Tagged DNA (Deoxyribonucleic Acid)

Breast-Fed Babies May Have Longer Telomeres, Tied to Longevity

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Credit Roberto Schmidt/Agence France-Presse — Getty Images

Breast-fed babies have healthier immune systems, score higher on I.Q. tests and may be less prone to obesity than other babies.

Now new research reveals another possible difference in breast-fed babies: They may have longer telomeres.

Telomeres are stretches of DNA that cap the ends of chromosomes and protect the genes from damage. They’re often compared to the plastic tips at the end of shoelaces that prevent laces from unraveling. Telomeres shorten as cells divide and as people age, and shorter telomeres in adulthood are associated with chronic diseases like diabetes. Some studies have linked longer telomeres to longevity.

The new study, published in The American Journal of Clinical Nutrition, is a hopeful one, its authors say, because it suggests telomere length in early life may be malleable. The researchers, who have been following a group of children since birth, measured the telomeres of 4- and 5-year-olds, and discovered that children who consumed only breast milk for the first four to six weeks of life had significantly longer telomeres than those who were given formula, juices, teas or sugar water.

Drinking fruit juice every day during the toddler years and a lot of soda at age 4 was also associated with short telomeres.

Socioeconomic differences among mothers can muddy findings about breast-feeding because the practice is more common among more educated mothers. However, this group of children was fairly homogeneous. All of them were born in San Francisco to low-income Latina mothers, most of whom qualified for a government food program.

“This adds to the burgeoning evidence that when we make it easier for mothers to breast-feed, we make mothers and babies healthier,” said Dr. Alison M. Stuebe, an expert on breast-feeding who is the medical director of lactation services at UNC Health Care in Chapel Hill, N.C., and was not involved in the study. “The more we learn about breast milk, the more it’s clear it is pretty awesome and does a lot of cool stuff.”

The study did not establish whether or not breast-feeding enhanced telomere length. It may be that babies born with longer telomeres are more likely to succeed at breast-feeding. A major drawback of the research was that telomere length was only measured at one point in time, when the children were 4 or 5 years old. There was no data on telomere length at birth or during the first few months of life.

“We don’t have a baseline to see if these kids were different when they came out,” Dr. Stuebe said. “It could be that really healthy babies can latch on and feed well, and they already had longer telomeres. It could be successful breast-feeding is a sign of a more robust kid.”

The researchers were following children who were part of the Hispanic Eating and Nutrition study, a group of 201 babies born in San Francisco to Latina mothers recruited in 2006 and 2007 while they were still pregnant. The goal of the research was to see how early life experiences, eating habits and environment influence growth and the development of cardiac and metabolic diseases as children grow.

Researchers measured the babies’ weight and height when the children were born. At four to six weeks of age, they gathered detailed information about feeding practices, including whether the baby had breast milk and for how long, and whether other milk substitutes were used, such as formula, sugar-sweetened beverages, juices, flavored milks and waters. Information was also gathered about the mothers.

Children were considered to have been exclusively breast-fed at 4 to 6 weeks of age if they received nothing but breast milk, as well as medicine or vitamins.

When the children were 4 and 5 years old, researchers took blood spot samples that could be used to measure the telomeres in leukocytes, which are white blood cells, from 121 children. They found that children who were being exclusively breast-fed at 4 to 6 weeks of age had telomeres that were about 5 percent longer, or approximately 350 base pairs longer, than children who were not.

The new findings may help explain the trove of benefits that accrue from breast-feeding, said Janet M. Wojcicki, an associate professor of pediatrics and epidemiology at the University of California, San Francisco, and the paper’s lead author.

“What’s remarkable about breast-feeding is its ability to improve health across organ systems,” Dr. Wojcicki said. “Telomere biology is so central to the processes of aging, human health and disease, and may be the link to how breast-feeding impacts human health on so many levels.”

There are several possible explanations for the correlation between breast-feeding and longer telomeres. Breast milk contains anti-inflammatory compounds, which may confer a protective effect on telomeres. It’s also possible that parents who exclusively breast-feed their babies are more scrupulous about a healthy diet generally.

Yet another possibility is that breast-feeding is a proxy for the quality of mother-child attachment and bonding, said Dr. Pathik D. Wadhwa, who was not involved in the research but studies early-life determinants of health at the University of California, Irvine School of Medicine. “We know from studies looking at telomere length changes in babies who came from orphanages that the quality of the attachment and interaction, and more generally the quality of care that babies receive, plays a role in the rate of change in telomere length,” he said.

When children are exposed to adversity, neglect or violence at an early age, “psychological stress creates a biochemical environment of elevated free radicals, inflammation and stress hormones that can be harmful to telomeres,” said Elissa Epel, one of the authors of the study who is a professor at the University of California, San Francisco, and director of the Aging, Metabolism and Emotions Lab.

