Many people don’t eat enough fruit and vegetables, and at a population level we seem to score under par. However, I’ve noticed an interesting seasonal trend with some of my clients over summer. One where if they tend to be prone to metabolic issues like weight gain and blood sugar control these tend to spike; and the common thread is fruit.
This got me to investigate, how much fruit should you eat? Is there such thing as consuming too much, and if so, what is it?
How much fruit according to the Australian Dietary Guidelines
Now back in the 2000s there was a relatively successful campaign called “Go for 2 and 5” which educated us on the Australian Dietary Guidelines. This tells us how much fruit and vegetable we should be consuming. The evidence seems to show that as a population we should be aiming for 2 serves of fruit and 5 serves of vegetables per day.
We know that it was a successful campaign, as over the campaign period the awareness of these ads went from 20% to 70% of survey respondents (Department of Health & Ageing, 2007). Interesting though, while 94% of respondents were able to correctively give the fruit consumption guidelines of 2 or more serves per day, only 32% correctly gave the correct response of 5 or more serves of vegetables.
This got me thinking. Do we have a confirmation bias when it comes to fruit and vegetable consumption? By this I mean that we tend to hear the message that we should be eating more of the lovely sweet stuff. But ignore the message regarding boring old vegetables.
Perhaps we thought the message was go for 5 and 2 rather than 2 and 5?
So does excessive fruit consumption matter to our health?
At least if we look at the report published on the success of the Go for 2 and 5 campaign we see that people were already consuming the guidelines of two serves of fruit per day on average. While the average serves of vegetables scraped in at just over half of the guideline at 2.6 serves. Interestingly, while we already succeeded as a nation at consuming 2 serves of fruit 43% indicated that they planned on increasing their fruit consumption. Only 28% planned on increasing their vegetables.
Certainly this appears as though the message of eating more fruit was much more palatable to survey respondents.
So it doesn’t surprise me then when I see a dramatic spike in how much fruit some of my clients eat over summer. This amount for some was up to 5-10 serves per day. Now clinically we saw increases in 1-2 kg of weight and spikes in blood sugar levels, even though these clients were doing what they thought was best for their health. They have listened to part of the message (the part which is most palatable for us sweet tooths!) and simply didn’t consider that you might be able to have too much fruit!
In summer we tend to have an explosion of seasonal fruit to the market. Stone fruits, melons, and tropical fruits all tend to hit our grocery stores at a cheaper price. Interestingly, all of my clients who have drastically increased their consumption of fruits over summer had a stone fruit tree such as peaches and nectarines in their backyard.
So how much fruit should you eat per day?
Well that depends on what you may want to prevent health wise, but somewhere between 2-3 serves per day seems to be the “sweet spot”. If you want to know the science to this conclusion, and what fruits tend to work best for you, please read part two of this blog!
About the author
So we established in Part 1 of this blog that the guidelines suggest that two or more serves is how much fruit we should consume. However, for some of us, it’s really easy to over consume. And this may well be having a negative impact on our health. Now I finished the previous blog with suggesting that somewhere between 2 to 3 serves is most ideal. But what if I have metabolic issues? Are there better and worse fruits to consume?
How much fruit should I consume to protect the heart?
Interestingly, many studies have looked into this question. However, they tend to combine fruit and vegetables together making it hard to conclude. One study by Lai et al (2015) looked into this and found that in a group of UK women the risk of death from a cardiovascular event decreased with more fruit even with over 4 serves per day. It’s would be easy from this to conclude that more is better right?
Another UK study looked at the risk of death from cardiovascular disease or cancer in both men and women (Oyebode et al 2013). What they found was that increased vegetable consumption was more protective than fruit. When they looked at just fruit intake the greatest benefit was at 3 serves per day. Depending on the model used, an increase in serves beyond this either had no further benefit or increased your risk.
How much fruit should I eat for metabolic health?
So we know that 3-4 serves of fruit is good for the heart. But what about people who are at risk of or want to prevent diabetes?
We have a good amount of evidence here that perhaps we shouldn’t be eating too much fruit. In fact a very large meta-analysis of 7 studies by Li et al (2015) concluded that those who had a fruit intake of around 200 grams per day (about 1.5 serves) were less at risk of developing diabetes. While it certainly is not good to have no fruit in a day, having 3-4 serves increased your risk comparatively. And from there, things tended to get worse with increased fruit consumption.
Furthermore, a study by Zhang & Jiang (2015) tended to corroborate this finding with two serves a day being the “sweet spot” for reducing the risk of developing diabetes in a study of over 200,000 individuals. And similar to the Li et al (2015) meta-analysis, they found a similar U shaped curve when consumption increased above 2 serves with 4 serves being as high a risk as having no fruit at all.
