Soy ( Glycine max ) is a bushy plant, belonging to the Fabaceae or Leguminosae family .
Soybeans are consumed from the pods, which contain up to 5 seeds each; it is a traditional food of the Far East (Asia), where it is of primary importance in the collective food regime.
Why reduces cholesterol?
Soy is a legume with excellent properties; most of its nutritional components (some more and some less) have a remarkable IPOcolesterolemizing effect; for this reason it is an advisable food in nutritional therapy aimed at combating this form of dyslipidemia.
The soy nutrients that fight excess cholesterol are: proteins, polyunsaturated lipids, phospholipids, dietary fiber and phytosterols.
Protein
Soy proteins have a good amino acid profile, are rich in arginine and their biological value (VB) is 75 on a scale from 0 to 100.
In addition to this excellent nutritional characteristic, several studies have shown a correlation between the intake of ISOLATE soy protein and decrease in TOTAL cholesterol and LDL cholesterol in subjects suffering from hypercholesterolemia. To tell the truth, it is not yet clear what the mechanism that determines a similar effect is, even if several researches have formulated and proposed some interesting theories.
Among the most quoted there is the receptor interaction of soy proteins with hepatic receptors; it seems that by increasing the soy proteins in the diet, the expression of specific LDL receptors (commonly called bad cholesterol) in liver cells is favored; in this way, the circulating LDLs are picked up more effectively and their plasma concentration decreases significantly. A regular intake of 25-40g / day of soy protein reduces LDL cholesterol and total about 20mg / dl ( Food and Drugs Administration - USA).
It is possible that the mechanism is regulated by the prevalence of the amino acid arginine on lysine ( Diet and heart disease - David Kritchevsky ), furthermore involved in the reduction of arterial pressure; arginine, as a precursor of nitric oxide (NOS), determines an improvement in vessel elasticity and a reduction in cardiovascular risk both for hypertensives and for dysmetabolic drugs in general.
Lipids
Soy lipids useful for the reduction of cholesterol are: polyunsaturated fatty acids, phospholipids and phytosterols .
The polyunsaturated fatty acids (undifferentiated 18: 2 = 3.338g / 100g of soy; 18: 3 = undifferentiated 0.445g / 100g of soy) are known for their ability to positively influence blood lipid levels. Omega-3s mainly act on triglycerides while omega-6s indiscriminately reduce LDL and HDL resulting in a significant reduction in total cholesterol.
The phospholipids contained in soy are made up of lecithin, present in concentrations of about 1500mg / 100g of soy; this emulsifying molecule (which also represents a widespread food additive) acts on hypercholesterolemia in two ways:
- It interacts with cholesterol in the intestinal lumen and, especially in the presence of dietary fiber, reduces its absorption
- After being absorbed, it forms the enzyme ( Lecithin Cholesterol Acyl Transferase - LCAT ) which facilitates the incorporation of free cholesterol into high-density lipoproteins (HDL - "good cholesterol") by raising blood levels.
NB . Lecithin is also a cholesterol stabilizer in bile, in which it plays a protective role against lithiasis (calculosis).
Phytosterols
Soy contains some steroid molecules of vegetable origin, phytosterols; these substances are directly involved in reducing the intestinal absorption of cholesterol because, being chemically related, they bind it and prevent it from passing through the intestinal mucosa.
To be honest, phytosterols (such as isoflavones) are also powerful antioxidants and, regardless of interaction with cholesterol, reduce cardiovascular risk. This happens due to the reduction of oxidative stress on LDL ("bad cholesterol") preserving its ability to bind to hepatic receptors; greater uptake is useful to prevent vascular deposition, therefore atherosclerosis.
NB : Phytosterols are also called phytoestrogens because, after conversion to aglycones by the intestinal bacterial flora, they are absorbed, reprocessed by the liver and poured back into the blood in the form of estrogenic molecules. A greater concentration in phytoestrogens in the diet of those who frequently consume soy may be the key to:
- Less perception of the climacteric syndrome (menopause)
- A lower incidence of osteoporosis
both characteristic of the eastern female population in spite of the western female population.
Soluble fiber
Last but not least, dietary fiber; this component (also contained in other plant foods) retains water and gels the intestinal contents, thus modulating the absorption of nutrients. In addition to regulating the transit inside the digestive tract, the dietary fiber reduces the glycemic curve and hinders the absorption of cholesterol; this capacity, associated with the function of all the other components mentioned above, gives soya a remarkable cholesterol-lowering effect both in absorption and from a metabolic point of view.
