treated when they inhale alcohol vapors rather than just engaging in breathing exercises.


What do you think of still using the alcohol pads even though they were shown to offer no additional benefit? I have a whole video on such questions: The Lie That Heals: Should Doctors Give Placebos?

For those who can swallow, I offer more about powdered ginger in my video Dangerous Advice From Health Food Store Employees.

There's more on aromatherapy here:

What about actually eating the peppermint?

Of course, the best way to avoid postsurgical nausea is to try to avoid surgery in the first place. Those that eat healthy may be less likely to go under the knife. See Say No to Drugs by Saying Yes to More Plants.

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. This image has been modified.

Original Link

Estrogen in Meat, Dairy, and Eggs

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Estrogen hormones can be thousands of times more estrogenic than typical endocrine-disrupting chemicals. Dietary exposure to natural sex steroids (in meat, dairy, and eggs) is "therefore highly relevant in the discussion of the impact of estrogens on human development and health." And chicken estrogen is identical to human estrogen--they're identical molecules. So it doesn't matter if it ends up in our drinking supply from women taking birth control pills excreting it in their urine, or cows excreting it into their milk. The source doesn't matter; the quantity does.

If you check out my video Estrogen in Meat, Dairy, and Eggs, you can see that a child's exposure to estrogens in drinking water is about 150 times lower than exposure from cow's milk, so our day-to-day estrogen exposure levels are more likely determined by whether or not we happen to eat dairy products that day.

Human urine is "often cited as the main source of natural and synthetic estrogens in the aquatic environment," but the level of estrogen even in the urine of heavy meat-eaters, who have significantly higher levels, pales in comparison to the estrogen excreted by the farm animals themselves. Pig, sheep, cattle, and chickens produce literally tons of estrogen every year.

Women may excrete 16 mg every day, but farm animals may release ten times more, or in the case of pregnant cows, thousands of times more. Animal waste may contribute an estimated 90% of total estrogens in the environment. Five gallons of runoff water contaminated with chicken manure may contain a birth control pill's worth of estrogen.

Estrogen levels in poultry litter are so high that when farmers feed chicken manure to their animals to save on feed costs, it may trigger premature development. Poultry manure has among the highest hormone content, quadruple the total estrogens, and nine times more 17-beta estradiol, the most potent estrogen and a "complete" carcinogen, as it exerts both tumor initiating and tumor promoting effects.

From a human health standpoint, do we really care about feminized fish, or the appearance of "intersex roaches"? The problem is that the hormones get into the food supply. Endogenous steroid hormones in food of animal origin are unavoidable as they occur naturally in these products. It's not a matter of injected hormones, which are banned in places like Europe in order to protect consumers' health. Sex steroid hormones are part of animal metabolism, and so all foodstuffs of animal origin contain these hormones, which have been connected with several human health problems. (See Why Do Vegan Women Have 5x Fewer Twins?)

What effects might these female hormones have on men? See Dairy Estrogen and Male Fertility.

The implications of this relatively new practice of milking cows even when they're pregnant is further explored in:

More on xenoestrogens in:

In health,
Michael Greger, M.D.

PS: If you haven't yet, you can subscribe to my free videos here and watch my live, year-in-review presentations--2013: Uprooting the Leading Causes of Death, More Than an Apple a Day, 2014: From Table to Able: Combating Disabling Diseases with Food, 2015: Food as Medicine: Preventing and Treating the Most Dreaded Diseases with Diet, and my latest, 2016: How Not To Die: The Role of Diet in Preventing, Arresting, and Reversing Our Top 15 Killers.

Image Credit: BruceBlaus

Image Credit: [Nakhorn Yuangkratoke] © 123RF.com

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The Role of Caffeine in Artery Function

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There are dietary guidelines for food, but what about for beverages? A Beverage Guidance Panel was "assembled to provide guidance on the relative health and nutritional benefits and risks of various beverage categories." They ranked them from one to six, and water was ranked number one.

Soda ranked last at number six. Whole milk was grouped with beer, with a recommendation for zero ounces a day, in part out of concern for links between milk and prostate cancer, as well as aggressive ovarian cancer due to IGF-1. Number two on the list, though, after water, was tea and coffee, preferably without creamer or sweetener.

