HOW DIET AFFECTS BLOOD PRESSURE

Hypertension Day, a day earmarked for raising awareness about high blood pressure and encouraging individuals to have their blood pressure checked and adopt heart healthy lifestyles. But first we need to know what blood pressure is and why high blood pressure is so dangerous.

WHAT IS BLOOD PRESSURE AND HYPERTENSION?

Blood pressure is the pressure or force that the blood exerts on the arterial wall. The systolic blood pressure (upper value) refers to the force of the blood on the arterial wall when the heart beats whereas the diastolic pressure (lower value) refers to the force when the heart rests. High blood pressure, also called hypertension, is when the pressure of the blood being pumped is abnormally high1. 

Blood pressure has also been described as how easy or difficult it is for your heart to pump the blood throughout the body.  With increased blood pressure the heart works a lot harder to circulate the blood which can cause an enlarged heart and heart failure. When your blood pressure is high for an extended period it can damage arteries that can burst or clog more easily, leading to a stroke or heart attack. As hypertension damages blood vessels, it can also cause visual impairment, kidney disease and dementia1.

HYPERTENSION AS A GLOBAL SILENT KILLER

Globally, hypertension causes 7.5 million deaths annually and nearly 1 billion people have uncontrolled hypertension2.  Hypertension usually presents without any symptoms and most individuals are unaware that they are hypertensive. Hypertension has therefore been described as the “silent killer” and is responsible for 13% of all deaths in South Africa3. Hypertension increases the risk for a stroke four-fold, while doubling the risk for a heart attack4.

WHAT CAUSES HIGH BLOOD PRESSURE? 

There are many risk factors for high blood pressure, including medical conditions and genetics. Lifestyle factors like unhealthy eating, stress, not exercising, smoking, being overweight and alcohol abuse can also lead to hypertension5.

SALT AND HYPERTENSION

Making a habit of consuming more than the recommended amount of salt can lead to hypertension6. According to the World Health Organization, we should be consuming less than 5g of salt (1 level teaspoon) a day7. South Africans consume 6 to 11g of salt every day, double the recommended amount8. This puts South Africans at an increased risk for developing hypertension and the consequent diseased. 

But when we think about salt and reducing our consumption, it’s not only the salt found in the saltshaker that is the culprit. Only 40% of the salt that we consume is added while cooking. More than half (55%) of the salt South Africans consume are already present in processed foods when we buy them9. In South Africa, the top contributors to daily salt intake are bread, processed meat products, soup/gravy powder, meat and vegetable extract, hard/block margarine, savoury snacks (including crisps) and breakfast cereals8&9.

Fortunately, the South African government took charge and implemented legislation that regulate the amount of salt present in foods sold in South Africa. Even though these foods may contain less salt than they used to, it is still our responsibility to decrease the amount of high salt foods we consume and to stop adding high salt ingredients to our food when cooking and eating. 

OTHER DIETARY AND LIFESTYLE CHANGES TO LOWER BLOOD PRESSURE

As discussed, there are many risk factors for hypertension. Some of these risk factors cannot be changed, like your age, gender and family history. There are however lifestyle adjustments that can prevent or control hypertension. Unhealthy behaviours need to be modified and changed:

• Stop smoking. Even reducing the number of cigarettes smoked daily can improve your blood pressure.
• If you are living a sedentary lifestyle, your risk for developing hypertension is greater. Being active lowers blood pressure levels and reduces stress. You don’t necessarily need to join a gym to be active. Walking in your neighbourhood at a brisk pace for 30min, three times or more a week is sufficient.
• Being overweight significantly increases blood pressure. If you are overweight or obese, you need to lose weight to reach a normal BMI. BMI refers to your Body Mass Index or more simply put, your weight for height ratio. A BMI above 24.9 kg.m2 means that you are overweight, and you need to lose those extra kilograms.
• Eat five fruits and vegetables a day. The antioxidants in fruit and vegetables helps to protect blood vessels.

CONCLUSION

Although there are many factors that contribute to the development of hypertension, many of these factors are modifiable. It is up to every individual to take responsibility for their health by adopting healthy lifestyles and limiting behaviour that might increase one’s risk for hypertension. 

As hypertension can develop at any age, it is important to have your blood pressure checked at least once a year. If you do not know what your blood pressure is, have it tested today, in order to stop this silent killer in its tracks.

1. American Heart Association: https://www.heart.org/en/health-topics/high-blood-pressure/the-facts-about-high-blood-pressure/what-is-high-blood-pressure
2. WHO: https://www.who.int/gho/ncd/risk_factors/blood_pressure_prevalence_text/en/
3. Heart and Stroke Foundation South Africa: http://www.heartfoundation.co.za/
4. International Society of Hypertension: https://ish-world.com/public/background-info.htm
5. American Heart Association: https://www.heart.org/en/health-topics/high-blood-pressure/why-high-blood-pressure-is-a-silent-killer/know-your-risk-factors-for-high-blood-pressure
6. Health effects of dietary risks in 195 countries, 1990-2017: a systematic analysis for the Global Burden of Disease Study 2017. Lancet 2019;393:1958-72.
7. WHO: https://www.who.int/news-room/fact-sheets/detail/salt-reduction
8. Wentzel-Viljoen et al. “Use salt and foods high in salt sparingly”: a food-based dietary guideline for South Africa. South African Journal of Clinical Nutrition 2013; 26(3): S105-S113.
9. Charlton et al. Diet and blood pressure in SA: intake of foods containing sodium, potassium, calcium, and magnesium in three ethnic groups. Nutrition 2005, 21: 39-50. 

Author: Bianca Tromp RD (SA)