You can train your nose – and 4 other surprising facts about your sense of smell

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Would you give up your sense of smell to keep your hair? What about your phone?

A 2022 US study compared smell to other senses (sight and hearing) and personally prized commodities (including money, a pet or hair) to see what people valued more.

The researchers found smell was viewed as much less important than sight and hearing, and valued less than many commodities. For example, half the women surveyed said they’d choose to keep their hair over sense of smell.

Smell often goes under the radar as one of the least valued senses. But it is one of the first sensory systems vertebrates developed and is linked to your mental health, memory and more.

Here are five fascinating facts about your olfactory system.

DimaBerlin/Shutterstock

1. Smell is linked to memory and emotion

Why can the waft of fresh baking trigger joyful childhood memories? And why might a certain perfume jolt you back to a painful breakup?

Smell is directly linked to both your memory and emotions. This connection was first established by American psychologist Donald Laird in 1935 (although French novelist Marcel Proust had already made it famous in his reverie about the scent of madeleines baking.)

Odours are first captured by special olfactory nerve cells inside your nose. These cells extend upwards from the roof of your nose towards the smell-processing centre of your brain, called the olfactory bulb.

Diagram showing odour particles travelling through the nose into the brain.
Smells are first detected by nerve cells in the nose. Axel_Kock/Shutterstock

From the olfactory bulb they form direct connection with the brain’s limbic system. This includes the amygdala, where emotions are generated, and the hippocampus, where memories are created.

Other senses – such as sight and hearing – aren’t directly connected to the lymbic system.

One 2004 study used functional magnetic resonance imaging to demonstrate odours trigger a much stronger emotional and memory response in the brain than a visual cue.

2. Your sense of smell constantly regenerates

You can lose your ability to smell due to injury or infection – for example during and after a COVID infection. This is known as olfactory dysfunction. In most cases it’s temporary, returning to normal within a few weeks.

This is because every few months your olfactory nerve cells die and are replaced by new cells.

We’re not entirely sure how this occurs, but it likely involves your nose’s stem cells, the olfactory bulb and other cells in the olfactory nerves.

Other areas of your nervous system – including your brain and spinal cord – cannot regenerate and repair after an injury.

Constant regeneration may be a protective mechanism, as the olfactory nerves are vulnerable to damage caused by the external environment, including toxins (such as cigarette smoke), chemicals and pathogens (such as the flu virus).

But following a COVID infection some people might continue to experience a loss of smell. Studies suggest the virus and a long-term immune response damages the cells that allow the olfactory system to regenerate.

3. Smell is linked to mental health

Around 5% of the global population suffer from anosmia – total loss of smell. An estimated 15-20% suffer partial loss, known as hyposmia.

Given smell loss is often a primary and long-term symptom of COVID, these numbers are likely to be higher since the pandemic.

Yet in Australia, the prevalence of olfactory dysfunction remains surprisingly understudied.

Losing your sense of smell is shown to impact your personal and social relationships. For example, it can mean you miss out on shared eating experiences, or cause changes in sexual desire and behaviour.

In older people, declining ability to smell is associated with a higher risk of depression and even death, although we still don’t know why.

An older woman in a hat leans towards a tomato vine to sniff it.
Losing your sense of smell can have a major impact on mental health. Halfpoint/Shutterstock

4. Loss of smell can help identify neurodegenerative diseases

Partial or full loss of smell is often an early indicator for a range of neurodegenerative diseases, including Alzheimer’s and Parkinson’s diseases.

Patients frequently report losing their sense of smell years before any symptoms show in body or brain function. However many people are not aware they are losing their sense of smell.

There are ways you can determine if you have smell loss and to what extent. You may be able to visit a formal smell testing centre or do a self-test at home, which assesses your ability to identify household items like coffee, wine or soap.

5. You can train your nose back into smelling

“Smell training” is emerging as a promising experimental treatment option for olfactory dysfunction. For people experiencing smell loss after COVID, it’s been show to improve the ability to detect and differentiate odours.

Smell training (or “olfactory training”) was first tested in 2009 in a German psychology study. It involves sniffing robust odours — such as floral, citrus, aromatic or fruity scents — at least twice a day for 10—20 seconds at a time, usually over a 3—6 month period.

Participants are asked to focus on the memory of the smell while sniffing and recall information about the odour and its intensity. This is believed to help reorganise the nerve connections in the brain, although the exact mechanism behind it is unclear.

Some studies recommend using a single set of scents, while others recommend switching to a new set of odours after a certain amount of time. However both methods show significant improvement in smelling.

