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As wildfires become more frequent due to climate change and drier conditions, more of us and more of our communities are at risk for harm. Here is information to help you prepare and protect yourself and your family.

How does wildfire smoke affect air quality?

Wildfire smoke contributes greatly to poor air quality. Just like fossil fuel pollution from burning coal, oil, and gas, wildfires create hazardous gases and tiny particles of varying sizes (known as particulate matter, or PM10, PM2.5, PM0.1) that are harmful to breathe. Wildfire smoke also contains other toxins that come from burning buildings and chemical storage.

The smoke can travel to distant regions, carried by weather patterns and jet streams.

How does wildfire smoke affect our health?

The small particles in wildfire smoke are the most worrisome to our health. When we breathe them in, these particles can travel deep into the lungs and sometimes into the bloodstream.

The health effects of wildfire smoke include eye irritation, coughing, wheezing, and difficulty breathing. The smoke may also increase risk for respiratory infections like COVID-19. Other possible serious health effects include heart failure, heart attacks, and strokes.

Who needs to be especially careful?

Those most at risk from wildfire smoke include children, older adults, outdoor workers, and anyone who is pregnant or who has heart or lung conditions.

If you have a chronic health condition, talk to your doctor about how the smoke might affect you. Find out what symptoms should prompt medical attention or adjustment of your medications. This is especially important if you have lung problems or heart problems.

What can you do to prepare for wildfire emergencies?

If you live in an area threatened by wildfires, or where heat and dry conditions make them more likely to occur:

• Create an evacuation plan for your family before a wildfire occurs.
• Make sure that you have several days on hand of medications, water, and food that doesn't need to be cooked. This will help if you need to leave suddenly due to a wildfire or another natural disaster.
• Regularly check this fire and smoke map, which shows current wildfire conditions and has links to state advisories.
• Follow alerts from local officials if you are in the region of an active fire.

What steps can you take to lower health risks during poor air quality days?

These six tips can help you stay healthy during wildfire smoke advisories and at other times when air quality is poor:

• Stay aware of air quality. AirNow.gov shares real-time air quality risk category for your area accompanied by activity guidance. When recommended, stay indoors, close doors, windows, and any outdoor air intake vents.
• Consider buying an air purifier. This is also important even when there are no regional wildfires if you live in a building that is in poor condition. See my prior post for tips about pollution and air purifiers. The EPA recommends avoiding air cleaners that generate ozone, which is also a pollutant.
• Understand your HVAC system if you have one. The quality and cleanliness of your filters counts, so choose high-efficiency filters if possible, and replace these as needed. It's also important to know if your system has outdoor air intake vents.
• Avoid creating indoor pollution. That means no smoking, no vacuuming, and no burning of products like candles or incense. Avoid frying foods or using gas stoves, especially if your stove is not well ventilated.
• Make a "clean room." Choose a room with fewer doors and windows. Run an air purifier that is the appropriate size for this room, especially if you are not using central AC to keep cool.
• Minimize outdoor time and wear a mask outside. Again, ensuring that you have several days of medications and food that doesn't need to be cooked will help. If you must go outdoors, minimize time and level of activity. A well-fitted N95 or KN95 mask or P100 respirator can help keep you from breathing in small particles floating in smoky air (note: automatic PDF download).

About the Author

Wynne Armand, MD, Contributor

Dr. Wynne Armand is a physician at Massachusetts General Hospital (MGH), where she provides primary care; an assistant professor in medicine at Harvard Medical School; and associate director of the MGH Center for the Environment and … See Full Bio View all posts by Wynne Armand, MD

If you’ve ever tried to lose excess weight, you’ve probably gotten this advice: drink more water. Or perhaps it was more specific: drink a full glass of water before each meal.

The second suggestion seems like a reasonable idea, right? If you fill your stomach with water before eating, you’ll feel fuller and stop eating sooner. But did that work for you? Would drinking more water throughout the day work? Why do people say drinking water can help with weight loss — and what does the evidence show?

Stretching nerves, burning calories, and thirst versus hunger

Three top theories are:

Feel full, eat less. As noted, filling up on water before meals has intuitive appeal. Your stomach has nerves that sense stretch and send signals to the brain that it’s time to stop eating. Presumably, drinking before a meal could send similar signals.

• The evidence: Some small, short-term studies support this idea. For example, older study subjects who drank a full glass of water before meals tended to eat less than those who didn’t. Another study found that people following a low-calorie diet who drank extra water before meals had less appetite and more weight loss over 12 weeks than those on a similar diet without the extra water. But neither study assessed the impact of drinking extra water on long-term weight loss.

Burning off calories. The water we drink must be heated up to body temperature, a process requiring the body to expend energy. The energy spent on this — called thermogenesis — could offset calories from meals.

