The Famine’s Lessons: How Disease Stayed With Irish Americans for Generations—and Why It Still Matters

Today is St. Patrick’s Day, when more than 30 million Americans of Irish ancestry will celebrate their heritage,¹ alongside friends with forebears from across the globe. Parades, drinking, and “wearin’ of the green” can eclipse why this country celebrates a fifth-century missionary—and has done so intensely since the late 1800s.

Ireland’s famine of 1845-1851, called An Gorta Mor or “The Great Hunger,” was triggered by a potato blight that destroyed the chief food source; it caused 1 million deaths and scattered starving people around the globe.² A nation of 8.2 million people lost half its population by the century’s end.

Some 2 million Irish came to the US in the decade between 1845 and 1855.^1-3 As their ranks grew, St. Patrick’s Day parades were a way for the Irish to show their strength and flex their political clout.⁴ From its beginning, scholars have studied the famine’s political and social impact on Ireland and the US, 2 countries so connected the Irish prime minister brings a bowl of shamrocks to the White House each year.^3,5

Yet, despite its death toll, the famine’s multigenerational health effects—on those who stayed and those who left—have received comparatively little attention.

That is changing, as historians apply insights from famines in the Netherlands, China, and Nigeria to data from the past: from records kept by prisons and workhouses and asylums of Ireland, along with mortality data and census reports from the US. What scholars are learning has implications for today’s policy makers, from those fighting wars to those executing $186 billion in cuts to the US nutrition program, the largest in its history.⁶

H.R. 1, the “One Big Beautiful Bill Act,” signed into law in 2025, makes historic changes to the Supplemental Nutrition and Assistance Program (SNAP) that could have a disproportionate effect on young men, along with disrupting the pathway between SNAP and the program that serves pregnant women, the Supplemental Nutrition Program for Women, Infants, and Children (WIC).

This comes as science tell us when populations lack food, the health effects last well beyond individual lifetimes. The effects of malnutrition on a pregnant woman—and a man before he becomes a father—burrow into the body of a child not yet born, changing behavior of genes, shrinking organs, and causing neurological effects that can be detected decades later, before being passed to that child’s children and grandchildren. Stress, if it lasts long enough, adds to the misery.

Examining the Irish Famine Through Epigenetics

Epigenetics examines how factors such as diet, stress, or toxins cause reversible changes in the way genes function, without altering DNA. These signals, which can last 3 to 4 generations, have allowed scientists and historians on both sides of the Atlantic to look at the Irish famine and others through a new lens. Health effects that scientists today most strongly connect with poor fetal nutrition—cardiovascular disease, diabetes, obesity, and mental health disorders—can be documented among the generations of Irish in America after the famine, records and studies show.^7,8

In the 2004 article “Hurling Alone,” experts from University College Dublin and the University of Michigan looked at 80 years’ worth of data from both Ireland the US, notably from the Boston area, trying to explain why “the Irish were consistently at increased risk of cardiovascular diseases, a risk that related initially to material deprivation, across the life course of at least 2 generations,” lasting from 1850 through 1970. This was in contrast with Italian immigrants, who had similar social patterns but lacked the famine experience.⁷

Fifty years after the famine, a 1904 US Census report, “Insane and Feeble-Minded in Hospitals and Institutions,” spelled out how the Irish were overrepresented when it came to taking up space in US mental health wards:⁸

“Ireland furnished only 15.6% of all foreign born in the United States in 1900, but 29% of all foreign born [White] insane enumerated in hospitals on December 31, 1903. Similar relations between the 2 percentages will be observed for each geographic division; that is to say, the percentage of Irish born in the foreign born [White] insane in each division is about twice as large as the percentage of Irish born in the total foreign born population for the same group….

