Soya and Cholesterol: Cholesterol-Lowering Eating

Soy foods may help to prevent heart disease by reducing total cholesterol, LDL-cholesterol, blood pressure and possibly preventing plaque build-up in the arteries (atherosclerosis). 

Fact:

  • By lowering LDL-cholesterol, the risk of cardiovascular disease is lowered
  • Dietary changes can lower LDL-cholesterol by 10- 20%

Definitions:

Total Cholesterol: One of the fat (lipid) components in the blood stream (the other one being triglycerides).
It is transported in the blood by lipoproteins, 2 of which are the LDL and HDL cholesterol.
Only found in animal foods and NOT in plants.
Performs several important functions in the body, eg hormone production, skin tone, cell membrane functions, and bone integrity.
An excess can place added stress on the heart tissue.
Ideal level: <4.9mmol/l
LDL Cholesterol: Transports cholesterol to peripheral tissues and liver.
+/- 75% of total cholesterol is found in the LDL fraction; High levels of LDL is a positive risk factor for heart disease.
Ideal level: <2.9mmol/l
HDL Cholesterol: Removes cholesterol from the tissues and transfers it to the liver.
Has a protective role to play because of its function in reverse transport of cholesterol from the peripheral tissues to the liver.
Ideal level: >1.1mmol/l

Cardiovascular / Heart Disease (CVD) = atherosclerosis:

This is a build-up of fatty deposits (called plaque) within the walls of the arteries. As plaque grows, it hinders the flow of blood that carries oxygen and nutrients throughout the body. The very small arteries that thread through the heart and nourish it with blood are particularly susceptible to plaque accumulation. If any of these minute arteries block, a heart attack / stroke can occur.

What blood test is done to check for heart disease?

A LIPOGRAM:

This tests for certain blood fats: cholesterol, triglycerides, LDL cholesterol (= the bad cholesterol) and HDL (= the good cholesterol).

Healthy ranges for blood fats:

Total cholesterol:                    < 4.9 mmol/l

Triglyceride:                           < 1.6 mmol/l

HDL cholesterol:                     > 1    mmol/l

LDL cholesterol:                      < 2.9 mmol/l

WHAT DOES THE RESEARCH SAY ABOUT SOYA AS A DIETARY COMPONENT TO REDUCE RISK OF HEART DISEASE AND AS TREATMENT OF HIGH LIPID LEVELS

 An extensive body of literature indicates that soy food consumption leads to significant decreases in total cholesterol (10– 19%), LDL cholesterol (14–20%), and triglycerides (8–14%). 

  • Soluble fibre in soy beans assists with: Lowering of blood cholesterol levels, especially LDL (the “bad”) Cholesterol

The US Food and Drug Administration’s health claims on viscous fibres, soy protein, plant sterols, and nuts indicate that substantial research of these foods supports their ability to lower serum lipids and, as a result, reduce the risk of heart disease.

In a 2012 study it was  demonstrated that a beverage consisting of 30 g soy protein and 4 g phytosterols added to a Mediterranean-style, low-glycaemic-index diet led to better improvements in lipid markers, such as triglycerides and total cholesterol, in women who were postmenopausal, overweight and had high lipid levels than a low-fat diet without these key phytochemical-rich foods.

  • Essential fatty acids found in soya products (omega-3 and omega-6 fatty acid): Protect cell membranes (including blood vessel lining): admitting healthy nutrients and barring damaging substances, i.e. protecting one from developing atherosclerosis, and thus protective against heart disease
  • Soya products do not contain and of the unhealthy saturated fats which accelerate a build-up of plaque in the arteries.
  • Isoflavones / plant sterols found in soya have proven cholesterol-lowering effects.

Prevention of heart disease:

  • Soy foods may help to prevent heart disease by reducing total cholesterol, LDL-cholesterol, blood pressure and possibly preventing plaque build-up in the arteries (atherosclerosis). 
  • A huge collective research study done in 2012 showed that soy (isoflavones) had an effect of lowering blood pressure in people with hypertension (high blood pressure), but not in those with normal blood pressure.

