Soy and cardiovascular disease PART 1
While in the United States occur annually one million of deaths caused by cardiovascular diseases, which is the main cause of morbidity and mortality, in Japan, the frequency of these diseases is incomparably lower.
It is known that high levels of fats in the blood, especially cholesterol LDL faction, is the major risk factor for cardiovascular diseases.
In recent years, 38 studies show that the replacement of animal proteins in the diet with soy protein is accompanied by a significant decrease of the total cholesterol, low density lipoproteins (LDL) and triglycerides, to maintain high-density lipoprotein concentrations (HDL), ie the “good” cholesterol. Changes in the total cholesterol levels and LDL depends on the initial values. People with the most accentuated hypercholesterolemia benefits the most from the effects of soy proteins.
The lowering of blood lipids occurs through various mechanisms. These include: Hepatobiliary ducts circulation interruption, changes in the hepatic metabolism of cholesterol and lipoprotein and the influencing of the endocrine system.
The increase of bile acids excretion achieved by eating soy “attracts” or removes cholesterol from the body.
Hepatic metabolism is modified by eating soy, in the meaning of growth of the cholesterol synthesis necessary for bile acids production, at the same time with the increasing of the LDL receptors activity, which will fix a higher amount of this cholesterol fraction, thus reducing the blood levels of LDL.
Lowering blood fats is not the only mechanism by which soy lowers the cardiovascular disease risk.
Soy Isoflavones act as antioxidants modifying the metabolic processes involved in the development of atherosclerotic lesions.
It is known that the oxidation of LDL molecules makes them more atherogenic. For this reason, powdered milk and eggs, which currently are used in pastry, bakery, cheeses, especially parmesan, smoked meat, including smoked fish, containing oxidized cholesterol, are particularly harmful.
There are several mechanisms by which components of soy can reduce the LDL oxidation. For example, the phytic acid from soy, by fixing some of the iron in the intestine, can reduce its absorption and can diminish its oxidizing action on proteins and blood lipids. Or genistein, besides the fact that acts as an antioxidant, it increases the activity of several antioxidant enzymes, reducing in this way the oxidation of blood lipoprotein.
Another beneficial effect of genistein is to block the growth factors action, involved in the development of atherosclerotic lesions. But the list has not been exhausted. Genistein inhibits cell adhesion, cell proliferation and angiogenesis, essential processes for the growth of atheroma plaque. Finally, the inhibition by genistein of the tyrosine kinase enzyme activity prevents the forming of the thrombosis at atherosclerotic lesions level.
Feeding monkeys with soy protein and isoflavones that it contains, or casein, the main protein in cow’s milk, showed that after 14 months of atherosclerotic lesions were 90% reduced to those that received soy, compared with monkeys that were casein fed.