Play Tennis For A Longer Life. Science Proves It.

Chris Evert and former President George H.W. Bush playing
tennis at Camp David during Bush's presidency.
Tennis might just be the best thing you can do to extend your life.

A new study from Denmark, published just last week by Peter Schnohr and colleagues, shows that playing tennis may extend your life by nearly 10 years. That's a remarkably big benefit, one that even the study authors were surprised at.

It's been well-established for a while now that exercise helps you live longer. For example, the Cardiovascular Health Study found that people over the age of 75 can expect to gain 1 to 1.5 years of healthy living by being active rather than sedentary. Others studies have looked at the effects of running or walking and found similar positive benefits.

The authors of the new study wanted to look at other sports activities, not just running. Using a large cohort of 20,000 healthy people in the Copenhagen City Heart Study, they identified 8,577 who were in the study from the early 1990s until 2017 and who met a variety of other criteria for inclusion. This gave them 25 years of followup, long enough to ask the question: how does participation in sports affect life expectancy?

In particular, they looked at tennis, badminton, soccer, jogging, cycling, calisthenics, swimming, and health club activities (which included treadmills, ellipticals, and weights).

The bottom line: compared to a sedentary lifestyle, playing tennis extends one's life expectancy by 9.7 years. The other sports all provided benefits too, though tennis was the clear winner. Here's a summary:

  • Tennis: 9.7 years gain in life expectancy
  • Badminton: 6.2 years
  • Soccer: 4.7 years
  • Cycling: 3.7 years
  • Swimming: 3.4 years
  • Jogging: 3.2 years
  • Calisthenics: 3.1 years
  • Health club activities: 1.5 years

The authors didn't expect tennis to do so well, as you can see in this quote:
"Surprisingly, we found that tennis players had the longest expected lifetime among the 8 different sports."
For those who don't read scientific papers regularly, I should point out that the word "surprisingly" rarely gets past the editors unless the result truly is surprising. One part of the surprise is that spending more time exercising did not correlate with the greatest benefits. In fact, the cohort of people who spent the longest time on their exercise was the health club group, who showed the smallest increase in longevity.

One possible reason for tennis, badminton, and soccer doing so well is that out of the 8 sports studied, these are the ones that require 2 or more people and involve social interaction. As the authors explain,
"Belonging to a group that meets regularly promotes a sense of support, trust, and commonality, which has been shown to contribute to a sense of well-being and improved long-term health."
Or it might be that the type of exercise you get in tennis – short bursts of activity rather than slow, steady plodding exercise – might be better for you. The authors noted that
"short repeated intervals of higher intensity exercise appear to be superior to continuous moderate intensity physical activity for improving health outcomes."
If you're still skeptical, the only other study similar to this one, a very large study from Britain published last year, came to the same conclusion: racquet sports had the greatest benefit on all-cause mortality, followed by swimming and aerobics.

So if you're not doing it already, take up tennis! It's easy to find clinics and teams at almost any level (in the U.S., that is), thanks to the thousands of local clubs and to the huge network of USTA leagues, with play ranging from beginners on up, and age groups up to 85 and even 90.

That's right, there are tennis leagues for the 90-and-over set. Maybe tennis players really do live longer.

(Caveats: this was an observational study, based on surveys of people's behavior over a 25-year time span. The scientists tried to take into account all the other variables that might affect life expectancy, but humans are complicated and surveys are never entirely reliable. We don't know that tennis, badminton, and the other sports were the cause of longer life–it might be that people who play sports are generally healthier, and that both leads to longer life and allows them to play more sports.)

Can fasting help you burn off those vacation pounds?


Vacation's over, and with it comes the end of the french fries, ice cream, and other delicious but fattening foods that are hard to resist. "I'm on vacation," we tell ourselves, "I can diet later."


Well, it's later now. How about fasting? Is that an effective way to take off the weight?

Fasting has been growing in popularity in recent years. One of the latest fads is intermittent fasting, in which you fast at regular intervals and then eat all you want in between. There's the 5-2 fast, where you eat for 5 days and fast for 2, every week. Or there's alternate-day fasting, where you eat one day and fast the next, for as long as you can. Or you can fast every day for 16 hours and get all your eating done in the other 8.

Here's the thing: eating is easy, and fasting is hard. If you're going to fast to lose weight, you probably will lose a bit, but the evidence is that most people gain the weight back fairly soon once the fasting diet is over. So fasting might provide a quick reward in terms of weight loss, but the loss will be fleeting.