Even without creamer, though, lots of unfiltered coffee can raise cholesterol, but the cholesterol-raising compounds are trapped by the paper filter in brewed coffee, so filtered coffee is probably better.

But about ten years ago, a study was published on the effects of coffee on endothelial function, the function of our arteries. I profile this study in my video Coffee and Artery Function, showing that within 30 minutes of drinking a cup of coffee there was a significant drop in the ability of our arteries to dilate, whereas decaf did not seem to have a significant effect. This was the first study to demonstrate an acute unfavorable effect on arterial function of caffeinated coffee, but one cup of decaf didn't seem to affect performance. And two cups of decaf appeared to have a beneficial effect. So maybe it's a "battle between caffeine and antioxidants." Something in caffeinated coffee appears to be hurting arterial function, whereas something in decaf appears to be helping.

It's similar to red wine. De-alcoholized red wine significantly improves arterial function, as there are grape components trying to help, but the presence of alcohol counteracts and erases the benefit.

Drinking really high antioxidant coffee, by preparing it Greek style for example (where we actually drink the grounds), coffee drinkers may actually be at an advantage

It might not be the caffeine in caffeinated coffee that appears to be harmful, though. In a randomized, double-blind, placebo-controlled, cross-over study, researchers found that caffeine alone--about two and a half cups of coffee worth--significantly improved arterial function in both people with and without heart disease.

Coffee contains more than a thousand different compounds other than caffeine, many of which are also removed by the decaffeination process, so there must be something else in the coffee bean that's causing the problem. In fact, caffeine may even enhance the repair of the fragile inner lining of our arteries by enhancing the migration of our endothelial progenitor cells, the stem cells that patch up potholes in our artery walls.

But how might we get the potential benefit of caffeine without the risky compounds in caffeinated coffee? Tea consumption enhances artery function, and there are substantial beneficial effects of both green tea and black tea. Instead of other components in tea leaves undermining caffeine's potential benefits, they appear to boost the benefit in healthy individuals, as well as heart disease patients, reversing some of their arterial dysfunction, both immediately and long-term.

All the measurements in the studies I've talked about so far were done on the brachial artery, the main artery in the arm (just because it's easier to get to). What we care about, though, is blood flow to the heart. And caffeine appears to impair blood flow to our heart muscle during exercise even in healthy folks, but especially in those with heart disease. Thankfully caffeine in tea form appears to have the opposite effect, significantly improving coronary blood flow, suggesting that tea consumption has a beneficial effect on coronary circulation, though the addition of milk may undermine the protective effects.

I'm fascinated by how complicated such a simple question can get. The take-home is that water is the healthiest beverage, followed by tea.

The effects of coffee on cancer risk are more salutary:

I've previously covered Walnuts and Artery Function and Dark Chocolate and Artery Function. Stay tuned for a few more coming up further exploring the effects of tea, olive oil, and plant-based diets on our lovely endothelium.

Low Carb Diets and Coronary Blood Flow is one of the few other studies I've done that measured blood flow within the coronary arteries themselves. For more background on the brachial artery test, see my video The Power of NO.

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.

Original Link

What About All the Sugar in Fruit?

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If the fructose in sugar and high fructose corn syrup has been considered "alcohol without the buzz" in terms of the potential to inflict liver damage, what about the source of natural fructose, fruit?

If you compare the effects of a diet restricting fructose from both added sugars and fruit to one just restricting fructose from added sugars, the diet that kept the fruit did better. People lost more weight with the extra fruit present than if all fructose was restricted. Only industrial, not fruit fructose intake, was associated with declining liver function and high blood pressure. Fructose from added sugars was associated with hypertension; fructose from natural fruits is not.

If we have people drink a glass of water with three tablespoons of table sugar in it, which is like a can of soda, they get a big spike in blood sugar within the first hour (as you can see in my video If Fructose is Bad, What About Fruit?). Our body freaks out and releases so much insulin we actually overshoot, and by the second hour we're relatively hypoglycemic, dropping our blood sugar below where they were when we started out fasting. In response, our body dumps fat into our blood stream as if we're starving, because our blood sugars just dropped so low so suddenly.

