One Heartbeat per Second to Beat the Clock

Immanuel Kant, the famed 18th century philosopher, described the chemistry of his day as a science, but not really science, as it wasn’t grounded in mathematics—at least not until a century later. The same could be said for biology, the study of life.

In math, physics, and quantum physics, there are constants: physical quantities thought to be both universal and unchanging. Biology, though, was considered too complex and too messy to be governed by simple, natural laws. In 1997, however, a theoretical high-energy physicist from Los Alamos joined two biologists to describe universal scaling laws that appear to apply across the board. Are there any clinical implications of these types of theories?

A fascinating observation was published. As I discuss in my video Finger on the Pulse of Longevity, the number of heartbeats per lifetime is remarkably similar whether you’re a hamster all the way up to a whale. So, mice, who typically live less than two years, have a heart rate of about 500 to 600 beats a minute—up to 10 beats a second. In contrast, the heart of a Galapagos tortoise beats 100 times slower, but they live about 100 times longer. There’s such a remarkable consistency in the number of heartbeats animals get in their lifetimes that a provocative question was asked: “Can human life be extended by cardiac slowing?” In other words, if humans are predetermined to have about three billion heartbeats in a lifetime, then would a reduction in average heart rate extend life? This is not just some academic question. If that’s how it works, then one might estimate that a reduction in heart rate from an average of more than 70 beats per minute down to what many athletes have, 60 beats per minute, could theoretically increase life span by more than a decade.

This reasoning may seem a bit off the wall, but that’s how the scientific method works: We start out with an observation, such as this striking heartbeat data, and then make an educated guess (or hypothesis) that is then put to the test. How might one demonstrate “a life-prolonging effect of cardiac slowing in humans”? Perhaps a first attempt would be to see if people with slower heart rates live longer lives. Unfortunately, researchers couldn’t just give subjects drugs that only lower heart rate. Drugs like beta blockers at the time lowered both heart rate and blood pressure, so they weren’t ideal for testing the question at hand. We can, however, do that first part and look at whether people with slower heart rates live longer.

“From the evidence accumulated so far, we know that a high resting heart rate,” meaning how fast our heart beats when we’re just sitting at rest, “is associated with an increase in…mortality in the general population,” as well as in those with chronic disease. A faster heart rate may lead to a faster death rate. Indeed, faster resting heart rates are associated with shorter life expectancies and are considered a strong independent risk factor for heart disease and heart failure. Researchers found that those with higher heart rates were about twice as likely over the next 15 years to experience heart failure. This was seen in middle-aged people, as well as observed in older people. It was also found in men and women. What’s critical is that this link between how fast our heart goes and how fast our life goes is independent of physical activity.

At first, I thought this was painfully obvious. Of course lower resting heart rates are associated with a longer lifespan. Who has a really slow pulse? Athletes. The more physically fit we are, the lower our resting pulse. But, no: Researchers “found that irrespective of level of physical fitness subjects with higher resting heart rates fare worse than people with lower heart rates,” so it appears a high resting heart rate is not just a marker of risk, but a bona-fide risk factor independent of how fit we are or how much we exercise.

Why? If our heart rate is up 24 hours a day, even when we’re sleeping, all that pulsatile stress may break some of the elastic fibers within the arterial wall, causing our arteries to become stiff. It doesn’t allow enough time for our arteries to relax between beats, so the faster our heart, the stiffer our arteries. There are all sorts of theories about how an increased resting heart rate can decrease our time on Earth. Regardless, this relationship is now well recognized.

It is not just a marker of an underlying pathology nor can it be said to be merely a marker of inflammation. The reason it’s important to distinguish a risk factor from a risk marker is that if you control the risk factor, you control the risk. But, if it were just a risk marker, it wouldn’t matter if we brought down our heart rate. We now have evidence from drug trials—indeed, there are now medications that just affect heart rate—that lowering our heart rate lowers our death rate.

