America's most widely consumed oil causes genetic changes in the brain

by University of California - Riverside

Edible fats and oils consumed in the U.S., 2017/18. Credit: USDA

New UC Riverside research shows soybean oil not only leads to obesity and diabetes, but could also affect neurological conditions like autism, Alzheimer's disease, anxiety, and depression.

17 jan2020--Used for fast food frying, added to packaged foods, and fed to livestock, soybean oil is by far the most widely produced and consumed edible oil in the U.S., according to the U.S. Department of Agriculture. In all likelihood, it is not healthy for humans.

It certainly is not good for mice. The new study, published this month in the journal Endocrinology, compared mice fed three different diets high in fat: soybean oil, soybean oil modified to be low in linoleic acid, and coconut oil.

The same UCR research team found in 2015 that soybean oil induces obesity, diabetes, insulin resistance, and fatty liver in mice. Then in a 2017 study, the same group learned that if soybean oil is engineered to be low in linoleic acid, it induces less obesity and insulin resistance.

However, in the study released this month, researchers did not find any difference between the modified and unmodified soybean oil's effects on the brain. Specifically, the scientists found pronounced effects of the oil on the hypothalamus, where a number of critical processes take place.

"The hypothalamus regulates body weight via your metabolism, maintains body temperature, is critical for reproduction and physical growth as well as your response to stress," said Margarita Curras-Collazo, a UCR associate professor of neuroscience and lead author on the study.

The team determined a number of genes in mice fed soybean oil were not functioning correctly. One such gene produces the "love" hormone, oxytocin. In soybean oil-fed mice, levels of oxytocin in the hypothalamus went down.

The research team discovered roughly 100 other genes also affected by the soybean oil diet. They believe this discovery could have ramifications not just for energy metabolism, but also for proper brain function and diseases such as autism or Parkinson's disease. However, it is important to note there is no proof the oil causes these diseases.

Additionally, the team notes the findings only apply to soybean oil—not to other soy products or to other vegetable oils.

"Do not throw out your tofu, soymilk, edamame, or soy sauce," said Frances Sladek, a UCR toxicologist and professor of cell biology. "Many soy products only contain small amounts of the oil, and large amounts of healthful compounds such as essential fatty acids and proteins."

A caveat for readers concerned about their most recent meal is that this study was conducted on mice, and mouse studies do not always translate to the same results in humans.

Also, this study utilized male mice. Because oxytocin is so important for maternal health and promotes mother-child bonding, similar studies need to be performed using female mice.

One additional note on this study—the research team has not yet isolated which chemicals in the oil are responsible for the changes they found in the hypothalamus. But they have ruled out two candidates. It is not linoleic acid, since the modified oil also produced genetic disruptions; nor is it stigmasterol, a cholesterol-like chemical found naturally in soybean oil.

Identifying the compounds responsible for the negative effects is an important area for the team's future research.

"This could help design healthier dietary oils in the future," said Poonamjot Deol, an assistant project scientist in Sladek's laboratory and first author on the study.

"The dogma is that saturated fat is bad and unsaturated fat is good. Soybean oil is a polyunsaturated fat, but the idea that it's good for you is just not proven," Sladek said.

Indeed, coconut oil, which contains saturated fats, produced very few changes in the hypothalamic genes.

"If there's one message I want people to take away, it's this: reduce consumption of soybean oil," Deol said about the most recent study.

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More information: Poonamjot Deol et al, Dysregulation of Hypothalamic Gene Expression and the Oxytocinergic System by Soybean Oil Diets in Male Mice, Endocrinology (2020). DOI: 10.1210/endocr/bqz044

Journal information: Endocrinology 

Provided by University of California - Riverside 

Soy may alleviate hot flashes in menopause, large-scale study finds

In the most comprehensive study to date to examine the effects of soy on menopause, researchers have found that two daily servings of soy can reduce the frequency and severity of hot flashes by up to 26 percent, compared to a placebo.

7 april 2012--The findings, published in Menopause: The Journal of the North American Menopause Association, reviewed 19 previous studies that examined more than 1,200 women.

Although the effectiveness of soy in alleviating hot flashes has been inconclusive, with some studies suggesting soy to be beneficial and others suggesting otherwise, much of the discrepancy is due to small sample sizes and inconsistent methodology, according to the authors.

"When you combine them all, we've found the overall effect is still positive," said Melissa Melby, a medical anthropology professor at the University of Delaware and co-author of the study.

Examining the impact of soy isoflavones, chemicals found in soy that exert a mild estrogen-like effect, Melby and her colleagues found:

• Ingesting at least 54 milligrams of soy isoflavones daily for six weeks to a year reduces menopause hot flash frequency by 20.6 percent and severity by 26 percent, compared to a placebo.
• The total reduction in frequency and severity might be even greater due to the placebo effect.
• In longer duration studies (where women consumed soy isoflavones for 12 weeks or more), the decrease in hot flash frequency was approximately threefold greater than in shorter-duration trials.
• Isoflavone supplements with higher levels (at least 19 milligrams) of genistein, one of the two main types of isoflavones, were more than twice as effective at reducing hot flash frequency than lower amounts.

