Most of us grew up hearing constant reminders of how sugar is bad for us. As children, we were reminded to put down those chocolate bars and eat an apple instead. While the idea behind that advice is good – chocolates and sweets are both nutritionally void, high in calories and bad for your teeth – fruit is not as sin-free as you might think.

Up until recently, dieticians and doctors believed that fructose was a good alternative to cane sugar, because it has a lower glycemic index than normal sugar, meaning that it does not cause the insulin spikes that are associated with chocolates, soda and other sweetened foods. While this is a clear benefit, it does not make fructose a ‘good’ substance.

Eating fruit year round is not naturalĀ 

The guiding principle of the paleo diet is that you should only eat foods which the human body is designed to eat. Or, put more simply, only eat foods that a caveman would eat. Avoiding highly processed foods, or foods that were made in a lab and that contain synthetic, unpronounceable ingredients makes sense from a health point of view.

The human digestive system was not made to process the kinds of preservatives and artificial flavourings found in the average ready-meal. What many people who are just starting the paleo diet do not realise is that fruit and hence fruit sugar, was not something consumed daily by cavemen either.

Cavemen did have some access to fruit, but only during short time periods when fruits were in season in the area that they lived. They would live off the land when foods were in season and eat a more meat-focused diet for the rest of the year. The fruits that cavemen ate were smaller and not as sweet as modern fruits which are bred to grow as large and as juicy, as possible.

The average modern diet contains far too much sugar. When we overdose on fructose our liver cannot process it properly, so it turns the sugars into fat and releases triglycerides into the bloodstream. This can be a contributing factor for heart disease.

In addition, it can still cause insulin resistance, elevating your IGF-1 levels, increasing your risk of developing Type 2 Diabetes. Some recent research suggests that high IGF-1 levels is a contributing factor in causing cancer.

Another downside to a high fruit sugar intake is that fructose does not create the same feeling of satiety that glucose does. This means that you are more likely to feel hungry soon after eating high-fructose foods, even though those foods are quite calorie dense.

If you are trying to control your weight, this is a massive downside. If you follow the paleo diet, which focuses on meat, nuts, vegetables and berries, you will find that you feel fuller for far longer after eating your meals, making it easier to avoid snacking during the day. In addition, because you avoid foods rich in sugars, you will not experience insulin spikes and rapidly fluctuating energy levels.