What if you eat blended berries in addition to the sugar? They have sugars of their own in them, in fact an additional tablespoon of sugar worth, so the blood sugar spike should be worse, right?

Not only is there no additional blood sugar spike, there was no hypoglycemic dip afterwards. Blood sugar just went up and down without that overshoot and without the surge of fat into the blood.

This difference may be attributed to the semisolid consistency of the berry meals, which may have decreased the rate of stomach emptying compared with just guzzling sugar water. In addition, the soluble fiber in the berries has a gelling effect in our intestines that slows the release of sugars. To test to see if it was the fiber, researchers repeated the experiment with berry juice that had all the sugar but none of the fiber. A clear difference was observed early on in the blood sugar insulin responses. At the 15-minute mark, the blood sugar spike was significantly reduced by the berry meals, but not by the juices, but the rest of the beneficial responses were almost the same between the juice and the whole fruit, suggesting that fiber may just be part of it. It turns out there are fruit phytonutrients that inhibit the transportation of sugars through the intestinal wall into our blood stream. Phytonutrients in foods like apples and strawberries can block some of the uptake of sugars by the cells lining our intestines.

Adding berries can actually blunt the insulin spike from high glycemic foods. For example, white bread creates a big insulin spike within two hours after eating it. Eat that same white bread with some berries, though, and we're able to blunt the spike. So, even though we've effectively added more sugars in the form of berries, there's less of an insulin spike, which has a variety of potential short and long-term benefits. So if you're going to make pancakes, make sure they're blueberry pancakes.

Surprised about the juice results? Me too! More on juice:

A few videos I have on industrial sugars:

How else can we blunt the glycemic spike?

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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Aluminum Levels in Tea

NF-May12 Is There Too Much Aluminum in Tea?.jpeg

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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Rinse Your Mouth After Sour Foods and Drinks

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Hibiscus tea has been found to be as effective at lowering blood pressure as a leading hypertension drug without the potential side-effects (which include everything from lack of strength to impotence, including rare cases of potentially fatal liver damage). Hibiscus, though, may have adverse effects of its own.

As I've reviewed previously in Plant-Based Diets: Oral Health, people who eat plant-based diets appear to have superior periodontal health, including less gum disease and fewer signs of inflammation, like bleeding. However, they also have twice the prevalence of dental erosions, areas on the teeth where the enamel has thinned due to more frequent consumption of acidic fruits and vegetables. Therefore, after we eat something like citrus, we should swish our mouths with water to clear the acid from our teeth.

This includes beverages. I'm a big fan of hibiscus tea, but it's not called "sour tea" for nothing. In a study highlighted in my video, Protecting Teeth from Hibiscus Tea, researchers at the University of Iowa dental school tested 25 different popular teas and found two with a pH under 3 (as acidic as orange juice or coca cola): Tazo's passion and Bigelow's red raspberry, both of which contain hibiscus as their first ingredient.

To see if these teas could actually dissolve teeth, the researchers took 30 extracted molars from people and soaked them in different teas. And indeed, out of the five teas tested, the greatest erosion came from the tea with the most hibiscus. The researchers left the tooth sitting in the tea for 25 hours straight, but this was to simulate a lifetime of exposure. The bottom line is that herbal teas are potentially erosive, particularly fruity and citrusy teas like hibiscus. To minimize the erosive potential, we can use a straw to drink the beverage. And as I mentioned above, after consuming an acidic food or drink we should also rinse our mouth with water to help neutralize the acid.

For more on the effects of hibiscus on blood pressure, see the previous video, Hibiscus Tea vs. Plant-Based Diets for Hypertension.

Are there other potential downsides to tea drinking? That's the topic of my videos: Is There Too Much Aluminum in Tea? and How Much Hibiscus Tea is Too Much?

For more on avoiding drug side-effects by choosing more natural treatments can be found in videos like:

For more on diet and oral health, 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: T.Kiya / Flickr

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