Field of Science

A true fountain-of-youth drug combo?

This is really, really interesting. Can we alleviate the effects of aging by getting rid of "bad" cells in the body?

A new study from the Mayo Clinic and the Scripps Research Institute reports that a novel cocktail of two unrelated drugs 
dramatically slows the aging process—alleviating symptoms of frailty, improving cardiac function and extending a healthy lifespan.” 
The scientists who conducted the study, led by James Kirkland, Laura Niedernhofer, and Paul Robbins, screened 46 different compounds to find ones that would interfere with the ability of senescent cells to survive. The two that seemed to work best were quercetin and dasatinib. They call these drugs "senolytic" for their ability to kill senescent cells.

Old cells are supposed to die and let the body replace them. Most of them do, but some cells become senescent: old geezers who just won’t go away. The problem is, these cells just don’t sit quietly in the living room reading a book. Instead, they make lots of noise, throwing things around that can mess up the living room and make all the other cells miserable. At a molecular level, they secrete enzymes that cause inflammation and other problems, which may explain the relationship between these cells and age-related chronic diseases such as heart disease and osteoporosis. 

This current line of research started about four years ago, when the Mayo Clinic's Jan van Deursen published a study (in mice) showing that if you could selectively destroy senescent cells, the mice had fewer age-related diseases and lived up to 25% longer. Senescent cells, it seems, are definitely a problem.

The challenge is that very few cells are senescent, even in very old people, and it's difficult to destroy these cells without harming all the healthy cells around them. In the new study, Kirkland and his team screened 46 different compounds to find ones that could interfere with what they called “pro-survival” genes in senescent cells. The theory is that the senescent cells have a special ability to survive, and if we can interfere with that ability, the cells will die.

The two compounds they found are very different. Quercetin is a common plant extract, found in a wide variety of fruits and vegetables, especially capers, red onions, plums, and cranberries. Dasatinib, in contrast, is a highly specialized cancer drug made by Bristol-Myers Squibb (NYSE:BMY) and sold under the name Sprycel®. Dasatinib is used to treat CML, a form of leukemia. Quercetin is cheap and easily available, while dasatinib is very expensive and cannot be obtained without a prescription.

The study results were very impressive: after a single dose, mice had improved heart function that lasted up to 7 months. Periodic doses worked too: mice showed improvements in a wide range of age-related symptoms, including bone loss, tremors, grip strength, and overall body condition.

Before everyone runs out and buys a giant bag of red onions (or a quercetin supplement), I should inject a dose of skepticism. Quercetin’s effect on lifespan has been studied before, and it came up short. A study in 2013 by Stephen Spindler and colleagues looked at extracts of blueberry, pomegranate, green tea, black tea, quercetin, and other plants, feeding each of them to mice in a controlled experiment. None of the mice lived longer, and Spindler reported that 
our results do not support the idea that isolated phytonutrient anti-oxidants and anti-inflammatories are potential longevity therapeutics.”

However, the method of delivery for quercetin and dasatinib in the new experiment was different, and the combination of the two might have benefits that quercetin alone does not offer. As Kirkland point out, dasatinib and quercetin “are both approved for use in humans and appear to be relatively safe,” although they then go on to point out a variety of possible side effects, some of them harmful. They end, though, on a remarkably optimistic note: 
If senolytic agents can indeed be brought into clinical application, they could be transformative. With intermittent short treatments, it may eventually become feasible to delay, prevent, alleviate, or even reverse multiple chronic diseases and disabilities as a group, instead of one at a time.”
Of course, results in mice often fail when we try them out in humans–but not always. Let’s hope this drug combination shows the same effects in humans that Kirkland and colleagues observed in mice. None of us are getting any younger.

NIH distorts report showing risk of stroke after chiropractic

Why would an NIH center try to mislead the public about a newly published study that it funded? Last month NIH’s alternative medicine center, NCCIH, highlighted one of its studies with this headline: “Low risk of stroke after chiropractic spinal manipulation in older patients with neck pain, study finds.” 

This sounds reassuring, unless you read the study. It turns out that the risk of stroke was 10% higher in patients who saw a chiropractor compared to those who saw a regular doctor. Yet NIH wants us to believe that the study found no serious risk.

