Does intermittent fasting have benefits for our brain?
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Intermittent fasting has become a popular dietary approach to help people lose or manage their weight. It has also been promoted as a way to reset metabolism, control chronic disease, slow ageing and improve overall health.
Meanwhile, some research suggests intermittent fasting may offer a different way for the brain to access energy and provide protection against neurodegenerative diseases like Alzheimer’s disease.
This is not a new idea – the ancient Greeks believed fasting enhanced thinking. But what does the modern-day evidence say?
First, what is intermittent fasting?
Our diets – including calories consumed, macronutrient composition (the ratios of fats, protein and carbohydrates we eat) and when meals are consumed – are factors in our lifestyle we can change. People do this for cultural reasons, desired weight loss or potential health gains.
Intermittent fasting consists of short periods of calorie (energy) restriction where food intake is limited for 12 to 48 hours (usually 12 to 16 hours per day), followed by periods of normal food intake. The intermittent component means a re-occurrence of the pattern rather than a “one off” fast.
Food deprivation beyond 24 hours typically constitutes starvation. This is distinct from fasting due to its specific and potentially harmful biochemical alterations and nutrient deficiencies if continued for long periods.
4 ways fasting works and how it might affect the brain
The brain accounts for about 20% of the body’s energy consumption.
Here are four ways intermittent fasting can act on the body which could help explain its potential effects on the brain.
1. Ketosis
The goal of many intermittent fasting routines is to flip a “metabolic switch” to go from burning predominately carbohydrates to burning fat. This is called ketosis and typically occurs after 12–16 hours of fasting, when liver and glycogen stores are depleted. Ketones – chemicals produced by this metabolic process – become the preferred energy source for the brain.
Due to this being a slower metabolic process to produce energy and potential for lowering blood sugar levels, ketosis can cause symptoms of hunger, fatigue, nausea, low mood, irritability, constipation, headaches, and brain “fog”.
At the same time, as glucose metabolism in the brain declines with ageing, studies have shown ketones could provide an alternative energy source to preserve brain function and prevent age-related neurodegeneration disorders and cognitive decline.
Consistent with this, increasing ketones through supplementation or diet has been shown to improve cognition in adults with mild cognitive decline and those at risk of Alzheimer’s disease respectively.
2. Circadian syncing
Eating at times that don’t match our body’s natural daily rhythms can disrupt how our organs work. Studies in shift workers have suggested this might also make us more prone to chronic disease.
Time-restricted eating is when you eat your meals within a six to ten-hour window during the day when you’re most active. Time-restricted eating causes changes in expression of genes in tissue and helps the body during rest and activity.
A 2021 study of 883 adults in Italy indicated those who restricted their food intake to ten hours a day were less likely to have cognitive impairment compared to those eating without time restrictions.
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3. Mitochondria
Intermittent fasting may provide brain protection through improving mitochondrial function, metabolism and reducing oxidants.
Mitochondria’s main role is to produce energy and they are crucial to brain health. Many age-related diseases are closely related to an energy supply and demand imbalance, likely attributed to mitochondrial dysfunction during ageing.
Rodent studies suggest alternate day fasting or reducing calories by up to 40% might protect or improve brain mitochondrial function. But not all studies support this theory.
4. The gut-brain axis
The gut and the brain communicate with each other via the body’s nervous systems. The brain can influence how the gut feels (think about how you get “butterflies” in your tummy when nervous) and the gut can affect mood, cognition and mental health.
In mice, intermittent fasting has shown promise for improving brain health by increasing survival and formation of neurons (nerve cells) in the hippocampus brain region, which is involved in memory, learning and emotion.
Shutterstock
There’s no clear evidence on the effects of intermittent fasting on cognition in healthy adults. However one 2022 study interviewed 411 older adults and found lower meal frequency (less than three meals a day) was associated with reduced evidence of Alzheimer’s disease on brain imaging.
Some research has suggested calorie restriction may have a protective effect against Alzheimer’s disease by reducing oxidative stress and inflammation and promoting vascular health.