So there may be such thing as too much of a good thing. And like most things we need to consume fruit in moderation, especially if we’re at risk of diabetes and metabolic conditions.
But are some fruits better than others? Well the short answer to this question is “yes”
Fruits that when you consume more to have a health benefit
Interestingly, most studies will show that vegetables have a stronger association in reducing premature death than fruit (Oyebode et al 2013). However, some fruits, when you consume more tend to reduce your risk of either cardiovascular disease or diabetes.
Lai et al (2015) found that a greater intake of citrus was associated with a lower risk of fatal stroke in women. While grapes were seen to be more protective against a fatal cardiovascular event. When we look at the risk of diabetes, Alperet et al (2017) found that temperate fruit such as apples was associated with a loser risk of diabetes in women. Both citrus and grapes tended to lower the risk of diabetes for both men and women.
So it appears there are some common threads: citrus and grapes tend to reduce our risk. But what about fruits that perhaps aren’t so good for us to overconsume?
Fruits that may not be good for us when we over consume
Firstly, a common theme in most studies is that fruit juice is not fruit! Imamura et al (2015) found that while not quite as bad as soft drink (every serve a day increased your risk of diabetes by 18%), every serve of fruit juice increased your risk by 5%.
When it comes to increasing your risk of cardiovascular disease it seems that any canned fruit will do this (Oyebode et al, 2013). They found that every daily serve increased your risk by 17%.
Now there it appears that too much tropical fruits (bananas, mangoes, melons) will increase your risk of diabetes and these should be limited to less than one serve a day (Alperet et al 2017). Interesting Huang et al (2017) found that tropical fruit increased the risk of gestational diabetes.
Finally, Alperet et al (2017) also found that higher glycaemic index (GI) fruits had a greater risk than lower GI fruits. While these fruits tend to be more tropical in nature here’s a list of fruits with a GI greater than 50:
- Watermelon – 72
- Pineapple – 66
- Rock melon – 65
- Paw Paw – 60
- Canned Peaches – 58
- Banana – 56 (although increases with ripeness)
- Kiwi Fruit – 52
The take home message about how much fruit you should eat
- The amount of fruit you eat is important. 2-3 serves per day is probably best for your long term health but more than 4 may increase your your risk of metabolic conditions such as diabetes.
- Try and limit your consumption of high glycaemic fruits like tropical fruits and treat them as “treats”.
- Don’t count fruit juice as a fruit, if anything it should be treated more like soft drink
- Aim to get the bulk of your 2-3 serves of fruit a day from lower or moderate GI fruits. Fruits like grapes, apples and citrus all appear to reduce your risk of health conditions as you age.
About the author
What do exercise and a diet high in fibre have in common? We’ve known for some time now that both of these are good for our gut health and decrease our risk of colon cancer. However, it seems as though there may something extra that fibre and exercise have in common, and it comes as a fatty acid called butyrate. This link between exercise, fibre and gut health will be explored, and you’ll see that the effects travel as far as the brain.
What actually is butyrate and what does it do?
Butyrate is a short chain fatty acid produced by our gut bacteria as they break down foods that are high in fibre. Resistant starches are a type of fibre, that are some of the best fuels for these butyrate producing bacteria (Bourassa 2016). These starches come in foods such as legumes, oats and starches that are cooked and cooled like potato and rice salads.
Now butyrate is an important fuel for the cells of our colon. In fact it supplies up to 70% of their energy (Bourassa 2016). Keeping your colon cells healthy is thought to be one of the reasons why higher butyrate levels decrease your risk of colon cancer by 50% (Matsumoto et al, 2008).
However, the benefits of butyrate go well beyond reducing our risk of colon cancer. This is because healthier gut membranes improve their integrity (how closely they bond together) allowing them to act as a better barrier, which has flow on effects to improving our immunity and reducing inflammation (Ji Wang et al, 2018).
What’s the evidence on exercise and gut health?
Most of the interest on the effect of exercise on butyrate levels started back in 2008. Matsumoto and colleagues showed that butyrate levels, and the bacteria that produce butyrate, were higher in rats that exercised versus a sedentary control.
In 2014 a group of Irish researchers found that professional rugby players had a greater diversity of gut microbiota than a group of sedentary controls (Clarke et al, 2014). However a signifiant limitation in this study was that professional athletes eat very differently than the general population. And these results could possibly be related to their diet and not their activity.
We had to wait until late last year when a group from the University of Illinois designed a study that looked at the impact of aerobic exercise on butyrate. Previously sedentary individuals were asked to exercise three times a week for a 6 week period (Allen et al 2017). What they found was that there is a link between butyrate, exercise, and gut health in humans.