Why ask this question? Because earlier studies showed a small but frightening risk of stroke in younger people (45 and below) after chiropractic, caused by dissection of the vertebral artery. Strokes caused by a tear in this artery are extremely rare, but even a tiny possibility of a fatal stroke after a chiropractic manipulation is alarming. As Forbes writer Larry Husten reported last August, the American Heart Association and the American Stroke Association issued a statement warning that chiropractic neck adjustments might cause strokes. The AHA stated:
  • "Manipulating the neck has been associated with cervical dissection, a type of arterial tear that can lead to stroke.
  • Although a direct cause-and-effect link has not been established between neck manipulation and the risk of stroke, healthcare providers should inform patients of the association before they undergo neck manipulation."
I’ve written about this as well, both at Forbes and in The Atlantic Monthly. The risk is small but the consequences can be extremely serious.

So what's in this new study? The study, led by chiropractor James Whedon at Dartmouth College, was a large-scale survey of Medicare claims involving people aged 66 to 99. Its aim was to answer this question: "what is the probability of stroke following chiropractic spinal manipulation, as compared to a control group of subjects evaluated for neck pain by a primary care physician?" Key findings from the study included these (all from Table 2):

                     Hazard ratio for stroke at 30 days
All patients         1.10 (10% increase)
Patients aged 75-79  1.93 (93% increase)
Patients aged 80-84  2.50 (2.5 times more likely)
Patients over 85     3.59 (over 3.5 times more likely)

This looks bad: for all patients, the risk of stroke was 10% higher if they'd seen a chiropractor versus a regular doctor. In the older patients, the risk of stroke after 30 days was 1.9 to 3.6 times higher than for patients aged 66-69. (All four of these results were reported as statistically significant.) Yet the conclusions of the study–and the NIH press release–make no mention of these findings. The study itself concludes only that 
Among Medicare B beneficiaries aged 66 to 99 years with neck pain, incidence of vertebrobasilar stroke was extremely low. Small differences in risk between patients who saw a chiropractor and those who saw a primary care physician are probably not clinically significant.”
Talk about spin! The study provides no support for the dismissive statement that the increase in risk of stroke after chiropractic is "not clinically significant"; it seems they are trying to downplay their own finding of a statistically significant increase in risk. The NIH’s press release is just as bad: it merely parrots the study's conclusions, opening with the statement that “cervical spine manipulation is unlikely to cause a stroke,” and never mentioning the statistically significant 10% increase in risk or that the study was led by a chiropractor.

Despite the misleading press release, this new study adds to the evidence that chiropractic carries an increased risk of stroke, especially for older patients. As the American Heart Association recommends, patients should be informed of this risk before submitting themselves to a possibly dangerous neck manipulation. And NIH press officers should read the study before issuing a press release.

A really bad week for the supplements industry

If the ingredients in your pills don’t really work, does it matter if they’re correct?

Well, yes. Even if that echinacea pill doesn’t cure the common cold, if a supplement manufacturer sells you an echinacea pill, they have to put echinacea in it. 

Supplement makers can and do make all kinds of claims about the health benefits of the stuff they’re selling you. They claim that supplements can "boost your immune system," relieve aches and pains, improve memory, and promote "wellness," whatever the heck that means. Most this is nonsense, but thanks to the manufacturers’ special friend in the U.S. Senate, Senator Orrin Hatch, the federal government has almost no power to regulate these claims. Over the years, the supplement companies have been very generous to Senator Hatch, and he has returned the favor by defending them (though of course he denies any quid pro quo).

Even supplement makers have limits: they can’t sell you ground-up house plants, or rice powder, claiming that it’s St. Johns Wort. But as New York attorney general Eric Schneiderman revealed last week, that’s exactly what some of them have been doing. Amazingly, 79% of the supplements tested did not contain the primary ingredient listed on the label. Many of them contained other plant material, including plants that might cause an allergic reaction in unsuspecting customers.

You see, as cheap as most supplements are (compared to real medicine, that is), rice powder is even cheaper.