When we look at the effects of overall energy restriction (rather than intermittent fasting specifically) the evidence is mixed. Among people with mild cognitive impairment, one study showed cognitive improvement when participants followed a calorie restricted diet for 12 months.
Another study found a 25% calorie restriction was associated with slightly improved working memory in healthy adults. But a recent study, which looked at the impact of calorie restriction on spatial working memory, found no significant effect.
Bottom line
Studies in mice support a role for intermittent fasting in improving brain health and ageing, but few studies in humans exist, and the evidence we have is mixed.
Rapid weight loss associated with calorie restriction and intermittent fasting can lead to nutrient deficiencies, muscle loss, and decreased immune function, particularly in older adults whose nutritional needs may be higher.
Further, prolonged fasting or severe calorie restriction may pose risks such as fatigue, dizziness, and electrolyte imbalances, which could exacerbate existing health conditions.
If you’re considering intermittent fasting, it’s best to seek advice from a health professional such as a dietitian who can provide guidance on structuring fasting periods, meal timing, and nutrient intake. This ensures intermittent fasting is approached in a safe, sustainable way, tailored to individual needs and goals.
Hayley O’Neill, Assistant Professor, Faculty of Health Sciences and Medicine, Bond University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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Quit Drinking – by Rebecca Dolton
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Many “quit drinking” books focus on tips you’ve heard already—cut down like this, rearrange your habits like that, make yourself accountable like so, add a reward element this way, etc.
Dolton takes a different approach.
She focuses instead on the underlying processes of addiction, so as to not merely understand them to fight them, but also to use them against the addiction itself.
This is not just a social or behavioral analysis, by the way, and goes into some detail into the physiological factors of the addiction—including such things as the little-talked about relationship between addiction and gut flora. Candida albans, found in most if not all humans to some extent, gets really out of control when given certain kinds of sugars (including those from alcohol); it grows, eventually puts roots through the intestinal walls (ouch!) and the more it grows, the more it demands the sugars it craves, so the more you feed it.
Quite a motivator to not listen to such cravings! It’s not even you that wants it, it’s the Candida!
Anyway, that’s just one example; there are many. The point here is that this is a well-researched, well-written book that sets itself apart from many of its genre.
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To Medicate or Not? That is the Question! – by Dr. Asha Bohannon
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Medications are, of course, a necessity of life (literally!) for many, especially as we get older. Nevertheless, overmedication is also a big problem that can cause a lot of harm too, and guess what, it comes with the exact same “especially as we get older” tag too.
So, what does Dr. Bohannon (a doctor of pharmacy, diabetes educator, and personal trainer too) recommend?
Simply put: she recommends starting with a comprehensive health history assessment and analysing one’s medication/supplement profile, before getting lab work done, tweaking all the things that can be tweaked along the way, and—of course—not neglecting lifestyle medicine either.
The book is prefaced and ended with pep talks that probably a person who has already bought the book does not need, but they don’t detract from the practical content either. Nevertheless, it feels a little odd that it takes until chapter 4 to reach “step 1” of her 7-step method!
The style throughout is conversational and energetic, but not overly padded with hype; it’s just a very casual style. Nevertheless, she brings to bear her professional knowledge and understanding as a doctor of pharmacy, to include her insights into the industry that one might not observe from outside of it.
Bottom line: if you’d like to do your own personal meds review and want to “know enough to ask the right questions” before bringing it up with your doctor, this book is a fine choice for that.
Click here to check out To Medicate Or Not, and make informed choices!
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Ikigai – by Héctor García and Francesc Miralles
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Ikigai is the Japanese term for what in English we often call “raison d’être”… in French, because English is like that.
But in other words: ikigai is one’s purpose in life, one’s reason for living.
The authors of this work spend some chapters extolling the virtues of finding one’s ikigai, and the health benefits that doing so can convey. It is, quite clearly, an important and relevant factor.
