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Sales of air fryers are skyrocketing. But how do they work? Are they healthier than other cooking methods? And – as listener Sally was keen to know – will using an air fryer reduce energy consumption and save her money?

A similar size to a breadmaker, an air fryer sits on your kitchen counter. It cooks by blowing very hot air, at high speed, all around the food. "It is essentially the same as a fan oven," explains Dr Jakub Radzikowski, Culinary Education Designer at Imperial College London. "But because the fan is more powerful and the compartment smaller, the whole device is more efficient."

They're great for crispy food: a chicken thigh will take just 20 minutes to cook and its skin will "shatter like glass", says Jakub. If you consider high fat levels to be unhealthy "compared to deep-fat frying it is obviously healthier because it has lower fat content and the perforated basket means that excess fat will drip to the bottom." Many models have grill and steam functions too.

There's a vast range of options on the market. A standard air fryer can be picked up for under £50 whereas models like the Ninja Foodi MAX Health Grill & Air Fryer will set you back around £249, but come with bells and whistles like integrated meat thermometers.

But can they save you money? After a Sliced Bread comparison test in producer Simon’s kitchen, the team can conclude that the answer is yes. "Cooking in the air fryer uses less than half of the energy required to cook a chicken or a jacket potato in the oven," says Greg. An air fryer can only cook in small batches however, so for larger meals it may still be more economical to use a conventional oven, so it will never fully replace your cooker.

Read more about Greg's investigations. And listen to the Sliced Bread air fryers episode in full here.

Razors

Does a simple manual razor count as a gadget? Well, with the more desirable razors on the market boasting features like multiple blades and lubricating strips, the answer is yes. But listener Tim wants to know, do all the advertised fancy features, multiple blades and higher price tags really make a difference to your shave?

Some shaving brands claim to have superior blades coated in chromium, or shaped like a 'gothic arch', but consultant dermatologist Dr Bav Shergill says the single most important feature is that the blade is "really sharp".

Many of the more expensive razors have five blades. Dr Frauke Neuser from Gillette says the point of multiple blades is that you're cutting each hair multiple times, achieving a closer shave. But the main driver for more blades is actually comfort. It spreads the pressure, which means "less skin bulging, less tug and pull, and an easy glide".

Are there benefits to lubricating strips? Bav isn’t convinced. "You're already hopefully putting a lubricant on your face with the shaving oil or shaving gel," he flags. But Frauke insists that the added lubrication is for when you take a second stroke, so you "still get that protection and the easier glide".

Gillette Labs Exfoliating Razor is 75 times the cost of a Bic disposable razor. Is it worth it? "It's the engineering that goes into them," Frauke claims. "Durability also plays a big role." Bav agrees that it is worth splashing out – on more blades and bells and whistles – because, as you're essentially doing a cosmetic treatment every time you shave, ease of use is key. That doesn't, however, mean you need to go absolutely top of the range.

And a 'closer shave' isn’t for everyone. This can actually lead to ingrowing hairs and irritation. If you have sensitive skin, five blades may not be for you. And perhaps avoid 'exfoliating bars', as these could irritate the skin further.

Listen here to decide for yourself whether expensive razors are right for you.

Electric toothbrushes

Manual toothbrush user Holly got in touch to ask if an electric brush would save her costly trips to the dentist. And will a more expensive model really clean her teeth better?

The big players in the market are Oral-B and Philips. Oral-B's toothbrush heads oscillate at about 70 times a second. Philips's brushes use vibrations, with the bristles moving side to side at high speed. "In terms of the different technologies, there’s not a lot in it," says Damien Walmsley, Professor of Restorative Dentistry.

Prices can be eyewatering: Oral-B's top brush – the iO9 – retails at £500. In this price range, brushes come with features like apps that feedback on your brushing technique. Paying more may also get you a longer battery life, suggests Which? researcher Matt Knight.