• The evidence: Though older studies provided some support for this explanation, more recent studies found no evidence that drinking water burned off many calories. That calls the thermogenesis explanation for water-induced weight loss into question.

You’re not hungry, you’re thirsty. This explanation suggests that sometimes we head to the kitchen for something to eat when we’re actually thirsty rather than hungry. If that’s the case, drinking calorie-free water can save us from consuming unnecessary calories — and that could promote weight loss.

• The evidence: The regulation of thirst and hunger is complex and varies over a person’s lifespan. For example, thirst may be dulled in older adults. But I could find no convincing studies in humans supporting the notion that people who are thirsty misinterpret the sensation for hunger, or that this is why drinking water might help with weight loss.

Exercise booster, no-cal substitution, and burning fat demands water

Being well-hydrated improves exercise capacity and thus weight loss. Muscle fatigue, cramping, and heat exhaustion can all be brought on by dehydration. That’s why extra hydration before exercise may be recommended, especially for elite athletes exercising in warm environments.

• The evidence: For most people, hydrating before exercises seems unnecessary, and I could find no studies specifically examining the role of hydration to exercise-related weight loss.

Swapping out high calorie drinks with water. Yes, if you usually drink high-calorie beverages (such as sweetened sodas, fruit juice, or alcohol), consistently replacing them with water can aid weight loss over time.

• The evidence: A dramatic reduction in calorie intake by substituting water for higher-calorie beverages could certainly lead to long-term weight loss. While it’s hard to design a study to prove this, indirect evidence suggests a link between substituting water for high-cal beverages and weight loss. Even so, just as calorie-restricting diets are hard to stick with over the long term, following a water-only plan may be easier said than done.

Burning fat requires water. Dehydration impairs the body’s ability to break down fat for fuel. So, perhaps drinking more water will encourage fat breakdown and, eventually, weight loss.

• The evidence: Though some animal studies support the idea, I could find no compelling evidence from human studies that drinking extra water helps burn fat as a means to lose excess weight.

The bottom line

So, should you bump up hydration by drinking water before or during meals, or even at other times during the day?

Some evidence does suggest this might aid weight loss, at least for some people. But those studies are mostly small or short-term, or based on animal data. Even positive studies only found modest benefits.

That said, if you think it’s working for you, there’s little downside to drinking a bit more water, other than the challenge of trying to drink if you aren’t particularly thirsty. My take? Though plenty of people recommend this approach, it seems based on a theory that doesn’t hold water.

About the Author

Robert H. Shmerling, MD, Senior Faculty Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing

Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School. … See Full Bio View all posts by Robert H. Shmerling, MD

The holiday season is one of the hardest times of the year to resist salty, fatty, sugary foods. Who doesn’t want to enjoy the special dishes and treats that evoke memories and meaning — especially during the pandemic? Physical distancing and canceled gatherings may make you feel that indulging is a way to pull some joy out of the season.

But stay strong. While it’s okay to have an occasional bite or two of marbled roast beef, buttery mashed potatoes, or chocolate pie, gorging on them frequently can lead to weight gain, and increased blood pressure, blood sugar, and “bad” LDL cholesterol.

Instead, skip the butter, cream, sugar, and salt, and flavor your foods with herbs and spices.

The bounty of nature’s flavor-makers go beyond enticing tastes, scents, and colors. Many herbs and spices contain antioxidants, flavonoids, and other beneficial compounds that may help control blood sugar, mood, and inflammation.

Amp up holiday foods with herbs and spices

Try flavoring your foods with some of the herbs and spices in the list below. Play food chemist and experiment with combinations you haven’t tried before. The more herbs and spices you use, the greater the flavor and health rewards. And that’s a gift you can enjoy all year through.

Allspice: Use in breads, desserts, and cereals; pairs well with savory dishes, such as soups, sauces, grains, and vegetables.

Basil: Slice into salads, appetizers, and side dishes; enjoy in pesto over pasta and in sandwiches.

Cardamom: Good in breads and baked goods, and in Indian dishes, such as curry.

Cilantro: Use to season Mexican, Southwestern, Thai, and Indian foods.

Cinnamon: Stir into fruit compotes, baked desserts, and breads, as well as Middle Eastern savory dishes.

Clove: Good in baked goods and breads, but also pairs with vegetable and bean dishes.

Cumin: Accents Mexican, Indian, and Middle Eastern dishes, as well as stews and chili.

Dill weed: Include in potato dishes, salads, eggs, appetizers, and dips.

Garlic: Add to soups, pastas, marinades, dressings, grains, and vegetables.

Ginger: Great in Asian and Indian sauces, stews, and stir-fries, as well as beverages and baked goods.