DIETARY COMPONENTS THAT PLAY A ROLE IN HEART DISEASE

Dietary Components:What Is Main function in treatment of heart disease:Where are these found in foods:
Saturated Fatty Acids

SFAs
A type of fatty acid found concentrated in certain animal and vegetable foods. The more saturated the fat, the harder it is at room temperature (except coconut oil, which is highly saturated but liquid at room temperature).

Saturated fat is associated with raising blood cholesterol.
Coconut oil, butter fat.

Most fats and oils, cocoa butter, fully hydrogenated vegetable oils.

Most fast foods contain saturated fats and oils.
Polyunsaturated Fatty Acids

PUFAs
Main PUFA is linoleic acid. This fatty acid is found in vegetable seeds and the oils they produce. PUFAs have many important roles to play in the treatment of heart disease.Liquid vegetable oils, nuts, seeds.

Meat, poultry, fish, eggs.
Monounsaturated Fatty Acids

MUFAs
Most common MUFA is Oleic acid. Some fish oils, beef fat.

Most fats and oils, nuts, seeds, avocados.
Essential Fatty Acids

EFAs (omega-3,6,9)
Must be supplied in the diet to prevent deficiency symptoms as they cannot be produced in the human body.

Play an essential role in health.

The most important one required on a daily basis is omega-3.
Omega-3 is found predominantly in the flesh of fatty fish, and in fish oils.
Trans Fatty AcidsA dietary fat that is altered during food processing, whereby an oil (liquid) is converted through a process called hydrogenation, into a fat that is solid at room temperature. In this way food manufacturers are able to produce a fat consistency appropriate to the texture of the desired food. This process changes the fatty acids into a trans-fat, which behaves in the body like saturated fats (not good!). Small quantities occur in beef and mutton.
MOST dietary trans-fat comes from margarine (specifically hard brick margarine: contain up to 40-50% of fatty acids in the trans form) and other manufactured foods containing hydrogenated fats, e.g. biscuits, cakes, chocolates, pies, sauces and other manufactured food products.
(Soft margarines are usually free of trans fats).
Plant Sterols Lower cholesterol and risk of heart disease Sterol-enriched margarines (e.g. Flora Pro-Active), also yoghurt and cereal bars.
Soluble Fibre Pectins, gums, mucilages, and some hemicelluloses that form gels with water.
Reduce cholesterol and risk of heart disease.
Fruits and vegetables, especially apples, oranges and carrots;
Oat Bran, barley and legumes, SOYA
Soy protein Proven to lower cholesterol SOYA drinks, SOYA porridges and meat substitutes (be cautious of higher sodium levels in some meat substitutes).
Antioxidants Specific vitamins (Vitamin E, Vitamin C and beta-carotene), also zinc, selenium and flavonoids (found in vegetables and fruit*) which have been proven to reduce the risk of heart disease. Vit E: seed oils, especially wheat-germ oil; salad oil, and margarine.
Vit C: fruits & vegetables, preferably acidic and fresh.
Beta-carotene: yellow and dark green leafy vegetables
* onions, apples, berries and tea

Most important proven dietary strategies to lower cholesterol:      

Research confirms that certain nutrients can provide many heart-healthy benefits.

  • Replace Saturated Fatty Acids and Trans-fats with Polyunsaturated- and Monounsaturated fatty acids
  • Increase intake of plant sterols
  • Lose weight if necessary
  • Increase daily soluble fibre intake

(Oat Bran, legumes and SOYA have definite cholesterol- lowering properties)

In addition, follow these tips to reduce CVD:

  • Include SOY protein
  • Include high doses of antioxidants
  • Decrease sodium (salt) intake
  • Improve lifestyle by exercising regularly

Practical Dietary tips to lower cholesterol

  • Read food labels: minimise intake of Saturated Fatty Acids and trans-fats
  • Eat more vegetables and fruit throughout the day
  • Choose whole-grain, high fibre foods
  • Eat more fish, especially fatty fish: include two servings (200g-400g)/week of oily fish.
  • Include more omega-3 fatty acids daily: found in oily fish, nuts, seeds, canola/olive/avocado/macadamia oils.
  • Include Oat Bran daily (1 tablespoon/day)

NB: References available on request

 

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