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Can Your Fitness Tracker Detect When You're Getting Sick?

fitness tracker

Story at-a-glance -

  • Fitness trackers were originally designed to help count your steps and encourage movement throughout the day, to reduce your potential for illness and disease
  • Recent research identifies new ways that fitness trackers may be used in the near future to individualize and personalize health care for those located in distant geographic areas, and those who may be at higher risk of chronic disease
  • Today you can use your fitness tracker to identify when you might be getting a cold in order to begin using natural remedies in the first 24 hours and reduce the duration and severity of your cold

By Dr. Mercola

Fitness trackers have come a long way since the original wristband that tracked your steps. Today’s models can track steps, monitor your sleep, give you GPS location, monitor heart rate and even your VO2 max data for runners. There is a model on the market to meet your specific needs.

With 300 joints in your body, you’re capable of twisting, turning, bending and moving through three planes in space.1 Unfortunately, many spend the day sitting, increasing their risk of heart disease, diabetes and early death, even after a daily workout.2

Exercise plays a critical role in both your immune system and your overall health and wellness.3

Originally designed to help motivate movement throughout the day, or track your workout routine, today’s fitness trackers now have the ability to monitor your health and may even give you fair warning when you’re starting to get sick.

Your Fitness Tracker May Warn You’re Getting Sick

A recent study, published from Stanford University, found over-the-counter fitness trackers may share enough data with the user to warn of an impending illness.4  Recognition and treatment of illness and disease early in development may reduce the overall physical and financial burden to the individual, family and community.

Researchers recorded over 250,000 daily measurements on over 40 people for up to two years, tracking circadian and physiological parameters, making several observations leading to a recommendation for further study.

Changes in baseline heart rate and temperature measurements indicating oncoming illness were detected, sometimes before the individual recognized feeling sick.5

The study was prompted by lead author and geneticist Michael Snyder, Ph.D., after evaluating his own genetic profile and determining he was at high risk for type 2 diabetes.6

Strapping up to eight different monitors on himself and over 40 other people for nearly two years, Snyder measured and analyzed the data. Snyder commented:7

“Too much of the time we spend time measuring people when they’re sick. What we really want to understand is what does it mean to define a healthy state, then quickly identify deviations from that state. I think the wearables are going to be a big part of that.”

Information about weight, heart rate, blood oxygen, skin temperature, calories burned and activity were gathered on the participants.

Snyder was able to detect early signs of getting sick himself several times in those two years by watching data from his fitness trackers. Once, while on a trip to Norway, he found his blood oxygen levels didn’t return to normal and he developed a low-grade fever.

Recalling his exposure to a tick-infested area of Massachusetts a week earlier, he sought medical care for Lyme disease.

Snyder believes that without tracking his symptoms he may have ignored the symptoms and waited to seek care after the illness became more advanced.8 With higher heart rate and temperature came higher levels of C-reactive protein, a measurement of inflammation.

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Variation From Baseline Measurements May Personalize Healthcare

Higher levels of C-reactive protein may indicate the presence of disease. Researchers theorize that if wearable fitness trackers could be used to produce baseline measurements for specific health markers, then healthcare could not only be personalized to the individual, but algorithms could be designed to detect changes and help physicians reach a diagnosis.9

Interest in wearable sensors is growing for both individual and science-based use. The authors determined the data collected from continuous physiological information and activity may be used to analyze and guide health discussions and decisions as wearable technology improves and further study enables scientists to set baseline measurements.10

However, researchers also found several instances when skin temperature and heart rate were elevated but the individual didn’t develop symptoms.11

The researchers wrote that it may be possible wearables may lead to false alarms or overdiagnosis of disease, but the number will depend upon the threshold set by the user and physicians.

Researchers also envision health tracking devices would be a powerful means of tracking health for individuals who are responsible for others, such as caregivers of elderly parents.

Individuals living in remote areas or who have limited access to health care may also benefit from devices that load data to a computer or the cloud for analysis each day.

