Historically, doctors would recommend their patients go to the seaside to improve various ills. They would actually issue prescriptions detailing exactly how long, how often and under what conditions their patients were to be in the water.

Using seawater for medical purposes even has a name: thalassotherapy.

In 1769, a popular British doctor Richard Russell published a dissertation arguing for using seawater in “diseases of the glands”, in which he included scurvy, jaundice, leprosy and glandular consumption, which was the name for glandular fever at the time. He advocated drinking seawater as well as swimming in it.

To this day, healing and spa resorts by the seaside abound. They are thought of as places where people can not only let go of their troubles but, in some cases, even cure arthritis.

But does the evidence actually stack up? Does seawater cure skin conditions and improve mental health symptoms?

Skin conditions and wounds

Ocean water differs from river water in that it has significantly higher amounts of minerals, including sodium, chloride, sulphate, magnesium and calcium. This is why it’s highly useful for skin conditions such as psoriasis.

Psoriasis is a chronic, autoimmune (where the immune system attacks healthy cells) skin condition. People with prosiasis suffer often debilitating skin rashes made of itchy, scaly plaques.

Bathing in natural mineral-rich water, including in mineral springs, is called balneotherapy and has long been used to treat psoriasis. There is also evidence for climatotherapy (where a patient is relocated to a specific location for treatment) in the Dead Sea being an effective remedy for the condition.

Patients suffering from psoriasis have themselves reported feeling better after swimming in the ocean, but this may also have to do with sun exposure, which has been found to improve psoriasis symptoms.

Ocean swimming also has benefits for eczema, another immune-mediated condition. Swimming in the sea can be a good exercise option for those with severe eczema as they often struggle to exercise in the heat and chlorinated pools.

But the response of eczema sufferers to saltwater is variable: some find it soothing, others uncomfortable.

There is some evidence to support the idea magnesium absorption is beneficial for the skin of eczema sufferers – presumably because it makes it less dry – as those using Epsom salt baths will attest. This may happen because magnesium-rich seawater may improve moisture retention in the skin, making it stronger and more rigid.

Because it is rich in other mineral salts such as sodium and iodine, ocean water can be considered an antiseptic, meaning it may have wound-healing properties. On the other hand, swimming in the ocean with open wounds may expose you to potential bacterial infections.

Hay fever and sinus issues

Nasal irrigation, or flushing of the nasal cavity, with salty solutions is used as a complementary therapy by many people suffering from hay fever as well as inflammation and infection of the sinuses.

Ocean swimming and exposure to the salt environment are possibly associated with reduced symptoms of hay fever and sinusitis, as well as other respiratory symptoms.

This is because the saline effect on the lining of sinuses may reduce inflammation, although scientific evidence for this is less robust.

The director of clinical services at the medical charity Allergy UK claims people who live by, and swim in, the sea tend to have healthier respiratory systems.

She says because seawater is cleansing and mimics the body’s own fluids in the lining of the airways, it doesn’t irritate them.

Meditation and relaxation

Exercising in natural environments has been shown to have greater benefits for mental health than exercising elsewhere. This is because it combines the benefits of exercise with the restorative effects of being in nature. Swimming in the ocean is no less the case.

It can be relaxing, meditative and reduce stress. In his 2014 book Blue Mind, marine biologist Wallace J. Nichols brought together evidence for why people find themselves in a meditative and relaxed state when they are in, on or under water.

One reason is the breathing patterns used during swimming and diving. These stimulate the parasympathetic nervous system (the system that controls organ function and quietens the brain) and have effects on brain waves and hormones that influence the brain positively.

The weightlessness of water can also have a calming effect on the mind, even changing or slowing down brain waves.

It can help provide a distraction from life, giving a sense of mindfulness, which is a state in which one is aware of one’s surroundings in a meditative sort of fashion.

Hydrotherapy (water therapy) and swimming have also been shown to decrease symptoms of depression and anxiety. One study showed the effects of balneotherapy were comparable to a commonly used anti-depressant drug called paroxetine.

Cold water therapy

Hydrotherapy has been extensively used in rehabilitation, but here I will focus on the health benefits of swimming in cooler ocean water.

