Still or sparkling? It’s a question you’ll commonly hear in a café or restaurant and you probably have a preference. But is there any difference for your health?

If you love the fizz, here’s why you don’t have to pass on the sparkling water.

What makes my water sparkle?

This article specifically focuses on comparing still filtered water to carbonated filtered water (called “sparkling water” or “unflavoured seltzer”). Soda water, mineral water, tonic water and flavoured water are similar, but not the same product.

The bubbles in sparkling water are created by adding carbon dioxide to filtered water. It reacts to produce carbonic acid, which makes sparkling water more acidic (a pH of about 3.5) than still (closer to neutral, with a pH around 6.5-8.5).

Which drink is healthiest?

Water is the best way to hydrate our bodies. Research shows when it comes to hydration, still and sparkling water are equally effective.

Some people believe water is healthier when it comes from a sealed bottle. But in Australia, tap water is monitored very carefully. Unlike bottled water, it also has the added benefit of fluoride, which can help protect young children against tooth decay and cavities.

Sparkling or still water is always better than artificially sweetened flavoured drinks or juices.

Isn’t soda water bad for my teeth and bones?

There’s no evidence sparkling water damages your bones. While drinking a lot of soft drinks is linked to increased fractures, this is largely due to their association with higher rates of obesity.

Sparkling water is more acidic than still water, and acidity can soften the teeth’s enamel. Usually this is not something to be too worried about, unless it is mixed with sugar or citrus, which has much higher levels of acidity and can harm teeth.

However, if you grind your teeth often, the softening could enhance the damage it causes. If you’re undertaking a home whitening process, sparkling water might discolour your teeth.

In most other cases, it would take a lot of sparkling water to pass by the teeth, for a long period of time, to cause any noticeable damage.

How does drinking water affect digestion?

There is a misconception drinking water (of any kind) with a meal is bad for digestion.

While theoretically water could dilute stomach acid (which breaks down food), the practice of drinking it doesn’t appear to have any negative effect. Your digestive system simply adapts to the consistency of the meal.

Some people do find that carbonated beverages cause some stomach upset. This is due to the build-up of gases, which can cause bloating, cramping and discomfort. For people with an overactive bladder, the acidity might also aggravate the urinary system.

Interestingly, the fizzy “buzz” you feel in your mouth from sparkling water fades the more you drink it.

Is cold water harder to digest?

You’ve chosen still or sparkling water. What about its temperature?

There are surprisingly few studies about the effect of drinking cold water compared to room temperature. There is some evidence colder water (at two degrees Celsius) might inhibit gastric contractions and slow down digestion. Ice water may constrict blood vessels and cause cramping.

However other research suggests drinking cold water might temporarily boost metabolism, as the body needs to expend energy to warm it up to body temperature. This effect is minimal and unlikely to lead to significant weight loss.

Which water wins?

The bottom line is water is essential, hydrates us and has countless other health benefits. Water, with carbonated bubbles or without, will always be the healthiest drink to choose.

And if you’re concerned about any impact to teeth enamel, one trick is to follow sparkling water with a glass of still. This helps rinse the teeth and return your mouth’s acidity back to normal.

Christian Moro, Associate Professor of Science & Medicine, Bond University and Charlotte Phelps, Senior Teaching Fellow, Medical Program, Bond University

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

The United States Department of Agriculture last week reported that a pig on a backyard farm in Oregon was infected with bird flu.

As the bird flu situation has evolved, we’ve heard about the A/H5N1 strain of the virus infecting a range of animals, including a variety of birds, wild animals and dairy cattle.

Fortunately, we haven’t seen any sustained spread between humans at this stage. But the detection of the virus in a pig marks a worrying development in the trajectory of this virus.

How did we get here?

The most concerning type of bird flu currently circulating is clade 2.3.4.4b of A/H5N1, a strain of influenza A.

Since 2020, A/H5N1 2.3.4.4b has spread to a vast range of birds, wild animals and farm animals that have never been infected with bird flu before.

While Europe is a hotspot for A/H5N1, attention is currently focused on the US. Dairy cattle were infected for the first time in 2024, with more than 400 herds affected across at least 14 US states.

Bird flu has enormous impacts on farming and commercial food production, because infected poultry flocks have to be culled, and infected cows can result in contaminated diary products. That said, pasteurisation should make milk safe to drink.