Marjoram: Add to stews, soups, potatoes, beans, grains, salads, and sauces.

Mint: Flavors savory dishes, beverages, salads, marinades, and fruits.

Nutmeg: Stir into fruits, baked goods, and vegetable dishes.

Oregano: Delicious in Italian and Mediterranean dishes; it suits tomato, pasta, grain dishes, and salads.

Parsley: Enjoy in soups, pasta dishes, salads, and sauces.

Pepper (black, white, red): Seasons soups, stews, vegetable dishes, grains, pastas, beans, sauces, and salads.

Rosemary: Try it in vegetables, salads, vinaigrettes, and pasta dishes.

Sage: Enhances grains, breads, dressings, soups, and pastas.

Tarragon: Add to sauces, marinades, salads, and bean dishes.

Thyme: Excellent in soups, tomato dishes, salads, and vegetables.

Turmeric: Essential in Indian foods; pairs well with soups, beans, and vegetables.

About the Author

Heidi Godman, Executive Editor, Harvard Health Letter

Heidi Godman is the executive editor of the Harvard Health Letter. Before coming to the Health Letter, she was an award-winning television news anchor and medical reporter for 25 years. Heidi was named a journalism fellow … See Full Bio View all posts by Heidi Godman

About the Reviewer

Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing

Dr. Howard LeWine is a practicing internist at Brigham and Women’s Hospital in Boston, Chief Medical Editor at Harvard Health Publishing, and editor in chief of Harvard Men’s Health Watch. See Full Bio View all posts by Howard E. LeWine, MD

It used to be that radiation therapy for prostate cancer involved weeks or months of repeat visits to a clinic for treatment. Today that’s not necessarily true. Instead of giving small doses (called fractions) per session until the full plan is completed, radiation delivery is moving toward high-dose fractions that can be given with fewer sessions over shorter durations.

This “hypofractionated” strategy is more convenient for patients, and mounting evidence shows it can be accomplished safely. With one technology called stereotactic body radiation therapy (SBRT), patients can finish their treatment plans within a week, as opposed to a month or more. Several devices are available to deliver hypofractionated therapy, so patients may also hear it referred to as CyberKnife or by other brand names.

An SBRT session takes about 20 to 30 minutes, and the experience is similar to receiving an x-ray. Often, doctors will first insert small metal pellets shaped like grains of rice into the prostate gland. Called fiducials, these pellets function as markers that help doctors target the tumor more precisely, so that radiation beams avoid healthy tissue. During treatment, a patient lies still while the radiation-delivery machine rotates around his body, administering the therapy.

How good is SBRT at controlling prostate cancer? Results from a randomized controlled clinical trial show that SBRT and conventional radiotherapy offer the same long-term benefits.

How the study was conducted

The trial enrolled 874 men with localized prostate cancer, meaning cancer that is still confined to the prostate gland. The men ranged between 65 and 74 years in age, and all of them had prostate cancer with a low or intermediate risk of further progression. The study randomized each of the men to one of two groups:

• Treatment group: The 433 men in this group each got SBRT at the same daily dose. The treatment plan was completed after five visits given over a span of one to two weeks.
• Control group: The 441 men in this group got conventional radiotherapy over durations ranging from four to 7.5 weeks.

None of the men received additional hormonal therapy, which is a treatment that blocks the prostate cancer–promoting effects of testosterone.

What the study showed

After a median duration of 74 months (roughly six years), the research found little difference in cancer outcomes. Among men in the treatment group, 26 developed visibly recurring prostate cancer, or a spike in prostate-specific antigen (PSA) levels suggesting that newly-forming tumors were somewhere in the body (this is called a biochemical recurrence). By contrast, 36 men from the control group developed visible cancer or biochemical recurrence. Put another way, 95.8% of men from the SBRT group — and 94.6% of men in the control group — were still free of prostate cancer.

A word of caution

Earlier results published two years into the same study showed higher rates of genitourinary side effects among the SBRT-treated men. Typical genitourinary side effects include inflammatory reactions that increase pain during urination, or that can make men want to urinate more often. Some men develop incontinence or scar tissues that make urination more difficult. In all, 12% of men in the SBRT group experienced genitourinary side effects at two years, compared to 7% of the control subjects.

“Interestingly, patients who were treated with CyberKnife appeared to have lower significant toxicity at two years compared with those treated on other platforms,” said Dr. Nima Aghdam, a radiation oncologist at Beth Israel Deaconess Medical Center and an instructor of radiation oncology at Harvard Medical School. By five years, the differences in side effects between men treated with SBRT or conventional radiation had disappeared.

The authors advised that men might consider conventional radiation instead of SBRT if they have existing urinary problems before being treated for cancer. Patients with baseline urinary problems are “more likely to have long-term toxic effects,” the authors wrote, adding that the new findings should “allow for better patient selection for SBRT, and more careful counseling.”