“Relative to their numbers the Irish furnish a much larger proportion of the White foreign born insane in hospitals than any other nationality,” the report continued. “This is in keeping with the very high ratio of insanity in Ireland….”⁸

Medical historian Oonagh Walsh, PhD, a professor at Glasgow Caledonian University, is familiar with this last part. Walsh has spent more than a decade examining the Irish famine’s epigenetic effects on both cardiovascular and mental health; in particular, she has studied the growth of Ireland’s asylum system from 3000 to 17,000 patients over a 50-year period after the famine, even as the island’s population fell to 4.4 million by 1900.⁹

What happened in The Great Hunger was not just a physical but also an emotional and psychological shock to the country, Walsh said in an interview with The American Journal of Managed Care^® (AJMC^®). Before the famine, she said, “The average Irish man was taller and fitter than his United Kingdom (UK) counterparts, even on the potato diet,” although one did have to eat a lot of them.

“There's probably something of an epigenetic effect already happening in that population before the famine, [but] the famine is an absolute catastrophe,” Walsh said. “I would say that the populations that survive infancy and that mature into adulthood are probably those that are, as a result of epigenetic change, best adapted for that environment of periodic food shortages and a general level of food scarcity.”

Americans may not appreciate that although the first year of the potato blight caught people off guard, the tragedy of the 5 years that followed—the shipping of cash crops and butter off to Britain, the policies that pushed tenants off their land—was largely man-made.

“What happens in the famine is it's absolute starvation all down the western seaboard in particular, but it's also a period of intense psychological stress,” Walsh said. “They get a protracted period in which they are constantly undernourished and, in many cases, outright starved. They are also in terror for their lives. So, I think it's the combination of that food deprivation and psychological stress that really is what causes epigenetic change on a much larger scale in the postfamine years.”

Economists Mattias Blum, Christopher L. Colvin, and Eoin McLaughlin bolstered this theory with 2026 research that examined measurements of Irish prisoners recorded in different parts of the country; they compared bone measurements of those born before, during, and soon after the famine. Harder hit areas came away from the famine years appearing healthier overall, but that is because the most vulnerable members were wiped out. Those left behind in less hard-hit areas remained weakened. “These findings contribute to debates on the biological consequences of extreme catastrophic risks, demonstrating how selection effects can obscure long-term health deterioration,” the authors wrote.¹⁰

The lessons of the Irish famine should not be left for the history books, these experts say. They should inform our policies on nutrition, as well as how we treat those fleeing famine today. Blum et al note that the famine, “permanently changed the structure of Irish agriculture,” and that British polices “helped provide industrializing cities with cheap labour.” ¹⁰

During an Irish American heritage talk in 2022, Walsh discussed the implications of her work, before the crisis in Gaza or current debates over immigration policy and food assistance. “The Irish famine and discussions of epigenetic change are terribly important,” she said. “Its utility may well lie in helping to inform debates about public policy in relation to intervention in famines and war zones,” especially if food supplies are scarce.⁹

Questions about who should receive aid are challenging, she said; thus, knowledge of how epigenetics affects populations can inform decisions of “who should be prioritized in order to best protect subsequent generations….Given the current global refugee crisis, how we can help to protect people who are fleeing persecution and trauma and ensure that we alleviate the worst long-term effects of those trauma for the survivors and their descendants?”

Fetal Nutrition and Adult Chronic Disease

Walsh’s work on the Irish famine aligns with decades of scholarship on the long-term effects of fetal and early childhood nutrition, beginning with the breakthrough 1986 study by David Barker, MD, PhD, then affiliated with the University of Southampton in the UK. The “Barker Hypothesis” on fetal origins of adult disease, was based on analyses of historical birth records in Hertfordshire, UK.^11,12 Barker proposed that poor nutrition and stress during fetal life and infancy resets the body's physiology, increasing a child’s risk for cardiovascular disease, type 2 diabetes, hypertension, and stroke in adulthood.

He theorized that malnutrition during fetal development forces the developing baby into survival mode, resulting in a “thrifty phenotype.”¹³ Permanent changes to the metabolism—such as smaller organs and insulin resistance—prepare the child for a life low in nutrients. But if the child is then moved to a nutrient-rich environment, the body is thrown into chaos. Thus, epigenetics explains why overfeeding children born during a famine, or their descendants, can actually do harm. Instead, their diets need to be carefully managed.