Attorney General Schneiderman sent letters to four of the largest retailers of supplements in the country: Walmart, Walgreens, GNC, and Target, demanding them to immediately stop selling supplements that were falsely labelled, including echinacea, ginseng, St. John’s Wort, gingko biloba, and others.

What did Schneiderman's office do? Well, they conducted a scientific study, using DNA sequencing to test the ingredients in six types of herbal supplements, looking at different brands from multiple stores. They tested each sample 5 times to ensure accuracy. They collected 78 different samples and ran 390 tests in all.

Here's what they found:
  • GNC "Herbal Plus" supplements: gingko biloba, St. John's wort, ginseng, garlic, echinacea, and saw palmetto were tested. Garlic was the only one that consistently contained what the label indicated. One out of four bottles of saw palmetto tested positive, and none of the other four supplements contained the labeled herb. Overall, 22% of the DNA tests identified the labeled ingredient. Contaminants included rice, alfalfa, and houseplant DNA.
  • Target's "Up & Up" supplements: gingko biloba, St. John's wort, Valerian root, garlic, echinacea, and saw palmetto were tested. Three supplements–garlic, saw palmetto, and echinacea–contained what they were supposed to. The other three had no DNA at all from the labeled ingredient. 
  • Walgreens "Finest Nutrition" supplements: gingko biloba, St. John's wort, ginseng, garlic, echinacea, and saw palmetto were tested. Only one of these, saw palmetto, consistently contained its labeled ingredient. One sample of garlic actually contained garlic, and none of the other samples contained any DNA from the labeled ingredient. Overally, 18% of the DNA tests found the expected ingredients. Contaminants included rice, wheat, daisy, and houseplant DNA.
  • Walmart's "Spring Valley" supplements: gingko biloba, St. John's wort, ginseng, garlic, echinacea, saw palmetto were tested. Walmart had the worst results: of 90 DNA tests on 18 bottles, only 4% found any DNA from the labeled ingredient. Only one bottle of garlic and one bottle of saw palmetto contained what they were supposed to. Contaminants included pine, grass, citrus, and cassava.
This is pretty stunning, and it's only a sample; see the AG's letters to each retailer for more details. According to the New York Times, the retailers agreed to pull the supplements off their shelves (in New York, at least) after receiving the AG's letter.

Just a couple of years ago, Senator Orrin Hatch successfully fought off an amendment that would have required supplement makers to register their products with the FDA and provide details about their ingredients. As the NY Times also reported, Hatch has received hundreds of thousands of dollars from the supplements industry over the years.

Of course, even if these bottles did contain what they were supposed to, their claims to improve memory, boost your immune system, and fight off colds are entirely unproven. Thanks to a 1994 law championed by Senator Hatch, the FDA cannot require supplement makers to prove that any of their products work, as long as they avoid specific claims to cure a specific disease. 

But if they say they're selling you gingko biloba or St. John's wort, they're supposed to put that in the pills. Instead, it seems they are selling ground-up rice and house plants.

One supplement did actually contain what it’s supposed to: garlic pills. Garlic has been investigated for its effect on cholesterol levels, where it seems to have at most a very small benefit. Garlic lovers would argue that you're losing the real benefit if you take it in pills rather than simply eating it.

And garlic does have one unique benefit: it is 100% effective at warding off vampires.

Anti-vaxxers are to blame for a new epidemic of measles in the U.S.

Measles is now spreading outward from Disneyland in California, in the worst outbreak in years. The epidemic is fueled by growing enclaves of unvaccinated people. 

The CDC reports that in just the past month, 84 people from 14 states contracted measles, a number that is certainly an under-estimate, because the CDC doesn’t record every case. California alone has 59 confirmed cases, most of them linked to an initial exposure in Disneyland. A majority of people who have gotten sick were not vaccinated.

For years, scientists (including me) have warned that the anti-vaccination movement was going to cause epidemics of disease. Two years ago I wrote that the anti-vaccine movement had caused the worst whooping cough epidemic in 70 years. And now it’s happening with measles.

Finally, though, the public seems to be pushing back. Parents are starting to wake up to the danger that the anti-vax movement represents to their children and themselves. 