Physiological Differences Noted Between Insulin Resistance and Insulin Sensitivity

Twenty of the participants in the study using a variety of wearable trackers had clinical measurements indicating they were at risk for type 2 diabetes.

Prior to testing, steady-state plasma glucose (SSPG) measurements were obtained to determine which of the individuals may be insulin resistant, and therefore have a higher risk of suffering from type 2 diabetes.12

During the study, researchers were able to associate a higher heart rate during daytime hours with higher SSPG levels. This difference in heart rate was not associated with activity level or an increased body mass index (BMI).

Increased activity was associated with lower SSPG levels, consistent with studies demonstrating lower levels of blood glucose after activity.

Evidence does suggest that daily heart rate variations are associated with diabetes and changes in glucose levels.13 In this study, both daytime and delta (daytime minus nighttime) heart rates were associated with increases in SSPG, but not nighttime heart rates.14

Higher BMI has a positive correlation with increased heart rate, but the delta heart rate continued to be a strong predictor of SSPG elevation and insulin resistance, independent of any daily activity or individual BMI.

This means when a fitness tracker has been developed to gather and report this type of data, individuals at higher risk for insulin resistance and type 2 diabetes may be able to track their health markers at home, making changes to both dietary intake and food that will affect their SSPG levels.

Do You Get Sleepy While Flying?

Another observation made during this study identified striking differences in baseline measurement when participants were in particular environments.

It is not uncommon to become sleepy while flying, an event you may have chalked up to hectic days, lack of sleep or boredom in the plane. However, the fitness trackers recorded lower blood oxygen levels during high-altitude flights.15

Low oxygen level is a known effect of flying at high-altitude and is associated with feeling fatigued and sleepy. The recorded measurements in this study were able to characterize the changes in greater detail than in previous reports. Snyder commented:16

"Many of us have had the experience of feeling tired on airplane flights. Sometimes people may attribute this to staying up late, a hectic work schedule or the stress of travel. However, it is likely that cabin pressure and reduced oxygen also are contributors."

Researchers also found blood oxygen levels began to rise once more toward the end of longer flights, before the plane began descending from high-altitude.17 Researchers theorized this happens as the body begins to adapt to the altitude.

Economic Burden of the Common Cold Higher Than You Might Think

Although there is a cold and flu “season,” you can suffer from either at any time of the year. Aches, pains, runny noses and missed work are the common signs and symptoms for both you and your employer. The “common cold” may not present a significant risk to your health, if you are relatively healthy and don’t fall into a high-risk category.

However, while it may be relatively innocuous and more irritating than dangerous for many people, these common illnesses also present a significant financial burden to your community. Research published by the University of Michigan found the cost of the common cold in 2003 to the U.S. economy was $40 billion.18

This included costs of over-the-counter cold remedies, doctor’s visits, missed school and missed work time. Dr. A. Mark Fendrick, lead author of the research, was surprised by the number of people who used the medical system to find treatment for a cold, saying:19

"From a bottle of cough syrup to missed time at work and school, the price tag of catching a cold really adds up. Since there is no cure for the common cold, it does not receive a lot of attention when compared to less common conditions. A cold is the most commonly occurring illness in humans, so it was no surprise that there are approximately 500 million colds each year in the U.S. What was a surprise is how often the public uses the health care system to treat a cold."

Health care costs racked up by medical treatments for the common cold included:20

  • 100 million physician visits costing $7.7 billion
  • $2.9 million in over-the-counter drug costs
  • $400 million in prescriptions for symptomatic relief
  • $1.1 billion on 41 million antibiotic prescriptions, even though they have no effect on viral illness

Children missed 189 million school days and parents missed 126 million workdays caring for their children. When added to the days employees missed for their own illness, the cost to employers in lost productivity amounted to $20 billion. The study published in the Journal of the American Medical Association21 found non-influenza viral respiratory tract infections imposed a greater economic burden than many other clinical conditions, such as asthma and heart failure.

Viral Respiratory Tract Infections Take a Higher Toll in Some Populations

The morbidity and mortality associated with viral respiratory illnesses is not trivial. The number of infections each year number 500 million,22 largely related to the high number of common viruses responsible for the condition and the high rate of transmission. In developing and industrialized nations these infections are the leading cause of death in children younger than 5 years.23

Fewer than 10 percent of upper respiratory tract infections (URI) are triggered by bacteria, making treatment with antibiotics useless — yet antibiotics account for a vast majority of the money spent on colds. The duration of a cold is usually between six and 10 days, with the median point at 7.4 days, and 25 percent of the cases lasting two weeks or longer. Although the elderly do not contract a URI more frequently than younger people, complications in this population are more common.24

While the complications may be different, children under the age of 5 also suffer from greater morbidity and mortality from URIs. Regardless of geographic location or economic situation, children suffer on average three to six episodes of respiratory infection in their first five years.25 Antibiotics have no effect on viral illness but may be prescribed for secondary infections, such as ear infections, sinusitis or pneumonia triggered by bacterial infection.

Vitamin D Deficiency May Increase Your Risk of an Infection

Recognizing early symptoms of a cold or the flu may help you to begin natural treatments early, but prevention continues to be the best medicine. One of the more cost effective ways you have of preventing a cold and other significant health conditions is to optimize your vitamin D level.

Vitamin D is a potent antimicrobial agent your body produces with exposure to sunshine, capable of killing bacteria, viruses and fungi. With suboptimal levels, your immune system is impaired and you will be more susceptible to infections and illnesses. Studies demonstrate an inverse relationship between upper and lower respiratory tract infections and your vitamin D level.

While your best source of vitamin D is direct sun exposure, it may not be practical during winter months, or if you live in northern climates. Your next best option is using an oral vitamin D3 supplement. As supplementation cannot compare to the benefits of direct sun exposure, you may want to continue to achieve sun exposure for some of your vitamin D. Ultraviolet radiation from the sun provides a number of other health benefits that are not available in pill form.

Vitamin D3 requirements vary and are dependent on a number of different factors, such as the color of your skin, your geographic location and sun exposure you receive on a regular basis. The most accurate way to determine how much vitamin D3 supplementation you may need is to get your blood tested. Ideally, you’ll want to maintain a level between 40 to 60 nanograms per milliliter (ng/ml) year-round.

Your vitamin D level will accurately predict your potential risk for contracting colds, flu and other respiratory tract infections. For an in-depth explanation of your vitamin D requirements, testing and supplementation, see my previous article, “Do You Need a Vitamin D Supplement to Maintain Ideal Levels?

Curtail Your Cold Early Using Natural Strategies

Using a fitness tracker to measure your resting heart rate may give you advanced notice your body is fighting a viral infection and enable you to take immediate counteractive measures. Over-the-counter drugs and medications to relieve cold symptoms are both financially costly and increase the toxic load on your kidneys and liver.

Using a more natural approach may help alleviate the cold before it costs you missed work time, a secondary infection or a doctor’s office visit.

Vitamin D

Vitamin D deficiency negatively impacts your immune system. Maintain appropriate levels using sun exposure or vitamin D3 supplementation along with vitamin K2.

Vitamin C

A potent antioxidant, look for the natural form such as acerola, which contains associated micronutrients.

Oregano Oil

The higher the carvacrol concentration, the more effective it is. Carvacrol is the most active antimicrobial agent in oregano oil.


A bee resin and one of the most broad-spectrum antimicrobial compounds in the world; propolis is also the richest source of caffeic acid and apigenin, two very important compounds that aid in immune response and even fight cancer.

Herbal Tea

A tea made from a combination of elderflower, yarrow, boneset, linden, peppermint and ginger; drink it hot and often for combating a cold or flu. It causes you to sweat, which is helpful for eradicating a virus from your system.

Olive Leaf extract

Ancient Egyptians and Mediterranean cultures used it for a variety of health-promoting uses and it is widely known as a natural, non-toxic immune system builder.

Hydrogen Peroxide

A simple treatment that is surprisingly effective against upper respiratory infections is hydrogen peroxide which often produces results within 12 to 14 hours.

Administer a few drops of 3 percent hydrogen peroxide (H2O2) into each ear. You will hear some bubbling, which is completely normal, and possibly feel a slight stinging sensation.

Wait until the bubbling and stinging subside (usually five to 10 minutes), then drain onto a tissue and repeat with the other ear.

High Quality Sleep

Your body is better able to fight a virus and repair damage when you have had at least eight hours of quality sleep. When sick, you may find you are more fatigued and require more rest than normal.

If you have difficulty falling asleep or staying asleep, follow the suggestions made in my previous article, “Want a Good Night's Sleep? Then Never Do These Things Before Bed

Regular Exercise

Regular exercise is a crucial strategy for increasing your resistance to illness. Regular, moderate exercise can reduce your risk for respiratory illness by boosting your immune system.

In fact, one study found that people who exercised regularly (five or more days a week) cut their risk of having a cold by nearly 50 percent.26

And, in the event they did catch a cold, their symptoms were much less severe than among those who did not exercise.

Reduce Stress

Stress can predispose you to an infection, while making cold symptoms worse. Finding ways to manage daily stress will contribute to a strong and resilient immune system.

My favorite stress buster is the Emotional Freedom Techniques (EFT), a system that helps balance your body's subtle energies and repair emotional "short-circuits."

Zinc Supplement

When taken within the first 24 hours of your first cold symptoms, zinc may reduce the duration of your cold and reduce the severity of your symptoms.27

Reduce or Eliminate Sugar

Sugar in any form (glucose, fructose, grains and others) unbalances gut flora and acts as "fertilizer" for pathogenic bacteria, yeast and fungi, impairing your immune system.

Remember, 80 percent of your immune system lies in your gastrointestinal tract, which is why limiting your sugar intake is vital for optimizing your immune system.

Sensible Hand Washing

Thorough hand washing is an important preventative measure, as you are at far greater risk of passing on an infection by shaking someone's hand than by sharing a kiss.

If you wash them too frequently, though, you can actually extract many of your skin's protective oils, causing your skin to crack and bleed providing potentially dangerous pathogens an entry into your body.

Avoid Antibiotics

Antibiotics, including penicillin, do not have any effect on viruses, but unfortunately have been vastly over-prescribed for this very (useless) purpose.

Coupled with excessive use of antibiotics in livestock, there has been a steep rise in antibiotic-resistant diseases.

Antibiotic-resistant infections now claim more lives each year than the "modern plague" of AIDS and cost the American health care system approximately $20 billion a year.


This herb has been used for centuries as a potent antibacterial, antiviral and antifungal. Much of garlic's therapeutic effect comes from sulfur-containing compounds, such as allicin, which gives it the characteristic smell.

Research28 reveals that as allicin digests in your body, it produces sulfenic acid, a compound that reacts with dangerous free radicals faster than any other known compound.


A combination of shitake, reishi, cordyceps, turkey tail and himematsutake mushrooms have antibacterial, antiviral and antifungal properties.

It is best to utilize a blend of mushroom species, as it is easier for pathogens in your body to adapt and become resistant to one mushroom than to several.

Also, each mushroom species has a unique arsenal of anti-infective and immunomodulating agents.

When Should You Call Your Doctor?

Sinus, ear and lung infections (bronchitis and pneumonia) may be bacterial and, if so, may respond to antibiotics. If you develop any of the following symptoms, these are signs you may be suffering from a bacterial infection rather than a cold, and you should call your physician's office:

  • Fever over 102 degrees F (38.9 degrees C)
  • Ear pain
  • Pain around your eyes
  • Shortness of breath or a persistent uncontrollable cough
  • Persistently coughing up green or yellow sputum

Generally speaking, however, if you have a cold, medical care is not necessary. Rest and attention to the lifestyle factors noted above will help you to recover quickly and, if you stick to them, will significantly reduce your chances of catching another one anytime soon.