“The idea that breast-feeding may be protective for telomeres is heartening because we don’t know much about what’s going to help protect them in children, besides avoiding toxic stress. And boy, do we want to know,” Dr. Epel said.

Although genes can’t be changed, Dr. Epel said, “This is part of the genome that appears to be at least partly under personal control.”

Meeting My DNA

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Marie Tae McDermott and her dog, Cody, at Bushwhick Inlet Park in Brooklyn.

Marie Tae McDermott and her dog, Cody, at Bushwhick Inlet Park in Brooklyn.Credit Andrew Renneisen for The New York Times

I was adopted when I was 6 months old, so I don’t know much about my family medical history. I don’t know, for example, whether I’m at increased risk for breast cancer, heart disease, mental illness. But home DNA testing is changing all that.

The tests are sent through the mail, no lab visits required. And they’re not limited to the human genome.

I tested the DNA waters with Cody, my four-legged adoptee. After shelling out $69 for a Wisdom Panel DNA test kit, I swabbed the inside of Cody’s cheek with a cotton swab from the kit and dropped it in the mail. Six weeks later I received Cody’s genealogy chart by email. While I’d always considered him pure mutt, with his apple-shaped head and stocky middle, results showed an uninterrupted lineage of Chihuahuas going back three generations.

I could only hope for such clarity. I ordered a kit from 23andMe, one of a handful of companies that now offer home testing for humans. Unlike the other major genetic testing companies Ancestry and Family Tree DNA, 23andMe offers both health and ancestry results. The cost is $199.

As with Cody, I collected a saliva sample and dropped it in the mail. A few weeks later, I got an email saying my results were ready. I logged on to the website to see my ancestry composition distilled into a pie chart. The chart showed that my ancestors hailed from Korea, something I’d already been told. What I didn’t expect to see were the smaller slices indicating I had Japanese and Chinese ancestors scattered in. Seeing my genealogy for the first time was thrilling.

23andMe also scanned its database of others who had submitted their genetic material to the company for potential DNA matches. It identified over a hundred of my relatives, ranging from fourth to eighth cousins. 23andMe predicts that the average person has around half a million eighth cousins. The number gets exponentially larger as you go back generations. Some geneticists believe that all humans are at least 50th cousins with one another.

A messaging tool on the 23andMe website also allows you to connect with DNA relatives who’ve also taken the test. I eagerly exchanged messages with four of my distant cousins: the parent of a Chinese adoptee living in the Netherlands, the stepfather of a fifth cousin in the Philippines and a fellow Korean adoptee. Nobody could tell me more about my genealogy.

Only a fourth cousin named Henry who lives in California could shed light on a common ancestor who lived in Japan in the 1700s. He wrote in an email: “It would be an okay assumption that you may have genes to my father’s side, as his family was not in the bushi/samurai class, but comfortable merchants. Also, my patriarchal prefecture was sort of a ‘doorway’ to Japan.” Henry and I became Facebook friends, but I still have no tangible information about my ancestors.

Joy Lieberthal, a clinical social worker who specializes in issues related to adoption, said that for adoptees digging into their past, it’s important to look at the big picture. She explained that genetic testing kits really just give adoptees a history lesson in migration and land conflict over time, and that it’s important not to overstate the importance of the results. The bottom line: Just have fun with it.

In my health report, some of the inherited traits ranged from the frivolous (my sensitivity to bitter tastes) to T.M.I. (my type of earwax). It did pinpoint some of my physical attributes, like eye and hair color. It confirmed that I was lactose intolerant and predicted my athletic performance, based on my type of muscle fiber, compared to world class athletes. It suggested that, were I a runner, I would be better suited for sprinting than cross-country. It also confirmed that I lacked an enzyme to process and detoxify ethanol, making me sensitive to alcohol.

Over all, I was tested for 122 health risks and 53 inherited conditions. It showed I had a slightly higher than average risk for developing rheumatoid arthritis and ulcerative colitis and no inherited conditions. I had an elevated risk for developing restless leg syndrome. Was that why I felt that strange, jumpy sensation in my legs a few months ago? I made a note to mention this to my doctor at my next physical.

Through social media, I found other adoptees who had used DNA testing. An adoptee named Bee told me that her DNA test confirmed that she suffered from a rare and incurable genetic disease that affects her kidneys; with the results from her test, she was able to go to her doctor for an official diagnosis. She later learned that she had passed on the disease to her daughter, she told me.

Another adoptee named Janine, who was born in Korea and told by her adoptive parents that she was of mixed race, ordered a DNA kit so that she could learn about her biological father’s European lineage. Her ancestry results indicated she was 99.9 percent East Asian and only 0.1 percent European – hardly mixed race.

For me, DNA confirmed what I already knew: that the past is murky. After Henry’s email, follow-up messages from the relatives I was in contact with remained unanswered. It’s fun to think that I share some of my 20,000 genes with total strangers. But I think I’ll leave it at that. Piecing together a 20,000-piece jigsaw puzzle is a task too monumental to think about.

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