What's sad about this – tragic, really – is that we eliminated measles from the U.S. in the year 2000, thanks to the measles vaccine. As this CDC graph shows, we've had fewer than 100 cases every year since. 

But we had 644 cases in 27 states in 2014, the most in 20 years. And 2015 is already on track to be worse. Measles may become endemic in the U.S, circulating continually, thanks to the increasing numbers of unvaccinated people. Until now, each outbreak was caused by someone traveling from abroad and bringing measles to us. The anti-vaccine movement has turned this public health victory into defeat.

Anti-vaxxers have been relentless in the efforts to spread misinformation. Despite overwhelming scientific evidence that vaccines are beneficial, they endlessly repeat a variety false claims, such as

Now, finally, some parents are pushing back. Parents and schools in California, where the epidemic began, are concerned that their children will be exposed to measles from unvaccinated children in schools. And the schools are starting to do something they should have done long ago: send the unvaccinated kids home.

The problem arises from California’s vaccine exemption policy: although public schools require kids to be vaccinated, parents can exempt their kids simply by saying they have a personal objection to vaccination. It’s not just California: only two states, Mississippi and West Virginia, don’t allow parents to claim a philosophical or religious exemption to vaccines  And Colorado has the worst rate of vaccination, at just 82%, primarily due to parents claiming a “philosophical” exemption.

These parents are the anti-vaxxers. Thanks to them, we now have large pockets of unvaccinated children through whom epidemics can spread further an faster than we’ve seen in decades. The CDC reports that in 2014, 79% of measles cases in the U.S. involving unvaccinated people were the result of personal belief exemptions.

Anti-vaxxers don't recognize the threat their behavior poses to others, especially to children whose immune systems aren’t functioning properly. CNN reported this week on the case of Rhett Krawitt, a 6-year-old California boy who has gone through 4 years of chemotherapy for childhood leukemia. His leukemia is in remission and he’s back in school, but the treatment wiped out his immunity, and he’s still not ready to get vaccinated. If Rhett gets measles, he might not survive. His father Carl wrote to school district officials to ask them to ban unvaccinated children from school.

Krawitt expects the schools to deny his request.

Meanwhile, the parents who refuse to vaccinate their kids aren’t budging. The New York Times reported on one mother, Crystal McDonald, who refused to vaccinate any of her four children, after “researching the issue” by reading anti-vaccine websites. When their high school sent her daughter home for two weeks, the daughter asked if she could get the measles shot so she could return. As quoted in the Times, McDonald told her daughter “I said ‘No, absolutely not.’ I said I’d rather you miss an entire semester than you get the shot.’”

Where does this breathtaking science denialism come from? It’s been building for years, as I and many others have written. The wave began with a 1998 paper published in The Lancet by Andrew Wakefield, claiming that the MMR vaccine was linked to autism. Wakefield’s work was later shown to be fraudulent, and his claims about the vaccine "dishonest and irresponsible." After lengthy investigations, the paper was retracted and Wakefield lost his medical license. Despite this very public repudiation, Wakefield has stuck to his claims, though, and has spent much of the past 15 years speaking (or perhaps “preaching” would be a better term) to anti-vaccine groups, to whom he is a kind of folk hero.

It’s not just Wakefield, though. Anti-vaccine messages have been broadcast aggressively by the group Generation Rescue, led by former Playboy playmate and MTV host Jenny McCarthy, and by Age of Autism, a group dedicated to the proposition that vaccines cause autism. (Age of Autism is doing it again right now.) And just last summer, Robert F. Kennedy Jr. published a new book further promoting the long-discredited claim that thimerosal causes autism. 

Most of the anti-vax crowd have no scientific training or expertise, which might explain (but doesn't excuse) their complete ignorance of the science. Over the past 15 years, dozens of studies involving hundreds of thousands of people have shown convincingly that neither vaccines nor any of the ingredients in them are linked to autism. Vaccines are not only safe, but they are perhaps the greatest public health success in the history of civilization.