“This is an important study that validates what’s becoming a standard practice,” said Dr. Marc Garnick, the Gorman Brothers Professor of Medicine at Harvard Medical School and Beth Israel Deaconess Medical Center, and editor in chief of the Harvard Medical School Guide to Prostate Diseases. “The use of a five-day treatment schedule has been well received by patients who live long distances from a radiation facility, given that treatment can be completed during the weekdays of a single week. As with any cancer treatment choice, the selection of the appropriate patient is crucial to minimize any potential side effects, and this can only be done after a careful consideration of the patient’s other medical conditions.”

“This elegant study will put to rest any questions regarding the validity of SBRT as a standard-of-care option for many patients with prostate cancer,” Dr. Aghdam added. “Importantly in this trial, we see excellent outcomes for many patients who were treated with radiation alone. As this approach gains broad acceptance in radiation oncology practices, it remains critical to carefully consider each patient based on their baseline characteristics, and employ the highest level of quality assurance in delivering large doses of radiation in fewer fractions. As the overall duration of radiation therapy gets shorter, every single treatment becomes that much more important.”

About the Author

Charlie Schmidt, Editor, Harvard Medical School Annual Report on Prostate Diseases

Charlie Schmidt is an award-winning freelance science writer based in Portland, Maine. In addition to writing for Harvard Health Publishing, Charlie has written for Science magazine, the Journal of the National Cancer Institute, Environmental Health Perspectives, … See Full Bio View all posts by Charlie Schmidt

About the Reviewer

Marc B. Garnick, MD, Editor in Chief, Harvard Medical School Annual Report on Prostate Diseases; Editorial Advisory Board Member, Harvard Health Publishing

Dr. Marc B. Garnick is an internationally renowned expert in medical oncology and urologic cancer. A clinical professor of medicine at Harvard Medical School, he also maintains an active clinical practice at Beth Israel Deaconess Medical … See Full Bio View all posts by Marc B. Garnick, MD

Approximately three million Americans have inflammatory bowel disease (IBD). IBD is an umbrella term for Crohn’s disease and ulcerative colitis, illnesses marked by chronic or repeated bouts of inflammation in the digestive tract. Both types of IBD represent a complex interplay of genes, environment, and immune factors.

Current therapies for IBD suppress the immune system to reduce inflammation. But emerging research on the human microbiome may help scientists better understand and manage IBD. And some preliminary studies on cells, animals, and humans have investigated whether probiotics — which are sometimes called “good” bacteria — are beneficial for people with IBD.

The healthy microbiome: Building a barrier

The human intestinal microbiome is the vast community of trillions of helpful and harmful bacteria, viruses, fungi, and other microorganisms that inhabit our gut. Ideally, the lining of the gut acts as a barrier that prevents harmful bacteria and toxins from entering the bloodstream.

A healthy microbiome helps this lining block out harmful bacteria while enabling it to absorb nutrients. Beneficial bacteria in the microbiome promote a healthy, hospitable gut environment that limits inflammation and helps crowd out harmful bacteria.

Recent studies on human cells and in mice suggest that a healthy microbiome produces substances that

• nourish cells lining the colon, so that they form a tight barrier difficult for harmful bacteria to penetrate
• interact with immune cells in the gut, reducing inflammation
• prompt the gut lining to make mucus that acts as an additional barrier to harmful bacteria.

In animal studies, a healthy microbiome is essential to help build and maintain an effective barrier. Animals raised in the laboratory without a microbiome, or whose microbiome has been depleted by antibiotics, have intestinal linings that are easily damaged.

An unbalanced microbiome: Inflammation and damage

What happens if the microbiome doesn’t have a good balance of helpful and harmful bacteria? The gut lining may become increasingly permeable. That may allow potentially harmful bacteria and their toxins to cross into the intestinal tissue and then into the bloodstream, triggering inflammation that can damage the gut.

An imbalanced microbiome is known as dysbiosis. And the inflammatory cascade linked to dysbiosis is a hallmark of IBD.

Probiotics: More promise than evidence

Probiotics — live microorganisms in supplements or in fermented foods like kombucha, kefir, yogurt, and sauerkraut — have been proposed as therapies for IBD. The idea is that by eating beneficial bacteria we can restore and maintain a balanced microbiome, reduce inflammation, and improve the gut barrier. But what does the evidence say?