Much like the rodent study back in 2008 they found that aerobic exercise increases the levels of butyrate along with the colonies of bacteria that produce butyrate. Interestingly this effect was most pronounced in lean subjects. The overweight group did still increase the colonies of the butyrate producing bacteria (not to the extent of the lean group) but they didn’t see an increase in butyrate levels in their stools.
Exercise and gut health can also improve your brain!
Now here is where it really gets interesting. The term “your gut is your second brain” has been well used over the last decade. This has been used to explain that the enteric nervous system of the gut is not only quite complex, but it also has the capacity to signal the brain via many neurotransmitters.
We know that butyrate can cross the blood brain barrier and it is well known to suppress HDAC (Histone deacetylase; Bourassa 2016). Now HDAC inhibitors will increase the expression of BDNF (Brain-derived neurotrophic factor) in the brain. This is important for memory and learning as BDNF is like fertiliser for the brain. It helps your brain cells grow in number and connections!
So where’s the research at?
An interesting experiment, albeit in mice, was published back in 2013 where mice were given an object recognition memory task that is usually not enough to form in either their short or long term memory (Intlekofer et al, 2013). They had a sedentary group and a group that was exercising 3 weeks before the task. They also had a sedentary and exercising group that was injected with butyrate.
The non-butyrate injected sedentary mice could not successfully remember the task 24 hours post initial exposure However, both the sedentary/butyrate injected group and the exercise group could. And when it came to remembering the task 7 days after the initial exposure, it was only the butyrate group that could.
It is important to know that the exercise group only did so for the 3 weeks leading up to the task, and not during the 7 days after the task. This highlights that to get the improved learning outcome, continual exercise exposure is needed.
This mechanism of increased BDNF release via butyrate is probably why we see that children who are fed a high fibre diet perform better in cognitive tasks than those on a low fibre diet (Bourassa 2016). And it could also be the reason why it shows promise in the treatment of neurodegenerative diseases (Bourassa 2016).
We also know that aerobic exercise has an effect on increasing BDNF levels, and this may be why individuals have a 20% improvement in learning tasks (Winter et al, 2007). So it makes sense to eat a high fibre diet and exercise at the same time right?
Take home points about exercise and gut health:
- It appears as though aerobic exercise continues to benefit our health in many different ways, and improving our gut health is another reason to be active. Aerobic exercise of around 30 to 60 minutes a few times a week can give you this benefit to your gut.
- Improve the diversity of your microbiota through eating foods that are high in butyrate producing fibre such as legumes, oats and potato salads.
- Combine this with regular exercise to improve the butyrate production of your gut as this have effects that travel to your brain.
- And while there is still much more research to be done, it seems to indicate that by doing this you are improving your capacity to learn and remember things, along with decreasing your risk of developing neurodegenerative conditions such as Alzheimer’s.
About the Author
Practical tips to reduce pain
Now understanding what pain is and how it protects us is useful, but now I would like to use this information to give some practical tips to reduce pain.
In Part 1 of this blog series we learnt that we need pain to survive, to avoid danger and protect us from injury. However in Part 2 we learnt that the protective response from an injury, such as muscle tightness and weakness can persist long after our tissue has healed. This can lead to pain being present for much longer than needed.
So if your pain has persisted for longer than the usual tissue healing time (around 3-6 months), then it might be useful to read below:
Tips to reduce pain:
Find movements that you feel comfortable with and progress slowly.
We know that pain is the result of our brain feeling as though we’ve pushed our tissue tolerance above a certain threshold (Butler & Moseley, 2013). So it’s firstly important to know where that threshold is at and gradually challenge this over time. For example, if your back gets sore after 10 minutes of continuous walking, start with less. Then you gradually build this up minute by minute until you get to an amount you’re happy with.
Now please understand, you will experience flare ups from time to time. However, it’s important not to worry about this. Unless there has been another injury/trauma (you will generally feel this at the time), these flare ups in pain are just a way of your brain telling you that you need to pull it back a bit. Go back to what was previously comfortable and then progress slowly once more.
Train your brain before you train your body
At times movement may be too much. You may know what types of movement give you pain. Quite often these movements are very similar to the movement that may have created your injury in the first place. So why not start with imagining the movement?
Motor skills studies show that just by imagining movements you can improve them. One in particular showed that basketballers who imagined free throws improved just as much as those that physically performed the task (Richardson, 1967).
Now when it comes to pain it’s important to imagine the movement pain free and in a relaxed state. Sometimes just thinking about an aggravating movement can make you feel anxious. It may bring up emotions that you need to recognise to move on. In this case you may need to relax yourself once more before you return to imagining the movement.