Melby called the genistein result particularly notable because the compound is the primary isoflavone in soybeans and soy foods, suggesting that, "Eating soy foods, or using supplements derived from whole soybeans, may work better for women."

Each gram of soy protein in soybeans and traditional soyfoods provides approximately 3.5 mg of isoflavones. Two glasses (16 oz) of soymilk or seven ounces of tofu provide approximately 50 mg of isoflavones.

The interest in soy and menopause stems from observational evidence in Japan, where researchers have found the low frequency of hot flashes in Japanese women might be attributed to the high soy consumption that often begins in utero and continues throughout their lifespan.

"Soy is probably more effective in these women," Melby said. "But if you're 50 and you've never touched soy, it's not too late. We've found that it still helps."

Provided by University of Delaware

Soybean Compound Improves Vascular Function in Stroke Patients

By Todd Neale
HONG KONG, 29 sept 2008 -- Endothelial function in ischemic stroke patients can be significantly improved by supplementation with a compound found in soybeans, a randomized placebo-controlled trial showed.
After 12 weeks, patients who had been taking once-daily oral isoflavone had significantly greater flow-mediated dilation of the brachial artery compared with those who had been taking placebo (P=0.035), Hung-Fat Tse, M.D., Ph.D., of the University of Hong Kong's Queen Mary Hospital, and colleagues reported online in the European Heart Journal.
"These findings may have important implications for the use of isoflavone for secondary prevention in patients with cardiovascular disease, on top of conventional interventions," the researchers said.
However, Dr. Tse said, patients should not start supplementing their diets with the compound or eating more foods rich with isoflavone on the basis of the results.
"At this juncture," he said, "regular isoflavone supplementation might not be advocated since the benefits and side effects of long-term supplementation are still unknown."
In addition, the researchers said, the treatment effect was comparable to that achieved through endurance training or statin therapy.
Dr. Tse and colleagues previously showed improved vascular endothelial function with isoflavone supplementation in patients at high risk for cardiovascular disease, but it remained unknown whether patients with established cardiovascular disease would derive the same benefits.
So they randomized 50 patients who had suffered a first or recurrent ischemic stroke more than six months previously to 80 mg of isoflavone daily and 52 to placebo for 12 weeks.
Overall, the mean age of the patients was 66, and 66% were men. Nine percent had had a recurrent stroke, 10% had coronary artery disease, and 47% had diabetes.
Fasting brachial flow-mediated dilation was measured using ultrasound at baseline and at 12 weeks. The dilation was induced by inflating and releasing a pneumatic tourniquet on the patients' forearms.
A flow-mediated dilation value of 3.7% or lower was considered impaired. The vast majority of the patients (80%) had impaired function at baseline and there were no significant differences between the groups.
By the end of the study, flow-mediated dilation was 1% better in the treatment group than in the placebo group (P=0.035).
In addition, the prevalence of impaired flow-mediated dilation was significantly lower in the treatment group (58% versus 79%, P=0.023).
After adjusting for baseline flow-mediated dilation, isoflavone supplementation was associated with a 68% reduction in the prevalence of endothelial impairment (OR 0.32, 95% CI 0.13 to 0.80, P=0.014).
The effect was greatest in patients with more severe endothelial dysfunction at baseline (P<0.001).
"The findings suggest that isoflavone exerts a secondary vascular protective effect in patients with established atherosclerosis, despite a lack of effect on conventional cardiovascular risk factors including blood pressure, lipid profile, and blood glucose," the researchers said.
Isoflavone supplementation also caused a significant 1.7 mg/dL decrease in high-sensitivity C-reactive protein (P=0.033), which might partly explain the improvement in endothelial function, the researchers said.
Other possible mechanisms include direct action on vasorelaxation, modulation of platelet function, and antioxidant and hypocholesterolemic effects, although the results suggested the latter two explanations do not apply, they said.
In addition, they said, isoflavone is a type of phytoestrogen and its function as a partial estrogen agonist may explain the cardiovascular benefits.
The researchers noted that the treatment effect of isoflavone supplementation may have been underestimated because background isoflavone consumption is higher in Asian populations than in those consuming western diets.
The study was funded by CRCG small project funding from the University of Hong Kong, the Sun Chieh Yeh Heart Foundation, an Outstanding Young Investigator Award from the University of Hong Kong, and an unconditional research donation from Great Liaison Limited in Hong Kong.
The authors did not declare any conflicts of interest.
Primary source: European Heart JournalSource reference:Chan Y-H, et al "Reduction of C-reactive protein with isoflavone supplement reverses endothelial dysfunction in patients with ischemic stroke" Eur Heart J 2008; DOI: 10.1093/eurheartj/ehn409.