Suprisingly, though, fasting may be a good idea. A recent review by Stephen Anton and colleagues, in the journal Obesity, found that intermittent fasting may come with a variety of health benefits, including reducing inflammation, improving the ratio of lean tissue to fat, improving cognitive function, preventing type 2 diabetes, and possibly even prolonging life span.

How does fasting produce these benefits? Professor Valter Longo of USC, one of the leading researchers on fasting and longevity, hypothesizes that fasting forces your body to recycle many of its immune cells, particularly white blood cells. Then your body works hard to replenish its white blood cells, essentially re-setting parts of your immune system. Longo is also the inventor of the fast-mimicking diet, where you eat a special diet for 5 days every month, one that makes your body think you're fasting even though you're getting adequate calories and nutrients. (See Alice Walton's story in Forbes for more about that.)

Another effect of fasting is a change in metabolism. As Anton's article explained:
"the key mechanism responsible for many of these beneficial effects appears to be flipping the metabolic switch." 
This happens when the body runs out of its normal fuel, glucose, and begins to burn fat, which means it's converting fat to fatty acids, which in turn produce ketones. The body then uses ketones instead of glucose.

So how much fasting do you need to flip the switch from glucose to ketones? Anton et al. write that
"The metabolic switch usually occurs between 12 and 36 hours after cessation of food consumption, depending on the liver glycogen content and on the amount of exercise during the fast."
This doesn't tell the whole story, because once the switch occurs, you need to burn ketones for some time to gain any benefits. Back in 2014, I wrote about new evidence (from Valter Longo's research) that a longer fast, such as 3 days or more provide significant long-term health benefits. Three days is a long time to fast, but Longo has said that you don't need to do it more than a few times per year.

If you do decide to try a fast, don't expect it to be easy: you're going to get really hungry, and fasting can also interfere with social obligations in an inconvenient way.

I should emphasize that the evidence isn't yet clear for any of these strategies, and there are multiple studies going on now that may provide a clearer picture. Nonetheless, despite the current fad of fasting strategies and diets, fasting really does seem to have some potential health benefits.

(A final caveat: fasting can be harmful, especially for people who have other health problems. If you’re seriously thinking of trying this, you should consult your doctor first.)

Conspiracy theories and snake oil, the perfect pair

Why on earth would people rely on a conspiracy theorist, someone with only a high school education, for medical or health advice? And yet, some people do.

Alex Jones, the far-right conspiracy theorist who runs the Infowars radio program and website, was temporarily suspended by Twitter this week, following bans by Apple, YouTube, and Facebook. These social media companies banned him for repeatedly violating their rules about hate speech and inciting violence. Among other notorious claims, Jones has falsely claimed that children murdered in the mass shooting in Sandy Hook were just actors and that their parents faked their deaths.

What many people don't know, though, is that Jones also runs a dietary supplement business from his Infowars site. Despite reports that Jones' supplements are little more than "overpriced, mundane vitamins," his supplement sales seem to be quite profitable–so much so, in fact, that Buzzfeed reported that the supplement business "largely funds Jones' highly controversial Infowars media empire."

I was curious to see what Jones was selling, so I looked at his Infowars web store. It features an array of products with names like:


Each of these products is marketed with breathless claims for what it can do, including testimonials from Jones himself. For example, Brain Force Plus claims to "supercharge your state of mind," and Jones plugs it with this quote:
"This is what I take before a hard-hitting show. I absolutely love it, and the crew does too. This stuff is over the top powerful!"
Well then. Never mind that Brain Force is really just a collection of herbal extracts and vitamin B-12, none of them proven to "supercharge" your mind or any other body part.

In a similar vein, Jones hypes Super Male Vitality with this claim:
"This product works so well for me that I actually had to stop taking it before I go on air or else I would want to do hours and hours of overdrive with complete focus on the topics at hand."
From the name, you might guess that Super Male Vitality has something to do with testosterone, and the website does state that it "may help support normal testosterone levels in men." What's in it? A collection of plant extracts, none of them proven to maintain or increase testosterone or to have any actual medical benefit.

Of course, if you follow the asterisks on both of these pages and read further down, you'll see that
"These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease."
This statement is the standard disclaimer that supplement manufacturers make in order to avoid FDA oversight. There's no actual scientific evidence (and Jones's Infowars pages don't attempt to cite any) that these products do what the text on the very same page says they do. You just have to take Jones' word for it.

This is pure snake oil. That shouldn't be surprising, not coming from a man who has accused grieving parents of faking their children's deaths, and who claims the U.S. government was behind the 9/11 attacks. It's hard to understand why anyone believes any of the outrageous claims this guy makes, and especially bewildering that people who trust him to advise them on health and diet. His supplements aren't even a good buy, as Buzzfeed reported a year ago. All I can say is, caveat emptor.


