“Cardiovascular diseases (CVDs) are the leading cause of death globally. An estimated 17.9 million people died from CVDs in 2019, representing 32% of all global deaths. Of these deaths, 85% were due to heart attack and stroke.”
– World Health Organization, 2021
These numbers have risen since 2021, with unhealthy eating habits, stress, smoking, and sedentary lifestyles being the prime contributing factors. There is some degree to which age contributes to the incidence of CVD, as arterial (blood vessel) walls lose their flexibility and elasticity over time, thereby restricting the rate and ease at which blood flows through them. However, the factors mentioned previously are all elements that can be monitored and controlled by our own accord. Before we see where tea comes into all of this, let’s take a brief look at the science behind CVD.
What is cardiovascular disease?
Cardiovascular disease refers to health conditions pertaining to the heart and blood vessels. The heart is responsible for pumping blood out to the body, and blood vessels are responsible for supplying every tissue and organ in the body with blood. This includes the supply and circulation of blood within the heart as well, via coronary arteries. Any blockage within these arteries could result in an interruption of blood flow to a particular part of the heart, resulting in a myocardial infarction, or what we commonly refer to as a ‘heart attack’. Complete blockage of a major coronary artery could potentially be fatal.
The occurrence of the same process in the brain is known as cerebrovascular disease, or what we commonly refer to as a ‘stroke’. Again, depending on the degree and location of blockage, the outcome could have lifelong consequences or potentially be fatal.
What causes CVD and stroke?
These types of CVDs develop over time, with a gradual deposition of fat, cholesterol or other substances on the inner arterial wall. This phenomenon, known as atherosclerosis, leads to plaque formation that eventually narrows the blood vessel, restricting blood flow through it. There are several factors to which this plaque formation could be attributed, including:
- High blood cholesterol, triglycerides, lipid (fat) levels.
- High blood pressure.
- High blood sugar (diabetes).
- Blood clotting.
- Oxidative stress.
- Inflammation.
These factors, therefore, inadvertently become risk factors for the incidence of CVD / heart attacks and strokes.
So, where does tea come into all of this? Let’s look into each aspect.
How can tea help to lower blood cholesterol levels?
Cholesterol and lipids bind onto proteins, forming lipoproteins, for circulation in the bloodstream. High density lipoproteins (HDL) carry cholesterol and lipids from the bloodstream to organs, while low density lipoproteins (LDL) carry cholesterol and lipids from organs into the bloodstream. Since elevated blood cholesterol and lipid levels increase the risk of CVD and stroke, we casually refer to HDL as ‘good cholesterol’ and LDL as ‘bad cholesterol’. Research shows that tea consumption is associated with a reduction in LDL levels, thereby reducing the absorption of cholesterol and lipids from the food we consume into the bloodstream, and subsequently reducing the risk of CVD and stroke.
How can tea help to regulate blood pressure?
The endothelium (inner wall of blood vessels) plays a role in regulating blood pressure as it modulates the constriction (narrowing) and dilation (widening) of blood vessels. Dysfunction of this layer, with age or otherwise, could result in an increase in blood pressure, which then becomes a predisposition to CVD and stroke. Tea is rich in flavonoids, which have been shown to improve endothelial function, which would help to maintain healthy blood pressure, and subsequently lower the risk of developing CVD and stroke.
How can tea help to lower blood sugar levels?
Elevated blood glucose levels can, over time, cause damage to different organs including the heart and blood vessels, thereby increasing the risk of CVD and stroke. While Type 1 diabetes has a genetic predisposition, Type 2 diabetes is generally caused by inefficient insulin function or excessive absorption of glucose from the digestive tract into the bloodstream. Studies show that tea consumption can improve the effectiveness of insulin, while also reducing or regulating the absorption of glucose into the bloodstream. This thereby reduces the risk of developing Type 2 diabetes, subsequently lowering the risk of CVD and stroke.
How can tea help to reduce blood clotting?
Platelet cells are involved in the blood clotting process in our body. The unwarranted formation and circulation of blood clots can lead to blockage of arteries and increase the risk of CVD and stroke. Tea has been found to reduce this risk by interfering with the clotting process of platelets, thereby lowering the potential for CVD and stroke.
How can tea help to reduce oxidative stress?
Oxidative stress – high levels of reactive oxygen species (ROS) and free radicals (FR) in the bloodstream – can increase plaque formation in arteries, which can lead to CVD and stroke. Tea is rich in antioxidants, which neutralise ROS and FR, thereby reducing oxidative stress and subsequently lowering the risk of CVD and stroke.
How can tea help to reduce inflammation?
While inflammation is an essential immunological process, chronic inflammation can lead to an increase in oxidative stress and contribute towards plaque formation in arteries. These, in turn, could cause CVD and stroke. Polyphenols in tea have been found to have anti-inflammatory properties, thereby countering the potential effects of inflammation and subsequently lowering the risk of CVD and stroke.
Considering the trove of scientific information that we have tried to summarise here, we can say with a large degree of certainty that the consumption of tea can help to lower the risk of incidence of CVD and stroke. You can learn more about the health benefits related to tea drinking in Prof. Tissa Amarakoon’s comprehensive compilation – Tea and Your Health.
