I recently did a lecture on fructose, debunking the hype from the reality. For those of you who are unaware, fructose has been touted as being the cause of obesity, metabolic syndrome, excessive weight gain, and impaired insulin response leading up to the development of diabetes…aaaaahhh!!!
Considering the facts, it should send Nutritionists and Dieticians running around waving balloons in jubilant celebration now that we have “finally” found the “culprit” to all of these problems:
• 50% of Australian adult males are considered to be overweight or obese
• 33% of Australian adult females are overweight or obese (and no, “big-boned” is not an adequate reason to carry excessive adipose (aka fat) on the body)
• 25% of Australian adults have metabolic syndrome (i.e. their metabolism, which is the system responsible for regulating how food is converted into energy and utilized in the body, is NOT working)
• 25% Australian adults have high blood glucose levels making them PRE-DIABETIC…and lastly;
• 33% of Australian children are considered to be overweight or obesity and are heading towards metabolic syndrome, diabetes, atherosclerosis (narrowing of arteries) and joint immobility (because excess weight is causing detrimental strain to the joints)
(Kids eat, Kids play survey 2008)
How cool is it that we have “finally” found the “culprit” for all of us getting large? And even though there is a societal shift to “accept” overweight individuals (which is great! No one should be stigmatized for their size, their clothing choice, the job they do, the AFL team they go for, or whether they are a NSW Blues supporter even though we all know that the mighty QUEENSLAND MAROONS are the State of Origin champs!), societal acceptance of an increase in body weight/size does NOT change the reality of associated health problems. Our bodies are not designed to carry excessive weight. There are no two ways around it. That is just a fact. Just like humans are not designed to flap their arms and fly like a hummingbird, we are also not designed like elephants, who are able to successfully carry excessive weight. The end.
According to many, it is apparently “well established” that carbohydrates are evil, they make you FAT and should be avoided at all costs! To be honest, this line of reasoning seems to make sense when you realize that obesity prevalence and carbohydrate intake has increased simultaneously over time (Figure 1) (Liu et al., 2004).
It’s highly unlikely to be a mere coincidence, so it’s gotta be the carbs that are bad…not the fact that we’re actually consuming TOO MUCH FOOD, TOO MUCH REFINED EVERYTHING, having excess energy intake yet SITTING FOR PRETTY MUCH THE WHOLE ENTIRE DAY expending minimal energy…
It is true that there are some carbohydrates that are refined beyond any usefulness except to make things taste nice (e.g. high fructose corn syrup). However it must be emphasized that there are different qualities of carbohydrates and one of the most convincing arguments to ensure that you should have the RIGHT AMOUNT of the RIGHT CARBOHYDRATES (i.e. complex carbs, not the refined nutrient-poor fillers) in your diet is the fact that the BRAIN FUNCTIONS ON GLUCOSE. While the brain can run on ketones (fat that is converted into a usable brain fuel), it is not ideal or sustainable in the long term. Glucose is the energy source of choice for the brain. You want your brain to work? You need to have carbohydrates in your diet. Carbohydrates also aide in protein metabolism, but that is something I will explain in another post.
Currently there is a buzz in the media demonizing a sugar called FRUCTOSE. And yes there is substantial scientific evidence to support the negative effects high fructose consumption has on health, weight gain, metabolism etc. Now that we’ve found the culprit, it should be easy to fix the problem right? Simply cut back, reduce, take out altogether this evil, vile sugar called FRUCTOSE!! Yet there is something fundamentally WRONG with this line of logic too… Everything, and I mean everything, that has fructose in it has to go, right? That means everything… including fruit… which naturally has fructose (hence where fructose gets its name from…).
Why is this complete demonization of fructose not correct? Well let’s take a step back first and define what sugar is first.
What is sugar?
To begin with, carbohydrates are composed of individual sugar units strung together in different chemical configurations to form the carbohydrate. Hence carbs are broken down into 2 groups: SIMPLE SUGARS and COMPLEX SUGARS. The complex sugars are often called “polysaccharides” (poly = many; saccharide = sugar) because they are composed of MANY SUGAR UNITS. The simple sugars are split into two groups: “monosaccharide” (mono=1) and “disaccharide” (di=2) because they are either composed of 1 individual sugar molecule (i.e. the monosaccharides) or 2 sugar molecules (i.e. the disaccharides) (refer to Figure 2) (Kinnear and Martin 2001).
From the chemistry perspective, all sugars are composed of only 3 things: carbon, hydrogen and oxygen. Different configurations result in different sugars. Different amounts of the different sugars strung together in different configurations results in complex carbohydrates like starch and fibre (Figure 3). The simplest carbohydrate (sugar) is glucose, but fructose and galactose are also simple sugars. These 3 have the same chemical formulation but have very different configurations. And this results in two things: different physical properties (e.g. sweetness) and different ways in which the body is able to metabolise (i.e. breakdown and use) these sugars. Glucose is the easiest and fastest. Normal table sugar is essentially 50% glucose + 50% fructose. Simple carbohydrates are generally sweet to taste, and hence found in all things sweet. Nevertheless bland or non-sweet foods that are high in complex carbohydrates like starch and dietary fibre are also great sources of glucose… it’s just that the glucose are strung together in a more complex formation that takes a longer time for the body to breakdown Figure 3.