Distraction can be a great way to reduce pain
Our levels of pain are amplified in the brain when we focus on them. It makes sense that when we add other stimuli it gives your brain more to process therefore it decreases the pain stimuli (Schreiber et al, 2014).
Distraction is a great way to do this. Some things to consider while you exercise are listening to music, changing your visual input (closing your eyes or using mirrors), performing cognitive tasks (like crosswords/sudoku), adding balance (standing on one leg or moving on an unstable surface), and changing your environment (try outdoors, indoors or in water).
Find an aerobic exercise that suits you and perform it regularly
Now I understand that sometimes when you’re in pain it’s hard to find an aerobic form of exercise that is tolerable. However, research shows that if you can tolerate it (even if it produces a 6/10 pain level), doing it regularly will reduce your pain. This is because aerobic exercise has been shown to reduce your central immune response via the glial cells (Cobianchi, et al, 2017). People with chronic pain can quite often have a hypersensitive central immune system. When this system is always on it creates an inflammatory response, even when it’s not needed. So when you exercise is down regulates this response, leading to less inflammation and in turn reduces pain.
Choose fun, enjoyable activities with people you love!
Finally, one of my favourite pieces of advice is to find activities and movements you love! Not only will this help you reduce pain, we know that people who have hobbies and activities they enjoy typically live longer (and happier) than those who don’t (Fushiki et al, 2012).
In our brainstem we have certain areas that pick up pleasure and displeasure. Interestingly the area of displeasure is closely associated with areas of the brain that detect and produce pain. The pleasure centre does not have this relationship but is closely related to movement and attraction. So let’s use this to our advantage and find activities you actually want to do. It may even help you stay motivated to doing things that aren’t as pleasurable (such as the homework exercises your exercise physiologist gives you), so long as you can relate it to the activity you love (for me this activity is trail running!).
So there you go. Hopefully I’ve given you some practical ideas to reduce your pain and help you get back to doing the things you love doing. Obviously if you need any help with any of the tips above, we are alway here to help you with your journey free of pain.
Butler, D.S., & Moseley, G.L. (2013). Explain Pain (2nd Ed). Adelaide: Noigroup Publications
Cobianchi, S., Arbat-Plana, A., López-Álvarez, V. M., & Navarro, X. (2017). Neuroprotective Effects of Exercise Treatments After Injury: The Dual Role of Neurotrophic Factors. Current Neuropharmacology, 15(4), 495–518. http://doi.org/10.2174/1570159X14666160330105132
Fushiki, Y., Ohnishi, H., Sakauchi, F., Oura, A., & Mori, M. (2012). Relationship of Hobby Activities With Mortality and Frailty Among Community-Dwelling Elderly Adults: Results of a Follow-up Study in Japan. Journal of Epidemiology, 22(4), 340–347. http://doi.org/10.2188/jea.JE20110057
Richardson, A.. (1967) Mental Practice: A Review & Discussion Parts 1 & 2, Research Quarterly. American Association for Health, Physical Education and Recreation. Volume 38, Issue 1.
Schreiber, K.L., Campbell, C., Martel, M.O., Greenbaum, S., Wasan, A.D., Borsook, D., Jamison, R.N., & Edwards, R.R. (2014) Distraction Analgesia in Chronic Pain Patients: The Impact of Catastrophizing. Anesthesiology;121(6):1292-1301. doi: 10.1097/ALN.0000000000000465.
If you’ve followed iNform’s blogs and social media we quite often comment that we are “Made to Move”. However, why do we (I’m talking society as a whole) find it so hard to get out and be active? Why is it so easy to be lazy? Well it seems our drive toward sedentarism is not a new thing. We’ve just happened to get really good at it in recent years!
You see the evolution of us humans has been occurring for hundreds of thousands of years and for around 95% of this time we were hunters and gatherers of our food. During this time we used to walk 15-20 km per day, mainly in search for food (Cordain et al., 1998). We are still physiologically built for this environment, hence we were made to move.
Evolution may drive our desire to be lazy
However, like most animals, we have an in built drive to maximising our energy intake while minimising our expenditure and become as lazy as possible. We needed to be efficient at gathering our food, but in the days of hunting and gathering it was most efficient to stay on the move (Park, 1988). Even the success of a tribe (as expressed by their fertility rates) were greater if they moved more (Surovell, 2000).
Our drive for dopamine kept us on the move
So during this time our physiology worked for us. The increase in protein from hunting, led to increased dopamine production, which led to brain development (Previc, 1999). Now dopamine is a hormone that drives us to explore and increases our desire to move and do things. This drive is what gives us the desire to travel and see the world. However in today’s environment this involves very little physical activity!