Thus far, no probiotic therapy is routinely prescribed for IBD. Small randomized studies have compared specific probiotics with standard immunosuppressive therapies for IBD. The studies measured IBD symptoms, remission rates, or quality of life. Results were mixed at best:

• Ulcerative colitis. Some studies suggest that certain bacterial strains, such as Bifidobacteria and Lactobacilli, are somewhat effective for ulcerative colitis, reducing symptoms, promoting remission, and improving quality of life. But these effects are modest compared to standard therapies, and probiotics have not shown enough benefit to be accepted in medical practice.
• Pouchitis. Some people with IBD may need surgery to remove the colon (large intestine). This can lead to inflammation in the remaining small intestine, which gets formed into a J-shaped pouch and attached to the anus. However, 25% to 45% of people who have a J-pouch later experience inflammation known as pouchitis. Several studies show that combining standard medication with a probiotic mix called VSL#3 effectively quells the symptoms and inflammation of pouchitis. VSL#3 contains eight strains of bacteria. It is used to treat chronic pouchitis, which is the only accepted use of probiotics in common practice for IBD.
• Crohn’s disease. Probiotics have not been studied as rigorously in Crohn’s disease as in ulcerative colitis. Most of the limited set of studies found that probiotics are no better than placebo in reducing symptoms or promoting remission.

Diet, fiber, and prebiotics: A role in IBD?

The makeup and activity of our microbiomes can be altered by diet. That’s true even if the foods you consume aren’t well-known probiotic stars like kombucha, yogurt, kefir, and other fermented foods.

Gut bacteria that break down dietary fiber are a cornerstone of a healthy microbiome. A high-fiber diet can boost the number of these bacteria, as well as their beneficial and anti-inflammatory effects.

Food ingredients that are not absorbed by the gut but are instead consumed by the gut microbiome are called prebiotics. We have limited — though promising — evidence supporting prebiotics for people with IBD. Currently, no specific prebiotic food or supplement is recommended for general use.

However, the Mediterranean diet, which encourages fiber-rich vegetables, whole grains, and legumes, may modestly reduce symptoms and markers of inflammation in IBD. While these effects are small and inconsistent, the Mediterranean diet improves overall health in people with or without IBD. Largely for this reason, the American Gastroenterology Association recommends it for people who have IBD.

The bottom line

Probiotics, and possibly even prebiotics, hold promise. But we don’t yet know how to harness their full potential for treating IBD. While current evidence suggests probiotics may one day be an effective way to help treat IBD, the complexity of the microbiome means that a one-size-fits-all approach is unlikely to work.

Many questions remain: Which strains of bacteria in the gut should we study? How do we determine the best cocktail of probiotics to reap maximum benefit? Given that everyone’s microbiome is different, is a personalized approach to probiotics the right strategy? How can we define ideal dosage and formulation of probiotics?

Delivery method (capsules, powders, foods), dosage, and duration of treatment all require more research. Until these questions are answered, probiotics and prebiotics remain complementary strategies in treating IBD alongside standard immunosuppressive therapies.

About the Authors

Jake Dockterman, MD, PhD, Contributor

Dr. Jake Dockterman is from Carlisle, MA and earned his bachelor’s degree in molecular and cellular biology from Harvard College. He completed his MD and PhD in immunology at Duke University, studying host-microbe interactions and mucosal … See Full Bio View all posts by Jake Dockterman, MD, PhD

Loren Rabinowitz, MD, Contributor

Dr. Loren Rabinowitz is an instructor in medicine Beth Israel Deaconess Medical Center and Harvard Medical School, and an attending physician in the Inflammatory Bowel Disease Center at BIDMC. Her clinical research is focused on the … See Full Bio View all posts by Loren Rabinowitz, MD

Not so long ago, a friend texted me from a coffee shop. He said, "I can't believe it. I'm the only one here without a tattoo!" That might not seem surprising: a quick glance around practically anywhere people gather shows that tattoos are widely popular.

Nearly one-third of adults in the US have a tattoo, according to a Pew Research Center survey, including more than half of women ages 18 to 49. These numbers have increased dramatically over the last 20 years: around 21% of US adults in 2012 and 16% of adults in 2003 reported having at least one tattoo.

If you're among them, some recent headlines may have you worried:

              Study Finds That Tattoos Can Increase Your Risk of Lymphoma (OnlyMyHealth)

              Getting a Tattoo Puts You At Higher Risk of Cancer, Claims Study (NDTV)

              Inky waters: Tattoos increase risk of lymphoma by over 20%, study says (Local12.com)

              Shocking study reveals tattoos may increase risk of lymphoma by 20% (Fox News)

What study are they talking about? And how concerned should you be? Let's go through it together. One thing is clear: there's much more to this story than the headlines.

Why are researchers studying a possible link between tattoos and lymphoma?

Lymphoma is a type of cancer that starts in the lymphatic system, a network of vessels and lymph nodes that twines throughout the body. With about 90,000 newly diagnosed cases a year, lymphoma is one of the most common types of cancer.