Cold-water swimming activates temperature receptors under the skin that release hormones such as endorphins, adrenalin and cortisol. These have therapeutic benefits for musculoskeletal conditions – such as fibromyalgia, which is a condition with chronic pain and tenderness all over the body – and skin discomfort.

Recurrent cold water exposure may also lead to enhanced function of the parasympathetic nervous system, which helps with organ function. This has been linked to an increase in the release of dopamine and serotonin.

Depending on the temperature, swimming in colder waters will use up more calories to preserve body temperature – although the overall effect on fat mass is controversial.

Frequent exposure to cold water has also been shown to increase the body’s immunity.

Overall, you would be wise to make ocean swimming a health habit.

The term is used by patients to describe a wide variety of abdominal sensations, usually associated with abdominal discomfort (feel like one’s going to burst) or tummy cramp. People suffering from bloating may also experience burping, diarrhoea, constipation, abdominal swelling and excessive passing of gas (flatulence).

If we are to understand bloating we need to look at some basic anatomy. The intestinal tract is made up of a hollow tube with a muscular wall. This tube serves different functions in different parts.

The stomach is like a bag that holds food while it mixes with acid to help break it down. The small intestine is long and thin allowing for digestion of food as it mixes with the body’s digestive juices. And the large intestine serves as a reservoir to allow for the final processing of stool.

What causes bloating?

These intestinal organs have nerves in their muscular wall and these nerves are able to sense when the organ is stretched or distended. It is this sensation of over stretching that the body may interpret as bloating. The intestinal organs are enclosed in a cavity that is lined by a membrane (the peritoneum) and this membrane is also able to sense stretching and thus any increase in the overall contents of the abdominal cavity will also be sensed as bloating.

Studies looking at the time taken for intestinal contents to flow through the gut have shown there may be pooling of liquid, gas or solid contents in parts of the gut sensed as bloating. This may be aggravated by the way certain people’s guts sense contents as they may be more prone to the sensation of distension, as may occur in irritable bowel syndrome (IBS).

Although people suffering from bloating often complain of symptoms that may be related to excess gas, it does not seem excess gas on its own is the problem.

Other factors that may be associated with swelling (especially in those who are constipated) includes slow movement of contents in the intestine and weak muscles in the abdominal wall, especially if someone recently gained weight, and a diaphragm muscle that contracts when it should relax.

What can make it worse?

Factors in the diet may well be involved in increasing the risk of bloating, with a small study linking bloating to the consumption of poorly digested sugars. This mechanism may underlie the bloating associated with lactose intolerance and the less commonly diagnosed fructose, fructan (similar to fructose) and sorbitol (corn syrup) intolerance.

The role of the bacteria in the gut (microbiome) in the development of bloating is poorly understood. There are some studies that say there are changes in the bacteria in the gut, especially in IBS. The type of gas the bacteria in the large intestine produce may be linked to bloating.

The gut is under the influence of many hormones, and certain hormones can make a person feel bloated, as is experienced by some women before their menstruation.

Irritable bowel syndrome

Bloating is experienced as part of many conditions, but probably the most common condition associated with bloating is IBS.

IBS is a condition in the family of functional gut disorders (as opposed to those that have a visible structural problem in the intestinal tract). There are two different types, those associated with constipation and associated with diarrohea.

The classic description is that IBS starts early in life and persists over time. Sufferers complain of bloating either after meals or progressively throughout the day. It’s often associated with tummy discomfort that improves with passing stool.

Recent studies in IBS have shown some benefit from a diet that avoids fermentable oligosaccharides, disaccharides, and monosaccharides and polyols (FODMAPs). FODMAPs are types of carbohydrates (sugars) fermented in the intestine by bacteria and increase the fluid content and distension of the gut.

What can you do?

Foods to avoid include those containing onion and garlic and wheat or rye, lactose products such as cow’s milk and stone fruit.

People suffering from other conditions associated with bloating such as lactose intolerance and gluten sensitivity or coeliac disease will need more specific elimination diets.

Since there may be changes in gut flora in IBS, the use of probiotics containing Lactobacillus and Bifidobacterium may help patients with bloating symptoms by reducing gas production in the gut. This may be particularly useful in children. The use of probiotics has also been found to be effective in those with bloating associated mainly with constipation.

