Islamabad - It is well known that consuming too much salt is linked to high blood pressure. Now, a new study suggests it may also lead to liver damage in adults and developing embryos.

Most of the salt we eat comes from processed foods and foods prepared in restaurants. The new study was led by Jinan University in Guangzhou, China. Our bodies need salt - the chemical name for which is sodium chloride - to carry out essential functions. For example, sodium ions help control the transport of water and carry electrical impulses in nerves. However, according to the Centers for Disease Control and Prevention (CDC), most Americans consume too much sodium - most of it from salt. Excess sodium intake is linked to high blood pressure, a major cause of heart disease and stroke.

The average daily sodium intake for Americans aged 2 years and older is over 3,400 mg of sodium - more than double the 1,500 mg limit recommended by national dietary guidelines for most American adults.

Most of the salt people consume in the US does not come from the salt shaker - it is already in food by the time it reaches the table - it comes from processed foods and foods prepared in restaurants. So, while asking people to reduce salt intake has some effect in that they can look at labels to pick lower salt products, there is also a need to get producers to reduce sodium content of packaged and prepared foods.

Previous studies have already suggested that too much sodium can damage the liver. In the new study, the researchers wanted to look in more detail at what happens at the level of cells.

The team carried out experiments where they fed adult mice on a high-salt diet and exposed chick embryos to a salty environment.

The results showed that too much sodium led to a number of changes in the liver - such as misshapen cells, higher rates of cell death and lower rates of cell division - all of which can lead to liver fibrosis. Liver fibrosis occurs when there is excessive accumulation of “extracellular matrix” proteins like collagen that support the cells that do the work of the liver - such as breaking down old and damaged cells and metabolizing fats for energy. The researchers suggest the mechanism through which too much salt may cause liver damage and fibrosis in both adults and developing embryos is through oxidative stress. Oxidative stress is where the balance between the production of reactive oxygen species (free radicals) and antioxidants is upset in favor of the former. Such an imbalance can increase inflammatory cells and promote the death of liver cells, leading to progressive fibrosis.

However, on a more promising note, the team also found that treating damaged cells with vitamin C - an antioxidant - appeared to counter some of the damage brought on by too much salt.

Meanwhile, Medical News Today recently learned how a new review of published evidence finds that coffee may protect against liver cirrhosis, an advanced stage of fibrosis.

Too much exercise BAD for heart

Extreme strenuous workouts such as high intensity training could be bad for the heart, a new study has warned. Australian researchers say intense endurance exercise may be ‘cardiotoxic’ and cause permanent structural changes in the heart.

This, in turn, can leave some people more at risk of heart rhythm problems - known medically as arrhythmias. The scientists say while there is no doubt a couch potato lifestyle is bad, when it comes to exercise, there really may be too much of a good thing.

Intense endurance exercise may cause permanent structural changes in the heart, warns a study. But they argue much more research is needed before a definitive link can be made.. 

Previous research has linked long-term sport and exercise with an increased risk of atrial fibrillation - an irregular and often abnormally fast heart rate.

But the issue is controversial, with other research not showing a link. 

In the new study, sports cardiologists at Baker IDI Heart and Diabetes Institute, Melbourne, reviewed data on the subject in an attempt to ascertain if high-intensity exercise does negatively affect the heart.

Head of Sports Cardiology, Dr André La Gerche, said: ‘This paper discusses the often questionable, incomplete, and controversial science behind the emerging concern that high levels of intense exercise may be associated with some adverse health effects.’

He added that all therapies, pharmacological or otherwise [such as exercise], have a dose-response relationship whereby benefits diminish at high doses and the risk of adverse events increases. 

An open mind would consider that this may even be possible for exercise, he said. 

The study, published in the Canadian Journal of Cardiology, explored whether intense exercise - particularly endurance exercise such as marathons - may cause adverse cardiac changes in some athletes.

It had been thought that athletes who suffered heart problems were already susceptible to them - due to an underlying abnormality - and exercise acted as a trigger.

This study looked at whether exercise alone can change the heart and trigger a heart rhythm condition in its own right (and excluded inherited conditions).

He noted many of these controversies are based on small studies that are dwarfed by the large population studies supporting the benefits of exercise, albeit in doses of exercise less than those commonly practiced by elite sportspersons.

He said: ‘The answers regarding the healthfulness of ‘extreme’ exercise are not complete and there are valid questions being raised.

‘Given that this is a concern that affects such a large proportion of society, it is something that deserves investment.

‘The lack of large prospective studies of persons engaged in high-volume and high-intensity exercise represents the biggest deficiency in the literature to date, and, although such work presents a logistical and financial challenge, many questions will remain controversies until such data emerge.’