It’s been shown in at least a dozen trials so far. Basically, we don’t want our heart to be beating more than about one beat per second at rest. (Measure your pulse right now!) For the maximum lifespan, the target is about one beat a second to beat the clock. Don’t worry if your heart’s beating too fast: Heart rate is a modifiable risk factor. Yes, there are drugs, but there are also lifestyle regimens, like eating beans, that can bring down our resting pulse. See Slow Your Beating Heart: Beans vs. Exercise.


Other lifespan-expanding strategies are detailed in:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

Fennel Seeds for a Nitrate Boost

Dozens of studies now suggest that the nitrates in vegetables, such as beets and green leafy vegetables, may help not only sick people “as a low-cost prevention and treatment intervention for patients suffering from blood flow disorders” like high blood pressure and peripheral vascular disease, but also healthy people as an effective, natural performance-enhancing aid for athletes. Most of the studies were done with beet juice, though, which is why I was so delighted to see a study on whole beets, which showed the same benefit. But what about studies on whole green leafy vegetables? That’s one of the topics I cover in my video Fennel Seeds to Improve Athletic Performance.

There was a study a while ago suggesting that one of the reasons the Okinawans in Japan looked forward to many more years of good health at the same age at which many Americans and Europeans were dying is all the nitrate in their green leafy vegetables, which tends to bring down blood pressures. The reason I didn’t report on this at the time is because I had never heard of the vegetables in the study. I know what chrysanthemum flowers are, but I didn’t think most of my viewers (or I) would be able to find garland chrisantemum, ta cai, chin gin cai, Osaka shirona, nozavana (or nozawana) pickles, or water dropwort at the local store.

What about less exotic greens, like frozen spinach? Researchers wanted to test the immediate effects on our arteries of a single meal containing a cooked box of frozen spinach, for both arterial stiffness and blood pressure. First, they needed a meal to increase artery stiffness and pressure, so they gave people a chicken and cheese sandwich, which lowered the elasticity of their arteries within hours of eating. But, when they added the spinach, the opposite happened. After chicken and cheese, the force the heart had to pump went up within minutes, but the spinach kept things level. So, a meal with lots of “spinach can lower blood pressure and improve measures of arterial stiffness.”

That’s great for day-to-day cardiovascular health, but what if you want a whole food source that can improve your performance when you’re out hiking, for example? Beets and spinach aren’t the most convenient of foods when you’re out and about. Is there anything we can add easily to our trail mix? Well, if you look at a list of high-nitrate vegetables, you see celery, endive, lettuce, Swiss chard, and the like—not much you can just stick in your pocket. But what about fennel? That’s on the list. Could fennel seeds (which actually aren’t seeds at all, but the whole little fruits of the fennel plant) be the convenient, high-nitrate source we’re looking for?

Fennel seeds are “often used as mouth fresheners after a meal in both the Indian sub-continent and around the world.” You’ll typically see a bowl of fennel seeds, sometimes candy-coated, as you walk out of Indian restaurants. When you chew them, you can get a significant bump in nitric oxide production, which has the predictable vasodilatory effect of opening up blood vessels. This makes them a cheap and easy way to carry a lightweight, nonperishable source of nitrates. Researchers singled out mountaineers, thinking chewing fennel seeds could help maintain oxygen levels at high altitudes and help prevent HAPE—high altitude pulmonary edema—which is one of the leading killers of mountain climbers once you get more than a mile and a half or so over sea level. Don’t confuse HAPE with HAFE, though, which is caused by the expansion of gas at high altitudes—a condition known as high altitude flatus expulsion or “Rocky Mountain barking spiders.”

Fennel seeds may help with that, too, as they’ve been used traditionally as a carminative, meaning a remedy for intestinal gas. “Fennel has also shown antihirsutism activity,” combatting excessive hair growth in women, the so-called bearded woman syndrome. Indeed, applying a little fennel seed cream can significantly reduce it.

