Who Should Avoid Coffee?

Oct 19 Coffee copy.jpeg

Do coffee drinkers live longer than non-coffee drinkers? Is it "wake up and smell the coffee" or don't wake up at all? I discuss these questions in my video, Coffee and Mortality.

The largest study ever conducted on diet and health put that question to the test, examining the association between coffee drinking and subsequent mortality among hundreds of thousands of older men and women in the United States. Coffee drinkers won, though the effect was modest, a 10-15% lower risk of death for those drinking six or more cups a day. This was due specifically to lower risk of dying from heart disease, respiratory disease, stroke, injuries and accidents, diabetes, and infections.

However, another study that amount of coffee was found to increase the death rate of younger people under age 55. It may be appropriate, then, to recommend that you avoid drinking more than four cups a day. But if you review all the studies, the bottom line is that coffee consumption is associated with no change or a small reduction in mortality starting around one or two cups a day, for both men and women. The risk of dying was 3% lower for each cup of coffee consumed daily, which provides reassurance for the concern that coffee drinking might adversely affect health, or at least longevity.

A recent population study found no link between coffee consumption and symptoms of GERD, reflux diseases such as heartburn and regurgitation. If you actually stick a tube down people's throats and measure pH, though, coffee induces significant acid reflux, whereas tea does not. Is this just because tea has less caffeine? No. If you reduce the caffeine content of the coffee down to that of tea, coffee still causes significantly more acid reflux. Decaf causes even less, so GERD patients might want to choose decaffeinated coffee or, even better, opt for tea.

Coffee intake is also associated with urinary incontinence, so a decrease in caffeine intake should be discussed with patients who have the condition. About two cups of coffee a day worth of caffeine may worsen urinary leakage.

A 2014 meta-analysis suggested that daily coffee consumption was associated with a slightly increased risk of bone fractures in women, but a decreased risk of fractures in men. However, no significant association was found between coffee consumption and the risk of hip fracture specifically. Tea consumption may actually protect against hip fracture, though it appears to have no apparent relationship with fracture risk in general.

Certain populations, in particular, may want to stay away from caffeine, including those with glaucoma or a family history of glaucoma, individuals with epilepsy, and, not surprisingly, people who have trouble sleeping. Even a single cup at night can cause a significant deterioration in sleep quality.

We used to think caffeine might increase the risk of an irregular heart rhythm called atrial fibrillation, but that was based on anecdotal case reports like one of a young woman who suffered atrial fibrillation after "chocolate intake abuse." These cases invariably involved the acute ingestion of very large quantities of caffeine. As a result, the notion that caffeine ingestion may trigger abnormal heart rhythms had become "common knowledge," and this assumption led to changes in medical practice.

We now have evidence that caffeine does not increase the risk of atrial fibrillation. Low-dose caffeine--defined as less than about five cups of coffee a day--may even have a protective effect. Tea consumption also appears to lower cardiovascular disease risk, especially when it comes to stroke. But given the proliferation of energy drinks that contain massive quantities of caffeine, one might temper any message that suggests that caffeine is beneficial. Indeed, 12 highly caffeinated energy drinks within a few hours could be lethal.


To learn more about various health aspects of coffee, see my videos Coffee and Cancer, What About the Caffeine?, Preventing Liver Cancer with Coffee?, and Coffee and Artery Function.

What else can we consume to live longer? Check out Nuts May Help Prevent Death, Increased Lifespan from Beans, Fruits and Longevity: How Many Minutes per Mouthful?, and Finger on the Pulse of Longevity.

And, for more on controlling acid reflux, see Diet and GERD Acid Reflux Heartburn and Diet and Hiatal Hernia.

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:

Original Link

Who Should Avoid Coffee?

Oct 19 Coffee copy.jpeg

Do coffee drinkers live longer than non-coffee drinkers? Is it "wake up and smell the coffee" or don't wake up at all? I discuss these questions in my video, Coffee and Mortality.

The largest study ever conducted on diet and health put that question to the test, examining the association between coffee drinking and subsequent mortality among hundreds of thousands of older men and women in the United States. Coffee drinkers won, though the effect was modest, a 10-15% lower risk of death for those drinking six or more cups a day. This was due specifically to lower risk of dying from heart disease, respiratory disease, stroke, injuries and accidents, diabetes, and infections.

However, another study that amount of coffee was found to increase the death rate of younger people under age 55. It may be appropriate, then, to recommend that you avoid drinking more than four cups a day. But if you review all the studies, the bottom line is that coffee consumption is associated with no change or a small reduction in mortality starting around one or two cups a day, for both men and women. The risk of dying was 3% lower for each cup of coffee consumed daily, which provides reassurance for the concern that coffee drinking might adversely affect health, or at least longevity.