Risk factors for it include:

• advancing age
• certain infections (such as Epstein-Barr virus, HIV, and hepatitis C)
• exposure to certain chemicals (such as benzene, or possibly pesticides)
• family history of lymphoma
• exposure to radiation (such as nuclear reactor accidents or after radiation therapy)
• having an impaired immune system
• certain immune diseases (such as rheumatoid arthritis, Sjogren's disease, or celiac disease).

Tattoos are not known to be a cause or risk factor for lymphoma. But there are several reasons to wonder if there might be a connection:

• Ink injected under the skin to create a tattoo contains several chemicals classified as carcinogenic (cancer causing).
• Pigment from tattoo ink can be found in enlarged lymph nodes within weeks of getting a tattoo.
• Immune cells in the skin can react to the chemicals in tattoo ink and travel to nearby lymph nodes, triggering a bodywide immune reaction.
• Other triggers of lymphoma, such as pesticides, have a similar effect on immune cells in lymph nodes.

Is there a connection between tattoos and lymphoma?

Any potential connection between tattoos and lymphoma has not been well studied. I could find only two published studies exploring the possibility, and neither found evidence of a compelling link.

The first study compared 737 people with the most common type of lymphoma (called non-Hodgkin's lymphoma) with otherwise similar people who did not have lymphoma. The researchers found no significant difference in the frequency of tattoos between the two groups.

A study published in May 2024 — the one that triggered the scary headlines above — was larger. It compared 1,398 people ages 20 to 60 who had lymphoma with 4,193 people who did not have lymphoma but who were otherwise similar. The study found that

• lymphoma was 21% more common among those with tattoos
• lymphoma risk varied depending on how much time had passed since getting the tattoo:
  • within two years, lymphoma risk was 81% higher
  • between three and 10 years, no definite increased lymphoma risk was detected
  • 11 or more years after getting a tattoo, lymphoma risk was 19%

There was no correlation between the size or number of tattoos and lymphoma risk.

What else should you know about the study?

Importantly, nearly all of the differences in rates of lymphoma between people with and without tattoos were not statistically significant. That means the reported link between lymphoma and tattoos is questionable — and quite possibly observed by chance. In fact, some of the other findings argue against a connection, such as the lack of a link between size or number of tattoos and lymphoma risk.

In addition, if tattoos significantly increase a person's risk of developing lymphoma, we might expect lymphoma rates in the US to be rising along with the popularity of tattoos. Yet that's not the case.

Finally, a study like this one (called an association study) cannot prove that a potential trigger of disease (in this case, tattoos) actually caused the disease (lymphoma). There may be other factors (called confounders) that are more common among people who have tattoos, and those factors might account for the higher lymphoma risk.

Do tattoos come with other health risks?

While complication rates from reputable and appropriately certified tattooists are low, there are health risks associated with tattoos:

• infection, including bacterial skin infections or viral hepatitis
• allergic reactions to the ink
• scarring
• rarely, skin cancer (melanoma and other types of skin cancer).

The bottom line

Despite headlines suggesting a link between tattoos and the risk of lymphoma, there's no convincing evidence it's true. We'll need significantly more research to say much more than that. In the meantime, there are more important health concerns to worry about and much better ways for all of us to reduce cancer risk.

About the Author

Robert H. Shmerling, MD, Senior Faculty Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing

Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School. … See Full Bio View all posts by Robert H. Shmerling, MD

Several evenings a week, as Tyler VanderWeele gathers around the dinner table with his wife and two young kids, the family deliberately pauses during the meal to do something simple but profound. Each member shares several things for which they’re grateful — an act that VanderWeele, co-director of the Initiative on Health, Spirituality, and Religion at the Harvard T.H. Chan School of Public Health, feels changes his family dynamic for the better.

“I do think it makes a difference and can be a very powerful practice,” he says. “Even on those bad days where life seems difficult, that effort is worthwhile.”

Gratitude, health, and longevity

How can the power of gratitude affect our lives? Recent research has pointed to gratitude’s myriad positive health effects, including greater emotional and social well-being, better sleep quality, lower depression risks, and favorable markers of cardiovascular health. Now, new data from the long-term Nurses’ Health Study shows that it may extend lives.

“Gratitude has been one of the most widely studied activities contributing to well-being, but we couldn’t find a single prior study that looked at its effects on mortality and longevity, much to our surprise,” says VanderWeele, co-author of the new research.

What did the study look at?

Published July 2024 in JAMA Psychiatry, the new study drew on data from 49,275 women enrolled in the Nurses’ Health Study. Their average age was 79. In 2016, participants completed a six-item gratitude questionnaire in which they ranked their agreement with statements such as, “I have so much in life to be thankful for,” and “If I had to list everything I felt grateful for, it would be a very long list.”

