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.

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.

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.

Many of us wish we could get a better night’s sleep. Wouldn’t it be great if it was as easy as a mocktail before bed?

That’s what the latest viral trend might have us believe. The “Sleepy Girl Mocktail” is a mix of tart cherry juice, powdered magnesium supplement and soda water. TikTok videos featuring the concoction have garnered hundreds of thousands of views. But, what does the science say? Do these ingredients actually help us sleep?

Tart cherry juice

There is research to show including tart cherry juice in your diet improves overall sleep. Clinical trials show tart cherry juice increases sleep quality and quantity, as well as a lessening insomnia symptoms (compared to a placebo). This could be due to the presence of melatonin, a sleep-promoting hormone, in cherries.

Tart cherry varieties such as Jerte Valley or Montmorency have the highest concentration of melatonin (approximately 0.135 micrograms of melatonin per 100g of cherry juice). Over the counter melatonin supplements can range from 0.5 milligram to over 100 milligrams, with research suggesting those beginning to take melatonin start with a dose of 0.5–2 milligrams to see an improvement in sleep.

Melatonin naturally occurs in our bodies. Our body clock promotes the release of melatonin in the evening to help us sleep, specifically in the two hours before our natural bedtime.

If we want to increase our melatonin intake with external sources, such as cherries, then we should be timing our intake with our natural increase in melatonin. Supplementing melatonin too close to bed will mean we may not get the sleep-promoting benefits in time to get off to sleep easily. Taking melatonin too late may even harm our long-term sleep health by sending the message to our body clock to delay the release of melatonin until later in the evening.

Magnesium – but how much?

Magnesium also works to promote melatonin, and magnesium supplements have been shown to improve sleep outcomes.

However, results vary depending on the amount of magnesium people take. And we don’t yet have the answers on the best dose of magnesium for sleep benefits.

We do know magnesium plays a vital role in energy production and bone development, making it an important daily nutrient for our diets. Foods rich in magnesium include wheat cereal or bread, almonds, cashews, pumpkin seeds, spinach, artichokes, green beans, soy milk and dark chocolate.

Bubbly water

Soda water serves as the base of the drink, rather than a pathway to better sleep. And bubbly water may make the mix more palatable. It is important to keep in mind that drinking fluids close to bedtime can be disruptive to our sleep as it might lead to waking during the night to urinate.

Healthy sleep recommendations include avoiding water intake in the two hours before bed. Having carbonated beverages too close to bed can also trigger digestive symptoms such as bloating, gassiness and reflux during the night.

Bottoms up?

Overall, there is evidence to support trying out the Sleepy Girl Mocktail to see if it improves sleep, however there are some key things to remember:

• timing: to get the benefits of this drink, avoid having it too close to bed. Aim to have it two hours before your usual bedtime and avoid fluids after this time

• consistency: no drink is going to be an immediate cure for poor sleep. However, this recipe could help promote sleep if used strategically (at the right time) and consistently as part of a balanced diet. It may also introduce a calming evening routine that helps your brain relax and signals it’s time for bed

• maximum magnesium: be mindful of the amount of magnesium you are consuming. While there are many health benefits to magnesium, the recommended daily maximum amounts are 420mg for adult males and 320mg for adult females. Exceeding the maximum can lead to low blood pressure, respiratory distress, stomach problems, muscle weakness and mood problems
  

• sugar: in some of the TikTok recipes sugar (as flavoured sodas, syrups or lollies) is added to the drink. While this may help hide the taste of the tart cherry juice, the consumption of sugar too close to bed may make it more difficult to get to sleep. And sugar in the evening raises blood sugar levels at a time when our body is not primed to be processing sugar. Long term, this can increase our risk of diabetes

• sleep environment: follow good sleep hygiene practices including keeping a consistent bedtime and wake time, a wind-down routine before bed, avoiding electronic device use like phones or laptops in bed, and avoiding bright light in the evening. Bright light works to suppress our melatonin levels in the evening and make us more alert.

What about other drinks?

Other common evening beverages include herbal tisanes or teas, hot chocolate, or warm milk.

Milk can be especially beneficial for sleep, as it contains the amino acid tryptophan, which can promote melatonin production. Again, it is important to also consider the timing of these drinks and to avoid any caffeine in tea and too much chocolate too close to bedtime, as this can make us more alert rather than sleepy.

Getting enough sleep is crucial to our health and wellbeing. If you have tried multiple strategies to improve your sleep and things are not getting better, it may be time to seek professional advice, such as from a GP.

Charlotte Gupta, Postdoctoral research fellow, CQUniversity Australia

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