Barker, who died in 2013, finished his career at Oregon Health & Science University (OHSU), where he continued his work with Kent Thornburg, PhD, an expert on cardiac and pulmonary physiology, on how the placenta affects fetal development. In an interview with AJMC, Thornburg said Barker’s study of birthweight data showed that babies born at both the lowest and highest weights were at risk of future chronic disease, with the ideal birth weight being around 7 to 8 pounds. “David Barker said that both heart disease and diabetes could be reversed by 50% in 1 generation, if we were able to get most kids born in the normal birth weight range and if we could prevent children from putting on a lot of weight before they’re 8 years old. Because this added weight to a child, especially a child that's been born at low birth weight during their early years, is a rock solid predictor of obesity and diabetes.”

In 2008, Barker’s theory was confirmed by the Maternal and Child Undernutrition Study Group through a review of 5 cohort studies. “We conclude that damage suffered in early life leads to permanent impairment and might also affect future generations. Its prevention will probably bring about important health, educational, and economic benefits. Chronic diseases are especially common in undernourished children who experience rapid weight gain after infancy.”¹⁴

The year 2008 also brought groundbreaking results from the Dutch Hunger Winter Study, in which investigators followed individuals whose mothers had been pregnant during the German food blockade of the Netherlands in 1944-1945.¹⁵ By evaluating the babies born during and after that famine, as well as siblings born before and after, investigators showed that those who experienced malnutrition in the womb in the early trimesters had less DNA methylation of the IGF2 gene compared with same-sex siblings. Loss of methylation to the IGF2 gene, which affects metabolism and growth, can result in higher rates of obesity, cardiovascular disease, or schizophrenia. Follow-up work showed health effects in the next generation: children of mothers exposed to famine in gestation were heavier at birth, more likely to have high adiposity and more likely to be in poor health, including a greater likelihood of breast cancer.¹⁶

More recently, a 2021 paper by Alexander Vaiserman, DSc, and Oleh Lushchak, PhD, explained how epigenetic effects of the Chinese famine of 1959-1961 may explain the country’s exploding rates of type 2 diabetes, and the Ukraine famine of 1934 could account for rising rates of chronic disease in the Eastern part of that country. More investigation is needed, the authors wrote.¹⁷

Although officially retired, Thornburg still lectures on the “the 100 Year Effect,” which describes how health effects are compounded and passed from one generation to the next, reaching back as far as 4 generations.¹⁸ What’s worse, Thornburg told AJMC in an interview, today’s Americans are not eating healthy, balanced diets to reverse the harms done to malnourished ancestors. In fact, they’re doing the exact opposite.

“We’re now living in the third or fourth generation of people who have eaten mainly industrial food—and in the more recent decades, it's been ultraprocessed foods that have been the primary source of diet for a lot of people,” Thornburg said. If it turns out that most pregnancies are nourished by this type of diet, this could account for the rising rates of colorectal cancer among young adults. “I wouldn't be surprised if that's a fact,” he said. “Our population is epigenetically vulnerable.”

Experiments Show Why Diets Matter for Fathers

Nutrition policy is focused on the idea that a pregnant woman should have a healthy, balanced diet. While that is certainly true, what a father eats before his sperm fertilizes an egg matters, too.

A 2024 paper by Giovane G. Tortelote, PhD, a pediatric nephrologist at Tulane University, and colleagues involved experiments with mice who were fed either normal or protein-restrictive diets. Tortelote’s team showed that restricting protein affects kidney development in mice for up to 4 generations; this can affect blood pressure or other chronic conditions. In particular, the experiments showed that when a male with a low-protein diet was bred with female with a normal diet, the pups still had a smaller kidneys.¹⁹

Nephron counts were normal by the third generation, but body and kidney weight remained low through 4 generations. “Our findings suggest that poor parental nutrition influences not just the first generation but extends its effects to multiple generations,” the authors wrote. “A similar pattern has been observed in humans whose parents or grandparents experienced starvation, with the second and third generations still showing the impact of these food restrictions.”¹⁹

In an interview with AJMC, Tortelote said prior studies have evaluated the effects of prenatal nutrition on obesity and type 2 diabetes, “but we were the first one show that it impact kidney development, and so it's clearly important.”

He said the findings show the importance of good nutrition for everyone in the family. “Once people get access to food and they bring food home, everybody at home benefits, right? The father also is going to eat that better meal.”