Difference between fructose and glucose?
Now when it comes to fructose, essentially fructose is either a) naturally found in fruit or b) a sweeter version of sucrose (i.e. table sugar) that is also cheaper to manufacture…!!! So you can see where this is heading right..? Fructose has the ability to provide MORE sweetness for less outlay = greater profit margins for the industry. It also has much better solubility, therefore allowing it to be a more versatile ingredient that table sugar.
Research published in the Journal of the American Medical Association in Jan 2013 has found some rather interesting results on brain functionality in terms of fructose vs. sugar, with possible explanations on how fructose is able to wreak havoc in the human body. In the article “Effects of Fructose vs Glucose on Regional Cerebral Blood Flow in Brain Regions Involved With Appetite and Reward Pathways” (2013; JAMA 309(1): doi:10.10001/jama.2012.116975), researchers show clinical evidence of decreased blood flow to certain lobes of the brain after ingestion of 75g fructose in a 300mL solution (very high dose) when compared with glucose. Bearing in mind that the brain runs off glucose to function, decreased blood flow, particularly to regions that control appetite, will not result in appetite suppression rather an increased desire to consume more food. And hence we eat more than we expand, we gain more weight. Very easy really. But why is this?
Well unlike glucose, which is readily absorbed and easily transported around the body to where it is needed as an energy source, fructose is only metabolised in the liver and absorption only takes place in the jejunum – the middle section of the small intestine. In humans, the small intestine is ~6m long of which the jejunum is only ~2-2.5m long (Gale 2008). So whilst fructose has the same chemical formulation, the structural changes do not improve digestion, metabolism and absorption. It’s the opposite actually… High doses of fructose has been found to be more “lipogenitic” than glucose and starch i.e. it has better ability to be converted into adipose tissue (aka FAT) and stored, increases blood triglyceride levels and cholesterol production and as it is only metabolised in the liver, excessive fructose can lead to fatty liver disease. Tappy 2010 has an amazing article in which the potential pathways that fructose leads to atherosclerosis, high blood pressure, insulin resistance and weight are discussed…in pictures.
So based on this, I should soooo freak out over the ½ cup of grapes and 1 medium mandarin I just consumed with my lean beef salad dark rye sourdough bread sandwich right??? Well… NO!
Let’s list the facts:
– Fructose is NOT metabolised the same as glucose
– HIGH DOSAGES of fructose being associated with detrimental effects
– Fructose is a CHEAPER, SWEETER alternative to sucrose (table sugar)
– Fruit naturally contains fructose. Processed foods also contain fructose
– Decreasing fructose intake will make me less disposed to storing fat, and hence type 2 diabetes, obesity etc…
Yes, all of the above is true. However in the case of fruit, unlike processed foods, fruit is a great source of fibre, antioxidants, polyphenols, vitamins and minerals. Unlike processed foods, most nutrients are located within the plant cell and are completely enveloped by a fibrous plant cell wall. In order for nutrients to be released, the cell wall has to be ruptured – i.e. broken open. Not only can nutrients be released and hence be absorbed, they are also able to bind to plant fibre. Interactions between fructose with glucose, plant fibre and other nutrients affect the rate of fructose metabolism. The main issue with the current clinical studies is that the dosage is very high. Considerably higher than what is found naturally in a piece of fruit. That’s not to say we should take it with a pinch of salt. But instead of going into a panic and throwing the baby out with the bath water, consider this: moderate-low doses of fructose intake are not associated with negative health effects, actually it has been found to improve glucose metabolism.
Nevertheless HIGH DOSES of fructose are associated with negative health effects from both clinical and epidemiological studies.
Don’t throw the baby out with the bath water is the moral of the story. The moral of the story is highly processed foods, jam packed with cheap, sweet fructose is definitely NOT A WISE FOOD CHOICE. How do you know which foods have fructose in it? READ THE LABEL: if it says fructose it has it. If it says sugar, it is referring to sucrose which is 50% glucose and 50% fructose. And if it says sugar and fructose, then you should immediately think a) HIGH DOSE OF FRUCTOSE and b) shiiiikes!! Super sweet!!!
Fruit is not evil. Fruit should still be consumed as part of a healthy diet. Fruit juice is on the other hand more concentrated in sugar. Think about it, most people will eat 1 apple. But to drink a glass of apple juice (250mL), about 4 apples would need to be juiced – and with it also is 4 apples worth of sugar… more concentrated than a plain apple hey.. ;-). Whole fruit is a source of fructose and also polyphenols, antioxidants, dietary fibre (that is resistant to digestion) and when fructose is bound in a network (like fruit), it does not behave the same as the free fructose floating around in processed foods. It is metabolised slightly differently and hence is not detrimental to health. Generally speaking, the foods high in fructose also have one of the following:
– High in saturated fat
– High in salt
– Low in complex carbohydrates
– High in refined everything – including sugars
– “empty” calories
– Low in satiety
– High GI
… commonly known as junk foods..!! Stuff that you already know you should not be eating. In Australia high fructose corn syrup is not used extensively like it is in the USA. But read your ingredient declaration.