This training has also been shown to alleviate depressive symptoms and improve cognitive decline both in older adults and those suffering from dementia.

Just like physiotherapy after a physical injury, olfactory training is thought to act like rehabilitation for your sense of smell. It retrains the nerves in your nose and the connections it forms within the brain, allowing you to correctly detect, process and interpret odours.

Lynn Nazareth, Research Scientist in Olfactory Biology, CSIRO

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

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  • 12 Foods That Fight Depression & Anxiety

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    Food impacts mental health, and while it won’t magically cure mental illness, dietary changes can do a lot to improve mood. Here’s how:

    Nutraceuticals

    We’ll not keep the 12 nutraceutical foods a mystery; here’s what they are and a few words on how they work (in many cases, we could write whole articles about them; in some cases, we already have! You can find many of them by using the search function in the top-right of each page).

    • Walnuts are rich in omega-3s for brain health; arguably the best nut for depression relief.
    • Fermented foods because probiotics in foods like yogurt and sauerkraut support the gut-brain connection as well as serotonin production there, enhancing mood.
    • Cherry tomatoes are rich in lycopene, which helps combat both depression and mood swings.
    • Leafy greens reduce brain inflammation linked to depression.
    • Apples and other fruit are high in fiber and antioxidants that stabilize blood sugar and mood, reducing brain inflammation.
    • Beans are high in B vitamins, crucial for neurotransmitter production and mood regulation (without also being high in brain-harmful things, as red meat is).
    • Berries are super-high antioxidants and cortisol-lowering anthocyanidins, promoting calmness and reducing stress.
    • Oats contain the healthiest kind of fiber, β-glucan, and additionally help stabilize blood sugar and mood; they’re also rich in selenium, which boosts mood.
    • Mushrooms help regulate blood sugar and act as prebiotics, supporting serotonin production in the gut.
    • Avocados are famously rich in healthy fats, including omega-3s and oleic acid, which support brain health and combat depression.
    • Dark chocolate contains antioxidants, magnesium, and gut-healthy prebiotics that indirectly reduce mental stress and improve brain function. Also a famous comfort food for many, of course, and that factor’s not to be overlooked either.
    • Pumpkin seeds are rich in tryptophan, which boosts serotonin production. As a bonus, they also help some kinds of antidepressant to work better—check with your doctor or pharmacist to be sure in your case, though.

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  • Uric Acid’s Extensive Health Impact (And How To Lower It)

    10almonds is reader-supported. We may, at no cost to you, receive a portion of sales if you purchase a product through a link in this article.

    Uric Acid’s Extensive Health Impact (And How To Lower It)

    This is Dr. David Perlmutter. He’s a medical doctor, and a Fellow of the American College of Nutrition. He’s a member of the Editorial Board for the Journal of Alzheimer’s Disease, and has been widely published in many other peer-reviewed journals.

    What does he want us to know?

    He wants us to know about the health risks of uric acid (not something popularly talked about so much!), and how to reduce it.

    First: what is it? Uric acid is a substance we make in our own body. However, unlike most substances we make in our body, we have negligible use for it—it’s largely a waste product, usually excreted in urine.

    However, if we get too much, it can build up (and crystallize), becoming such things as kidney stones, or causing painful inflammation if it shows up in the joints, as in gout.

    More seriously (unpleasant as kidney stones and gout may be), this inflammation can have a knock-on effect triggering (or worsening) other inflammatory conditions, ranging from non-alcoholic fatty liver disease, to arthritis, to dementia, and even heart problems. See for example:

    How can we reduce our uric acid levels?

    Uric acid is produced when we metabolize purine nucleotides, which are found in many kinds of food. We can therefore reduce our uric acid levels by reducing our purine intake, as well as things that mess up our liver’s ability to detoxify things. Offsetting the values for confounding variables (such as fiber content, or phytochemicals that mitigate the harm), the worst offenders include…

    Liver-debilitating things:

    • Alcohol (especially beer)
    • High-fructose corn syrup (and other fructose-containing things that aren’t actual fruit)
    • Other refined sugars
    • Wheat / white flour products (this is why beer is worse than wine, for example; it’s a double-vector hit)

    Purine-rich things:

    • Red meats and game
    • Organ meats
    • Oily fish, and seafood (great for some things; not great for this)

    Some beans and legumes are also high in purines, but much like real fruit has a neutral or positive effect on blood sugar health despite its fructose content, the beans and legumes that are high in purines, also contain phytochemicals that help lower uric acid levels, so have a beneficial effect.

