Are fruits bad for you?

Hello everyone, the topic today is controversial because involves fruits, which are highly perceived as healthy by most people, and the consumption of fruits is strongly recommended to the general population. However, several studies in humans and animals using acute or chronic fructose feeding, as well as epidemiological studies link fructose intake with the physiopathology of metabolic syndrome (obesity, hypertension, insulin resistance, type 2 diabetes). Because fructose is found in fruits, a concern has been raised regarding whether fruit consumption is bad for you. So, in order for us to understand this controversy and not be confused, we need to look at the scientific literature regarding this topic. Let’s begin by defining some basic concepts: What is fructose? Fructose is a simple sugar that is present in fruits and honey, but is also a major component in the two most commonly used sweeteners, sucrose (table sugar, a disaccharide of fructose and glucose), and high fructose corn syrup (HFCS, a mixture containing 55% fructose and 45% glucose or 65% fructose and 35% glucose). Fructose in our body can come from sources that are both exogenous (diet) and endogenous (produced internally). From dietary sources we get fructose from fruits, fruit juices, table sugar, sodas, and sports drinks. From endogenous production, we get fructose from the conversion of glucose to fructose via the sorbitol/polyol pathway, which takes place in several organs such as liver, kidneys, and brain for example when there is an abundance of glucose. So, it’s the combination of exogenous and endogenous fructose that matters in the end of the day. The next important thing is to understand how fructose is metabolized in our body. Dietary fructose is absorbed via GLUT5 in the small intestine and enters the portal vein that takes fructose directly into the liver. Once in the liver, fructose is phosphorylated by the enzyme fructokinase, which produces fructose-1-phosphate (F-1-P) and consumes a large amount of energy (ATP). As a consequence, a large amount of AMP accumulates in the cells and increases the production of Uric Acid. It’s the presence of both Uric Acid and F-1-P that causes deleterious effects such as the accumulation of fat in the liver (hepatic steatosis), inflammation, and insulin resistance. Uric acid escapes the liver and causes inflammation in the pancreas, blood vessels, adipose tissue, and other organs and tissues. Now, for us to put this in context, we need to address the following question: what is considered excessive intake of fructose? The answer is: more than 50g per day. The next question is: How much fructose do we get by eating fruits? In this graph we have fructose content in grams on the y axis and various fruits on the x axis. We can see that fruits can be classified as low, moderate, and high fructose content. However, even the ones that are considered high in fructose still fall way below 50g. In fact, one would have to eat one of the following fruit servings to surpass 50g of fructose per day: 7.5 bananas, 8.5 oranges, 3.5 mangos, 4.5 pears, 5 apples, 5 persimmons or 500g of dried figs. It’s possible, but very unlikely to occur, unless you are a fruitarian and consumes lots of fruits on a daily basis. Now, look at the amount of fructose in a typical serving of Pepsi (~39g), Sprite (~37g), and Coca Cola (37g). In fact, two servings of any of these beverages easily surpass the 50g per day of fructose. This is without mentioning the glucose content that also comes along. I also listed Gatorade as an example of sports drink just for comparison. So, what do we conclude from this? 1. The fructose content in fruits is generally low. One would have to frequently consume large amounts of fruits to reach fructose levels that could lead to detrimental health effects. 2. The ingestion of whole fruits contains nutrients (e.g., vitamin C, fiber, and flavonoids) that counteract the potentially deleterious effects of fructose. 3. The ingestion of sweetened beverages and processed foods should be the main concern with respect to fructose consumption because they contain HFCS. 4. From a health perspective, one should be more concerned with the total amount of sugar in fruits than with the specific fructose content. 5. It is crucial to limit the intake of total added sugar, including glucose and fructose, because elevated intake of both is associated with metabolic disorders. There you have it. Now you know enough to make up your own mind about fruits. Stay healthy and I’ll see you in the next.