The rest of the book goes beyond that, though, and takes a holistic look at why (and how) healthy longevity is enjoyed by:
- Japanese people in general,
- Okinawans in particular,
- Residents of Okinawa’s “blue zone” village with the highest percentage of supercentenarians, most of all.
Covering considerations from ikigai to diet to small daily habits to attitudes to life, we’re essentially looking at a blueprint for healthy longevity.
For a book whose title and cover suggests a philosophy-heavy content, there’s a lot of science in here too, by the way! From microbiology to psychiatry to nutrition science to cancer research, this book covers all bases.
In short: this book gives a lot of good science-based suggestions for adjustments we can make to our lives, without moving to an Okinawan village!
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Successful Aging – by Dr. Daniel Levitin
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We all know about age-related cognitive decline. What if there’s a flipside, though?
Neuroscientist Dr. Daniel Levitin explores the changes that the brain undergoes with age, and notes that it’s not all downhill.
From cumulative improvements in the hippocampi to a dialling-down of the (often overfunctioning) amygdalae, there are benefits too.
The book examines the things that shape our brains from childhood into our eighties and beyond. Many milestones may be behind us, but neuroplasticity means there’s always time for rewiring. Yes, it also covers the “how”.
We learn also about the neurogenesis promoted by such simple acts as taking a different route and/or going somewhere new, and what other things improve the brain’s healthspan.
The writing style is very accessible “pop-science”, and is focused on being of practical use to the reader.
Bottom line: if you want to get the most out of your aging wizening brain, this book is a great how-to manual.
Click here to check out Successful Aging and level up your later years!
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Coughing/Wheezing After Dinner?
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The After-Dinner Activities You Don’t Want
A quick note first: our usual medical/legal disclaimer applies here, and we are not here to diagnose you or treat you; we are not doctors, let alone your doctors. Do see yours if you have any reason to believe there may be cause for concern.
Coughing and/or wheezing after eating is more common the younger or older someone is. Lest that seem contradictory: it’s a U-shaped bell-curve.
It can happen at any age and for any of a number of reasons, but there are patterns to the distribution:
Mostly affects younger people:
Allergies, asthma
Young people are less likely to have a body that’s fully adapted to all foods yet, and asthma can be triggered by certain foods (for example sulfites, a common preservative additive):
Adverse reactions to the sulphite additives
Foods/drinks that commonly contain sulfites include soft drinks, wines and beers, and dried fruit
As for the allergies side of things, you probably know the usual list of allergens to watch out for, e.g: dairy, fish, crustaceans, eggs, soy, wheat, nuts.
However, that’s far from an exhaustive list, so it’s good to see an allergist if you suspect it may be an allergic reaction.
Affects young and old people equally:
Again, there’s a dip in the middle where this doesn’t tend to affect younger adults so much, but for young and old people:
Dysphagia (difficulty swallowing)
For children, this can be a case of not having fully got used to eating yet if very small, and when growing, can be a case of “this body is constantly changing and that makes things difficult”.
For older people, this can can come from a variety of reasons, but common culprits include neurological disorders (including stroke and/or dementia), or a change in saliva quality and quantity—a side-effect of many medications:
Hyposalivation in Elderly Patients
(particularly useful in the article above is the table of drugs that are associated with this problem, and the various ways they may affect it)
Managing this may be different depending on what is causing your dysphagia (as it could be anything from antidepressants to cancer), so this is definitely one to see your doctor about. For some pointers, though:
NHS Inform | Dysphagia (swallowing problems)
Affects older people more:
Gastroesophagal reflux disease (GERD)
This is a kind of acid reflux, but chronic, and often with a slightly different set of symptoms.
GERD has no known cure once established, but its symptoms can be managed (or avoided in the first place) by:
- Healthy eating (Mediterranean diet is, as usual, great)
- Weight loss (if and only if obese)
- Avoiding trigger foods
- Eating smaller meals
- Practicing mindful eating
- Staying upright for 3–4 hours after eating
And of course, don’t smoke, and ideally don’t drink alcohol.