Four years later, researchers combed through participants’ medical records to determine who had died. There were 4,608 deaths from all causes, as well as from specific causes such as cardiovascular disease, cancer, respiratory diseases, neurodegenerative disease, infection, and injury. Deaths from cardiovascular disease — a top killer of women and men in the United States — were the most common cause.

What did the researchers find?

Participants with gratitude scores in the highest third at the study’s start had a 9% lower risk of dying over the following four years than participants who scored in the bottom third. This did not change after controlling for physical health, economic circumstances, and other aspects of mental health and well-being. Gratitude seemed to help protect participants from every cause of death studied — including cardiovascular disease.

But what does this actually mean?

“A 9% reduction in mortality risk is meaningful, but not huge,” VanderWeele says. “But what’s remarkable about gratitude is that just about anyone can practice it. Anyone can recognize what’s around them and express thanks to others for what’s good in their life.”

While the study couldn’t pinpoint why gratitude is associated with longer life, VanderWeele believes several factors may contribute.

“We know that gratitude makes people feel happier. That in itself has a small effect on mortality risk,” he says. “Practicing gratitude may also make someone a bit more motivated to take care of their health. Maybe they’re more likely to show up for medical appointments or exercise. It may also help with relationships and social support, which we know contribute to health.”

What are the study’s limitations and strengths?

The study was observational. This means it can’t prove that gratitude helps people live longer — only that an association exists. And the particular sample of people analyzed is both the biggest strength and limitation of the research, VanderWeele says. All were older female nurses with high socioeconomic status. The vast majority were white.

“Does the longevity effect extend to men, to those who are younger, and to those with lower socioeconomic resources?” VanderWeele asks. “Those are all open questions.”

On the plus side, he says, the study sample’s large size is one of its biggest strengths. So is the extensive data gathered on potential confounding factors such as participants’ physical health, social characteristics, and other aspects of psychological well-being.

“Between the quality of the data and the size of the sample, we were able to provide reasonable evidence for this modest longevity effect,” he says.

Try this: Six questions to evoke gratitude

Not feeling especially grateful today? You have the power to change that. Asking yourself certain questions can evoke gratitude, such as

• What happened today that was good?
• What am I taking for granted that I can be thankful for?
• Which people in my life am I grateful for?
• What is the last book I read or movie, show, or social media clip I saw that I really appreciated, and why?
• What am I most looking forward to this week, month, and year, and why?
• What is the kindest thing someone has said or done lately?

Similarly, a few simple actions can infuse gratitude into your days. Try VanderWeele’s family routine of regularly expressing gratitude around the dinner table. Another well-known practice — that’s perhaps becoming forgotten in this digital age — is penning thank-you notes.

“I do think writing a thank-you note or gratitude letter gets your mind to dwell on something positive for a longer period, to think more deeply about it, because you have to put it not just in words, but in writing,” VanderWeele says. “It also deepens the relationship and builds that bond.”

One less-recognized but valuable gratitude practice is called a “savoring exercise,” which builds on aspects of mindfulness. All that’s required is “pausing, looking around you, and taking in and enjoying everything that’s good in your current setting,” VanderWeele says. “It’s not a big leap to go from recognizing the good to expressing gratitude for what you have.”

About the Author

Maureen Salamon, Executive Editor, Harvard Women's Health Watch

Maureen Salamon is executive editor of Harvard Women’s Health Watch. She began her career as a newspaper reporter and later covered health and medicine for a wide variety of websites, magazines, and hospitals. Her work has … See Full Bio View all posts by Maureen Salamon

About the Reviewer

Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing

Dr. Howard LeWine is a practicing internist at Brigham and Women’s Hospital in Boston, Chief Medical Editor at Harvard Health Publishing, and editor in chief of Harvard Men’s Health Watch. See Full Bio View all posts by Howard E. LeWine, MD

Celiac disease is a digestive and immune disorder that can keep the body from absorbing necessary nutrients. “Our conception and awareness of celiac disease has evolved over the past few decades, but there are still aspects that remain poorly understood,” says Dr. Ciaran Kelly, medical director of the Celiac Center at Beth Israel Deaconess Medical Center and professor of medicine at Harvard Medical School.

Perhaps not surprisingly, misconceptions are widespread among the general public. One example? Many people assume that everyone who has celiac disease is plagued by abdominal pain, bloating, or diarrhea. But actually, many adults newly diagnosed with this inherited gluten intolerance don’t have these symptoms.

What’s more, gluten — the sticky protein found in grains such as wheat, barley, and rye — can cause gastrointestinal distress and other symptoms in people who don’t have celiac disease. Read on for a deeper dive into four myths and facts about celiac disease and related digestive conditions.