Early Hunger Means Disease Later, Experts and Advocates Say

OHSU’s Thornburg said nutrition policies that account for “the 100 Year Effect” and take aim at chronic disease should include both prospective fathers and mothers. “What we need is WIC for mothers and fathers 6 months before pregnancy. That's the ideal,” he said. “It’s both a nutritional stress and an emotional stress, in many cases, that are actually passed on to the offspring in terms of epigenetic changes.”

“We need to organize this nationwide, so that we are sure that people of reproductive age are cared for—that they have good diets—and that the conditions in life that brings stress, like poor housing and food insecurity and things like that, are cared for in the population of people who are going to bear the next generation. That’s a really big public health issue.”

However, according to Feeding America, changes under H.R. 1 could remove 6 billion meals from SNAP^6,20:

• New eligibility restrictions could impact noncitizens, including refugees, asylum seekers, and survivors of human trafficking. In households with a mix of citizens and noncitizens, the changes mean the household’s overall food assistance will decline.
• Expanded work requirements call for documenting work, volunteering, or training for at least 80 hours a month. Work requirements for able-bodied adults without dependents took effect March 1, 2026. This provision now applies to adults aged 18 to 64, up from age 55; exemptions end for parents when children turn 14, down from age 18.
• Nonexempt individuals who do not meet these requirements are limited to 3 months of benefits within a 3-year period. The first persons who fail to meet requirements will start to lose benefits May 1, 2026.

Advocates have argued for months that the changes to SNAP would hit squarely on young adults of childbearing age, noting in particular that it will take longer for many income-eligible women to qualify for WIC if they are not already connected to SNAP. Thornburg said that this would be less problematic if most poor women went into pregnancy eating healthy diets. But that’s often not the case.

“What it does mean is there's a certain population that really needs WIC in order to be able to have the nutrients they need for their babies,” he said. “Obviously, if they don't get those until later in pregnancy, the early parts of the development of a human being will be compromised and epigenetic changes will be made, and that will put them at more risk for these chronic conditions later.”

Changes to SNAP are hitting especially hard on immigrant seniors and children who are in the country legally, the Florida Policy Institute said in a statement earlier this month. The institute argues investments in SNAP for children are miniscule compared with the health costs that will result from chronic disease later in life.²¹

“For seniors, who often rely on SNAP to buy groceries that they cannot otherwise afford on a fixed income, access to SNAP has significant health benefits,” the statement said, citing studies that link SNAP participation to protection against Alzheimer, diabetes, cardiovascular disease, and other conditions. “For children, SNAP helps them do better in school, live a longer and healthier life, and have higher-paying jobs as an adult. In fact, it is estimated that every dollar of SNAP going to feed a child has a $62 return over the course of their lifetime.”²²

The potential long-term health effects alarm the public health research community. Writing in JAMA Health Forum in January, Sara N. Bleich, PhD, of the Harvard TH Chan School of Public Health, and Gina Plata-Nino, JD, SNAP director for the Food Research and Action Center, said the changes to a program that serves 40 million people are “reshaping SNAP in historic ways with likely generational consequences.

“These changes raise serious questions about the nation’s long-standing commitment to reducing hunger.” ²³

Why Do We Know So Little About the Irish Famine’s Health Effects?

Although Ireland was poor, people were healthy before the famine. Fertility was fueling population growth that outstripped the rest of Europe. After 1845, starvation was only part of the story. The British were already looking for ways to free up small plots of land to create areas for more profitable grazing; a clause passed during 1847, or “Black 47,” forced tenants to surrender their small plots to receive food aid. “Roads to nowhere” still lace the countryside, a reminder of poorly planned work-for-food mandates conceived during the period.²⁴ Another law enticed landlords to force tenants off their plots rather than pay taxes. People with nothing to eat now had no place to live and no land to farm, hastening the exodus.²⁵

Walsh emphasizes that trauma was as much a culprit in epigenetic changes as the lack of food. However, although the Irish may be talkers, the famine was not talked about.