People suffering from bloating should also eat small meals and exercise regularly to improve abdominal wall muscle tone and enhance gas clearance. Being at a healthy weight helps, and in some cases there may be the option of laxatives for those with associated constipation. Abdominal “binders” such as those commercially available to reduce the distended tummy may help. “Anti-gas” remedies seldom have lasting effect but peppermint oil capsules may be helpful.

Certain medications such as antacids, narcotic pain killers, anti-diarrhoeal agents, iron tablets, fibre supplements and stool bulking agents may cause bloating and should be considered the cause if the bloating started soon after their commencement.

Insufficient sleep not only affects our overall performance, but can affect some physiological functions such as changes to hormones, metabolic factors and immunity. From a business perspective, insufficient sleep can translate into lost profits due to decreased worker productivity. This has led companies such as Google, Nike and Ben & Jerry’s to encourage or allow napping at work, providing employees with napping facilities such as napping pods and quiet rooms in which they can nap if desired.

The pros and cons

Naps have been shown to be effective in reducing and minimising some of the negative effects of insufficient sleep. For example, compared to when no nap is taken, naps have been shown to effectively reduce feelings of sleepiness and improve cognitive performance on tasks such as reaction time and vigilance. Naps may also help to improve short-term memory and overall mood.

Moreover, these improvements can last for a few hours after the nap has ended. Naps may also offer longer lasting improvements in cognitive performance and reduced sleepiness than other commonly used countermeasures of sleepiness such as caffeine.

But as with everything, there are downsides too. Although naps are associated with performance improvements and reduced sleepiness, these benefits may not be immediate. Naps can be associated with a period of sleep inertia, which is the feeling of grogginess most people experience immediately after waking.

Sleep inertia is also characterised by a decrease in performance ranging from slowed reaction time to decreased coordination.

While the effects of sleep inertia generally subside within 15-60 minutes after waking from a nap, this period of delayed responsiveness and grogginess may pose serious risks for individuals who are required to function at optimal levels shortly after waking, such as those in transportation, aviation and medicine.

Following a nap, a period of sleep inertia may occur, before sleepiness is reduced and performance improved.

There is some research showing naps may affect your ability to get to sleep at night. Following an afternoon or evening nap, night time sleep duration may be shortened and more disrupted according to some studies. But there is some debate about this. A majority of the research suggests naps have minimal impact on night time sleep.

It’s all about timing

The degree to which naps help, or hinder, largely depends on the timing and duration of the nap. Longer naps (two hours or longer) are associated with longer lasting performance improvements and reduced sleepiness than short (30 minutes or less) or brief naps (ten minutes or less). Longer naps, however, are also more susceptible to sleep inertia, with a worsening in performance immediately following the nap. Alternatively, the benefits of brief naps occur almost immediately and are without the negative side-effect of sleep inertia.

Longer naps may also have a greater impact on subsequent sleep periods than shorter naps, as they may decrease “sleep pressure”, which can make falling and staying asleep more difficult.

The time of day naps occur can also affect the benefits of napping. Naps taken in the early morning hours, when there is a high circadian drive for sleep, may worsen the effects of sleep inertia and may not offer as much recuperation compared to naps taken in the afternoon.

One sleep or two?

More recently it has been suggested that perhaps humans were not meant to have one sleep, but were meant to sleep bi-modally – two shorter sleeps instead of one long one a day. While there is still some debate about whether this is true or not, it seems the number of sleep episodes may not make much difference to waking performance.

Rather, the overall amount of sleep per day, seven to nine hours, is what is likely to have the biggest impact on performance. It’s possible splitting the sleep in this manner may affect different sleep stages such as non-rapid eye movement and rapid eye movement sleep, which may have long-term implications on general health and well-being, however these effects need to be investigated further.

While there are some disadvantages to napping, such as sleep inertia, for the most part, the benefits of improved performance and reduced sleepiness outweigh the negatives. Short naps, less than 30 minutes, may offer the most “bang for your buck” as they can improve performance quickly with minimal side-effects.