Do you struggle to eat your fruits and vegetables? You are not alone. Less than 5% of Australians eat the recommended serves of fresh produce each day (with 44% eating enough fruit but only 6% eating the recommended vegetables).

Adults should aim to eat at least five serves of vegetables (or roughly 375 grams) and two serves of fruit (about 300 grams) each day. Fruits and vegetables help keep us healthy because they have lots of nutrients (vitamins, minerals and fibre) and health-promoting bioactive compounds (substances not technically essential but which have health benefits) without having many calories.

So, if you are having trouble eating the rainbow, you might be wondering – is it OK to drink your fruits and vegetables instead in a juice or smoothie? Like everything in nutrition, the answer is all about context.

It might help overcome barriers

Common reasons for not eating enough fruits and vegetables are preferences, habits, perishability, cost, availability, time and poor cooking skills. Drinking your fruits and vegetables in juices or smoothies can help overcome some of these barriers.

Juicing or blending can help disguise tastes you don’t like, like bitterness in vegetables. And it can blitz imperfections such as bruises or soft spots. Preparation doesn’t take much skill or time, particularly if you just have to pour store-bought juice from the bottle. Treating for food safety and shipping time does change the make up of juices slightly, but unsweetened juices still remain significant sources of nutrients and beneficial bioactives.

Juicing can extend shelf life and reduce the cost of nutrients. In fact, when researchers looked at the density of nutrients relative to the costs of common foods, fruit juice was the top performer.

So, drinking my fruits and veggies counts as a serve, right?

How juice is positioned in healthy eating recommendations is a bit confusing. The Australian Dietary Guidelines include 100% fruit juice with fruit but vegetable juice isn’t mentioned. This is likely because vegetable juices weren’t as common in 2013 when the guidelines were last revised.

The guidelines also warn against having juice too often or in too high amounts. This appears to be based on the logic that juice is similar, but not quite as good as, whole fruit. Juice has lower levels of fibre compared to fruits, with fibre important for gut health, heart health and promoting feelings of fullness. Juice and smoothies also release the sugar from the fruit’s other structures, making them “free”. The World Health Organization recommends we limit free sugars for good health.

But fruit and vegetables are more than just the sum of their parts. When we take a “reductionist” approach to nutrition, foods and drinks are judged based on assumptions made about limited features such as sugar content or specific vitamins.

But these features might not have the impact we logically assume because of the complexity of foods and people. When humans eat varied and complex diets, we don’t necessarily need to be concerned that some foods are lower in fibre than others. Juice can retain the nutrients and bioactive compounds of fruit and vegetables and even add more because parts of the fruit we don’t normally eat, like the skin, can be included.

So, it is healthy then?

A recent umbrella review of meta-analyses (a type of research that combines data from multiple studies of multiple outcomes into one paper looked at the relationship between 100% juice and a range of health outcomes.

Most of the evidence showed juice had a neutral impact on health (meaning no impact) or a positive one. Pure 100% juice was linked to improved heart health and inflammatory markers and wasn’t clearly linked to weight gain, multiple cancer types or metabolic markers (such as blood sugar levels).

Some health risks linked to drinking juice were reported: death from heart disease, prostate cancer and diabetes risk. But the risks were all reported in observational studies, where researchers look at data from groups of people collected over time. These are not controlled and do not record consumption in the moment. So other drinks people think of as 100% fruit juice (such as sugar-sweetened juices or cordials) might accidentally be counted as 100% fruit juice. These types of studies are not good at showing the direct causes of illness or death.

What about my teeth?

The common belief juice damages teeth might not stack up. Studies that show juice damages teeth often lump 100% juice in with sweetened drinks. Or they use model systems like fake mouths that don’t match how people drinks juice in real life. Some use extreme scenarios like sipping on large volumes of drink frequently over long periods of time.

Juice is acidic and does contain sugars, but it is possible proper oral hygiene, including rinsing, cleaning and using straws can mitigate these risks.

Again, reducing juice to its acid level misses the rest of the story, including the nutrients and bioactives contained in juice that are beneficial to oral health.

So, what should I do?

Comparing whole fruit (a food) to juice (a drink) can be problematic. They serve different culinary purposes, so aren’t really interchangeable.

The Australian Guide to Healthy Eating recommends water as the preferred beverage but this assumes you are getting all your essential nutrients from eating.

Where juice fits in your diet depends on what you are eating and what other drinks it is replacing. Juice might replace water in the context of a “perfect” diet. Or juice might replace alcohol or sugary soft drinks and make the relative benefits look very different.

On balance

Whether you want to eat your fruits and vegetables or drink them comes down to what works for you, how it fits into the context of your diet and your life.

Smoothies and juices aren’t a silver bullet, and there is no evidence they work as a “cleanse” or detox. But, with society’s low levels of fruit and vegetable eating, having the option to access nutrients and bioactives in a cheap, easy and tasty way shouldn’t be discouraged either.

Emma Beckett, Adjunct Senior Lecturer, Nutrition, Dietetics & Food Innovation – School of Health Sciences, UNSW Sydney

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

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.