Throughout recorded history, our hair and nails played an important role in signifying who we are and our social status. You could say, they separate the caveman from businessman.

It was no surprise then that many of us found a new level of appreciation for our hairdressers and nail artists during the COVID lockdowns. Even Taylor Swift reported she cut her own hair during lockdown.

So, what would happen if all this hair and nail grooming got too much for us and we decided to give it all up. Would our hair and nails just keep on growing?

The answer is yes. The hair on our head grows, on average, 1 centimeter per month, while our fingernails grow an average of just over 3 millimetres.

When left unchecked, our hair and nails can grow to impressive lengths. Aliia Nasyrova, known as the Ukrainian Rapunzel, holds the world record for the longest locks on a living woman, which measure an impressive 257.33 cm.

When it comes to record-breaking fingernails, Diana Armstrong from the United States holds that record at 1,306.58 cm.

Most of us, however, get regular haircuts and trim our nails – some with greater frequency than others. So why do some people’s hair and nails grow more quickly?

Remind me, what are they made out of?

Hair and nails are made mostly from keratin. Both grow from matrix cells below the skin and grow through different patterns of cell division.

Nails grow steadily from the matrix cells, which sit under the skin at the base of the nail. These cells divide, pushing the older cells forward. As they grow, the new cells slide along the nail bed – the flat area under the fingernail which looks pink because of its rich blood supply.

A hair also starts growing from the matrix cells, eventually forming the visible part of the hair – the shaft. The hair shaft grows from a root that sits under the skin and is wrapped in a sac known as the hair follicle.

This sac has a nerve supply (which is why it hurts to pull out a hair), oil-producing glands that lubricate the hair and a tiny muscle that makes your hair stand up when it’s cold.

At the follicle’s base is the hair bulb, which contains the all-important hair papilla that supplies blood to the follicle.

Matrix cells near the papilla divide to produce new hair cells, which then harden and form the hair shaft. As the new hair cells are made, the hair is pushed up above the skin and the hair grows.

But the papilla also plays an integral part in regulating hair growth cycles, as it sends signals to the stem cells to move to the base of the follicle and form a hair matrix. Matrix cells then get signals to divide and start a new growth phase.

Unlike nails, our hair grows in cycles

Scientists have identified four phases of hair growth, the:

1. anagen or growth phase, which lasts between two and eight years
2. catagen or transition phase, when growth slows down, lasting around two weeks
3. telogen or resting phase, when there is no growth at all. This usually lasts two to three months
4. exogen or shedding phase, when the hair falls out and is replaced by the new hair growing from the same follicle. This starts the process all over again.

Each follicle goes through this cycle 10–30 times in its lifespan.

If all of our hair follicles grew at the same rate and entered the same phases simultaneously, there would be times when we would all be bald. That doesn’t usually happen: at any given time, only one in ten hairs is in the resting phase.

While we lose about 100–150 hairs daily, the average person has 100,000 hairs on their head, so we barely notice this natural shedding.

So what affects the speed of growth?

Genetics is the most significant factor. While hair growth rates vary between individuals, they tend to be consistent among family members.

Nails are also influenced by genetics, as siblings, especially identical twins, tend to have similar nail growth rates.

But there are also other influences.

Age makes a difference to hair and nail growth, even in healthy people. Younger people generally have faster growth rates because of the slowing metabolism and cell division that comes with ageing.

Hormonal changes can have an impact. Pregnancy often accelerates hair and nail growth rates, while menopause and high levels of the stress hormone cortisol can slow growth rates.

Nutrition also changes hair and nail strength and growth rate. While hair and nails are made mostly of keratin, they also contain water, fats and various minerals. As hair and nails keep growing, these minerals need to be replaced.

That’s why a balanced diet that includes sufficient nutrients to support your hair and nails is essential for maintaining their health.

Nutrient deficiencies may contribute to hair loss and nail breakage by disrupting their growth cycle or weakening their structure. Iron and zinc deficiencies, for example, have both been linked to hair loss and brittle nails.

This may explain why thick hair and strong, well-groomed nails have long been associated with perception of good health and high status.

However, not all perceptions are true.

No, hair and nails don’t grow after death

A persistent myth that may relate to the legends of vampires is that hair and nails continue to grow after we die.

In reality, they only appear to do so. As the body dehydrates after death, the skin shrinks, making hair and nails seem longer.

Morticians are well aware of this phenomenon and some inject tissue filler into the deceased’s fingertips to minimise this effect.

So, it seems that living or dead, there is no escape from the never-ending task of caring for our hair and nails.

Michelle Moscova, Adjunct Associate Professor, Anatomy, UNSW Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

One in three Australian adults has high blood pressure (hypertension). Excess salt (sodium) increases the risk of high blood pressure so everyone with hypertension is advised to reduce salt in their diet.