    Eggs (consumed in moderation) and tart cherries have a uric-acid lowering effect.

    Water is important for all aspects of health, and doubly important for this.

    Hydrate well!

    Lifestyle matters beyond diet

    The main key here is metabolic health, so Dr. Perlmutter advises the uncontroversial lifestyle choices of moderate exercise and good sleep, as well as (more critically) intermittent fasting. We wrote previously on other things that can benefit liver health:

    How To Unfatty A Fatty Liver

    …in this case, that means the liver gets a break to recuperate (something it’s very good at, but does need to get a chance to do), which means that while you’re not giving it something new to do, it can quickly catch up on any backlog, and then tackle any new things fresh, next time you start eating.

    Want to know more about this from Dr. Perlmutter?

    You might like his article:

    An Integrated Plan for Lowering Uric Acid ← more than we had room for here; he also talks about extra things to include in your diet/supplementation regime for beneficial effects!

    And/or his book:

    Drop Acid: The Surprising New Science of Uric Acid―The Key to Losing Weight, Controlling Blood Sugar, and Achieving Extraordinary Health

    …on which much of today’s main feature was based.

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  • Older people’s risk of abuse is rising. Can an ad campaign protect them?

    10almonds is reader-supported. We may, at no cost to you, receive a portion of sales if you purchase a product through a link in this article.

    Elder abuse is an emerging public health and safety issue for communities of high-income countries.

    The most recent data from Australia’s National Elder Abuse Prevalence Study, which surveyed 7,000 older people living in the community, found one in six self-reported being a victim of some form of abuse. But this did not include older people living in residential aged care or those with cognitive impairment, such as dementia – so is likely an underestimate.

    This week the Australian government announced a multi-million dollar advertising campaign it hopes will address this serious and abhorrent abuse.

    But is investing in community awareness of elder abuse the best use of scarce resources?

    Nuttapong punna/Shutterstock

    What is elder abuse?

    The World Health Organization (WHO) defines elder abuse as

    […] a single, or repeated act, or lack of appropriate action, occurring within any relationship where there is an expectation of trust which causes harm or distress to an older person.

    Australia usually defines older people as those over 65. The exact age varies between countries depending on the overall health status of a nation and its vulnerable population groups. The WHO definitions of an older adult for sub-Saharan Africa, for example, is over 50. And there are communities with poorer health status and shorter lifespans within country borders, including our First Nations people.

    Elder abuse can take on many different forms including physical, sexual, psychological, emotional, or financial abuse and neglect.

    Living longer and wealthier

    The number of older people in our society is greater than it has ever been. Around 17% Australians are aged 65 and over. By 2071, older Australians will make up between 25% and 27% of the total population.

    People are living longer, accumulating substantial wealth and are vulnerable to abuse due to cognitive, physical or functional limitations.

    Longer lifespans increase the time of possible exposure to abuse. Australian men aged 65 can expect to live another 20.2 years, while women aged 65 are likely to live another 22.8 years. (Life expectancy for First Nations men and women remains significantly shorter.)

    Australian men are now 143 times more likely to reach the age of 100 than they were in 1901. Women are 82 times more likely.

    Older people hold a large proportion of our nation’s wealth, making them vulnerable to financial abuse. Recent research by the Australian Council of Social Service and UNSW Sydney reveals older households (with people over 65) are 25% wealthier than the average middle-aged household and almost four times as wealthy as the average under-35 household.

    Finally, older people have higher levels of impairment in their thinking, reasoning and physical function. Cognitive impairment, especially dementia, increases from one in 67 Australians under 60 to almost one in two people aged over 90.

    Over half of Australians aged 65 years and over have disability. A particularly vulnerable group are the 258,374 older Australians who receive government-funded home care.

    Who perpetrates elder abuse?

    Sadly, most of the perpetrators of elder abuse are known to their victims. They are usually a member of the family, such as a life partner, child or grandchild.

    Elder abuse causes significant illness and even early death. Financial abuse (across all ages) costs the community billions of dollars. Specific data for financial elder abuse is limited but indicates massive costs to individual survivors and the community.

    Despite this, the level of awareness of elder abuse is likely to be much lower than for family violence or child abuse. This is partly due to the comparatively recent concept of elder abuse, with global awareness campaigns only developed over the past two decades.

    Is an advertising campaign the answer?

    The federal government has allocated A$4.8 million to an advertising campaign on television, online and in health-care clinics to reach the broader community. For context, last year the government spent $131.4 million on all media campaigns, including $32.6 million on the COVID vaccination program, $2 million on Japanese encephalitis and $3.2 million on hearing health awareness.

