People have a pretty intuitive sense of what is healthy – standing is better than sitting, exercise is great for overall health and getting good sleep is imperative.

However, if exercise in the evening may disrupt our sleep, or make us feel the need to be more sedentary to recover, a key question emerges – what is the best way to balance our 24 hours to optimise our health?

Our research attempted to answer this for risk factors for heart disease, stroke and diabetes. We found the optimal amount of sleep was 8.3 hours, while for light activity and moderate to vigorous activity, it was best to get 2.2 hours each.

Finding the right balance

Current health guidelines recommend you stick to a sensible regime of moderate-to vigorous-intensity physical activity 2.5–5 hours per week.

However mounting evidence now suggests how you spend your day can have meaningful ramifications for your health. In addition to moderate-to vigorous-intensity physical activity, this means the time you spend sitting, standing, doing light physical activity (such as walking around your house or office) and sleeping.

Our research looked at more than 2,000 adults who wore body sensors that could interpret their physical behaviours, for seven days. This gave us a sense of how they spent their average 24 hours.

At the start of the study participants had their waist circumference, blood sugar and insulin sensitivity measured. The body sensor and assessment data was matched and analysed then tested against health risk markers — such as a heart disease and stroke risk score — to create a model.

Using this model, we fed through thousands of permutations of 24 hours and found the ones with the estimated lowest associations with heart disease risk and blood-glucose levels. This created many optimal mixes of sitting, standing, light and moderate intensity activity.

When we looked at waist circumference, blood sugar, insulin sensitivity and a heart disease and stroke risk score, we noted differing optimal time zones. Where those zones mutually overlapped was ascribed the optimal zone for heart disease and diabetes risk.

You’re doing more physical activity than you think

We found light-intensity physical activity (defined as walking less than 100 steps per minute) – such as walking to the water cooler, the bathroom, or strolling casually with friends – had strong associations with glucose control, and especially in people with type 2 diabetes. This light-intensity physical activity is likely accumulated intermittently throughout the day rather than being a purposeful bout of light exercise.

Our experimental evidence shows that interrupting our sitting regularly with light-physical activity (such as taking a 3–5 minute walk every hour) can improve our metabolism, especially so after lunch.

While the moderate-to-vigorous physical activity time might seem a quite high, at more than 2 hours a day, we defined it as more than 100 steps per minute. This equates to a brisk walk.

It should be noted that these findings are preliminary. This is the first study of heart disease and diabetes risk and the “optimal” 24 hours, and the results will need further confirmation with longer prospective studies.

The data is also cross-sectional. This means that the estimates of time use are correlated with the disease risk factors, meaning it’s unclear whether how participants spent their time influences their risk factors or whether those risk factors influence how someone spends their time.

Australia’s adult physical activity guidelines need updating

Australia’s physical activity guidelines currently only recommend exercise intensity and time. A new set of guidelines are being developed to incorporate 24-hour movement. Soon Australians will be able to use these guidelines to examine their 24 hours and understand where they can make improvements.

While our new research can inform the upcoming guidelines, we should keep in mind that the recommendations are like a north star: something to head towards to improve your health. In principle this means reducing sitting time where possible, increasing standing and light-intensity physical activity, increasing more vigorous intensity physical activity, and aiming for a healthy sleep of 7.5–9 hours per night.

Beneficial changes could come in the form of reducing screen time in the evening or opting for an active commute over driving commute, or prioritising an earlier bed time over watching television in the evening.

It’s also important to acknowledge these are recommendations for an able adult. We all have different considerations, and above all, movement should be fun.

Christian Brakenridge, Postdoctoral research fellow at Swinburne University Centre for Urban Transitions, Swinburne University of Technology

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

Enzo Palombo, Swinburne University of Technology

Recent outbreaks of bird flu – in US dairy herds, poultry farms in Australia and elsewhere, and isolated cases in humans – have raised the issue of food safety.

So can the virus transfer from infected farm animals to contaminate milk, meat or eggs? How likely is this?

And what do we need to think about to minimise our risk when shopping for or preparing food?

How safe is milk?