But despite decades of strong recommendations we have failed to get Australians to cut their intake. It’s hard for people to change the way they cook, season their food differently, pick low-salt foods off the supermarket shelves and accept a less salty taste.

Now there is a simple and effective solution: potassium-enriched salt. It can be used just like regular salt and most people don’t notice any important difference in taste.

Switching to potassium-enriched salt is feasible in a way that cutting salt intake is not. Our new research concludes clinical guidelines for hypertension should give patients clear recommendations to switch.

What is potassium-enriched salt?

Potassium-enriched salts replace some of the sodium chloride that makes up regular salt with potassium chloride. They’re also called low-sodium salt, potassium salt, heart salt, mineral salt, or sodium-reduced salt.

Potassium chloride looks the same as sodium chloride and tastes very similar.

Potassium-enriched salt works to lower blood pressure not only because it reduces sodium intake but also because it increases potassium intake. Insufficient potassium, which mostly comes from fruit and vegetables, is another big cause of high blood pressure.

What is the evidence?

We have strong evidence from a randomised trial of 20,995 people that switching to potassium-enriched salt lowers blood pressure and reduces the risks of stroke, heart attacks and early death. The participants had a history of stroke or were 60 years of age or older and had high blood pressure.

An overview of 21 other studies suggests much of the world’s population could benefit from potassium-enriched salt.

The World Health Organisation’s 2023 global report on hypertension highlighted potassium-enriched salt as an “affordable strategy” to reduce blood pressure and prevent cardiovascular events such as strokes.

What should clinical guidelines say?

We teamed up with researchers from the United States, Australia, Japan, South Africa and India to review 32 clinical guidelines for managing high blood pressure across the world. Our findings are published today in the American Heart Association’s journal, Hypertension.

We found current guidelines don’t give clear and consistent advice on using potassium-enriched salt.

While many guidelines recommend increasing dietary potassium intake, and all refer to reducing sodium intake, only two guidelines – the Chinese and European – recommend using potassium-enriched salt.

To help guidelines reflect the latest evidence, we suggested specific wording which could be adopted in Australia and around the world:

Why do so few people use it?

Most people are unaware of how much salt they eat or the health issues it can cause. Few people know a simple switch to potassium-enriched salt can help lower blood pressure and reduce the risk of a stroke and heart disease.

Limited availability is another challenge. Several Australian retailers stock potassium-enriched salt but there is usually only one brand available, and it is often on the bottom shelf or in a special food aisle.

Potassium-enriched salts also cost more than regular salt, though it’s still low cost compared to most other foods, and not as expensive as many fancy salts now available.

A 2021 review found potassium-enriched salts were marketed in only 47 countries and those were mostly high-income countries. Prices ranged from the same as regular salt to almost 15 times greater.

Even though generally more expensive, potassium-enriched salt has the potential to be highly cost effective for disease prevention.

Preventing harm

A frequently raised concern about using potassium-enriched salt is the risk of high blood potassium levels (hyperkalemia) in the approximately 2% of the population with serious kidney disease.

People with serious kidney disease are already advised to avoid regular salt and to avoid foods high in potassium.

No harm from potassium-enriched salt has been recorded in any trial done to date, but all studies were done in a clinical setting with specific guidance for people with kidney disease.

Our current priority is to get people being managed for hypertension to use potassium-enriched salt because health-care providers can advise against its use in people at risk of hyperkalemia.

In some countries, potassium-enriched salt is recommended to the entire community because the potential benefits are so large. A modelling study showed almost half a million strokes and heart attacks would be averted every year in China if the population switched to potassium-enriched salt.

What will happen next?

In 2022, the health minister launched the National Hypertension Taskforce, which aims to improve blood pressure control rates from 32% to 70% by 2030 in Australia.

Potassium-enriched salt can play a key role in achieving this. We are working with the taskforce to update Australian hypertension management guidelines, and to promote the new guidelines to health professionals.

In parallel, we need potassium-enriched salt to be more accessible. We are engaging stakeholders to increase the availability of these products nationwide.

The world has already changed its salt supply once: from regular salt to iodised salt. Iodisation efforts began in the 1920s and took the best part of 100 years to achieve traction. Salt iodisation is a key public health achievement of the last century preventing goitre (a condition where your thyroid gland grows larger) and enhancing educational outcomes for millions of the poorest children in the world, as iodine is essential for normal growth and brain development.

The next switch to iodised and potassium-enriched salt offers at least the same potential for global health gains. But we need to make it happen in a fraction of the time.

Xiaoyue Xu (Luna), Scientia Lecturer, UNSW Sydney; Alta Schutte, SHARP Professor of Cardiovascular Medicine, UNSW Sydney, and Bruce Neal, Executive Director, George Institute Australia, George Institute for Global Health

This article is republished from The Conversation under a Creative Commons license. Read the original article.