But health authorities promote fruit..?
Most health authorities promote fruit as a healthy food, but recently I have been reading some conflicting articles. So I decided to spend some time and research this topic in more depth to find out what the downsides really are, if any, to eating fruit, and what the implications regarding Diabetes and fructose (the sugar in fruit).
After significant research, this turned out to be more difficult than I thought. There are many articles published within the medical community with conflicting views. There were also many articles from non medical sources which I discounted as I could not be sure of their validity. At least published medical articles are peer reviewed and will have some balance and scientific validity.
Why is fruit considered healthy..?
Fruit is promoted as being a healthy food by almost all health professionals. And why..? Because it is full of vitamins, minerals, antioxidants (including very potent “flavonoid” compounds e.g., resveratrol in grapes, quercetin in citrus, ellagic acid in pomegranates, and fisetin in strawberries) and of course its a natural food source, not processed and so considered a cleaner food source.
Fructose – the sugar in fruit, actually has a low glycemic index, meaning it has lower impact on blood glucose levels. This has made it a popular sweetener with people on low-carbohydrate and low-glycemic diets.
So on the surface this looks perfect for Diabetics..! But fruit and in particular the sugar within fruit – fructose, holds a dark secret and its for this reason we need to be careful as I will explain.
What are the downsides of fruit and fructose..?
When fructose (the sugar in fruit) and other sugars such as glucose are eaten they enter the digestive tract, where they are absorbed into the blood stream. At this point glucose is available for all the body’s cells to use (though insulin must be present before the cells will make use of the glucose).
But fructose is different. It is removed from the blood by the liver where it may be converted to glucose (30%-50%), stored as glycogen (a storage form of glucose), or converted into fats called triglycerides.
Now this is where some of the opinion is divided within the medical community. Some say the metabolism of fructose in the liver is similar to alcohol. Like fructose, alcohol also can only be metabolised by the liver, that part is fact and not contested by anyone.
But many have implied that there are similar harmful effects from metabolising fructose to that of metabolising alcohol. Others have contested that studies and published papers showing these harmful effects are flawed and that the results were not necessarily a direct result of fructose metabolism but due to their context, environment and other external contributing factors.
To read through and fully understand these medical articles you would definitely need a medical degree as expectedly they are very scientific. Therefore I am not in a position to make a judgement either way as I have no such qualifications.
The claimed harmful effects of fructose metabolism
- Causes increased Uric acid production which can lead to raised blood pressure
- Increases triglyceride levels can lead to non-alcoholic fatty liver disease (NAFLD).
- Can promote insulin resistance
- Fructose is the most lipophilic (fat-producing) carbohydrate thus can cause weight gain, (Notably increases belly fat).
- Fructose also undergoes the Maillard reaction with proteins, leading to the formation of super-oxide free radicals that can result in liver inflammation similar to acetaldehyde, an intermediary metabolite of ethanol (alcohol).
Fructose has often been described (rightly or not) as alcohol without the buzz..!
So is fructose harmful or not..?
Well nearly everyone agrees that excessive consumption of fructose may have some harmful effects. Those who dispute that regular amount of fructose have harmful effects will say that these harmful effects may only occur in persons with other medical issues, who maybe live a sedentary lifestyle and possibly smoke and who make other poor dietary choices and so the effects observed cannot be attributed to simply fructose in isolation. They dispute these effects occur with healthy individuals.
For those of us with diabetes, unfortunately we do not fall into the “healthy individuals” category so we may suffer some or more of these side effects. Here is a link to one medical article I read that concludes that fructose consumption in diabetics led to better blood sugar control but showed some adverse effects. http://care.diabetesjournals.org/content/35/7/1611.full
The change in how we now consume fruit
For thousands of years, mankind has consumed fruit on a seasonal basis. The apple tree bears fruit in the autumn, so we ate apples in the autumn. For the rest of the year we didn’t eat apples as they were not available. And this was always the case up until the last 50 years or so.
So our consumption of fruit has increased many fold over the past few decades due to globalisation and the year round availability of fruit in our supermarkets from all over the world. Today, we are consuming fruit and fructose in levels that our bodies may not ideally be adapted for.
And what about fruit Juice..?
You should really avoid fruit juices especially if you are diabetic. Through juicing and removal of the pulp/fibre, you lose some of the beneficial vitamins and minerals you would get by eating the fruit whole, and you increase the fructose content by virtue of the fact that you use a larger amount of fruit to create a fruit juice.
The other main problem with fruit juices is that due to the removal of all the fibre the fructose is digested and enters the blood stream very quickly. So the liver is made to work much harder. With eating fruit, the fibre slows down the digestion and the fructose enters the blood stream more slowly over a much longer period and so the liver is not put under as much stress.
For diabetics, we are more likely to suffer some of the fructose metabolism side effects. But the main issue is a lot simpler. When eating fruit you are still consuming quite a lot of sugar (fructose). Even though fructose is extracted from the blood by the liver, the liver will convert up to 50% to glucose, and release it back into your blood stream. This can still cause a spike in blood sugar, albeit there may be some delay. So if you are an insulin dependant diabetic you will still need to match this with insulin.
So I would suggest a little of some fruits are ok, especially those with a low Glycemic Index/Load and high in anti-oxidants, but again I would suggest in small quantities. When choosing fruit, choose fruits low in fructose such as
- Tomatoes and avocados (yes these are actually fruits!)
- Lemons and limes
- Cantaloupe melon
- Raspberries, blackberries & strawberries
- Kiwi fruit
When eating fruit, try to do so as part of a meal, or along with other foods high in protein or fat (not carbs). This will help slow down the absorption of fructose, cause less stress on the liver and slow the release of glucose converted from fructose (by the liver) back into the blood stream.
- Always eat fruit in its whole form – never juiced.
- Try to eat fruit as part of a meal or along with other foods high in protein or fat
- Opt for low-fructose fruit whenever you can.
- Preferably eat fruit that’s local and in season.
To answer the question posed “Is Fruit Unhealthy for Diabetics?”
- Small amounts of Low GI fruit along with other low or non-carb foods – NO
- Otherwise – Probably YES