
For patients: : basic resume of how blood normally moves through the heart
The start of a series of simple video explanations covering all of the main common medical conditions that can affect us, as we age.
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Posted on Tuesday October 8, 2024 in Health Screening
By Edward Leatham MRCP Consultant Cardiologist.
Tags: Salt, NaCl, BP, Hypertension, NH1 search website using Tags to find related stories.
Sodium chloride (NaCl) is an essential mineral vital for the survival of all mammals. Sodium, commonly consumed as table salt or in salt additives, is required in small amounts for various physiological functions. However, like many things in life, excessive intake of this element can be detrimental to long-term health. As a cardiologist, I am continually astonished by the misinformation circulating on the internet about salt. Some of these misconceptions have become so widespread that they are often accepted as truth without question. This article hopefully clarifies some misconceptions and shares a few insights gathered from countless patients I have looked after over the last 25 years in specialist cardiology practice.
Common Myths About Salt
Myth 1: Sea Salt and Himalayan Pink Salt Are Healthier Options
One of the most common misconceptions is that certain types of salt, like sea salt or Himalayan pink salt, are inherently healthier than regular table salt. This is not true. Regardless of their source or colour, all salts are primarily composed of sodium chloride. While sea salt and pink salt may contain trace minerals, their amounts are negligible and have no significant impact on health. In terms of sodium content—the component that affects blood pressure—all these salts are virtually identical to regular table salt.
Myth 2: Everyone Should Greatly Restrict Salt Intake
The body needs only a small amount of sodium, less than 500 mg per day to function properly, as healthy kidneys are efficient at retaining the sodium. That is less than 1/4 teaspoon of salt per day. However few people consume such a low amount.
Although most populations around the world do consume too much salt, the idea that everyone needs to drastically reduce their intake is an over simplification. The World Health Organisation (WHO) recommends a daily sodium intake of no more than 2,000 mg (roughly one teaspoon of salt). However, the US guideline, which suggests reducing sodium to 1,500 mg daily, may not be appropriate for everyone. For example, individuals who lose significant amounts of sodium through sweat, such as competitive athletes, foundry workers, firefighters, and others exposed to extreme heat, may require more sodium. People with certain medical conditions, such as congestive heart failure, should also be cautious with extreme salt restrictions, as too little salt could be harmful to them.
High salt intake can indeed contribute to developing high blood pressure in later life, particularly those with a family history of hypertension, but this is not a universal rule. People with low blood pressure, those living in hot climates, or those who sweat more than usual may benefit from a higher salt intake. In such cases, unless there is a family history of hypertension or a medical condition, there is less clear evidence linking moderate salt consumption to negative health outcomes. In fact, some individuals suffering from low blood pressure symptoms are advised to take salt supplements to manage their low blood pressure effectively.
If you have medical conditions or specific dietary requirements, it’s important to follow the advice of a qualified healthcare professional. Salt intake should be personalised based on individual health needs and circumstances, and blanket recommendations for everyone to drastically cut salt may not always be appropriate.
To understand the role of salt in our diets and why it has become such a controversial topic, it’s important to explore its history and evolution.
Salt entered the human food chain primarily as a preservative. Before modern refrigeration and canning techniques, salt was essential for preserving meat and other perishable items. In medieval times, salted meats like beef and pork were staples that sustained armies and navies on long voyages [2]. As newer methods of food preservation, such as canning and sterilisation, were developed in the 20th century, the need for salt as a preservative diminished. However, people had grown accustomed to the taste of salt, and it continued to be added for flavour enhancement, often at the expense of health.
Today, the modern food industry routinely adds salt to processed foods—not necessarily for preservation, but for flavour and as a marketing tool. This has led to an overconsumption of salt, particularly in parts of asia and in western diets, where processed foods are a significant part of daily intake.
The Physiology of Salt and Blood Pressure
Salt, or sodium chloride contributes significantly to the global issue of hypertension. Understanding how salt affects our physiology can help us make better dietary choices.
How Salt Affects Blood Pressure
In animal models of hypertension and in some people, high salt intake, especially in early life, has been shown to alter the body’s physiology, leading to increased blood pressure over time. In humans only 10% of adult patients with high blood pressure are ‘salt sensitive’ (meaning that the blood pressure fails to fall when salt intake is greatly reduced). It is quite possible that consuming high levels of sodium from a young age can “programme” the cardiovascular system to maintain higher blood pressure later in life. The genes and mutations that code for this predisposition are not fully characterised- although we know there are multiple genes that are involved with hypertension (so called polygenic ) and it is turning out to be a highly complex piece of medical research to unravel. Suffice to say that it is quite possible that individual susceptibility to developing high blood pressure in part relates to the genes we carry and pass on, explaining why raised blood pressure /hypertension and conditions linked to hypertension such as stroke, TIA and heart failure tend run in families and are also linked to ethnicity.