However, when Which? rated numerous electric models, they found that there was no direct link between price and the quality of the clean. "I'd be aware of the claims the toothbrush will clean your teeth better, because in many cases we found that isn’t necessarily the case," says Matt.

In terms of the cleaning properties of manual versus electric, Damien thinks that there is very little difference between the two. But manual toothbrushing does rely on good technique so electric toothbrushes remove the room for human error. Whether the snazzy apps (and associated price hike) will be a help or a hindrance is down to you.

Read more about Greg's investigations into electric toothbrushes here. And to find out whether Holly ditched her manual brush for an electric model, listen to the full episode here.

Massage guns

Massage guns are one of the biggest-selling fitness devices of the past few years. Listener Clare wanted to know, can they really help you warm up before exercise and recover more quickly after? And is it possible they might actually do some damage?

Massage guns can cost anything from £15 to more than £500. They have a vibrating silicone head that delivers percussive pressure onto the muscle. Manufacturers claim this 'vibration therapy’ increases blood flow and helps the user warm up before exercise, perform better during it and eases soreness afterwards by reducing inflammation.

By bringing more blood and oxygen to the muscle, they could help with warming up before a workout, suggests Ashley James, from the Chartered Society of Physiotherapy. With regards to recovery, research is in its infancy, he says, but "the evidence that does exist will demonstrate that localised vibration will improve delayed onset of muscle soreness, or DOMS." However, the numbers are small. A review on sports massage by the British Medical Journal found that it reduces DOMS by about 10%.

One Harvard study does outline how vibrational massage could help muscles heal quicker… in mice. Scientist Stephanie McNamara explained how they'd developed a massage gun for use on mice and showed it can flush out immune cells called neutrophils that can impair healing. Stephanie is sold: "I think it's an exceptional tool."

Ashley suggests there are recovery methods that are more proven to help – and cheaper to boot – like taking a walk, using a static bike or going for a swim. Plus, he warns, massage guns could cause further damage if used on an injury: "If you have pulled your hamstring, or pulled your calf, then I would absolutely avoid its use."

To decide whether massage guns should make your shopping list listen to the full episode here.

Air purifiers

Air purifiers promise to remove harmful pollutants and allergens from your home. But how effective are they? Listener Laura, a respiratory doctor, wanted to know whether they could help her patients. Is an air purifier better than good old-fashioned ventilation?

Most air purifiers contain a HEPA (high-efficiency particulate absorbing) filter. They remove particles like pollutants, allergens, bacteria and viruses up to a certain size. "On average," says Dr Elizabeth Cooper, a researcher at UCL, "these air purifiers reduce the particles by about 50%, so they do a pretty good job."

However, some purifiers claim to remove gases like formaldehyde from the atmosphere, and this is where it gets a little more 'murky', explains Alastair Lewis, Professor of Atmospheric Chemistry at the University of York. "Gases will pass through a filter relatively unharmed" so air purifiers claiming to filter gases will have various added technology, and "a lot of them are rather untested." Some types of filtration can even produce worrying bi-products: When an oxidative reaction is used to filter out VOCs (volatile organic compounds), it can create ozone, which in itself can irritate the lungs and impair breathing function.

There is not much evidence that air purifiers help long-term respiratory illnesses, says Elizabeth. But for short-term conditions like seasonal allergies, breathing problems – and in areas of high pollution – there's better evidence that air purifiers can help. Alastair says: "They could bring great relief to people who are acutely effected by air quality."

But for the majority of us, says Alastair, it could well be that you can get just as much of an effect by opening the window. A much cheaper fix (if the outside air isn't too polluted). Especially as, for real impact, you need an air purifier in every room in the house. "They're just not powerful enough to move enough air to purify the whole home," says Elizabeth.

To hear more about Greg's investigations into air purifiers, listen to the full episode here.

And for more of Greg's investigations into the latest ad-hyped products, listen to all the episodes of Sliced Bread so far on 91Èȱ¬ Sounds.

The information contained in this article was correct at the time of publish on 7 December, 2022.