Bird flu (or avian influenza) is a bird disease caused by specific types of influenza virus. But the virus can also infect cows. In the US, for instance, to date more than 80 dairy herds in at least nine states have been infected with the H5N1 version of the virus.

Investigations are under way to confirm how this happened. But we do know infected birds can shed the virus in their saliva, nasal secretions and faeces. So bird flu can potentially contaminate animal-derived food products during processing and manufacturing.

Indeed, fragments of bird flu genetic material (RNA) were found in cow’s milk from the dairy herds associated with infected US farmers.

However, the spread of bird flu among cattle, and possibly to humans, is likely to have been caused through contact with contaminated milking equipment, not the milk itself.

The test used to detect the virus in milk – which uses similar PCR technology to lab-based COVID tests – is also highly sensitive. This means it can detect very low levels of the bird flu RNA. But the test does not distinguish between live or inactivated virus, just that the RNA is present. So from this test alone, we cannot tell if the virus found in milk is infectious (and capable of infecting humans).

Does that mean milk is safe to drink and won’t transmit bird flu? Yes and no.

In Australia, where bird flu has not been reported in dairy cattle, the answer is yes. It is safe to drink milk and milk products made from Australian milk.

In the US, the answer depends on whether the milk is pasteurised. We know pasteurisation is a common and reliable method of destroying concerning microbes, including influenza virus. Like most viruses, influenza virus (including bird flu virus) is inactivated by heat.

Although there is little direct research on whether pasteurisation inactivates H5N1 in milk, we can extrapolate from what we know about heat inactivation of H5N1 in chicken and eggs.

So we can be confident there is no risk of bird flu transmission via pasteurised milk or milk products.

However, it’s another matter for unpasteurised or “raw” US milk or milk products. A recent study showed mice fed raw milk contaminated with bird flu developed signs of illness. So to be on the safe side, it would be advisable to avoid raw milk products.

How about chicken?

Bird flu has caused sporadic outbreaks in wild birds and domestic poultry worldwide, including in Australia. In recent weeks, there have been three reported outbreaks in Victorian poultry farms (two with H7N3 bird flu, one with H7N9). There has been one reported outbreak in Western Australia (H9N2).

The strains of bird flu identified in the Victorian and Western Australia outbreaks can cause human infection, although these are rare and typically result from close contact with infected live birds or contaminated environments.

Therefore, the chance of bird flu transmission in chicken meat is remote.

Nonetheless, it is timely to remind people to handle chicken meat with caution as many dangerous pathogens, such as Salmonella and Campylobacter, can be found on chicken carcasses.

Always handle chicken meat carefully when shopping, transporting it home and storing it in the kitchen. For instance, make sure no meat juices cross-contaminate other items, consider using a cool bag when transporting meat, and refrigerate or freeze the meat within two hours.

Avoid washing your chicken before cooking to prevent the spread of disease-causing microbes around the kitchen.

Finally, cook chicken thoroughly as viruses (including bird flu) cannot survive cooking temperatures.

Are eggs safe?

The recent Australian outbreaks have occurred in egg-laying or mixed poultry flocks, so concerns have been raised about bird flu transmission via contaminated chicken eggs.

Can flu viruses contaminate chicken eggs and potentially spread bird flu? It appears so. A report from 2007 said it was feasible for influenza viruses to enter through the eggshell. This is because influenza virus particles are smaller (100 nanometres) than the pores in eggshells (at least 200 nm).

So viruses could enter eggs and be protected from cleaning procedures designed to remove microbes from the egg surface.

Therefore, like the advice about milk and meat, cooking eggs is best.

The US Food and Drug Administration recommends cooking poultry, eggs and other animal products to the proper temperature and preventing cross-contamination between raw and cooked food.

In a nutshell

If you consume pasteurised milk products and thoroughly cook your chicken and eggs, there is nothing to worry about as bird flu is inactivated by heat.

The real fear is that the virus will evolve into highly pathogenic versions that can be transmitted from human to human.

That scenario is much more frightening than any potential spread though food.

Enzo Palombo, Professor of Microbiology, Swinburne University of Technology

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