You Think It's Hot Now? Just Wait.

Figure from Steffen et al.: a global map of potential
tipping cascades. The individual tipping elements are
color-coded according to estimated thresholds in global
average surface temperature (tipping points).
It's getting hotter all over the planet.

This week the temperature in Bar Harbor, Maine, reached 91° F (32.8° C). In my 20 years vacationing here, this is easily the hottest weather I've ever experienced.

Up and down the U.S. east coast, cities are sweltering, and temperatures out west are even hotter, with California seeing all-time high temperatures, including the hottest July on record in some areas, which has fed damaging fires across the state. Death Valley is always hot, but this week has been crazy, with temperatures on August 7 reaching 122° F (50° C).

At the same time, Europe is baking under a "heat dome" that has brought unprecedented high temperatures, including 45° C (113° F.) in Portugal. It's so hot that people aren't even going to the beach.

Global warming is here, folks. I know we're supposed to call it "climate change," because it's much more complex than simply warming, but warming is one of the most obvious consequences.

And yes, a single heat wave doesn't prove anything, and weather is not the same as climate. I know. But a just-released study from Oxford University found that climate change made this summer's heat wave in Europe twice as likely.

And now, a new study published last week in the Proceedings of the National Academy of Sciences, says it could get much, much hotter if we don't do something about it. In this paper, an international team of climate scientists led by Will Steffen and Hans Joachim Schellnhuber explain that, thanks to human activities, the planet is well on its way to a "Hothouse Earth" scenario.

In a Hothouse Earth, global average temperatures would rise 4–5° C (7–9° F) and sea levels will rise 10–60 meters (33–200 feet) above today's levels. This would be catastrophic for many aspects of modern civilization. Many agricultural regions would become too hot and arid to sustain crops, making it impossible to feed large swaths of humanity. Low-lying coastal areas would disappear or become uninhabitable without massive engineering efforts, displacing hundreds of millions of people. As Steffen et al. put it:
"The impacts of a Hothouse Earth pathway on human societies would likely be massive, sometimes abrupt, and undoubtedly disruptive."
That's putting it mildly.

One reason this scenario is happening, as the study explains, is that we are very close to "tipping points" beyond which certain changes cannot be stopped. (We may have already passed some of them.) These include losing the Arctic ice cap in the summer, and losing the Greenland ice sheet permanently: because they are basically white, these massive expanses of ice serve as giant reflectors to send much of the sun's heat back into space. Without the ice, the darker planet surface absorbs far more heat, creating a positive feedback effect. Another example is the melting of the permafrost, land that has been frozen for thousands of years and that contains a great deal of carbon in the form of methane. Once that methane is released, it will create further warming.

We are also likely to lose the Amazon rainforest, all of our coral reefs, and huge swaths of boreal forests. (See here for a global map of these tipping points.)

If this seems grim, Steffen and colleagues point out that we still have time to avoid it. They propose that societies must act collectively to create a "Stabilized Earth" at no more than 2° C above pre-industrial levels, which is possible but not easy:
"Stabilized Earth will require deep cuts in greenhouse gas emissions, protection and enhancement of biosphere carbon sinks, efforts to remove CO2 from the atmosphere, possibly solar radiation management, and adaptation to unavoidable impacts of the warming already occurring."
None of this is beyond our abilities. We know what we need to do, but it requires large-scale, coordinated action that many governments must agree on if it's to have an impact. Unfortunately, humans (and our governments) tend to do nothing until faced with an emergency, and the tipping points leading to a Hothouse Earth may not look like emergencies, not at first. For example, Arctic sea ice has been declining steadily for 25 years or more, but because few people are aware of this (and even fewer experience it first hand), it doesn't seem urgent. Yet it is.

So perhaps this summer's heat wave can serve as a wake-up call that we need to pay more attention to our planet's health. Otherwise it's going to get a lot hotter.

European Union gets it wrong on GMOS. Again.

Teosinte on the left, modern
corn on the right, a hybrid in
the center.
A European Union court just issued a new decision about GMOs. Disappointingly, this decision is likely to confuse rather than clarify this complex and contentious issue. The court announced that plants whose genomes have been modified with CRISPR technology, a very precise form of genome editing, are subject to the EU's very strict restrictions on genetically modified crops.