Myth # 1: Celiac disease is usually diagnosed at a young age

Not typically. While celiac disease can develop any time after a baby’s first exposure to gluten, it’s usually diagnosed much later in life. According to the National Celiac Association, the average age of diagnosis is between 46 and 56. Around 25% of people are diagnosed after age 60.

Celiac disease is slightly more common in women and among people with other autoimmune conditions, including type 1 diabetes, Hashimoto’s thyroiditis (a common cause of low thyroid levels), and dermatitis herpetiformis (a rare condition marked by an itchy, blistering rash).

“We don’t know why some people go from being susceptible to actually having celiac disease,” says Dr. Kelly. The prevailing theory is that some sort of physical or emotional stress — such as a viral infection, surgery, or anxiety from a stressful life event — may “flip the switch” and cause the disease to appear, he says. “Increasing numbers of people are being diagnosed at midlife and older, often after they’re found to have conditions such as anemia or osteoporosis caused by nutrient deficiencies,” says Dr. Kelly.

Myth #2: Celiac disease only affects the gut

When people have celiac disease, eating gluten triggers an immune system attack that can ravage the lining of the small intestine. A healthy small intestine is lined with fingerlike projections, called villi, that absorb nutrients. In celiac disease, the immune system attacks the villi, causing them to flatten and become inflamed — and thus unable to adequately absorb nutrients.

While gastrointestinal problems can occur, they aren’t always present. In fact, celiac disease can present with many different symptoms that affect the nervous, endocrine, and skeletal systems. A few examples are brain fog, changes in menstrual periods, or muscle and joint pain.

Myth # 3: Celiac disease versus gluten intolerance

If you feel sick after eating gluten, you probably have celiac disease, right? Actually, that may not be true. Some people have non-celiac gluten sensitivity (also called gluten intolerance), which can cause uncomfortable digestive symptoms after eating gluten. But gluten intolerance differs from celiac disease.

• Celiac disease is diagnosed with blood tests that look for specific antibodies. If antibodies are present, a definitive diagnosis requires an intestinal biopsy to look for signs of damage that characterize the condition.
• Non-celiac gluten sensitivity does not trigger antibodies or cause intestinal damage. Yet some people with this problem say they also experience brain fog, trouble concentrating, muscle aches and pain, and fatigue after eating gluten-containing foods.

“Non-celiac gluten sensitivity appears to be a real phenomenon, but it’s not well defined,” says Dr. Kelly. It’s unclear whether people experiencing it are intolerant to gluten or to something else in gluten-containing foods.

• One possibility is sugarlike molecules known as FODMAPs, which are found in many foods — including wheat. Short for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols, gas and bloating can occur when gut bacteria feed on FODMAPs.
• Another possibility is an allergy to wheat, which can cause symptoms such as swelling, itching, or irritation of the mouth and throat after eating wheat. Other symptoms include a skin rash, stuffy nose, and headache, as well as cramps, nausea, and vomiting. Some people may develop a life-threating allergic reaction known as anaphylaxis.

Myth #4: A gluten-free diet always relieves the symptoms and signs of celiac disease

The sole treatment for celiac disease — adopting a diet that avoids all gluten-containing foods — doesn’t always help. This problem is known as nonresponsive celiac disease.

“About 20% of people with celiac disease have ongoing symptoms, despite their best efforts to stick to a gluten-free diet,” says Dr. Kelly. Others have intermittent signs and symptoms, particularly when they are accidentally exposed to gluten. Accidental exposures often happen when people eat prepared or restaurant foods that claim to be gluten-free but are not. Cross contamination with gluten-containing foods is another potential route.

Potential solutions to nonresponsive celiac disease are being studied. Three promising approaches are:

• Enzymes that break down gluten, which people could take alongside gluten-containing foods. “It’s a similar concept to the lactase pills taken by people who are lactose intolerant to help them digest dairy products,” says Dr. Kelly.
• Dampening the immune response to gluten by inhibiting an enzyme called tissue transglutaminase that makes gluten more potent as an antigen.
• Reprogramming the immune response to prevent the body from reacting to gluten.

About the Author

Julie Corliss, Executive Editor, Harvard Heart Letter

Julie Corliss is the executive editor of the Harvard Heart Letter. Before working at Harvard, she was a medical writer and editor at HealthNews, a consumer newsletter affiliated with The New England Journal of Medicine. She … See Full Bio View all posts by Julie Corliss

About the Reviewer

Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing

Dr. Howard LeWine is a practicing internist at Brigham and Women’s Hospital in Boston, Chief Medical Editor at Harvard Health Publishing, and editor in chief of Harvard Men’s Health Watch. See Full Bio View all posts by Howard E. LeWine, MD