Can Long Lost Data Put Heart Healthy Oils To Rest?

Can Long Lost Data Put Heart Healthy Oils To Rest?

Randomized controlled trials—considered the gold standard for medical research—have never shown that linoleic acid-based dietary interventions reduce the risk of heart attacks or deaths.

There’s now more evidence that casts doubt on the traditional “heart-healthy” practice of replacing butter and other saturated fats with corn oil and other vegetable oils high in linoleic acid.

The findings, reported in the British Medical Journal, suggest that using vegetable oils high in linoleic acid might be worse than using butter when it comes to preventing heart disease, though more research needs to be done on that front.

This latest evidence comes from an analysis of previously unpublished data of a large controlled trial conducted in Minnesota nearly 50 years ago, as well as a broader analysis of published data from all similar trials of this dietary intervention.

The analyses show that interventions using linoleic acid–rich oils failed to reduce heart disease and overall mortality even though the intervention reduced cholesterol levels. In the Minnesota study, participants who had greater reduction in serum cholesterol had higher rather than lower risk of death.

“Altogether, this research leads us to conclude that incomplete publication of important data has contributed to the overestimation of benefits—and the underestimation of potential risks—of replacing saturated fat with vegetable oils rich in linoleic acid,” says co-first author Daisy Zamora, a researcher in the psychiatry department at the UNC School of Medicine.

Along with corn oil, linoleic acid-rich oils include safflower oil, soybean oil, sunflower oil, and cottonseed oil.

The belief that replacing saturated fats with vegetable oils improves heart health dates back to the 1960s, when studies began to show that this dietary switch lowered blood cholesterol levels. Since then, some studies, including epidemiological and animal studies, have suggested that this intervention also reduces heart attack risk and related mortality.

In 2009, the American Heart Association reaffirmed its view that a diet low in saturated fat and moderately high (5-10 percent of daily calories) amounts of linoleic acid and other omega-6 unsaturated fatty acids probably benefits the heart.

However, randomized controlled trials—considered the gold standard for medical research—have never shown that linoleic acid–based dietary interventions reduce the risk of heart attacks or deaths.

The largest of these trials, the Minnesota Coronary Experiment (MCE), took place at the University of Minnesota between 1968 and 1973. It enrolled 9,423 patients in six state mental hospitals and one state-run nursing home. Its results did not appear in a medical journal until 1989.

The investigators reported then that a switch to corn oil from butter and other saturated fats did lower cholesterol levels but made no difference in terms of heart attacks, deaths due to heart attacks, or overall deaths.

Data in storage

In the course of investigating the health effects of linoleic acid-rich oils, the team of investigators led by Chris Ramsden, a medical investigator at the National Institutes of Health, came across the MCE study and the 1989 paper.

“Looking closely, we realized that some of the important analyses that the MCE investigators had planned to do were missing from the paper,” Zamora says.

With the help of Robert Frantz, the son of the deceased MCE principal investigator, the team was able to recover much of the raw data from the study, which had been stored away for decades in files and on magnetic tapes. The team also found some trial data and analyses in a University of Minnesota master’s degree thesis written by written by Steven K. Broste, a student of one of the original investigators.

Using the recovered data to perform analyses that had been pre-specified by the MCE investigators but never published, the team confirmed the cholesterol-lowering effect of the dietary intervention. But they also found that in the recovered autopsy records, the corn oil group had almost twice the number of heart attacks as the control group.

Perhaps most strikingly, graphed summaries contained in Broste’s thesis indicated that in the intervention group, women and patients older than 65 experienced roughly 15 percent more deaths during the trial, compared to their control group counterparts.

“We did not recover the individual patient data underlying those graphs and so we couldn’t determine whether those differences were statistically significant,” says Zamora.

She also cautions that the other analyses were based on only partial recovery of patient data from the MCE files, so it would be premature to conclude from them that replacing saturated fats with corn oil is actually harmful to heart health.

Is inflammation the key?

In a much-cited study published in 2013, however, Ramsden, Zamora, and colleagues were able to recover unpublished data from a smaller trial, the Sydney Diet Heart Study, and there they also found more cases of heart disease and death among patients who received a linoleic acid intervention (safflower oil), compared to controls.

Following their recovery of data from the MCE study, the researchers added new data to their existing datasets from the Sydney study and the other three published randomized clinical trials of linoleic acid-based dietary interventions. In a meta-analysis of the combined data, they again found no evidence that these interventions reduced deaths from heart disease or deaths from all causes.

“There were some differences among these studies, but on the whole they didn’t really disagree,” says Zamora.

Why linoleic acid-containing oils would lower cholesterol but worsen or at least fail to reduce heart attack risk is a subject of ongoing research and lively debate. Some studies suggest that these oils can—under certain circumstances—cause inflammation, a known risk factor for heart disease. There is also some evidence they can promote atherosclerosis when the oils are chemically modified in a process called oxidation.