“I think it was a horrendous trauma,” she said. “Remember, the famine wasn't a uniform experience over the whole country; there were better resourced areas, but certainly all the way down the western seaboard, it was horrendous. There's perhaps an element of survivor's guilt. There's a reluctance, I think, to address the horrors that people saw and experienced. And for an awful lot of famine migrants, they fled and they remade themselves.”

Immigrants to America still carry trauma and just as often do not share it once they are here. It was true of the Irish, it was later true of Asian immigrants, and it is true of today’s Latino immigrants, who may experience extreme trauma yet be wary of seeking help.²⁶ In the current climate, the stress of emigrating to the US is compounded by other factors. More than half (55%) of immigrant parents in a KFF survey published March 2, 2026, reported problems paying for health care, housing, or food in the past 12 months.²⁷ Thornburg has studied the effect of long-term stress on children, which he calls adverse childhood experiences. These, too, can compound health effects in adulthood.

“If they're under this stress for a long period of time, these cortisol levels and other hormones that are important in stress, like norepinephrine, for example, those hormones will have detrimental effects, not only at the time, but on the epigenetic profile that will lead to problems later,” he said.

State-level responses to H.R. 1 vary. In Minnesota, where some of the most intense efforts to locate and deport undocumented immigrants have occurred, state officials told AJMC in an email that they do not track their Emergency Food Assistance Program or Minnesota Food Shelf Program by immigration status. Some distribution models have shifted to food delivery, allowing recipients to assign someone to pick up food on their behalf. “This has been helpful as community members have stepped in to pick up food for those impacted,” the email said.

By contrast, findings released by the office of US Senator Jon Ossoff (D, Georgia), show that immigrant families held in detention between January 2025 and 2026 have experienced dozens of incidents of inadequate food or water and separation of breastfeeding mothers from infants, in addition to other reports of abuse, neglect, and denial of medical care.²⁸

Walsh said her next research area on the Irish famine involves how starvation affects cognition, as there are often questions of why the Irish didn’t “rise up” against the British or why Jewish families didn’t attack the guards in the camps during the Holocaust. Starvation, she said, is a classic tool to prevent a population from fighting back.

“The best thing you can do if you are an invading force, or you want to control a population, is to starve them. It's not just that they're terrified that there'll be further punishments in terms of food being withdrawn, they become so quiescent,” the medical historian said.

The famine is the defining event of Ireland’s history. So, why have its effects on health received so little attention? “It’s a really interesting question, and it's one that I’ve asked myself,” Walsh said.

When it comes to studying the effects of fetal malnutrition, she said, the Dutch Hunger Winter Study is the gold standard because of the excellent record keeping. Certainly, the fact that the government did not collect measurements on starving people in the 1850s makes scholarship more challenging, but Walsh agrees that doesn’t fully explain it.

Historically, those in Ireland have been no better than Irish Americans at talking about the famine, she said, which is one reason why the health effects went unexamined for generations.

The famine’s cultural imprint is profound. “There is nothing more shaming for an Irish person than to be unable to be hospitable, and it does manifest itself in feeding, feeding, feeding,” Walsh said. “So, if somebody stops in for a second, you know you're pressing a cup of tea and a biscuit on them if they're in between meals. Meals are big—you’d be shamed to offer a guest a small portion.”

At 26%, obesity rates for adults in Ireland are rising faster than the rest of Europe (although more slowly than the US). Health officials are working to bring this under control.²⁹

When Walsh speaks about the famine’s epigenetic effects to the public, many instantly see connections in their own families, either in mental illness or in obesity and cardiovascular disease. For Irish Americans, “It’s not my fault” is a common reaction.

In Ireland, it took until the 1930s for the Irish Folklore Commission to collect stories of the famine’s remaining survivors. Every child was given a copybook to interview a grandparent or neighborhood elder about their experiences.³⁰

“It is capturing the last generation that might have had direct experience, or at least direct knowledge, from their parents or grandparents, and all sorts of interesting stories come out. But there's a real reluctance to talk about the famine,” Walsh said. Prior to that, most famine discussion involved rhetoric for political purposes, to sow distrust of the British. “It galvanized a lot of Fenian activity.”

“But there's a vast silence,” Walsh said. “It’s the great hunger, but it really is the great silence as well.”

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