Our Prehistoric Origins: Salt in Sub-Saharan Africa – A Salt-Free Habitat
In certain parts of the world, such as sub-Saharan Africa, salt was historically scarce. Prehistoric populations in these regions evolved without regular access to salt, and their bodies adapted to these conditions. It’s possible that genetic mutations enabled these populations to survive in environments with high temperatures and significant perspiration, without the need for high salt intake. This contrasts with other regions where salt was more abundant and essential for survival.
When considering early human migration patterns from sub-Saharan Africa to other parts of the world—such as northern Europe and Australasia 60,000 to 90,000 years ago—an interesting possibility emerges. The genetic adaptations that allowed these early Homo sapiens to thrive on minimal salt intake would have travelled with them as they dispersed globally. However, after these populations spread, salt became widely used as a preservative, particularly during the Middle Ages. This change in salt consumption, combined with these genetic adaptations, may have set the stage for significant global health issues we face today, such as hypertension, stroke, and heart failure.
The Link Between Hypertension and Heart Failure
It’s well-known that elevated blood pressure is a preventable cause of heart failure, where the heart’s pumping function is compromised. However, it’s less widely recognised that a gradual increase in blood pressure over decades causes “pressure loading” on the heart. In response to this increased workload, the heart thickens (hypertrophies) which accelerates age-related stiffening of the left ventricle. While some stiffening occurs naturally with age, it is exacerbated by conditions such as aortic stenosis, cardiomyopathy, glucose dysregulation, and high blood pressure.
Stiffening of the left ventricle is a leading cause of heart failure later in life, particularly heart failure with preserved ejection fraction (HFpEF), previously known as ‘diastolic heart failure’. In this condition, which affects millions of people in the UK alone, the left ventricle becomes too stiff to relax properly during diastole, the phase of the heart cycle when the heart muscle normally sucks blood in from the atria in preparation for the next heartbeat.
Over decades, individuals whose hearts pump against high blood pressure are much more likely to develop diastolic dysfunction. Diastolic dysfunction can trigger reflexes leading to salt and water retention, which causes symptoms like ankle swelling and breathlessness , a condition termed “heart failure.” In its severe forms, heart failure can severely impact a person’s quality of life in their later years, requiring multiple medications and repeated hospital admissions for intravenous diuretic treatments.
The answer to whether you should reduce your salt intake depends on several factors, including your family history, current blood pressure, and overall health status.
Consider Your Family History
Genetics plays a significant role in how your body responds to salt. By identifying those prone to hypertension—often by examining family history for high blood pressure, stroke, or heart failure—it is advisable to pay more attention to blood pressure from a younger age (over 20) and manage salt intake more effectively, certainly sticking to NHS consumption guidance [6].
Know Your Blood Pressure
Regular monitoring of blood pressure is important. If your blood pressure is within a normal range and you have no other risk factors such as a parent or older sibling affected by raised blood pressure, there may be less need to drastically reduce your salt intake. However, if you have high blood pressure, or family members affected by such medical conditions, reducing salt intake can be a key strategy in staying healthy as you age.
Educate Your Children About Salt
If you have high blood pressure, it is wise to educate your children early on about the importance of a balanced diet, including appropriate salt intake. Children accustomed to low salt diets are less likely to develop a taste for excessively salty foods and may have a lower risk of developing hypertension later in life.
Salt is an essential nutrient, but like many things, it should be consumed in moderation. Whether you need to reduce your salt intake depends largely on your individual health profile, including your family history and current blood pressure levels.
For those with a predisposition to high blood pressure or who already have hypertension, reducing salt intake is generally advisable. However, for individuals with normal blood pressure and no significant risk factors, the need for drastic reduction is less clear.
What is clear, though, is the importance of being informed and making decisions based on your health needs, not on myths or marketing claims.
By understanding the truth about salt, we can make better choices for ourselves and help guide the next generation towards healthier eating habits. It’s not about vilifying salt; it’s about using it wisely.
Further reading
The Naked Heart is an educational project owned and operated by Dr Edward Leatham. It comprises a series of blog articles, videos and reels distributed on Tiktok, Youtube and Instagram aimed to help educate both patients and healthcare professionals about cardiology related issues.
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