Measles, though, is dangerous. The CDC’s Anne Schuchat had a message for parents this week:
I want to make sure that parents who think that measles is gone and haven't made sure that they or their children are vaccinated are aware that measles is still around and it can be serious. And that MMR vaccine is safe and effective and highly recommended.”
Make no mistake, measles is a very dangerous infection. In the current outbreak, 25% of victims have ended up in the hospital. And it is extremely infectious: the CDC’s Schuchat explained that 
“You can catch it [measles] just by being in the same room as a person with measles even if that person left the room because the virus can hang around for a couple of hours.”

Perhaps the Disneyland epidemic, which has now spread to 14 states, will finally convince parents, schools, and state legislatures that they need to insist that children get vaccinated before going to school. Perhaps it will also convince parents to stop listening to nonsense, and choose wisely by getting their children vaccinated against measles. We won this battle before, and we can win it again.

No, Wi-Fi exposure is not killing your kids

Last week a blog post at Forbes on Wi-Fi devices went viral. That post, by fellow Forbes contributor Robert Szczerba, claimed that Wi-Fi exposures from cell phones, iPads, microwave ovens, and other mobile devices are "more dangerous to kids than previously thought."

Szczerba claimed that Wi-Fi devices might be causing cancer, especially in children." It was illustrated with a photo of a toddler playing with a tablet PC, possibly an iPad.

Well, that got some attention.

The problem is, it's all wrong. Even the premise is wrong: there was no "previous" evidence of danger from Wi-Fi devices, except from conspiracy theorists. Let's start where Szczerba started: he based his article on a newpaper published in the Journal of Microscopy and Ultrastructure, titled "Why children absorb more microwave radiation than adults: The consequences."

I read the article, painful though it was, to see what it actually claims. The first red flag is that it appeared in a very obscure journal that does not focus on radiation or environmental health. The second red flag is that two of the authors, Lloyd Morgan and Devra Davis, work for a private organization whose sole purpose seems to be to promote claims that cellphones and other wi-fi devices cause cancer. The remaining author, Santosh Kesari, seems to be a respectable neuroscientist at UC San Diego. I wrote to Kesari to ask for comment, but he did not respond.

Now to the article itself I have to say that this is perhaps the worst scientific paper I have read in years–and I read a lot. It purports to be a review of some sort on microwave radiation (MWR) exposure in children. It is nothing of the sort. It's not even written like a scientific paper.

Essentially, the article is a series of claims, most of them unrelated to one another, about the effects of MWR and other topics. The authors have cherry-picked several dozen studies that they believe support their hypothesis, which they cite without any explanatory details, while ignoring hundreds of studies that contradict their claims. For example, they write:
"In 2008 Joe Wiart, a senior researcher for French telecom and Orange reported that the brain tissue of children absorbed about two times more MWR than adults' brain tissue."
That's it: just one sentence, with no explanation of what the study was about (nor of what "Orange" is here). It turns out to be a simulation study with little or no relevance to the health risks of MWR on actual people.

Other cherry-picked examples in this so-called review include a 1972 study of myelin degeneration in guinea pigs and a 1977 study in rats, neither of which tell us anything about the risks of wi-fi devices. This paper is a dreadful mess.

The paper also includes many stunning non sequiturs, such as this:
"The Australian study reported, "an overall significant increase in primary malignant brain tumors was observed over the study period from 2000 to 2008." 
This study does indeed exist, but it has nothing to do with wi-fi or microwaves! It's a study of changing cancer rates in Australia, and the authors don't even mention wi-fi, much less suggest that it causes cancer. In a real journal, peer reviewers would have insisted that the studies cited have some relevance to the main topic of the paper. Not here, apparently.

I don't have time to debunk all the nonsense in this truly awful paper - nor should you want to read about it. My guess is that the Journal of Microscopy and Ultrastructure will publish anything as long as the authors pay the publication fees. In its entire history, the journal has only published 6 issues.

