LDL cholesterol: Soybean protein may help lower levels - Medical News Today

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Certain proteins in soybeans may have cholesterol-lowering effects. Lucas Ninno/Getty Images

• Researchers studied soybeans to determine why they may have the ability to lower cholesterol.
• The scientists studied different levels of two soybean proteins—glycinin and beta-conglycinin.
• They noted soybeans with increased levels of beta-conglycinin compared to glycinin were better able to regulate cholesterol metabolism and inhibit fatty acid oxidation.
• Eating soybeans with higher levels of beta-conglycinin may help to maintain healthy liver and cardiovascular function.

Since heart disease is the leading cause of death in the U.S., researchers are looking for ways to reduce this number. Having high cholesterol is a risk factor for heart disease, so finding ways to improve high cholesterol is important.

Previous studies have shown that eating soy can reduce the levels of LDL cholesterol—also known as "bad" cholesterol by as much as 4%.

Researchers from the University of Illinois Urbana-Champaign recently looked into different varieties of soybeans to figure out why they can lower LDL cholesterol.

The scientists found one protein in particular that provided benefits and published the study results in the journal Antioxidants.

According to MedlinePlus, cholesterol is a "waxy, fat-like substance that's found in all the cells in your body."

Low-density lipoprotein (LDL) cholesterol is one type that doctors consider to be "bad" cholesterol. The other cholesterol type is high-density lipoprotein (HDL) cholesterol, which doctors consider "good."

If LDL cholesterol levels get too high, the buildup can cause plaques in the walls of your arteries. This contributes to an increased risk of developing heart disease and strokes.

As Beata Rydyger, registered nutritionist based in Los Angeles and a clinical nutritional advisor to Zen Nutrients, noted in an interview with Medical News Today:

"Cholesterol imbalances may result in cardiovascular disease or even neurodegenerative diseases and cancer."

HDL vs. LDL cholesterol

According to the Centers for Disease Control and Prevention (CDC), HDL cholesterol "absorbs cholesterol in the blood and carries it back to the liver. The liver then flushes it from the body."

Having higher levels of HDL cholesterol is a good thing and can reduce heart disease and stroke risk.

The CDC recommends the following cholesterol levels:

• Total cholesterol: approximately 150 mg/dL
• LDL cholesterol: approximately 100 mg/dL
• HDL cholesterol: 40 mg/dL and higher in men and 50 mg/dL and higher in women

The CDC notes that high cholesterol does not typically have signs and symptoms, so it is best to have this checked by a primary health provider at annual physicals.

If someone does have high cholesterol, they can treat it with lifestyle changes (diet and exercise) or medications (statins or cholesterol absorption inhibitors).

Previous research has shown the positive effect of eating more soy on people's cholesterol levels. This new study aimed to understand the mechanism behind the findings.

They suspected this positive effect could be attributed to two proteins—glycinin and B-conglycinin.

The scientists selected 19 varieties of soybeans, each containing different levels of glycinin and B-conglycinin. The ground soybeans were defatted and studied in gastrointestinal digestion simulation experiments.

In the experiments to mimic food digestion, the defatted soybean flour was mixed with fluids and enzymes from oral, gastric, intestinal, and colonic digestion. The researchers ran the simulation using fatty cells.

After running each soybean flour variety through this process, the researchers measured how well the LDL cholesterol was absorbed.

"We measured several parameters associated with cholesterol and lipid metabolism and various other markers— proteins and enzymes—that positively or negatively affect lipid metabolism," says study author Dr. Elvira de Meji, professor of food science at the University of Illinois Urbana-Champaign.

The findings of the study supported the researchers' hypothesis—the two proteins found in soybeans, glycinin and B-conglycinin, contribute to the cholesterol-lowering ability of soybeans.

"The soybean variety affects the protein composition and peptide release under simulated gastrointestinal conditions," write the authors.

The protein B-conglycinin has especially good cholesterol-lowering abilities. The authors found that the peptide released from this protein "reduced HMGCR expression, the concentration of esterified cholesterol and triglycerides, the release of ANGPTL3, and the production of MDA during LDL oxidation."

Some soybean varieties blocked the synthesis of fatty acids as well as triggered LDL absorption into the liver. This could, in theory, lead to a reduction in fatty liver disease.

"These results indicate that the intake of selected soybean varieties might regulate cholesterol and LDL homeostasis and, consequently, foster the prevention of atherosclerotic cardiovascular diseases," write the authors.

Soybeans vs. statins

The researchers also compared the benefits of the soybean flour to Simvastatin, which is a medication used to treat high cholesterol.

The authors found that peptides from the soybean flours had a similar lipid-reducing property as Simvastatin.

"The digested soybeans' peptides were able to reduce lipid accumulation by 50%-70%, and that's very important. That was comparable to the statin, which reduced it by 60%," says Dr. de Mejia.

Dr. Jayne Morgan, cardiologist and clinical director of the Covid Task Force at the Piedmont Healthcare Corporation in Atlanta, spoke with MNT about the study.

"Soybeans have been known to lower triglycerides, total cholesterol, and LDL cholesterol, thereby possibly contributing to a healthier heart profile and becoming part of a heart-healthy lifestyle. This study further complements that," she said.

Dr. Morgan mentioned that she would like to see studies on how soy impacts women.

"The effects of soy on estrogen, especially in menopausal women for women's health, was not addressed, but rather a focus on different species and digestion. I would love to see information on soy and breast cancer as well. Again, more studies focused specifically on women," said Dr. Morgan.

While the researchers tested 19 varieties of soybeans, Rydyger noted that there are more than 2,500 varieties of soybeans. This makes it difficult for people to know what they should consume to receive benefits.

"They can come in all different colors and sizes so it is important to determine if some varieties are more beneficial for heart health than others," mentioned Rydyger.

Isabel Vazquez, registered dietician at Memorial Hermann in Houston, meanwhile, cautioned that "eating soy is not a miracle cure regarding heart health."

"I believe in the benefits of incorporating a plant-based diet for heart health; that would also include eating a variety of plant sources like oats, nuts, and beans," Ms. Vazquez told MNT.