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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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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How Phytates Fight Cancer Cells

NF-May26 Phytates for Rehabilitating Cancer Cells.jpg

Phytate is a compound found in beans, grains, nuts and seeds. The average daily intake of phytate in vegetarian diets is about twice that of those eating mixed diets of plant and animal foods, which may help explain their low cancer rates. Aside from helping to prevent cancer, dietary phytate has been reported to help prevent kidney stone formation, protect against diabetes mellitus, dental cavities, and heart disease.

Do all these potentially beneficial effects sound too good to be true? Are there other examples of compounds made by plants that can have benefits across multiple diseases? Why yes! Aspirin, for example, which is found throughout the plant kingdom may also account for a variety of plant-based benefits (See Aspirin Levels in Plant Foods).

But of all the things phytates can do, the anticancer activity of phytate (also known as phytic acid, IP6, or inositol hexaphosphate), is considered one of its most important beneficial activities. Dietary phytates are quickly absorbed from the gastrointestinal tract and rapidly taken up by cancer cells throughout the body, and have been shown to inhibit the growth of all tested cancerous cell lines in vitro. Phytates have been shown to inhibit the growth of human leukemia cells, colon cancer cells, both estrogen receptor-positive and negative breast cancer cells, voicebox cancer, cervical cancer, prostate cancer, liver tumors, pancreatic, melanoma, and muscle cancers. All at the same time not affecting normal cells. That's the most important expectation of a good anticancer agent: the ability to only affect cancerous cells and to leave normal cells alone.

In my video, Phytates for Rehabilitating Cancer Cells, you can see how leukemia cells taken from cancer patients are killed by phytates, whereas normal bone marrow cells, are spared. This may explain why bean extracts kill off colon cancer cells in vitro, but leave normal colon cells alone.

What are the mechanisms of action by which phytates battle cancer? In other words, how do phytates fight? How don't they fight? Phytate targets cancer through multiple pathways, a combination of antioxidant, anti-inflammatory, immune-enhancing activities, detox, differentiation, and anti-angiogenesis. In other words, phytate appears to affect all the principal pathways of malignancy.

The antioxidative property is one of the most impressive characteristics of phytate. In fact that's why the meat industry adds phytates to meat to prevent the fat oxidation that begins at the moment of slaughter. Phytates can also act on our immune functions by augmenting natural killer cell activity, the cells in our body that hunt down and dispose of cancer cells, as well as neutrophils, which help form our first line of defense. And then phytates starve tumors as more of a last line of defense. Not only can phytates block the formation of new blood vessels that may be feeding tumors, but disrupt pre-formed capillary tubes, indicating that phytates may not just help blockade tumors, but actively cut off existing supply lines.

What's really remarkable about phytate, though, is that unlike most other anti-cancer agents, it not only causes a reduction in cancer cell growth but also enhances differentiation, meaning it causes cancer cells to stop acting like cancer cells and go back to acting like normal cells. You can see this with colon cancer cells for example. In the presence of phytates, human colon cancer cells mature to structurally and behaviorally resemble normal cells. And this has been demonstrated in leukemia cells, prostate cancer, breast cancer, and muscle cancer cells as well.

For more on the cancer and phytate connection, check out Phytates for the Prevention of Cancer and Phytates for the Treatment of Cancer.

This video reminds me of my video on the spice, turmeric, Turmeric Curcumin Reprogramming Cancer Cell Death.

What else can we eat to improve the cancer-fighting front of our immune system? See Boosting Natural Killer Cell Activity.

More on the concept of starving tumors of their blood supply in Anti-Angiogenesis: Cutting Off Tumor Supply Lines.

Is there clinical evidence of plants actually reversing cancer progression? You won't believe your eyes:

-Michael Greger, M.D.

PS: If you haven't yet, you can subscribe to my free videos here and watch my live year-in-review presentations Uprooting the Leading Causes of Death, More Than an Apple a Day, and From Table to Able.

Image Credit: Avi / Flickr

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How to Prevent Heart Disease

NF-Nov6 What You Need to Know About Preventing Heart Disease.jpg

Many of today's lifestyle medicine doctors, myself included, were greatly influenced by Nathan Pritikin, the nutrition pioneer who started reversing heart disease with a plant-based diet and exercise back in the 70s. (More on Nathan Pritikin in Engineering a Cure, Our Number One Killer Can Be Stopped, and The Answer to the Pritikin Puzzle.) But how did he come up with the idea of opening up arteries without drugs or surgery? We tend to think of rural China as a place with a fraction of our disease rates, but we may forget about Africa.

Pritikin was 43 when he was told by his cardiologist that he was going to die from a heart attack, so he began to live on a diet patterned after the black population in Uganda, a population living off plants that was essentially free from death from heart attacks. After curing his own heart disease with a plant-based diet, he went on to save the lives of thousands of others. What was the data that so convinced him?

Last year, the International Journal of Epidemiology reprinted a landmark article from the '50s that started out with a shocking statement: "In the African population of Uganda, coronary heart disease is almost non-existent." Our number one cause of death almost nonexistent? What were they eating? Plantains and sweet potatoes, other vegetables, corn, millet, pumpkins, tomatoes, and "green leafy vegetables are taken by all." Their protein was almost entirely from plant sources, and they had the cholesterol levels to prove it, similar to modern-day plant-eaters. "Apart from the effects of diet and of the blood cholesterol levels," the researchers couldn't figure out any other reasons for their freedom from heart disease.