A recent population study found no link between coffee consumption and symptoms of GERD, reflux diseases such as heartburn and regurgitation. If you actually stick a tube down people's throats and measure pH, though, coffee induces significant acid reflux, whereas tea does not. Is this just because tea has less caffeine? No. If you reduce the caffeine content of the coffee down to that of tea, coffee still causes significantly more acid reflux. Decaf causes even less, so GERD patients might want to choose decaffeinated coffee or, even better, opt for tea.

Coffee intake is also associated with urinary incontinence, so a decrease in caffeine intake should be discussed with patients who have the condition. About two cups of coffee a day worth of caffeine may worsen urinary leakage.

A 2014 meta-analysis suggested that daily coffee consumption was associated with a slightly increased risk of bone fractures in women, but a decreased risk of fractures in men. However, no significant association was found between coffee consumption and the risk of hip fracture specifically. Tea consumption may actually protect against hip fracture, though it appears to have no apparent relationship with fracture risk in general.

Certain populations, in particular, may want to stay away from caffeine, including those with glaucoma or a family history of glaucoma, individuals with epilepsy, and, not surprisingly, people who have trouble sleeping. Even a single cup at night can cause a significant deterioration in sleep quality.

We used to think caffeine might increase the risk of an irregular heart rhythm called atrial fibrillation, but that was based on anecdotal case reports like one of a young woman who suffered atrial fibrillation after "chocolate intake abuse." These cases invariably involved the acute ingestion of very large quantities of caffeine. As a result, the notion that caffeine ingestion may trigger abnormal heart rhythms had become "common knowledge," and this assumption led to changes in medical practice.

We now have evidence that caffeine does not increase the risk of atrial fibrillation. Low-dose caffeine--defined as less than about five cups of coffee a day--may even have a protective effect. Tea consumption also appears to lower cardiovascular disease risk, especially when it comes to stroke. But given the proliferation of energy drinks that contain massive quantities of caffeine, one might temper any message that suggests that caffeine is beneficial. Indeed, 12 highly caffeinated energy drinks within a few hours could be lethal.


To learn more about various health aspects of coffee, see my videos Coffee and Cancer, What About the Caffeine?, Preventing Liver Cancer with Coffee?, and Coffee and Artery Function.

What else can we consume to live longer? Check out Nuts May Help Prevent Death, Increased Lifespan from Beans, Fruits and Longevity: How Many Minutes per Mouthful?, and Finger on the Pulse of Longevity.

And, for more on controlling acid reflux, see Diet and GERD Acid Reflux Heartburn and Diet and Hiatal Hernia.

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:

Original Link

Currant Treatment for Glaucoma

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In my video, Dietary Prevention for Age-Related Macular Degeneration, I discussed how eating goji berries with nuts and seeds can help build up yellow plant pigments such as lutein and zeaxanthin in our eyes to help fight age-related macular degeneration.

But once we've preserved the pigment in our retinal pigment epithelial cells, we need to keep them alive. This may be where anthocyanin phytonutrients come in. Anthocyanins (from the Greek anthos, meaning flower, and kyanos, meaning blue) are natural plant pigments that make pansies look purple and turn green cabbage into purple cabbage, yellow corn into purple corn, brown rice to purple rice, white potatoes to blue potatoes, orange carrots to purple carrots, and keeps blueberries blue and blackberries black.

As we age, our critical retinal pigment epithelium (RPE) layer starts to break down. However, we may be able to decelerate that aging with blueberries. In the study I profile in my video, Dietary Treatment of Glaucoma, human RPE cells bathed in blueberry anthocyanins had fewer free radicals and a lower proportion of aged cells, suggesting that blueberries and other red, blue, and purple pigmented fruits and vegetables may help prevent age-related macular degeneration. Blueberries may be especially important for blue eyes, as can be seen in my video Greens vs. Glaucoma.

Preventing disease is nice, but what if we already have a disease like glaucoma, an incurable eye disease in which our optic nerve (which connects our eyes to our brain) starts deteriorating, and we start losing our visual fields?

A few years ago, Japanese researchers showed they could apparently halt the progression of glaucoma with black currants. They gave people black currants for six months and found that black currants significantly boosted the blood flow to their optic nerve. The results suggest that black currants might be a safe and valuable option, but because the study was not double-blind and there was no control group, I didn't report on it when it was initially published. But now we've got just such a study. Glaucoma patients were split into two groups--half got black currants; the other half didn't.

The study measured the deterioration of the patients' visual fields in both groups in the two years leading up to the study. Despite taking the best glaucoma drugs on the market, the subjects' visual fields deteriorated. Then the study starts. The berry-free control group continued to worsen, but the berries appeared to stop the disease in its tracks after both one and two years. And since there's no downside to berries (only good side-effects), in my professional opinion everyone with glaucoma should be eating berries every day.