While farmers have suffered major losses due to H5N1 bird flu, it also has the potential to mutate to cause a human pandemic.

Birds and humans have different types of receptors in their respiratory tract that flu viruses attach to, like a lock (receptors) and key (virus). The attachment of the virus allows it to invade a cell and the body and cause illness. Avian flu viruses are adapted to birds, and spread easily among birds, but not in humans.

So far, human cases have mainly occurred in people who have been in close contact with infected farm animals or birds. In the US, most have been farm workers.

The concern is that the virus will mutate and adapt to humans. One of the key steps for this to happen would be a shift in the virus’ affinity from the bird receptors to those found in the human respiratory tract. In other words, if the virus’ “key” mutated to better fit with the human “lock”.

A recent study of a sample of A/H5N1 2.3.4.4b from an infected human had worrying findings, identifying mutations in the virus with the potential to increase transmission between human hosts.

Why are pigs a problem?

A human pandemic strain of influenza can arise in several ways. One involves close contact between humans and animals infected with their own specific flu viruses, creating opportunities for genetic mixing between avian and human viruses.

Pigs are the ideal genetic mixing vessel to generate a human pandemic influenza strain, because they have receptors in their respiratory tracts which both avian and human flu viruses can bind to.

This means pigs can be infected with a bird flu virus and a human flu virus at the same time. These viruses can exchange genetic material to mutate and become easily transmissible in humans.

Interestingly, in the past pigs were less susceptible to A/H5N1 viruses. However, the virus has recently mutated to infect pigs more readily.

In the recent case in Oregon, A/H5N1 was detected in a pig on a non-commercial farm after an outbreak occurred among the poultry housed on the same farm. This strain of A/H5N1 was from wild birds, not the one that is widespread in US dairy cows.

The infection of a pig is a warning. If the virus enters commercial piggeries, it would create a far greater level of risk of a pandemic, especially as the US goes into winter, when human seasonal flu starts to rise.

How can we mitigate the risk?

Surveillance is key to early detection of a possible pandemic. This includes comprehensive testing and reporting of infections in birds and animals, alongside financial compensation and support measures for farmers to encourage timely reporting.

Strengthening global influenza surveillance is crucial, as unusual spikes in pneumonia and severe respiratory illnesses could signal a human pandemic. Our EPIWATCH system looks for early warnings of such activity, which can speed up vaccine development.

If a cluster of human cases occurs, and influenza A is detected, further testing (called subtyping) is essential to ascertain whether it’s a seasonal strain, an avian strain from a spillover event, or a novel pandemic strain.

Early identification can prevent a pandemic. Any delay in identifying an emerging pandemic strain enables the virus to spread widely across international borders.

Australia’s first human case of A/H5N1 occurred in a child who acquired the infection while travelling in India, and was hospitalised with illness in March 2024. At the time, testing revealed Influenza A (which could be seasonal flu or avian flu), but subtyping to identify A/H5N1 was delayed.

This kind of delay can be costly if a human-transmissible A/H5N1 arises and is assumed to be seasonal flu because the test is positive for influenza A. Only about 5% of tests positive for influenza A are subtyped further in Australia and most countries.

In light of the current situation, there should be a low threshold for subtyping influenza A strains in humans. Rapid tests which can distinguish between seasonal and H5 influenza A are emerging, and should form part of governments’ pandemic preparedness.

A higher risk than ever before

The US Centers for Disease Control and Prevention states that the current risk posed by H5N1 to the general public remains low.

But with H5N1 now able to infect pigs, and showing worrying mutations for human adaptation, the level of risk has increased. Given the virus is so widespread in animals and birds, the statistical probability of a pandemic arising is higher than ever before.

The good news is, we are better prepared for an influenza pandemic than other pandemics, because vaccines can be made in the same way as seasonal flu vaccines. As soon as the genome of a pandemic influenza virus is known, the vaccines can be updated to match it.

Partially matched vaccines are already available, and some countries such as Finland are vaccinating high-risk farm workers.

C Raina MacIntyre, Professor of Global Biosecurity, NHMRC L3 Research Fellow, Head, Biosecurity Program, Kirby Institute, UNSW Sydney and Haley Stone, Research Associate, Biosecurity Program, Kirby Institute & CRUISE lab, Computer Science and Engineering, UNSW Sydney

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