You can read more about this (and the different ways it can go from there), here:
NICE | Gastro-oesophageal reflux disease
Note: this above page refers to it as “GORD”, because of the British English spelling of “oesophagus” rather than “esophagus”. It’s the exact same organ and condition, just a different spelling.
Take care!
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Monosodium Glutamate: Sinless Flavor-Enhancer Or Terrible Health Risk?
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What’s The Deal With MSG?
There are a lot of popular beliefs about MSG. Is there a grain of truth, or should we take them with a grain of salt? We’ll leap straight into myth-busting:
MSG is high in salt
True (technically) False (practically)
- MSG is a salt (a monosodium salt of L-glutamic acid), but to call it “full of salt” in practical terms is like calling coffee “full of fruit”. (Coffee beans are botanically fruit)
- It does contain sodium, though which is what the S stands for!
- We talked previously about how MSG’s sodium content is much lower than that of (table) salt. Specifically, it’s about one third of that of sodium chloride (e.g. table salt).
MSG triggers gluten sensitivity
False!
Or at least, because this kind of absolute negative is hard to prove in science, what we can say categorically is: it does not contain gluten. We understand that the similar name can cause that confusion. However:
- Gluten is a protein, found in wheat (and thus wheat-based foods).
- Glutamate is an amino acid, found in protein-rich foods.
- If you’re thinking “but proteins are made from amino acids”, yes, they are, but the foundational amino acid of gluten is glutamine, not glutamate. Different bricks → different house!
The body can’t process MSG correctly
False!
The body has glutamate receptors throughout the gut and nervous system.
The body metabolizes glutamate from MSG just the same as from any other food that contains it naturally.
Read: Update on food safety of monosodium l-glutamate (MSG) ← evidence-based safety review
MSG causes “Chinese Restaurant Syndrome”
False!
Racism causes that. It finds its origins in what was originally intended as a satirical joke, that the papers picked up and ran with, giving it that name in the 1960s. As to why it grew and persisted, that has more to do with US politics (the US has been often at odds with China for a long time) and xenophobia (people distrust immigrants, such as those who opened restaurants), including nationalistic rhetoric associating immigrants with diseases.
Read: Xenophobia in America in the Age of Coronavirus and Beyond ← academic paper that gives quite a compact yet comprehensive overview
Research science, meanwhile, has not found any such correlation, in more than 40 years of looking.
PS: we realize this item in the list is very US-centric. Apologies to our non-US subscribers. We know that this belief isn’t so much of a thing outside the US—though it certainly can crop up elsewhere sometimes, too.
Are there any health risks associated with MSG, then?
Well, as noted, it does contain sodium, albeit much less than table salt. So… do go easy on it, all the same.
Aside from that, the LD50 (a way of measuring toxicity) of MSG is 15.8g/kg, so if for example you weigh 150lb (68 kg), don’t eat 2.2lb (a kilogram) of MSG.
There have been some studies on rats (or in one case, fruit flies) that found high doses of MSG could cause heart problems and/or promote obesity. However:
- this has not been observed to be the case in humans
- those doses were really high, ranging from 1g/kg to 8g/kg. So that’d be the equivalent of our 150lb person eating it by the cupful
- it was injected (as a solution) into the rats, not ingested by them
- so don’t let someone inject you with a cup of MSG!
Read: A review of the alleged health hazards of monosodium glutamate
Bottom line on MSG and health:
Enjoy in moderation, but enjoy if you wish! MSG is just the salt form of the amino acid glutamate, which is found naturally in many foods, including shrimp, seaweed, and tomatoes.
Scientists have spent more than 40 years trying to find health risks for MSG, and will probably keep trying (which is as science should be), but for now… Everything has either come up negative, or has been the result of injecting laboratory animals with megadoses.
If you’d like to try it in your cooking as a low-sodium way to bring out the flavor of your dishes, you can order it online. Cheapest in bulk, but try it and see if you like it first!
(I’ll be real with you… I have 5 kg in the pantry myself and use about half a teaspoon a day, cooking for two)
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