More specifically, the Court of Justice of the European Union (ECJ) decided that:
"Organisms obtained by mutagenesis are GMOs."
If we take this literally, then here’s a list of all the foods that have never been subjected to mutagenesis, and are therefore NOT GMO:
  1. Salt
  2. Wild boar
  3. Wild blueberries
That’s it. (OK, maybe there are a few others.)

We have been modifying the genes of the foods we eat for millenia. Every loaf of organic, non-GMO bread is made from wheat that humans have modified since ancient times. Every glass of milk from your grass-fed, bovine-growth-hormone-free cow comes from a cow that humans have bred for centuries. All cows are genetically modified. Those delicious croissants you bought at the organic bakery? Sorry, those are GMOs, no matter how organic you think they are.

And corn? Have you seen what ancient corn, called teosinte, looks like? I encourage you to Google it (or see the image on this blog, above). Modern corn is the result of many generations of human-driven genetic modifications.

To be fair, the EU court recognized that many of our foods have been genetically modified for a long time, and that it might be impractical to remove all of them from our food supply. So they carved out an exception:
"varieties [of plants] obtained by means of mutagenesis techniques which have conventionally been used in a number of applications and have a long safety record are exempt...."
What's ironic here–though I'm confident that the EU court didn't mean this–is that by this definition, virtually all of the GMO crops in the U.S. are exempt. You see, we've been eating them for decades, and they have a phenomenal safety record.

Two years ago, the US National Academies of Sciences, Engineering, and Medicine issued a massive report that reviewed over 1,000 studies of GMOs. The bottom line: there are no health risks whatsoever from eating genetically modified foods.

Earlier gene editing technology sometimes added foreign genes to an organism, such as adding a bacterial gene to a plant. The EU court's new decision is intended to clarify that even if a foreign gene is not involved, plants bred using the newest form of gene editing (CRISPR technology) are nonetheless GMOs.

Banning GMOs doesn't make sense, and it never did. Genetic technology is just a tool, one that can be used for countless purposes, some of them highly beneficial–such as golden rice, which has the potential to prevent blindness in countries where many people depend on rice as their main staple food. If someone objects to a particular use of GM technology, such as Monsanto's use of it to create herbicide-resistant plants, that's something we can reasonably debate. But banning all GMOs is throwing out the baby with the bathwater.

Now if you'll excuse me, I've got to go out to my grill and see how my wild boar is doing. It might need a bit more salt.

Should we all take aspirin? Not so fast.

I thought we'd put this one to bed. A large-scale study showed that low-dose aspirin (one quarter of a standard 325 mg pill, or about 81 mg) taken once a day can prevent heart attacks and some common types of cancer, including colon cancer.

I wrote about this topic just over a year ago, and I've followed my own advice, taking daily 81mg aspirins since then. The US Preventative Services Task Force recommends this too: regular, low-dose aspirin for people between the ages of 50 and 69 helps to prevent heart attacks, strokes and some types of cancer.

But now, a new study just published in The Lancet upends that advice. It's not that the previous study was wrong–it wasn't. It's just that the effects of aspirin vary significantly based on body weight. Essentially, the new study finds, almost all of the benefits accrue to people who weigh 70 kilograms (154 pounds) or less.

The study, a re-analysis by Peter Rothwell and colleagues of ten large trials that included 117,279 participants, is too long and complex to summarize here, so I'll just highlight a few key points. (Because the paper is open access, anyone can read it for free, just by clicking here.)

The good news, for people who weigh between 50 and 70 kg (110-154 lbs), is that the benefits of daily low-dose aspirin are quite good, possibly even better than we thought. The relative risk of a heart attack, stroke, or other major heart-related event is about 25% lower for people in this group.

The bad news, for the rest of us, is that we seem to get no heart-related benefits from taking a daily low-dose aspirin.

So perhaps those of us who weigh more than 70 kg just need a slightly larger daily aspirin pill. There is some good news here: Rothwell and colleagues found that, indeed, higher doses of aspirin are effective at reducing the risk of heart attacks for people who weigh more than 70 kg. This makes sense: adjusting the dosage based on weight is how most drugs are given. The problem is that aspirin generally comes in only 3 pill sizes: 81, 325, and 500 mg. So the studies have only looked at these 3 doses, and 325 mg is likely too large a dose for most people, because it increases the risk of bleeding events.

What about the cancer risk? As I wrote in 2017, the biggest benefit from daily low-dose aspirin is its reduction in the risk of colon cancer, breast cancer, and prostate cancer. Here, the new study doesn't quite give the whole picture, because it didn't look at breast cancer or prostate cancer. For colon cancer, low-dose aspirin reduces the risk significantly for people who weigh less than 70 kg. For heavier people, low-dose aspirin had little to no effect on colon cancer risk, but regular-sized aspirin (325 mg) worked for people up to 80 kg (176 lbs).