Treats are exactly that… “Treats”. I.e. they are not meant for everyday, or every second day or even 3 times per week… THEY ARE TREATS. KEEP THEM WHERE THEY BELONG.
The constant quest to find “the culprit” in the weight gain race is not ideal. There are many factors that affect both the weight of the nation as well as the weight of an individual. Large population based strategies are able to move A LOT of people in the right direction. Yet personalized treatment and solutions is able to change an individual’s life around completely. Essentially excessive consumption will lead to excessive weight gain. It’s as simple as that. Cutting out all things that contain fructose, including healthy whole fruits, yet sitting at your desk for 8 hours, sitting in traffic for 2 hours, sitting at dinner, sitting in front of the television before sleeping and consuming MORE food than your body actually needs is not going to do anything beneficial really.
Follow the Australian Dietary Guidelines. Get moving. Keep active. Eat correct portions for your age, sex and physical activity levels and you will either A) lose weight or B) maintain a healthy weight.
Glucose syrup instead of table sugar?
I received this question from a student – “After the special lecture you gave… I was wondering if that in baking/cooking would it be more healthy to use pure glucose syrup instead of table sugar which contains fructose? I always see glucose syrup and I’ve never really known whether it would be a healthier option to table sugar?”
Great question. And like most things, nutrition is fairly logical. The glycaemic index is used to determine how sugar is metabolised in the body. Essentially the longer it takes for a carbohydrate rich food to metabolised, the longer it keeps you full so you don’t feel hungry or the need to snack. Foods which are able to do this are called low GI (e.g. lentils, rolled oats). The higher the GI, the faster the food is metabolised. Glucose is very rapidly metabolised and absorbed, so it makes sense that glucose is considered a HIGH GI food. Hence in terms of using glucose syrup over table sugar, think about it in terms of GI. Glucose syrup is high GI. Sugar is High GI. High GI is going to spike your blood glucose levels immediately. And glucose syrup – being pure glucose is going to be straight into the blood stream ASAP. Sure glucose syrup does not contain fructose, unlike table sugar, but when fructose is attached to glucose (to form sucrose which table sugar is), it is not in the free form. Hence it is not fully metabolized the same way as free-fructose.
Nevertheless regardless of the fine details of metabolic rate, an important aspect that must be honed in on is this: HEALTHIER OPTION
And here is where it is super logical. Whether you choose HIGH GI glucose syrup or HIGH GI table sugar, decreasing the amount of sweetener that you use is always going to be healthier. And if you can change the sweetener to a low GI option (e.g. pure honey, agave nectar) or substituting sweetener partially for apple puree or some dried fruit (which are very sweet, so you only need to use 50%) will always be a better option.
What’s the deal with Stevia?
Another student question: “What’s the deal with stevia?” Stevia is a natural sweetener derived essentially the Stevia rebaudiana plant, a member of the sunflower family. The leaves from the stevia plant are naturally sweet. Apparently stevia is 300 times sweeter than sugar and hence is suitable for use as a low calorie, low sugar sweetener. Unlike artificial sweeteners, Rebaudioside A – the sugar compounds naturally found in stevia are extracted from the plant leaves. This sugar compound is composed of glucose and steviol. The apparent mechanism for action is that rebaudioside A gives the sweetness on the palate, yet is broken down into glucose and steviol in the colon by gut bacteria. Steviol cannot be digested further and hence is excreted whilst the gut bacteria use the freed glucose for energy, hence why it is minimally absorbed into the bloodstream (Fisberg http://www.globalsteviainstitute.com/en/Default/ResourceLibrary/Articles/MetabolismoftheZeroCalorieSweetenerStevia.aspx).
So yes stevia is a sugar alternative. It is low GI. It is natural… and it is about 8 times the price of normal table sugar and honey. It is expensive… which is understandable considering how extensive the refining process is. Take home message: if you can afford stevia, and you like it, it’s not a bad option. As a nutritionist would I personally use it? No. Why? My tastebuds are well accustomed to the flavour of things natural. I do not need the extra “sweetness” to make something palatable. And ideally that should be the aim of everyone. The more accustomed you are to more sweet things, the more sweet things you desire and consume. The less accustomed your palate is to sweet things, the less you need and the more “unpleasant” very sweet food is as well. A piece of dark chocolate very occasionally hits the spot. You desire healthy flavours over plain out “sweet”…No desire to consume a whole jumbo chocolate bar or jar of nutella.
If you aim to clean your palate of the very strong flavours of “SWEET” and “SALTY”, highly processed foods become less palatable, and you’ll find yourself reaching for the apple instead of the sweet muffin.