For more on the latest science on preventing and treating vision loss, check out Greens vs. Glaucoma, where I detailed the best foods to help prevent glaucoma. My previous treatment of glaucoma can be found here: Prevent Glaucoma and See 27 Miles Farther.

I've mentioned anthocyanins before in:

They may be why purple potatoes (Anti-Inflammatory Effects of Purple Potatoes) and purple cabbage (Superfood Bargains) may be preferable. Anthocyanins are the pigments in red and purple cabbage that allow for the kitchen chemistry in Testing Your Diet with Pee & Purple Cabbage.

More on currants in Enhanced Athletic Recovery Without Undermining Adaptation.

-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: Rachel / Flickr

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Foods for Macular Degeneration

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Anyone who has gotten a bad sunburn knows how damaging the UV rays in sunlight can be. Imagine what those same rays are doing to back of our eyeballs (our retinas). The eye is designed to take sunlight and focus it like a magnifying glass into the back of our eyes. Thankfully, we have a layer of cells called the retinal pigment epithelium that supports and protects our delicate retinal eyesight machinery. The layer builds up yellow plant pigments like zeaxanthin from our diet, absorbing blue light and protecting the retina from photo-oxidative damage. The yellowing of our corneas when we develop cataracts may actually be our bodies' defense mechanism to protect our retinas. In fact, when cataracts are removed, the risk of blindness from macular generation shoots up (because we removed the protection). Instead of trading one type of vision loss for another, it's better to pigment the back of our eyes through diet instead of pigmenting the front of our eyes with cataracts. The pigment in the back of our eyes is entirely of dietary origin, "suggesting that the most common cause of blind registration in the Western World could be delayed, or even averted, with appropriate dietary modification," according to authors of a study on age-related macular degeneration.

Where in our diet do we get these pigments? The egg industry brags that eggs are a good source, but have nearly six high-lutein, free-range, certified organic eggs a week for three months and the pigmentation in one's eyes may only marginally increase (see Egg Industry Blind Spot). Instead of getting the phytonutrients from the egg that came from the chicken that came from the corn and blades of grass the chicken pecked on, we could get it from the source. One cup of corn and a half cup of spinach a day for three months seems to dramatically boost the protective eye pigment in subjects. In the video, Dietary Prevention of Age Related Macular Degeneration, you can see a comparison of the amount of these phytonutrients from eggs compared to corn and spinach. If we cut out the middlehen and get these nutrients from plants directly, we see a substantially larger increase in protective eye pigment.

Three months after the subjects stopped eating the corn and spinach, the levels of these pigments remained relatively high, indicating that once we build our macular pigment up with a healthy diet, our eyeballs really try to hold on to it. So even if we go on vacation and end up eating more iceberg lettuce than spinach, our eyes will hold out until we get back.

Eggs can increase zeaxanthin levels in the blood, but they can also raise bad cholesterol levels and increase the risk of heart disease. Thus, as researchers conclude, "an egg yolk-based dietary strategy to increase plasma zeaxanthin cannot be recommended, and an alternative, cholesterol-free, food source is desirable." One such alternative would be goji berries, which have up to 60 times more zeaxanthin than eggs. A modest dose of goji markedly increases levels in our body. Consumption of goji berries may be an effective, safe whole food strategy to increase zeaxanthin in the bloodstream.

But we don't need it in our blood, we need it in our eyes. A group of researchers performed a double-blind randomized placebo-controlled trial to test the effectiveness of goji berries at increasing pigment levels. To preserve eyesight in the elderly in traditional Chinese medicine, people are often prescribed 40 to 100 goji berries a day. In this study, participants consumed only about 15 berries a day for three months. Even at this small dose researchers found that goji berries could protect against loss of pigment and prevent the buildup of debris that builds up in the back of the eye. Both loss of pigment and debris buildup are associated with age-related macular degeneration.

Macular degeneration is the leading cause of legal blindness in older men and women, affecting more than ten million Americans, so increasing our consumption of these pigments as a society could significantly decrease the prevalence of blindness. In the above study, researchers gave the goji berries in milk so the butterfat could increase the absorption of these carotenoid pigments. A healthier way to get the same effect would just be to eat goji berries with nuts or seeds--in other words, goji trail mix.

Though they didn't appear to boost a measure of immune function (Boosting Natural Killer Cell Activity), goji berries are one of the most antioxidant packed snacks out there. A tip on getting them inexpensively can be found in my video Are Goji Berries Good for You?

-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: Marufish / Flickr

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Foods for Glaucoma

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

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

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

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

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

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

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

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

-Michael Greger, M.D.

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

Image Credit: bruno garciact / Flickr

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