What to do now? The new study concludes that:
"The one-dose-fits-all strategy for daily aspirin use is unlikely to be optimal."
 In other words, you will probably benefit from daily aspirin, but the amount you should take depends on your weight. If you weigh less than 70 kg, the 81-mg tablets that you can find almost anywhere will do nicely. 

But what if you weigh more (as most men and many women do)? The science doesn't yet give us an answer: you could simply take 2 low-dose pills a day, but too much aspirin increases the risk of serious bleeding events. You could instead take a few extra pills per week, depending on your weight, which is what I'm going to do, at least until we get better data and more precise guidelines.

(Final note: as always, before you make any changes in your medication, ask your physician.)

Mosquito wars: what works to keep these little buggers away?

It's summer time, and with it comes outdoor dining, sports, and strolls through the neighborhood. But the loveliest evening can be spoiled by mosquitos, who torment us as they suck our blood and leave itchy welts behind.

How can we keep these pests away? Do citronella candles work? How about Victoria's Secret Bombshell perfume? (No, I'm not kidding. Read on.)

First, about mosquitos: they are more than just a nuisance. They also carry diseases, including West Nile virus, which now affects the entire U.S., and far more deadly diseases in other countries, including malaria, yellow fever, and Zika virus.

(Aside: West Nile virus first appeared in the U.S. in 1999, in New York, after a mosquito apparently hitched a ride on a plane from somewhere in the Middle East. A few years later it started spreading rapidly across the country, and now it's basically everywhere. West Nile fever usually manifests as a flu-like illness, but about 1 in 150 people get severe, life-threatening symptoms.)

One of the most popular ways to keep mosquitos off the backyard patio is easy to spot on a summer night in my neighborhood: burning citronella candles (such as this one from Cutter), which contain a natural oil made from grass whose scent is supposed to repel mosquitos. These are very popular and widely sold, but do they work?

Fortunately, the Journal of Insect Science published a study just last year, by Stacy Rodriguez and colleagues from the University of New Mexico, that gives us an answer. The scientists purchased a dozen different products, all from Amazon or local stores, and ran a very nice experiment to figure out how well each product worked.

Here's the setup: the scientists placed a cage full of mosquitos near a human volunteer, who sat 1-3 meters away, with a gentle breeze blowing from the humans towards the mosquitos. (This made it easier for the mosquitos to smell the humans, and also meant that they had to fly against the breeze if they wanted to bite the subjects.) The scientists applied each mosquito repellent (or device) to the volunteers, opened the cage, and counted how many mosquitos were attracted. They also ran controls where the subject had no protection.

So what worked? First off, with no protection, about 88% of the mosquitos were attracted to the human subjects. The three products that worked best at repelling mosquitos were:

  1. OFF!® Clip On™, where just 27% of the mosquitos were attracted
  2. Cutter® Lemon Eucalyptus, with 30%, and
  3. Ben’s® Tick & Insect Repellent, with 34%. 

Nothing else worked nearly as well as these, although several products reduced the proportion of mosquitos from 88% down to 60-70%.

Notably, some of the products did not work at all, including citronella: Cutter Citro Guard had no effect on the mosquito's attraction to the human volunteers. Other failures were Invisaband™ and Mosquitavert, wrist bracelets containing geraniol oil, and the PIC® Personal Sonic Mosquito Repeller, a clip-on ultrasonic device that emits a sound that mosquitos presumably don't like. Mosquitos basically ignored these devices.

So what's the secret in the products that do work? The OFF! device contains metofluthrin, which appears to be the most effective repellent on the market. Lemon eucalyptus oil is a natural product that is nearly as effective, and Ben's Tick & Insect Repellent contains DEET, which has long been known as an effective defense against mosquitos.

The only one of these products that purports to work on a whole area (like your backyard patio) rather than just one person is the citronella candle, which unfortunately just doesn't work. So if you want your garden party guests to be protected, you may have to keep on hand a basket full of products with metofluthrin, lemon eukalyptus oil, or DEET.

And what about Victoria's Secret Bombshell perfume? Well, the same scientists looked at Bombshell in a 2015 study, where they included the perfume thinking that it would attract (rather than repel) mosquitos. Surprisingly, it had the opposite effect: even though DEET and metofluthrin are more effective, the scientist found that:
"Victoria Secret Bombshell repelled mosquitoes quite effectively 120 min post application."
And what is the active ingredient? According to the same study, that's unknown.