The National Institutes of Health funded this research.

Additional coauthors are from UNC, National Institute on Alcohol Abuse and Alcoholism, NIH/NIAAA, Medtronic Inc., and the Mayo Clinic in Minneapolis, Minnesota.

Source: UNC Chapel Hill

You May Also Like

AVAILABLE LANGUAGES

enafarzh-CNzh-TWdanltlfifrdeeliwhihuiditjakomsnofaplptroruesswsvthtrukurvi

INNERSELF VOICES

happy woman 's face
How To Experience A Mystical State of Consciousness
by Ora Nadrich
Whatever it is we seek pleasure from, relying on external things to give us the high or a feeling…
a blurred clock expanding over a starry background
Horoscope Current Week: December 6 - 12, 2021
by Pam Younghans
This weekly astrological journal is based on planetary influences, and offers perspectives and…
12 05 from rigidity to change 647528 complete
From Rigidity to Change
by Marie T. Russell, InnerSelf.com
In order for things, or people, to change they need to be flexible. A willow tree bends in the wind…
man and dog in front of giant sequoia trees in California
The Art of Constant Wonder: Thank you, Life, for this day
by Pierre Pradervand
One of the greatest secrets of life is to know how to constantly marvel at existence and at the…
Photo: Total Solar Eclipse on August 21, 2017.
Horoscope: Week of November 29 - December 5, 2021
by Pam Younghans
This weekly astrological journal is based on planetary influences, and offers perspectives and…
young boy looking through binoculars
The Power of Five: Five Weeks, Five Months, Five Years
by Shelly Tygielski
At times, we have to let go of what is to make room for what will be. Of course, the very idea of…
man eating fast food
It's Not About the Food: Overeating, Addictions, and Emotions
by Jude Bijou
What if I told you a new diet called the "It's Not About the Food" is gaining popularity and…
woman dancing in the middle of an empty highway with a city skyline in the background
Having the Courage to Be True to Ourselves
by Marie T. Russell, InnerSelf.com
Each one of us is a unique individual, and thus it seems to follow that each one of us has a…
Universal myths legends and prophecies in history
Universal Myths, Legends and Prophecies in our Shared History
by Gwilda Wiyaka
From culture to culture there are similar themes. Ancient civilizations and societies including…
Finally Believing in Yourself: Love Yourself, Love Life, Love Others
Finally Believing in Yourself: Love Yourself, Love Life, Love Others
by Diana Rowan
Many peo­ple suffer from Impostor Syndrome. Even those who have the highest academic, artistic, and…
Searching for the Key to Happiness?
Searching for the Key to Happiness?
by Nancy E. Yearout
Many people are searching for fulfillment. It seems we are all searching for happiness in our…

Selected for InnerSelf Magazine

MOST READ

How Living On The Coast Is Linked To Poor Health
How Living On The Coast Is Linked To Poor Health
by Jackie Cassell, Professor of Primary Care Epidemiology, Honorary Consultant in Public Health, Brighton and Sussex Medical School
The precarious economies of many traditional seaside towns have declined still further since the…
The Most Common Issues for Earth Angels: Love, Fear, and Trust
The Most Common Issues for Earth Angels: Love, Fear, and Trust
by Sonja Grace
As you experience being an earth angel, you will discover that the path of service is riddled with…
How Can I Know What's Best For Me?
How Can I Know What's Best For Me?
by Barbara Berger
One of the biggest things I've discovered working with clients everyday is how extremely difficult…
Honesty: The Only Hope for New Relationships
Honesty: The Only Hope for New Relationships
by Susan Campbell, Ph.D.
According to most of the singles I have met in my travels, the typical dating situation is fraught…
An Astrologer introduces the Nine Dangers of Astrology
An Astrologer introduces the Nine Dangers of Astrology
by Tracy Marks
Astrology is a powerful art, capable of enhancing our lives by enabling us to understand our own…
Giving Up All Hope Could Be Beneficial For You
Giving Up All Hope Could Be Beneficial For You
by Jude Bijou, M.A., M.F.T.
If you're waiting for a change and frustrated it's not happening, maybe it would be beneficial to…
Chakra Healing Therapy: Dancing toward the Inner Champion
Chakra Healing Therapy: Dancing toward the Inner Champion
by Glen Park
Flamenco dancing is a delight to watch. A good flamenco dancer exudes an exuberant self-confidence…
Taking A Step Toward Peace by Changing Our Relationship With Thought
Stepping Toward Peace by Changing Our Relationship With Thought
by John Ptacek
We spend our lives immersed in a flood of thoughts, unaware that another dimension of consciousness…

New Attitudes - New Possibilities

InnerSelf.comClimateImpactNews.com | InnerPower.net
MightyNatural.com | WholisticPolitics.com | InnerSelf Market
Copyright ©1985 - 2021 InnerSelf Publications. All Rights Reserved.