Experts explain how soya reduces blood pressure
Stories by Sade Oguntola
Soya milk is very nutritious
SOYFOODS said to lower cholesterol levels and
benefit the heart by keeping blood pressure levels
down, a new animal study is suggesting does this by stimulating the working of the enzyme that help to relax the blood vessels and achieve a better blood flow, experts have said.
High blood pressure is a major risk factor for heart disease, and recent evidence suggests that it is increasing across the globe, with more than 1.5 billion people expected to have high blood pressure by 2025, or around one in three adults over the age 20.
According to the study, soya stimulates a better flow of blood due to an isoflavone, genistein, it contains and so could have implications for high blood pressure in humans.
Rats, bred to suffer from high blood pressure (hypertension), were found to benefit from dietary supplementation of genistein. Not only was the level of this enzyme required to relax the blood vessels restored, it also improved on its amount, thus ensuring better health of blood vessels, reported the new study in the Journal of Nutrition.
Hongwei Si and Dongmin Liu from Virginia Polytechnic Institute and State University wrote that the effect of genistein on the blood vessel wall was different from its formal known actions, leading to increased expression and synthesis of these enzymes responsible for relaxation of these blood vessels by 1.8 to 2.6-fold, thereby improving hypertension.
The amount genistein required to achieve this, they said are “physiologically achievable concentrations in individuals consuming soy products.
Initially several small-scale clinical trials suggested that short-term soy consumption can lower blood pressure and that the usual intake of soyfoods has effect on blood pressure in general populations.
A trial, assessing the effect of the protein-rich food over two to three years, found that soy intake was inversely associated with both systolic and diastolic blood pressure, particularly among elderly women.
A team from the Vanderbilt University Medical Centre in the US and the Shanghai Cancer Institute in China measured the usual intake of soyfoods at baseline among 45,694 participants of the Shanghai Women’s Health Study. The women were aged 40 to 70 years old and had no history of hypertension, diabetes, or cardiovascular disease when they started the trial. Blood pressure levels were measured two to three years after the initial data were collected.
Analysis of the new data revealed that soy protein intake was inversely associated with blood pressure, after adjustment for age, body mass index, and lifestyle and other dietary factors.
In women who consumed at least 25g of soy protein each day, the adjusted mean systolic blood pressure was 1.9 mm Hg lower and the diastolic blood pressure was 0.9 mm Hg lower than in women consuming less than 2.5g per day, reported the researchers in an issue of the American Journal of Clinical Nutrition.
They also found that the inverse associations became stronger with increasing age. Among women who were over 60 years old, the corresponding differences were -4.9 mm Hg for systolic BP and -2.2 mm Hg for diastolic BP.
Meanwhile experts said that the cholesterol-lowering effects of soy protein may by located in the liver according to a new research from Korea University and Nestlé Research Center, filling in the gaps in the understanding of the heart healthy benefits of soy.
Soybean protein hydrolysate (SPH) was found to stimulate the low-density lipoprotein receptor (LDL-R) transcription in liver cells, reported the researchers in the Journal of Agricultural and Food Chemistry.
The researchers, led by Cherl-Ho Lee, incubated liver cells with a treated form of soy protein and found that LDL-R transcription was strongly stimulated. They said more work is yet to be done to demonstrate the exact target of these soybean peptides in the lever cells.
Of the isoflavones contained in soybeans, two - genistein and daidzein - seem to hold the most promise from the preventive and therapeutic point of view. Genistein and daidzein are present in high concentrations (up to 3 mg/g) in natural soybeans.
Soy also contains genistin and daidzin (glucosides), which are sugar containing isoflavones molecules. During digestion, intestinal bacteria cleave or cut off the sugar molecules, creating still more genistein and daidzein (aglycones) to be used by the body.
Researchers are increasingly looking at dietary intervention to high blood pressure, with evidence for the positive effect of milk proteins on hypertension leading to new functional foods. Meanwhile, evidences continue to support dietary soybean protein supplementation to prevent and treat hypertension, attesting to the link between blood pressure and dietary macronutrient intake.
Grapefruit may help combat hepatitis C
A compound that
naturally occurs
in grapefruit and other citrus fruits may be able to block the secretion of hepatitis C virus (HCV) from infected cells, a process required to maintain chronic infection.
Scientists at the Massachusetts General Hospital Centre for Engineering in Medicine (MGH-CEM), reported that a common flavonoid, naringenin, found naturally in these fruits, aids in blocking the secretion of HCV from infected cells.
The study led by Yaakov Nahmias, PhD, of the MGH-CEM, reported that HCV is bound to very low-density lipoprotein (vLDL, a so-called bad cholesterol) when it is secreted from liver cells, adding that the viral secretion required to pass infection to other cells may be blocked this way.
It is said that because the virus does not integrate its genetic material into the DNA of infected cells like HIV, it is possible to totally clear the virus if secreted virus was not infecting new cells.
According to the report that is in an online issue of the journal Hepatology, if the results of this study extend to human patients, a combination of naringenin and antiviral medication might allow patient to clear the virus from their livers.
HCV is the leading cause of chronic viral liver disease in the world. The current antiviral medications are effective in only half of infected patients, 70 per cent of whom develop chronic infection that can lead to cirrhosis or liver cancer. Since the virus does not integrate its genetic material into the DNA of infected cells the way HIV does, totally clearing the virus could be possible if secreted virus was not infecting new cells.
Yaakov Nahmias, PhD, of the MGH-CEM, the paper’s lead author said identifying the route by which HCV is released from cells introduces a new therapeutic target. “That pathway’s dependence on cholesterol metabolism could allow us to interfere with viral propagation to other cells and tissues, using tools already developed for atherosclerosis (a disease in which plaque builds up on the insides of your arteries) treatment, “ he stated.
This work presented the possibility that non-toxic levels of a dietary supplement, such as naringenin, could effectively block HCV secretion. This approach might eventually be used to treat patients who do not respond to or cannot take traditional interferon-based treatment or be used in combination with other agents to boost success rates.
Grapefruit’s bitter taste is caused the presence of the flavonoid naringenin, which is metabolised into naringenin, an antioxidant previously reported to help lower cholesterol levels.
Considerable research has suggested that HCV infects liver cells by, in essence, “hitching a ride” onto the natural lipoprotein-cholesterol metabolic pathway.
Since earlier evidence has shown that naringenin can reduce secretion of vLDL from liver cells, the researchers examined whether the compound might also lower HCV secretion from infected cells.
Their experiments confirmed that naringenin does reduce the secretion of HCV from infected cell lines and showed that the compound inhibits the mechanism for secreting a specific lipoprotein that binds HCV.
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