Fiber and cardiovascular disease

Diets rich in fiber clearly reduce the risk of suffering from cardiovascular disease or dying from it, although this effect is due to the fiber from cereals and fruits (insoluble fiber).

Different factors have been identified that play an important role in the origin and maintenance of cardiovascular disease, including cholesterol (hypercholesterolemia), sugar (diabetes mellitus) and obesity.

The benefits of fiber in the prevention of cardiovascular disease are due to its effects on these factors: fiber lowers cholesterol and blood sugar levels, lowers blood pressure, reduces blood sugar peaks that occur When we eat, it increases the sensitivity of the tissues to the action of insulin, and promotes weight loss.

But, in addition, fiber is usually accompanied by a type of diet that provides other elements that are also beneficial to reduce cardiovascular disease, such as polyphenols, antioxidants, vitamins, omega 3 acids, etc.

Interestingly, soluble fiber, which has not convincingly shown a protective role against the onset of cardiovascular disease, is the one that produces all these effects on cholesterol and blood sugar, on blood pressure figures and on weight bodily. On the other hand, insoluble fiber would not have these effects that soluble fiber has, although it does help you lose weight and it does reduce cardiovascular disease.

The reduction of cholesterol in the blood by soluble fiber is due to several mechanisms:

• Fiber sequesters bile acids and cholesterol in the intestine and favors their elimination with the feces, which prevents the absorption of saturated fats and cholesterol, and their arrival in the liver and blood.
• Fiber is broken down in the large intestine by the bacteria there, producing short-chain fatty acids (acetate and propionate) that reach the liver and inhibit cholesterol synthesis.
• Fiber forms viscous gels in the intestine along with food; This gel acts as a physical barrier for the absorption of bile acids, cholesterol and saturated fats.
• Some foods rich in fiber also contain considerable amounts of substances with vitamin E activity, which would inhibit the synthesis of cholesterol by the liver.
• Fiber reduces blood sugar spikes, so less insulin is made to counteract those spikes in blood sugar. Insulin stimulates the main enzyme involved in the synthesis of cholesterol in the liver. Therefore, as there is less insulin, this enzyme would be less active and less cholesterol would be manufactured.

We must also consider that diets rich in fiber tend to contain less saturated fat, which helps reduce cholesterol levels.

Although it lowers total cholesterol and LDL cholesterol, soluble fiber would not lower HDL cholesterol and triglycerides. And it seems that the effect of lowering cholesterol is greater in patients with higher blood cholesterol levels.

However, the decrease in blood cholesterol produced by fiber is not very important: approximately 2 mg / dL for each gram of soluble fiber added to the diet. For example, eating two apples a day supposes 2 g of pectin, so it can be expected that LDL cholesterol will be reduced by about 4 mg / dL as long as the consumption of this fruit is maintained.

The effect of reducing blood sugar peaks that soluble fiber has is related to its degree of viscosity, which adsorbs sugars and delays their absorption, while causing a delay in stomach emptying causes sugars to arrive more slowly to the intestine to be absorbed.

In addition, if the amount of sugar that reaches the blood is decreased, less insulin is also produced. High levels of insulin or hyperinsulinemia are also a risk factor for the presentation of cardiovascular disease.

The mechanisms by which soluble fiber reduces blood pressure figures would be the reduction of insulin (as we have just discussed) and the improvement of the function of the arterial wall. The improvement in the function of the artery would prevent it from reducing its diameter, which is a cause of hypertension.

On the other hand, the low levels of insulin in the blood cause the kidney to lose little sodium (salt), with the consequent increase in sodium in the blood and the amount of water in the blood, which is another mechanism of production of. The antihypertensive effect of fiber can also contribute to the potassium content of foods that are also rich in fiber.

The mechanisms by which a diet rich in fiber would contribute to reducing obesity are, on the one hand, the ability of fiber to retain water and increase the volume of the food bolus in the stomach, which reduces the speed of gastric emptying and increases the feeling of satiety.

On the other hand, more chewing of foods containing fiber is needed, which leads to prolong the time for their ingestion.