These fifty-year-old findings are still relevant today. They showed "dietary intake to be a key, modifiable, established and well-recognized risk factor for heart attacks. This contrasts with the rather desperate search in recent decades for even newer cardiovascular risk factors." We have the only risk factor we need--cholesterol. We've known it for 50 years, and we can do something about it. See One in a Thousand: Ending the Heart Disease Epidemic.

As you can see in the video Cavities and Coronaries: Our Choice, according to the Editor-in-Chief of the American Journal of Cardiology, the only risk factor required for atherosclerotic plaques to form is elevated LDL, or "bad" cholesterol in our blood. Dr. William Clifford Roberts is the distinguished cardiac pathologist who doubles as the Editor-in-Chief of the American Journal of Cardiology. More from him in Eliminating the #1 Cause of Death and Heart Attacks and Cholesterol: Purely a Question of Diet.

To drop our LDL cholesterol, we need to drop our intake of three things: trans fat (found in junk food and animal foods - See Trans Fat in Meat and Dairy); saturated fat (found in mostly animal foods); and dietary cholesterol (found exclusively in animal foods). More on lowering LDL in Trans Fat, Saturated Fat, and Cholesterol: Tolerable Upper Intake of Zero.

What Dr. Shaper discovered is that heart disease may be a choice.

Like cavities.

People who lived over 10,000 years before the invention of the toothbrush pretty much had no cavities. Didn't brush a day in their lives, never flossed, no Listerine, no Waterpik--and yet, no cavities. Why? Because candy bars hadn't been invented yet! So why do people continue to get cavities when we know they're preventable though diet? Simple: because the pleasure people derive from dessert may outweigh the cost and discomfort of the dentist.

As long as people understand the consequences of their actions, as a physician what more can I do? If you're an adult and decide that the benefits outweigh the risks for you and your family, then go for it--I certainly enjoy the occasional indulgence (I've got a good dental plan!). But what if instead of the plaque on our teeth, we're talking about the plaque building up in our arteries? Then we're no longer just talking about scraping tarter. We're talking life and death.

The most likely reason our loved ones will die is heart disease. It's still up to each of us to make our own decisions as to what to eat and how to live, but we should make our choices consciously, educating ourselves about the predictable consequences of our actions.

-Michael Greger, M.D.

PS: If you haven't yet, you can subscribe to my free videos here and watch my live year-in-review presentations Uprooting the Leading Causes of Death, More Than an Apple a Day, and From Table to Able.

Image Credit: Knar Bedian / Flickr

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Tea and Flouride Risk

 

 

 

 

 

 

 

 

Childhood Tea Drinking May Increase Fluorosis Risk

If cranberries are so good at keeping bacteria from sticking to the wall of the bladder (see my video Can Cranberry Juice Treat Bladder Infections?), what about keeping bacteria from sticking to other places? There is in vitro research suggesting cranberry phytonutrients may reduce adhesion of H. pylori bacteria in the wall of the stomach, so maybe cranberries should be given along with antibiotics to help eradicate the ulcer-causing bacteria. But hey, what about our teeth?

Dental plaque is bacteria sticking to our teeth, particularly Streptococcus mutans. We’ve known that those with different drinking habits—be they coffee, tea, barley coffee, or wine—have about 10 times less of these plaque bacteria. Since those are all beverages from plants, maybe phytonutrients are fighting back at plaque.

If bacteria cause plaque and cavities, why not just swish with some antibiotic solution? There are downsides to just indiscriminately wiping out bacteria both good and bad, as I detailed in my Don’t Use Antiseptic Mouthwash video. So maybe it would be better if we just stop the bad bugs from sticking to our teeth.

There is some evidence that cranberries might affect the adhesion of bacteria to fake teeth in a petri dish, but nothing yet definitive. Green tea also appears to help prevent cavities, but that may be because of its natural fluoride content in the tea plant. I have a video about a woman who developed fluoride toxicity drinking up to the equivalent of about five dozen cups a day, but what about just regular consumption?

During the tooth development years, up to about age 9, children exposed to too much fluoride can develop dental fluorosis, a mottled discoloration of the teeth. It’s just a cosmetic issue and usually just manifests as faint white spots, but it’s the main reason the EPA is reconsidering current tap water fluoridation levels. If you watch my 3-min video Childhood Tea Drinking May Increase Fluorosis Risk, you’ll see that herbal teas are fine–about 100 fold under the limit–but caffeinated teas exceed the suggested limit, and decaf teas exceed the mandatory limit. Those limits are for tap water, though, so tea drinking would only pose much of a risk if drank all day long as one’s primary beverage. Kids who primarily drink non-herbal tea as a source of hydration would be at risk for dental fluorosis.

What may be the best source of hydration for kids? Might tea also cause dehydration? Find the answers to these beverage-related questions in my videos Does a Drink of Water Make Children Smarter? and Is Caffeinated Tea Dehydrating?

What about all those folks that say fluoride is a poison to be avoided at all costs? I offer my brief two cents in the Q&A The Dangers of Fluoride? There are elements for which there is no safe level of exposure, though. I explore a few in my video Fukushima and Radioactivity in Seafood.

Beyond cosmetic issues, what should we eat and drink to keep our mouth healthy? See my videos Plant-Based Diets: Oral Health and Plant-Based Diets: Dental 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 and More Than an Apple a Day.

Image credit: Josconklin / Wikimedia Commons

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