If fennel seeds have such a strong hormonal effect, should we be worried about chewing them? There have been cases reported of premature breast development among young girls drinking fennel seed tea a couple times a day for several months. Their estrogen levels were elevated, but, after stopping the tea, their chests and hormone levels went back to normal.

Current guidelines recommend against prolonged use in vulnerable groups—children under 12 and pregnant and breastfeeding women—and perhaps your pet rat, as rodents metabolize a compound in fennel called estragole into a carcinogen, but our cells appear able to detoxify it.


If you’re interested in learning more about using nitrates to improve athletic performance, check out:

Curious about non-nitrate athletic performance tweaks? See:

And what about sports drinks? See: Are Sports Drinks Safe and Effective? and Coconut Water for Athletic Performance vs. Sports Drinks

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:

Chlorella May Help Preserve Immune Function During High Intensity Athletic Training

Sedentary women who start walking briskly on a treadmill for 45 minutes a day for a few months may cut their risk of upper respiratory tract infections in half. How exactly does exercise improve our immune system?

Approximately 95 percent of all infections are initiated at the mucosal surfaces—the moist surfaces, like our eyes, nose, and mouth. These are protected by antibodies like IgA, which provide “an immunological barrier by neutralizing and preventing viral pathogens from penetrating the body through the mucosal surfaces.” The IgA in our saliva, for example, is “the first line of defense against respiratory tract infections such as pneumonia and influenza.” As you can see in my video Preserving Athlete Immunity with Chlorella, moderate aerobic exercise—even just 30 minutes in the gym three times a week—may be all it takes to significantly boost IgA levels and significantly decrease the risk of coming down with flu-like symptoms.

We’ve known for a long time that prolonged heavy exercise, though, may reduce resistance to infectious disease, manifested by an apparent two- to six-fold increase in upper respiratory tract infection symptoms for several weeks following marathon running.

Sport coaches are advised to monitor immune function, since illness could ultimately lead to a decrease in performance. Therefore, it may be necessary to take protective actions to minimize contact with cold viruses, for example. Athletes can’t get away with just washing their hands and wearing a mask, though, because upper respiratory tract infections are often triggered by reactivations of latent viruses already inside our bodies, such as Epstein-Barr virus (EBV). As soon as our immune function dips, the virus becomes reactivated. Researchers found that IgA levels drop the day before EBV comes out of hiding and causes a spike in symptoms. “These results suggest that the appearance of [upper respiratory symptoms] is associated with reactivation of EBV and reduction of [salivary] IgA during training.”

How can we preserve immunity in athletes? In Preserving Immune Function in Athletes with Nutritional Yeast, I discussed the efficacy of using a one-celled fungi—nutritional yeast—to boost the immune systems of athletes. What about a one-celled plant?

Researchers in Japan found that IgA concentrations in breast milk could be increased by giving mothers chlorella, a unicellular, freshwater, green algae sold as powder or compressed into tablets. What about other parts of the body? Thirty tablets of chlorella a day for a month increased IgA secretion in the mouth, too. But does that actually help in a clinically meaningful way? Researchers in Canada tried to see if they could boost the efficacy of flu shots, but a chlorella-derived dietary supplement did not appear to have any effect. They were using some purified extract of chlorella, though, not the real thing.

What about giving it to athletes during training camp? High-intensity physical activity and group living create an environment ripe for infection, and, indeed, the training was so intense IgA levels significantly dropped—but not in those given chlorella each day. So, chlorella intake may attenuate the reduced IgA secretion during athletic training.


There is a caveat to the use of chlorella. See Treating Hepatitis C with Chlorella and Is Chlorella Good for You? to make up your own mind about whether the benefits outweigh the risks.

Interested in some other ways to decrease your risk of upper respiratory tract infections? See:

For the cuddliest way to protect your immune function, see my Are Cats or Dogs More Protective For Children’s Health? video.

What else can exercise do? See:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations: