Category: Public Health

Categories
Public Health

Is Fast Food Changing Our Genes To Make Our Children Obese?

The United States is leading the international pandemic of obesity. Once a child becomes obese, it is incredibly difficult to sustainably return to a normal weight as an adult. Is obesity due to genetics or overeating? There is increasing evidence that obesity changes our genes making both us and our children more susceptible to obesity. The explanation is in the science of epigenetics.

What is epigenetics?

The concept that our environment can change our genes is “epigenetics”. Each person’s genes are composed of a fixed sequence of the four nucleotide bases: adenine, cytosine, guanine, and thymine in our DNA. These genes are “read” in the nucleus of cells and the reading of the genes determines how and when to make various proteins. These proteins determine everything from our bodily appearance to how our organs function. But environmental factors can affect the structure of genes and how these genes turn on and off. There are three main mechanisms by which our environment can change our genes:

  • DNA methylation. A methyl group is a chemical structure that can be attached to our DNA. Adding a methyl group to a cytosine nucleotide is “methylation” which can turn on a gene. Removing a methyl group is “demethylation” which can turn off a gene. Our genes can become methylated or demethylated by various environmental factors such as chemicals, drugs, diet, and aging. Importantly, when a parent’s genes become methylated, their baby can inherit those methylated genes. In other words, our environment can change our offsprings’ DNA.
Image: NIH Common File
  • Histone modification. Histones are proteins that wrap around DNA. When histones are packed tightly together on DNA, they can cover up genes, making them unreadable. By adding or removing chemical groups from histones, genes can be turned on or turned off.

  • Non-coding RNA. The genes located in DNA tell our cells what kinds of proteins to make by creating mRNA (messenger RNA) molecules that function as the signal or template for ribosomes located in the cytoplasm of the cells to make those proteins. Some non-coding RNAs can inactivate mRNA thus short-circuiting the messages generated by our genes. In other words, the DNA sends out a signal to make a protein but the ribosomes never receive that signal.

Many different environmental factors can cause epigenetic effects resulting in disease. For example, smoking causes demethylation of the AHRR gene. Tuberculosis can cause increased histone aggregation that can turn off the IL-12B gene. DNA methylation of the BRCA1 gene can increase the risk of breast cancer.

One of the most famous examples of how epigenetics affects both people and their offspring was the Dutch famine of the winter of 1944-45.   At the end of World War II, the Nazis blocked food to the Netherlands beginning in November 1944 until Allied liberation in May 1945. This resulted in a precipitous 6-month serious food shortage in the Netherlands and as a result, the typical caloric intake of Dutch citizens fell to 400-500 calories per day; 22,000 people died of hunger. The children of women who were pregnant during this famine had life-long health problems including a high rate of schizophrenia, heart disease, and type II diabetes compared to their siblings who were not in utero during the famine. Research 60 years after the famine found that these children (now older adults) had increased methylation of some genes and decreased methylation of other genes, indicating that when mothers were starved during pregnancy, their fetuses’ genes underwent methylation changes and these changes lasted the entire lifetime of the sons and daughters.

Epigenetics and obesity

Since 1975, the number of obese humans worldwide has tripled. Genetics alone does not explain why some people become obese and others do not. Studies have shown that genes linked to obesity such as the leptin, adiponectin, PGC1A, and insulin genes are regulated by methylation. There is growing evidence that obesity can cause DNA methylation. For example, researchers at the Medical College of Georgia reported in 2019 that in 1,485 subjects, obesity caused changes in DNA methylation that persisted over a 6.2 year period. It follows, therefore, that if a pregnant woman is obese, her child’s genes that regulate obesity can be altered and that alteration can persist for the child’s entire life.

For years, physicians’ recommendations for weight loss was straightforward: just take in fewer calories than you burn up. This led to a perception that obesity was simply due to the chosen behavior of the obese person – if they could just eat less and exercise more, they wouldn’t weigh so much. But many of my patients have told me that no matter how much they diet, they cannot lose weight. And those who do lose weight soon gain it back after a year or two. Epigenetics suggest that obesity is not simply due to a person making a conscious choice to eat too many calories and not exercise enough. Instead, it is due to changes in their genetic make-up.

The change to the majority of Americans now being overweight has resulted in a cultural normalization of obesity. But obesity comes with many health consequences that can reduce quality of life and reduce life expectancy. Obesity-related arthritis contributes to disability. Obesity-related diabetes contributes to heart disease. During the pandemic, COVID preferentially killed obese people. Just because everyone else is overweight doesn’t make being overweight right from a public health standpoint.

Epigenetic implications for reducing obesity

 

Another implication of the epigenetic basis of obesity is that we cannot just treat obese adults and we cannot just treat obese children who will later become obese adults. We need to think of obesity as a consequence of maternal conditions. If a woman is obese during pregnancy, then that woman’s child may be destined to become obese, regardless of the child’s diet after birth. In other words, the best predictor of whether a person will be obese as an adult may be whether or not that person’s mother was obese when she was pregnant.

Of even greater concern is that there is animal evidence that methylation of sperm and ova DNA can be passed on for multiple generations. If this is true with obesity, then it suggests that if your grandfather was obese because his DNA was methylated, then you are also more likely to be obese because you now carry that methylated DNA. If this is true, then the U.S. may be entering a vicious cycle of each generation getting more and more obese.

If our DNA can be methylated by environmental and nutritional factors, then it is likely that our DNA can also be demethylated with targeted therapeutic medications. By changing the direction of research into obesity treatments to focus on how we can pharmacologically manipulate DNA methylation of obesity-related genes, we may be able to develop more effective and more lasting treatments for obesity. The emerging field of genetic engineering could perhaps better be termed epigenetic engineering when applied to obesity treatment.

We should place a high priority for ensuring optimal maternal nutrition. The Dutch famine of 1944-45 shows us that maternal starvation is bad and recent research implies that maternal obesity is also bad. Both better nutritional education of women before pregnancy and better access to high quality nutrition before and during pregnancy are needed.

Because methylation of obesity genes early in childhood may persist throughout a person’s entire life, avoidance of excessive caloric intake by children is also critically important. The methylation research implies that once a person becomes obese, they are likely to remain obese. Prevention of obesity in childhood is likely to be more effective than treatment of obesity in adulthood.

What is the solution?

The new theoretic paradigm of obesity is that it is caused by (1) the amount of calories consumed, (2) the amount of calories burned, and (3) the modification of genes that regulate metabolism. Until we have effective ways of pharmacologically modifying methylation of obesity genes, we are left with the following tactics to reduce obesity in the U.S.:

  1. Increase caloric expenditure. Our country has an epidemic of exercise deficiency. There are many social and technologic reasons for this: a shift from a physical labor workforce to a skilled labor workforce, increased reliance on automobiles and mass transportation, and increased sedentary television and computer screen time. Judicious exercise during childhood and even during pregnancy is warranted.
  2. Decrease caloric consumption. During the past 75 years, the U.S. diet has shifted from home-prepared foods to highly processed foods. We have become increasingly reliant on fast food restaurants for a regular part of our diet. These are foods that are not only calorically dense, but they are also specifically taste engineered to make you want to eat more of them. Moreover, serving sizes have increased substantially in the past few decades. A major obstacle to weaning Americans off of fast food and highly processed food is that they are tasty, cheap, and convenient.
  3. Treat obesity earlier in life. Given that DNA methylation can last a lifetime, we need to aggressively treat obesity early – in childhood and perhaps even in parents prior to conception. In this sense, adult obesity is really a childhood disease and needs to be treated as such. This means more aggressive pharmacologic and bariatric surgery treatments of obese children.

What can hospitals do?

Our nation’s hospitals cannot cure the obesity epidemic by themselves but they can set the right examples. Our hospital cafeterias can serve food with correct serving sizes. We can eliminate high-calorie soft drinks containing sugar in our hospital vending machines. We can avoid leasing space to fast food restaurants with calorically dense menu items on our hospital campuses. We can provide and promote comprehensive weight management clinics.

As physicians, we need to be more proactive discussing obesity with our patients in a non-judgmental way. We need to identify children whose growth curves show weight percentiles that significantly exceed height percentiles. We can become more comfortable prescribing medications to lose weight, not only for our adult patients but also our pediatric patients. And we can become community educators and advocates for better nutrition and obesity prevention.

It turns out that obesity is a lot more complicated than we thought it was just a few years ago. The prevention and treatment of obesity is also a lot more complicated. But just because a problem is complicated does not mean we should just give up and accept it as the new normal. We have to take a more multi-faceted approach to obesity treatment and start that treatment earlier in life. We need to take back control of our own genes.

March 1, 2023

Categories
Epidemiology Public Health

The Overlooked U.S. Health Disparity That We Aren’t Talking About

Last month, I was giving the annual lung cancer lecture to our first year medical students. As part of that lecture, I discussed the demographics of cigarette smoking. American Indians have by far the highest rate of smoking and in 25 years, that will translate into the highest rate of lung cancer in the United States. As the medical director of an urban community hospital, I saw the results of racial healthcare disparities first hand. Our hospital’s demographic has a high percentage of Black and immigrant patients. These populations have a low rate of cancer screening, high infant mortality rate, and high rate of insufficiently treated chronic diseases. But the health disparities between Black and White Americans often get more public attention than the disparities between Indian and other Americans. We need to broaden the discussion on health disparities to include what is in many ways our greatest national health disparity.

Summary Points:

  • The greatest health disparities in the U.S. currently exist among American Indians
  • The prevalence of cigarette smoking is twice as high among American Indians compared to other racial/ethnic groups
  • Higher rates of cigarette smoking today will amplify health disparities in the future
  • We have the opportunity to reduce health disparities in the future by reducing cigarette smoking among American Indians today

 

When we talk about health disparities, we usually are talking about differences between the big 4 racial/ethnic groups in the United States: White, Black, Hispanic, and Asian. The group that gets less public attention is American Indian. For the purposes of this post, I will use “Indian” as a term of simplicity for Native American, Alaskan Native, and American Indian peoples. This demographic group is often lost in our discussions of American health disparities. A minority among minorities, American Indians comprise 1.3% of the U.S. population versus White (59.3%), Hispanic (18.9%), Black (13.6%), and Asian (6.1%) Americans (Native Hawaiian/Pacific Islanders comprise 0.3%). What disparities exist between American Indian and these other racial/ethnic groups?

Life expectancy

The United States has a relatively poor life expectancy compared to other developed countries. The OECD reports that in 2021 the average American life expectancy from birth was 77.0 years – slightly better than Mexico but slightly worse than China.

Within the U.S., there is considerable variation in life expectancy by race/ethnicity. The National Institutes of Health reports that the U.S. Asian population has the longest life expectancy at 85.7 years, followed by the Latino population (82.2 years), White population (78.9 years), and Black population (75.3 years). The lowest life expectancy is in the American Indian population at 73.1 years.

Chronic health conditions

The National Health Interview Survey has been conducted by the Centers for Disease Control annually since 1957. The most recent data is through 2021 and consists of interviews with 30,000 adults and 9,000 children. The Survey is one of the most comprehensive assessments of the current health status of Americans. Once again, we find that health and healthcare disparities disproportionately affect American Indians in the United States.

American Indians are much more likely to report having chronic medical conditions and chronic psychologic conditions than any other racial/ethnic group in the U.S. In addition, American Indians are more likely to report that they have overall poor health and to have some form of disability. They are more likely to have had at least one emergency department visit in the past year and are a close second to Hispanics in high percentages lacking health insurance. Suicide rates are also higher among American Indians than any other racial/ethnic group in the U.S.

COVID has uncovered preventative care disparities affecting American Indians. The vaccination rate (receipt of at least 1 dose of a COVID vaccine) is lowest among American Indians (77%) compared to White (87%), Hispanic (88%), Black (89%), and Asian (98%) Americans. Not surprisingly, the COVID death rate among American Indians (yellow curve in the graph below) is also higher than other American racial/ethnic groups:

Not only were American Indians more likely to die of COVID during the pandemic, but they were also more likely to be diagnosed with COVID and more likely to be hospitalized with COVID, according to a report from the CDC:

Smoking as a forecast of future health problems

As a pulmonologist, one of the public health metrics that concerns me the most is the prevalence of cigarette smoking. The health effects of smoking can be divided into those that affect people now and those that affect people 25 years from now. If a person starts smoking today, the main short-term health effects that they will experience are cough, bronchitis, and wheezing. For most smokers, these are minor problems and are consequently ignored so they continue to smoke. The greater health problems are those that occur decades later, namely lung cancer, COPD, and heart disease. The best reflection of this can be seen in the graph below that compares per-capita cigarette consumption to the death rate from lung cancer in the United States. Annual cigarette consumption peaked in 1965 at about 4,300 cigarettes per person in the U.S. The lung cancer death rate peaked 25 years later in 1990.

Smoking can kill people in a lot of ways other than lung cancer: heart disease, COPD, stroke, esophageal cancer, kidney cancer, and other cancers. Overall, about 1 out of every 5 deaths in the U.S. is related to smoking. Because of this, a woman who smokes a pack of cigarettes a day can expect to live 11 years less than a woman who does not smoke. Men who smoke a pack a day will live 12 years less than men who do not smoke. Overall, this works out to about 14 minutes of life lost for every cigarette smoked.

What this means is that people who smoke today will be dying from lung cancer, COPD, and heart disease 25 years from now. So, we can use today’s smoking demographics to predict the future’s health disparities. Today’s smokers are more likely to have a lower income and lower education level than non-smokers. Americans who have the lowest income are nearly 4-times more likely to smoke than those who make over $100,000 per year. Those whose education is limited to a GED are 10-times more likely to smoke than those who have a graduate degree:

The good news is that we have made great headway in reducing the percentage of cigarette smokers in the United States. Because 90% of smokers start smoking before age 18, much of the reduction in smoking prevalence can be attributed to preventing adolescents from starting to smoke in the first place. Currently, 14.1% of U.S. men smoke and 11.0% of U.S women smoke. This is a vast improvement from the 1960’s when approximately half of all American adults smoked.

However, smoking cessation and prevention efforts have not been uniform across all racial and ethnic groups. Here is where one of the most glaring health disparities exist with American Indians. The CDC reports that they are twice as likely to smoke as Black Americans and White Americans. They are three and a half times more like to smoke the Hispanic Americans and Asian Americans:

The implication of this is that 25 years from now, there will be even greater health disparities among American Indians, with much higher rates of lung cancer, COPD, stroke, heart disease, and other cancers compared to all other U.S. racial/ethnic groups. Furthermore, the life expectancy for Indian Americans (which is already considerably shorter than for White, Black, Hispanic, and Asian Americans) will be even shorter.

Why have we failed American Indian populations?

For many years, we’ve known that American Indian populations have a higher incidence of cirrhosis than other racial/ethnic groups and this has been attributed to a higher rate of alcohol abuse among American Indians. We now must face that the rate of other chronic health problems will also be higher in American Indians in the near future. How did these disparities come to exist?

As the first European immigrants arrived at our Eastern shores, they brought with them European diseases, such as smallpox and measles. An estimated 90% of Native Americans subsequently died of these diseases. Those who survived were pushed westward. As a consequence, most tribal reservations are located west of the Mississippi River and in the northern part of Alaska. These are largely remote, rural areas that distant from large cities. This also means being distant from higher paying urban jobs, distant from tertiary care hospitals, and distant from institutions of higher learning. Data from the 2021 U.S. census shows that the median annual household income for all Americans was $69,717. American Indians had a median annual household income of only $53,148. In contrast, Asian Americans had the highest median income at $100, 572. The U.S. Department of Eduction reports that American Indians also have the lowest college enrollment rate of all U.S. racial/ethnic groups at 19%. Asians had the highest college enrollment rate at 58%, followed by White (42%), Hispanic (39%), and Black (36%) Americans.

Health disparities in the U.S. are usually a consequence of discrimination. Discrimination against Blacks has its roots in slavery. Discrimination against Indians has its roots in geographic displacement. Discrimination against Asians backfired as I outlined in a previous post – the restriction of immigration to only Asian merchants and teachers in the 19th and early 20th century in the U.S. had the unintended consequence of an Asian American demographic that had a higher education level and higher income than other Americans (the intention of the Chinese Exclusion Act of 1882 was to prevent unskilled Chinese workers from competing with American-born U.S. citizens for labor jobs). The Indian Health Service is an attempt to overcome healthcare disparities but this has by necessity resulted in a “separate but equal” healthcare delivery system. Separate but equal did not work in the education of Black Americans in the 1950’s and it wasn’t working in 1913 when my grandmother became the first non-white child to attend Atlanta public schools.

So, what can we do?

Last month, at the end of my lecture to the medical students on lung cancer, I challenged them to address disparities in lung cancer. Specifically, I challenged them to address the high prevalence of cigarette smoking in the American Indian population. If we can reduce smoking now, we can reduce health disparities in the future.

On December 20, 2019, the United States Congress passed legislation amending the Family Smoking Prevention and Tobacco Control Act of 2009. This amendment raised the age that anyone can buy cigarettes to 21 years old in all U.S. states and on all tribal lands. This will help reduce the number of American Indians who start to smoke as teenagers. But cigarette smoking is often a symptom of employment and educational disparities so another way of reducing health disparities in the future is by improving employment and education today.

Historically, tribal lands were geographically distant from high-paying urban jobs. A silver lining of the COVID pandemic has been the normalization of working remotely and so we need to promote remote-working jobs to those living on tribal lands. An implication of this is that we need to prioritize high-speed internet access to these areas. Because many of the jobs that are amenable to remote work require education beyond a high school level, we need to eliminate barriers to higher education. Educational debt forgiveness is fiercely debated in political circles but if there is any one group that could really benefit by reducing the cost to attend 2-year community colleges and 4-year universities, it is those living on tribal lands. An 18-year old growing up in a U.S. city can live with his/her parents and commute across town to attend a public university at minimal cost but a 100-mile commute from a family home on tribal lands to an urban university is unrealistic. In addition, sustainable change has to come from within and effective reduction in smoking prevalence also requires engagement and advocation by tribal leaders.

All too often, public health is reactive, we wait until there is a health problem and then we react to that problem. We have a rare opportunity to make public health proactive… by reducing American Indian smoking rates today we can reduce health disparities in the future. When the ocean waters recede from the beach just before a tsunami, there are two kinds of people: those who walk around picking up newly uncovered seashells and those who run to high ground. There is a public health tsunami coming for American Indians, let’s not act like people on the beach picking up seashells.

February 25, 2023

Categories
Outpatient Practice Public Health

A Pulmonologist’s Opinion About Gas Ranges

Recently, there have been health concerns raised about gas ranges. This has led some cities to prohibit their installation in new homes, including Los Angeles, New York and San Francisco. I am interested in these health concerns for two reasons. First, as a pulmonologist, I want to be sure that the people in our community are safe from health risks. Second, I am getting ready to buy a new range for myself. So, what are the health risks of gas ranges and should you be worried about them?

The basics of cooking ranges

First, some definitions. Many people use the terms “range”, “stove”, and “oven” interchangeably. Technically, an oven is the enclosed box that you bake in. A stove is the surface heating area that you heat pots on. A range is when a stove and an oven are combined into a single appliance. Sometimes the term “cooktop” is used when the stove is separate from the oven. For the purpose of this post, I will use the term “range” for the appliance that combines an oven with a stove.

In the United States, there are essentially four types of ranges: electric, gas, duel fuel, and induction. Electric ranges work by passing an electric current through a metal coil that heats up as it creates resistance to that current. These electric coils (“burners”) can be exposed on the top of the stove or covered underneath a flat sheet of glass. Electric ranges also use electric heating elements inside the ovens. Gas ranges work by igniting a jet of natural gas. The resultant flame is used to heat pots and pans on the stove. Gas ranges also use gas flames inside the oven for baking purposes. Duel fuel ranges use gas flames for the stove to heat pots and pans but use electric heating elements in the oven for baking purposes. Induction ranges work by using electricity to create a magnetic field on the stove that then heats up any pot or pan placed on the stove that contains iron or steel. Induction ranges generally use a standard electric heating element in the oven for baking purposes.

For many years, electric ranges dominated the U.S. appliance market. However, gas ranges are preferred by many cooks because of the better control over the amount of heat generated, for example, allowing the cooking surface to instantly increase or decrease in temperature. Duel fuel ranges combine the advantages of the gas stove for surface cooking with the more even heating of an electric oven for baking. Induction ranges offer the advantages of using electricity, thus avoiding an open flame, while also offering the advantage of being able to instantly control the temperature applied to the pot or pan. Consumer Reports found that induction ranges out-performed electric and gas ranges in cooking tests.

As a general rule, when things burn, the resultant products of combustion are bad for our lungs. Whether that be burning cigarettes, military burn pits, house fires, or indoor wood/charcoal cooking. Natural gas is often called “clean-burning” because it does not produce visible smoke, unlike a wood fire or charcoal fire. However, just because we cannot see or smell the products of combustion from natural gas does not mean that those products of combustion cannot hurt us.

What is natural gas?

Natural gas is a type of fossil fuel produced by the decay of long-dead plants. It accumulates in large gas pockets deep underground and then can be removed by drilling gas wells into those pockets. The main component of natural gas is methane which in pure form, creates water and carbon dioxide when it burns. However, natural gas is not pure methane and instead contains small amounts of other gases and chemicals. The typical components of natural gas include:

  • Methane
  • Ethane
  • Butane
  • Propane
  • Hydrogen sulfide
  • Carbon dioxide
  • Oxygen
  • Nitrogen
  • Trace elements: helium, hydrogen, Xenon, and Neon

When natural gas is burned, these components produce new gases, including carbon dioxide, nitrous oxide, methane, carbon monoxide, formaldehyde, nitrogen dioxide, and particulate matter. Many of these gases can cause lung disease.

Carbon dioxide

It is estimated that a typical U.S. family cooking with a gas stove produces slightly less than a pound of carbon dioxide each day from the combustion of natural gas. This is about the same amount of carbon dioxide produced by coal or gas power plants to generate the amount of electricity required to cook using an electric range or an induction range. So, we don’t really produce more carbon dioxide by using a gas range but we do concentrate that carbon dioxide inside our homes. To illustrate this, I measured the concentration of carbon dioxide in my kitchen before and during the use of my gas range. At baseline, the carbon dioxide level in my kitchen was 646 parts per million.

After turning on 4 burners on the gas stove for five minutes, the carbon dioxide level increased to 1609 parts per million.

I then turned on the overhead exhaust fan for five minutes and the carbon dioxide level fell to 821 parts per million.

Carbon dioxide is a by-product of living animals. Our bodies normally produce carbon dioxide that we exhale with every breath. If the levels of carbon dioxide in our bloodstream builds up, it can be toxic to the human body. Similarly, if the level of carbon dioxide in the air increases and then we breath that air, we can suffer ill health. NIOSH considers breathing air containing over 5,000 parts per million over the course of a 10-hour day to be toxic and over 30,000 parts per million for a 15-minute period to be toxic. It would require cooking for a long period of time in a poorly ventilated kitchen to reach these levels using a gas range.

Carbon monoxide

Like carbon dioxide, carbon monoxide is produced when things burn. However, carbon monoxide is much more toxic to humans than carbon dioxide. It is an invisible, odorless gas. When inhaled, it tightly binds to the hemoglobin molecules in our red blood cells thus preventing oxygen from binding to those hemoglobin molecules. Without oxygen, the cells in our bodies suffocate. We all inhale small amounts of carbon monoxide from our environments so there are always low levels of carbon monoxide in our blood stream. Cigarette smokers have higher levels of blood carbon monoxide than non-smokers. Very high levels of carbon monoxide are fatal. This is how most people die in house fires or die by suicide from running their car in a closed garage. Lower levels of carbon monoxide can cause headaches, ringing in the ears, and confusion. Every house with a gas range should have a carbon monoxide detector installed.

Nitrogen dioxide

The air we breathe is mostly made up of nitrogen – it constitutes about 80% of the gases in air. Nitrogen gas is considered inert – it does not cause any direct harm to the body except when nitrogen dissolved in the bloodstream “boils” and creates nitrogen gas bubbles in the tissues when SCUBA divers ascend too rapidly and get the bends. But when gases are burned, pure nitrogen can be converted into nitrogen oxides. One of these is nitrogen dioxide, which can be very toxic and poses the greatest health risks to our lungs from gas ranges.

Nitrogen dioxide can also build up from decay of certain types of plant materials. In pulmonary medicine, an important result of nitrogen dioxide toxicity is in “silo-filler’s disease”. This occurs when nitrogen dioxide builds up inside of poorly ventilated silos storing silage. If a farm worker enters that silo and inhales high concentrations of nitrogen dioxide, the lungs can become injured. In the short-term this can result in ARDS (acute respiratory distress syndrome), where the lungs are damaged and fill up with inflammation and fluid, thus blocking air from getting into the lung’s alveoli (air sacks) where oxygen normally transfers into the bloodstream. In the long-term, small airways in lungs exposed to high concentrations of nitrogen dioxide can fill up with scar tissue, resulting in permanent blockage of air getting to the alveoli. This is called “bronchiolitis obliterans“. A famous event resulting in pulmonary nitrogen dioxide toxicity occurred in Cleveland in 1929. At that time, a fire arose in the Cleveland Clinic in a room where large amount of old x-rays films that were made of nitrocellulose were stored. The resultant nitrogen dioxide gas produced by the burning x-ray films resulted in 129 deaths, including one of the Clinic’s founders, Dr. John Philips.

In lower concentrations, nitrogen dioxide can irritate small airways causing asthma. This can be particularly insidious because nitrogen dioxide does not cause allergic reactions, unlike many allergic triggers of asthma such as cats dander or pollens. For this reason, most people with asthma worsened by nitrogen dioxide do not realize that it is their gas cooking range that is making them sick. A 2013 meta-analysis of 41 studies found that indoor gas stove use increases the incidence of asthma in children. A recent study estimated that 12.7% of childhood asthma is due to nitrogen dioxide and other by gases produced by gas ranges. Adults with asthma may be less affected by gas ranges than children based on a 2003 study of 445 subjects.

Formaldehyde

Every middle school student who accidentally opened the jar of preserved frogs in biology class knows how noxious inhaling formaldehyde is. It is another toxic by-product of natural gas combustion. Formaldehyde is also produced by burning cigarettes and can be released by wood adhesives in newly constructed houses. It is often one of the suspected culprits in patients with “sick building syndrome”. When inhaled, formaldehyde can cause eye irritation, nose irritation, throat irritation, and cough. Meta-analyses in 2010 and 2018 showed that environmental formaldehyde in homes is associated with asthma in children. Formaldehyde is also considered a carcinogen. A 2018 study found that using even 1 gas burner turned on low increased air formaldehyde levels above safe thresholds.

Particulate matter

Natural gas is often called “clean-burning” but that is not exactly true. Tiny particles (< 10 μm) of soot are produced when gas is burned, even if those particles cannot be easily seen with the naked eye. Breathing particulate matter can cause cough and worsened asthma. It is one of the main causes of respiratory symptoms when outdoor air quality is poor, due to air pollution. Some particulate matter is produced from food as it is cooked, however, gas ranges produce particulate matter even if there is no food being cooked.

Fire

Accidental house fires are another harmful consequence of gas ranges. It surprises me that there are not more of these. Spilled cooking oil or a dishtowel accidentally dropped onto an open flame can quickly develop into a kitchen fire. The National Fire Protection Association estimates that there are 179,500 fires due to cooking in the United States, accounting for 49% of all house fires. Ranges account for 61% of cooking-related house fires and 87% of cooking-related fire deaths. Interestingly, electric ranges are more likely to cause house fires than gas ranges. There is very little research in fire risk from induction ranges compared to electric or gas ranges but given that induction cooktops produce no heat if a pan is removed, it would seem that there would be less risk of fire if the induction range was accidentally left on after cooking. Grease fires may also be less frequent given the absence of a flame (gas ranges) or hot electric coil (electric ranges).

Fire is a particular risk for people with lung disease who require supplemental oxygen. As pulmonologists, we caution our patients to never use their oxygen in the kitchen when using a gas range. However, there is no risk of fire when using supplemental oxygen around an induction range.

Thermal injuries

Both electric ranges and gas ranges produce high heat. Small children who don’t know any better can get severe hand and finger burns from reaching up to an electric or gas burner. Even experienced cooks often burn their hands from accidentally touching a hot burner. Induction ranges substantially reduce the risk of burns. Only the bottom of a pot or pan gets hot; the surface of the range does not heat up. So unless a toddler touches the bottom of a pan, there is no danger of thermal injury with an induction range.

So, what are the downsides of induction ranges?

The main problem with induction ranges is that they are expensive. The cheapest electric or gas range is several hundred dollars less than the cheapest induction range. However, a provision of the Inflation Reduction Act to discourage gas ranges provides a tax credit of up to $840 to replace gas ranges with electric or induction ranges. This only applies to Americans with lower incomes. Those with middle incomes can qualify for a reduced amount of the tax credit while those with higher incomes are not eligible for any tax credit. Although induction ranges can be expensive, it is anticipated that prices will come down in the future as the market for induction ranges increases. Consumer Reports recently rated ranges and found that the top rated induction ranges cost about the same as the top rated gas or electric ranges. The least expensive of the top four rated induction ranges costs $1,200.

A second problem with induction ranges is that the bottom of pots and pans must contain iron or steel. Copper, purely ceramic, aluminum, and glass cookware will not work with an induction range. If you have to buy all new steel/iron plated cookware, it can considerably add to the cost of a new induction range. An easy way to determine if a given pot or pan will work is to see if a refrigerator magnet sticks to the bottom.

A final problem with induction ranges is that you cannot generate extremely high heat. This is especially a problem for restaurants using very high heat output gas flames for wok cooking. These high heat levels are generally not achievable with an induction cooktop. However, there are now “induction woks” being marketed that surround the wok bowl with an induction element, thus permitting cooking temperatures similar as can be produced using high-output gas burners.

“I have a gas stove. What can I do to reduce the risk of harm?”

If you have a gas range, the most important step you can take is to ventilate the kitchen. This can mean opening kitchen windows when the weather outside permits. If you have a fan that you can put in that window, even better. If you have an exhaust hood above your range, then turn it on when cooking. An exhaust hood that blows air outside is optimal. If a child in the house has asthma, then try to keep that child out of the kitchen when cooking. If you are unsure of how effective your kitchen ventilation is, you can buy a home CO2 monitor for about $80. If the CO2 level increases significantly when you are cooking, then your ventilation is likely inadequate.

A second way of minimizing harm from a gas range is to use other kitchen appliances for cooking instead of the range whenever possible. For example, an electric kettle can be used to heat water rather than boiling water in a pot on the gas stove. An air fryer can replace the use of a gas oven for many foods. And a slow cooker can be used instead of the range range for chili, stews, and soups.

“Should I switch out my gas range for an induction range?”

The short answer is that most people do not need to ditch their gas ranges if they already have one. However, if your kitchen is poorly ventilated or lacks an exhaust fan over the range, then replacing your gas range with an electric or an induction range may make sense. Also, if there are children in the house, the health risks of a gas range increase significantly, especially if one of the children has asthma or another lung disease. If someone in the home uses supplemental oxygen, then getting rid of the gas range can reduce the risk of a house fire, particularly if the oxygen-user does the cooking.

For climate-conscious people, changing gas to electric or induction ranges can appear on the surface to be the more responsible choice. However, if your local electricity producer uses fossil fuel power plants, then there really is not much advantage in electric or induction ranges since the overall CO2 production is similar. Here in Ohio, we can choose our electricity provider and for several years, I have purchased electricity from providers that only produce electricity from wind and solar sources. So for me, an induction range will result in less overall CO2 production than a gas range. People in other parts of the country where the electrical grid sources electricity from hydroelectric power-plants can also reduce their CO2 footprint by switching from gas to electric or induction ranges.

For me, I don’t have any lung disease and no longer have children in the house. I like breathing clean air in the home and I like to minimize my personal CO2 footprint. However, I also like the ability to easily regulate the cooking temperature that in the past was only achievable with a gas stove but is now achievable with induction stoves. We are building a new house and had to decide what kind of appliances to install. So, I just ordered my new induction range.

January 15, 2023