So what is the evidence for Wi-Fi and cancer? Just a few months ago I wrote an article explaining that high-voltage power lines do not cause cancer. But how about Wi-Fi devices like cell phones and iPads? It only took me a few minutes to find a recent review of the literature, published just a year ago in the journal Health Physics. Note that this is a journal that's actually about human health, unlike the microscopy journal that Szczerba relied upon. That study concluded:
"The overwhelming consensus of health agencies around the world is that RF [radio frequency] exposures below international exposure limits have not been shown to produce any health hazard (Verschaeve 2012). That conclusion would not be changed by the Wi-Fi–related studies reviewed here, some of which indeed were already considered in these expert reviews."
Or to put it in simpler terms: Wi-Fi is not more dangerous than previously thought, and your iPad is not going to give your kids cancer. That's what Robert Szczerba should have written, if he'd looked at the real science instead of one really bad paper.

But that wouldn't have gone viral, would it?

Research on artificially engineered flu strains expected to kill 2000 people per year

2,000 deaths expected for each year of research on how to turn avian flu into a more deadly virus. 

That’s the estimate in a new analysis by Harvard University’s Marc Lipsitch, professor and director of the Center for Communicable Disease Dynamics in the Harvard School of Public Health.

I heard Lipsitch present his results at an invitation-only hearing held at the National Academy of Sciences on December 15. The purpose of the two-day meeting, which was organized by the National Science Advisory Board for Biosecurity (NSABB), was to discuss the risks and benefits of “gain of function” research on viruses, especially the influenza virus.

What is gain-of-function (GOF) research? In this context, GOF means experiments designed to give a pathogen new powers, such as the ability to infect new species, or to jump from person to person more easily. Scientists have already conducted GOF experiments on the flu virus, and now they are considering other viruses including SARS and MERS.

What prompted the NSABB hearing was the series of experiments by researchers in the U.S. and the Netherlands designed to transform avian influenza (or “bird flu”) into a human-transmissible virus. These novel, lab-created flu strains have the potential to cause a worldwide pandemic. When virologists Ron Fouchier and Yoshi Kawaoka first published their experiments two years ago, the public, the press, and many members of the scientific community (including me; see here and here) expressed serious alarm. After a brief hiatus, though, the experiments continued. 

In mid-October, the U.S. government announced a “pause” in gain-of-function experiments, which has Fouchier, Kawaoka, and their colleagues very upset.

At the NSABB meeting in December, the vast majority of panelists were influenza researchers defending GOF research, arguing that it could lead to valuable insights about the flu. As a group, they seem to have convinced themselves that everything is fine, and they want to tell the rest of us that there’s nothing to worry about. Prof. Lipsitch (and a couple of other speakers) stood out as a voice of reason. He was one of the very few scientists who took a hard look at the risks and also pointed out alternative, low-risk methods for answering the same scientific questions.

Lipsitch conducted a careful risk analysis (something apparently not even considered by Fouchier and Kawaoka) looking at the chances of a virus escaping a lab, of such a virus causing further infections, the likely number of fatalities, and more. It turns out that the scientific community has excellent data quantifying all the key variables involved, as Lipsitch documented. He and his colleague Tom Inglesby just published these figures, with supporting data, in the journal mBio.

Using conservative estimates, many of them provided by influenza researchers themselves, Lipsitch calculated that for each year of gain-of-function research on pandemic viruses, we can expect at least 2,000 fatalities worldwide. And that’s only the low end: at the other extreme, this estimate rises to 1.4 million fatalities per year.

Lipsitch also described many other ways to study and defeat influenza, all of them with little or no risk, which he’s published in the journal PLoS Medicine. His point is that even if we accept the supposed benefits of GOF research, there are far less risky ways to obtain those same benefits.

One of the most ironic–or outrageous–claims of the pro-GOF scientists is that these experiments will help us predict future pandemic flu strains, and even help us design a vaccine in advance of outbreaks. The irony is that this year, the seasonal flu vaccine is a poor match to the strains that are circulating. This vaccine was chosen only 9 months ago, based on extensive surveillance of circulating flu strains, demonstrating how difficult it is to predict even the regular seasonal flu. As a result, we’re having a very bad flu season this year (aside: it's still worth getting the flu vaccine).

During the discussion at the NSABB meeting, an audience members observed that the claims of Fouchier, Kawaoka, and other pro-GOF scientists is hubris. She pointed out that not only are they claiming that they can predict future outbreaks–which no one has ever done accurately–but that we should invest billions of dollars stockpiling specially-designed vaccines based on their predictions. (This was indeed suggested by one of the presenters.) 