Interestingly a lack of dopamine production and sensitivity leads to decreased physical activity in animal studies (Ingram, 2000). Scientists have also found the “lazy gene” in rodents which decreases the amount of dopamine receptors making you less like to enjoy the exploratory movement benefits of dopamine (http://ajpregu.physiology.org/content/early/2013/03/28/ajpregu.00581.2012).
Now if we go back to our hunting and gathering days, exercise would have been in the form of chase hunting. This involved running with a prey until it dropped of exhaustion. Interestingly this type of exercise would have further increased our dopamine levels (Previc, 1999). This positive feedback loop was thought to help us develop into the intelligent species we are today!
So what happened, why did we become so lazy?
Why do so many of us lack the motivation to move? You see dopamine feeds on itself. It increases when you move more but to get it’s feel good exploratory effects you need to start moving! And in today’s environment we no longer need to move to survive!
And where did it all go wrong? As I stated above, most creatures are hardwired to conserve energy, and around 40,000 years ago we learnt that rather than adapting to our environment we could manipulate the environment to suit us. This period was toward the end of the Ice Age and as the Earth warmed cereal crops flourished. By 10,000 years ago we started to get really good at farming and hence the agricultural revolution began (Phelps, 1994).
This meant that we could stay in one place and tend to our crops. We could also store surplus grains for the winter. Where once our hunting and gathering tribes would have mobile camps, humans were now able to establish more permanent housing structures and areas to congregate, and create barriers to keep predators and the pressures of external nature away (Mumford, 1956).
Now over time we’ve gradually become better and better at food production, needing less physical energy to produce. The industrial revolution brought the machines that would end up doing the work for us. Now, the vast majority of us, no longer need to expend energy to get our food and being lazy has become an option.
Fighting our drive to become lazy
All of this came about due to our innate drive to conserve energy in order for us to feel safe and secure. It has now got the the point where high energy food is an abundance and we have to do very little to get it. We can literally sit in the comfort of our homes (even work from home like I’m currently doing!) and order our food to be delivered to us.
Think of how much movement you need to do in the day. Once it was part of life in order to survive but now movement, for most people is a choice. The problem being is that our physiological systems and hence our physical health are built in a stone-age time of when we were “made to move”.
Without thinking, our hardwiring will drive us to be as sedentary as possible and we now have the physical environment to allow us to do this. So this choice to move now needs to be a conscious one. What we do have going in our favour though is the dopaminergic system that feeds on itself. Once we start moving and exercising, we’ll be driven to do more, and as a consequence we’ll improve our brain function and overall health.
So your choice is simple.
Either you sit back and let this innate drive toward laziness and physical environment we’re creating push you toward and enclosed sedentary lifestyle; OR, you get back to your hunting and gathering roots and choose to move more and explore this world we live in!
Cordain, L., Gotshall, R. W., Boyd Eaton, S., & Boyd Eaton III, S. (1998). Physical activity, energy expenditure and fitness: An evolutionary perspective. International Journal of Sports Medicine, 19, 328-335.
Ingram, D. K. (2000). Age-related decline in physical activity: Generalization to nonhumans. Medicine and Science in Sports and Exercise, 32(9), 1623-1629.
Mumford, L. (1956). The natural history of urbanization. In W. L. Thomas (Ed.), Man’s role in changing the face of the earth (pp. 382-400). Chicago: University of Chicago Press.
Park, R. J. (1988). How active were early populations? Or squeezing the fossil record. In R. M. Malina & H. M. Eckert (Eds.), Physical activity in early and modern populations: American Academy of Physical Education papers No. 21 (pp. 13-21). Champaign, IL: Human Kinetics.
Phelps, M. T. (1994). How important is the role of intelligence in the rise of civilization? Mankind Quarterly, 34(4), 287-296.
Previc, F. H. (1999). Dopamine and the origins of human intelligence. Brain and Cognition., 41(3), 299-350.
Roberts, M.D., Brown, J.D., Company, J.M., Oberle, L.P., Heese, A.J., Toedebusch, R.G., Wells, K.D., Cruthirds, C.L., Knouse, J.A., Ferreira, J.A.,Childs, T.E., Brown, M., Booth, F.W. (2013). Phenotypic and molecular differences between rats selectively bred to voluntarily run high vs. low nightly distances American Journal of Physiology – Regulatory, Integrative and Comparative Physiology, 304(11) R1024-R1035.
Surovell, T. A. (2000). Early Paleoindian women, children, mobility, and fertility. American Antiquity, 65(3), 493-508.