    The campaign will likely benefit a small number of people who may be victims and have the capacity to report their perpetrators to authorities. It will generate some heartbreaking anecdotes. But it is unlikely to achieve broad community or systemic change.

    There is little research evidence to show media campaigns alter the behaviour of perpetrators of elder abuse. And suggesting the campaign raises awareness of the issue for older people who are survivors of abuse sounds more like blaming victims than empowering them.

    We don’t know how the government will judge the success of the campaign, so taxpayers won’t know whether a reasonable return on this investment was achieved. There may also be opportunity costs associated with the initiative – that is, lost opportunities for other actions and strategies. It could be more effective and efficient to target high-risk subgroups or to allocate funding to policy, practice reform or research that has direct tangible benefits for survivors. https://www.youtube.com/embed/DeK2kaqplTI?wmode=transparent&start=0 The Australian Human Rights Commission’s campaign from last year.

    But the campaign can’t hurt, right?

    Actually, the dangers that could come with an advertising campaign are two-fold.

    First it may well oversimplify a highly complex issue. Identifying and managing elder abuse requires an understanding of the person’s vulnerabilities, their decision-making capacity and ability to consent, the will and preferences of victim and the role of perpetrator in the older person’s life. Abuse happens in the context of family and social networks. And reporting abuse can have consequences for the victim’s quality of life and care.

    Consider the complexities of a case where an older person declines to have her grandson reported to police for stealing her money and medication because of her fear of becoming socially isolated. She might even feel responsible for the behaviour having raised the grandson and not want him to have a criminal record.

    Secondly, a public campaign can create the illusion government and our institutions have the matter “in hand”. This might slow the opportunity for real change.

    Ideally, the campaign will strengthen the argument for better policies, reporting procedures, policing, prosecution and judgements that are aligned. But these ends will also need investment in more research to build better communities that take good care of older people.

    Joseph Ibrahim, Professor, Aged Care Medical Research Australian Centre for Evidence Based Aged Care, La Trobe University

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

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  • Chickpeas vs Pinto Beans – Which is Healthier?

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    Why?

    Both are great! And an argument could be made for either…

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    When it comes to vitamins, technically chickpeas have more of vitamins A, B3, B5, C, K, and choline, but the margins are so small as to be almost meaningless. Meanwhile, pinto beans have more of vitamins B1, B6, and E, and/but the only one where the margin is enough to really care about is vitamin E (a little over 2x what chickpeas have). So, an argument could be made either way, but we’re going to call this category a tie.

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  • Adult Children of Emotionally Immature Parents – by Dr. Lindsay Gibson

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    Not everyone had the best of parents, and the harm done can last well beyond childhood. This book looks at healing that.

    Dr. Gibson talks about four main kinds of “difficult” parents, though of course they can overlap:

    1. The emotional parent, with their unpredictable outbursts
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  • The Worst Cookware Lurking In Your Kitchen (Toxicologist Explains)

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    Dr. Yvonne Burkart gives us a rundown of the worst offenders, and what to use instead:

    Hot mess

    The very worst offender is non-stick cookware, the kind with materials such as Teflon. These are the most toxic, due to PFAS chemicals.

    Non-stick pans release toxic gases, leach chemicals into food, and release microplastic particles, which can accumulate in the body.

    One that a lot of people don’t think about, in that category, is the humble air-fryer, which often as not has a non-stick cooking “basket”. These she describes as highly toxic, as they combine plastic, non-stick coatings, and high heat, which can release fumes and other potentially dangerous chemicals into the air and food.

    You may be wondering: how bad is it? And the answer is, quite bad. PFAS chemicals are linked to infertility, hypertension in pregnancy, developmental issues in children, cancer, weakened immune systems, hormonal disruption, obesity, and intestinal inflammation.

    Dr. Burkart’s top picks for doing better:

    1. Pure ceramic cookware: top choice for safety, particularly brands like Xtrema, which are tested for heavy metal leaching.
    2. Carbon steel & cast iron: durable and safe; can leach iron in acidic foods (for most people, this is a plus, but some may need to be aware of it)
    3. Stainless steel: lightweight and affordable but can leach nickel and chromium in acidic foods at high temperatures. Use only if nothing better is available.

    And specifically as alternatives to air-fryers: glass convection ovens or stainless steel ovens are safer than conventional air fryers. The old “combination oven” can often be a good choice here.

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