2000 deaths per year. And that’s only the direct risk: what about the risk from publishing these experiments? What happens when we provide instructions on how to build deadly biowarfare agents to anyone with an internet connection? Indeed, “gain of function” research on pandemic pathogens is really biowarfare research, which supposedly ended after the Cold War.

I’m a huge supporter of biomedical research and of NIH in general. NIH research has yielded tremendous benefits to the public health, as I’ve written before. We don’t need to overreact by cutting medical research in general, but we can make the “pause” in gain-of-function research permanent. There are far better things to do with our research funds. If you want to register your concerns, write to the NSABB at and tell them to recommend a permanent halt to gain-of-function research on pathogenic viruses.

Does a 3-day fast reset your immune system?

I’ve been hearing new reports lately that sound an awful lot like pseudoscience: that fasting for an extended time, two days or longer, can reset your immune system and provide other health benefits. I first heard about this when a friend and colleague at Stanford University announced he was going on a 3-day fast. To explain, he pointed to a recent study, which I’ve now read.

Diet advice, including fasting-based diets, can be found all over the Internet, and much of it is nonsense, so I was very skeptical about these latest claims.

This time, though, there might be something to it. The scientific study that my colleague told me about was published back in June by USC’s Valter Longo, who studies aging and longevity. In this paper, Longo and colleagues described remarkable metabolic changes that occurred as a result of prolonged fasting. They found that fasting for 3 days or longer–drinking only water and eating less than 200 calories per day–can truly “reset” some components of your immune system. 

The research looked at both mice and humans. (It’s far easier to run the experiments in mice, of course, but we can’t always trust that the same effects will occur in humans.) In both species, fasting lowered white blood cell counts, which in turn triggered the immune system to start producing new white blood cells. White blood cells (or lymphocytes) are a key component of your body’s immune system.

Longo’s hypothesis is that fasting (or starvation) forces your body to “recycle a lot of the immune cells that are not needed” which explains the drop in the white blood cell count. Two of the key mechanisms are an enzyme called PKA and a hormone called IGF-1, both of which are reduced by fasting. Once you start eating again, your stem cells kick back into high gear to replenish the cells that were recycled.

The human part of the study was much more limited: a group of cancer patients fasted for 1, 2, or 3 days prior to chemotherapy. The idea is that fasting might reduce the harmful side effects of chemotherapy, particularly the immunosuppression caused by some chemotherapeutic drugs. These results are very preliminary: the patients are participating in a phase I clinical trial, which is designed to assess safety, not effectiveness. Nonetheless, the results indicate that a 3-day fast (but not a 1-day fast) was beneficial for these patients.

A key finding in this research is that you have to fast for several days to get any benefit: basically, you have to fully deplete your energy reserves (in the form of glycogen), and it takes your body at least 24 hours, and probably 48 hours or more, to do this. This is much harder than a 1-day fast, which many people do routinely. 

On the other hand, Valter Longo has compared the effects of periodic fasting to long-term caloric restriction, which has been shown to prolong lifespan in mouse and other animals. In a separate review article, Longo wrote: 
“Fasting has the potential to delay aging and help prevent and treat diseases while minimizing the side effects caused by chronic dietary interventions.”
Caloric restriction is extremely difficult to achieve for humans: you have to nearly starve yourself for years. Compared to this, an occasional 3-day fast should be a snap.

Caveats: 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. And this preliminary evidence, though encouraging, is primarily based on mice, not people. We might eventually learn that the benefits of fasting are outweighed by other problems. Fasting for more than two days isn’t easy, either: you’re going to get really hungry. 

Does a 3-day fast truly reset your immune system? Well, maybe not a total reset, but at least a mild refresh. The science suggests that, if you can do it, a prolonged fast for 2-3 days or longer may induce your body to clean out some old immune cells and switch on production of new ones. Stay tuned.

[An interesting aside: this study was lengthy and complex, and the authors apparently went to great lengths to satisfy the peer reviewers: the paper was submitted in October 2012, re-submitted after revision in December 2013, and finally accepted in April 2014. 18 months is a very long time.]