Our understanding of the science of things is constantly evolving and this is most certainly true when it comes to the science of nutrition. There was a time when we in the health world were recommending fructose as an alternative to sucrose (table sugar) because fructose is sweeter, so less is needed and it does not trigger an insulin response, so great for blood sugar control and weight management. Well we now know we were wrong- -VERY WRONG!.
Another thing we know is definitely not true is that a calorie is a calorie from whatever source. Certain foods are metabolised and utilsed for different purposes in the body where other foods are considered pretty useless by the body and are therefore stored as fat. When it comes to sugar, it turns out not all sugars are equal either.
It is now known that the way fructose is metabolised, if it is eaten to excess, can have serious implications for your health. Fruit sugar when eaten in its natural form i.e. within a whole fruit, is not something to be concerned about, as long as you are not eating fruit to excess (2 – 3 pieces / servings per day is more than enough – berries being the best option and avocados and tomatoes don’t count). The problem is the concentrated amounts of fructose found in certain foods and drink, including some which are marketed and widely believed to be really healthy.
Sucrose (white/table/cane sugar), is made up of 2 types of sugar molecule, 50% glucose and 50% fructose, which are tightly bound together. When we eat cane sugar, our digestive system has to break down this tight bond to release the glucose and fructose. The body’s cells then readily use the glucose, as it is the preferred source of energy for all the cells in the body. Fructose is treated very differently. It goes from the digestive system straight to the liver where it is very readily converted to triglycerides and cholesterol – these fats can accumulate in the liver, circulate in the blood or get store in the fat cells.
Until the 1970s the amount of fructose in the diet was quite limited coming from fresh fruit and cane sugar (sucrose) added to foods. Remember, 50% of the sucrose we eat is fructose, so sugars in your tea and coffee, cakes, biscuits desserts etc will be contributing fructose to your diet, as does fruit. Fruits also contain glucose and fructose and different fruits have different ratios of fructose to glucose. Fructose is much sweeter than glucose, so the tropical, sweeter fruits generally contain more fructose. However, fresh fruit also contains lots of fibre. This is important as it slows down the release of sugar in to the blood and moderates the flow of fructose to the liver.
However, over the last 4 decades not only are western nations eating lots more fruit and loads more sucrose, they are also eating masses more fructose. Why? One reason is the increase in fruit juice consumption. Thought to be a healthy addition to the diet, fruit juice contains all the sugar in the fruit without the benefit of the fibre from the whole fruit. This means a high dose of fructose gets dumped in the liver very quickly. This puts a big burden on the liver and results in lipogenesis, where the fructose gets turned in to fats.
But there’s an even bigger problem. In the 1970s high fructose corn syrup (HFCS) was developed. This is a very sweet product extracted from the by-products of corn crops. The husks go through a really intense, chemical process to get all the sugars out of the leaves. This results in a sweetener that is very cheap to produce, is extremly sweet, but it is also very unnatural due to the processing it has gone through. HFCS is 55% fructose and 45% glucose but there are no bonds holding the glucose and fructose together. That results in ‘free fructose’, which passes to the liver incredibly quickly, dumping a huge load on the liver.
HFCS is increasingly being used in food manufacturing. It is in most soft drinks, especially sodas but also fruit juice; it is used extensively in confectionary, packaged foods, ready meals sauces, energy drinks etc. As a result, many people are consuming large amounts of fructose, especially free fructose and this poses some really serious health implications:
- Non-alcoholic fatty liver disease is a serious condition being seen in younger and younger people. This is very serious and is closely associated with excess fructose consumption.
- Excess uric acid is a by-product of fructose metabolism in the liver and is related to the arthritic, very painful condition gout and other inflammatory conditions.
- Excess fructose consumption is now known to induce insulin resistance. This is a major cause of type 2 diabetes.
- Poor insulin sensitivity affects Leptin production – this is the hormone that regulates our appetite, consequently the message to stop eating is not registered.
All of these factors can contribute to obesity, metabolic syndrome, high blood pressure, high cholesterol, type 2 diabetes and liver dysfunction.
Please, please, please check your food labels for HFCS, ensure your children are not consuming too much fructose, especially in the form of HFCS. If you want to know more about this, there is a lot of information about this online and some really good lectures by a main campaigner against HFCS, Dr Robert Lustig.
BTW, 2 important points I didn’t include that have just come to my attention: Pulp in fruit juice is not the same as fibre, so eat the whole fruit. Also, the corn producers are getting wise to the fact that HFCS is getting bad press so products are now being labeled as containing corn syrup and corn sugar – they are all BAD!