As a recent online medical Xpress article points out, before the 1960s, people consumed significantly less fructose than they do today. A century ago, the average person consumed only about 5–10 pounds of fructose annually, roughly the weight of a gallon of milk. In the 21st century, that amount has ballooned to the equivalent of 15 gallons of milk per year (Washington University in St. Louis, 2024, Secember 4).1 It may be more than just a coincidence that fructose consumption over the past half-century correlates with rising cancer rates, especially among younger populations. Fructose has always (at least for the last 10,000 years or so) been found in fruits, vegetables, dairy products, and grains. But beginning in the 1970s, high fructose corn syrup became available, and started becoming popular with the food industry because it was sweeter (and cheaper) than glucose. Fruit has traditionally been promoted as a healthy diet choice, because of its vitamins, minerals, and fiber content. As most of us are aware, the primary sugar in fruit is fructose, and unlike other sugars, fructose is digested by the liver, rather than being digested in the intestines like other sugars. And unlike other sugars, because of the unique digestion process, the digestion of fructose does not result in the production of insulin. So the body's built-in mechanism to signal when it is "satiated", does not apply to the digestion of fructose. In other words, the body has no way of knowing when it's hunger has been satiated by the consumption of fructose, which allows the possibility of overeating. We urgently need to reduce the fructose content of our diet. Research data recently published in Nature magazine reveal some disturbing facts associated with fructose (Fowle-Grider, et al., 2024).2 The research reveals that fructose indirectly promotes tumor growth by being metabolized in the liver, rather than directly by cancer cells. The liver converts fructose into lysophosphatidylcholines (LPCs), lipid molecules that circulate in the blood. LPCs serve as building blocks for cell membranes, which are essential for tumor growth and proliferation. Tumor cells uptake these LPCs to support rapid cell division. Various cancers appear to benefit from this unique conversion. The study tested various cancers, including melanoma, breast cancer, and cervical cancer, showing a consistent mechanism where fructose promotes tumor growth through interorgan lipid transfer. High-fructose diets in animals led to significantly faster tumor growth without changes in body weight or insulin levels. Isolated cancer cells did not metabolize fructose directly, confirming that tumor growth is mediated by liver-derived LPCs. Administering LPCs to mice independently accelerated tumor growth, mimicking the effects of high-fructose diets. The research found that: The enzyme Ketohexokinase (KHK), present in liver cells but not in tumor cells, is essential for fructose metabolism. Blocking KHK reduced circulating LPC levels and prevented fructose-driven tumor growth, suggesting a potential therapeutic target. Historically, people didn't eat much sugar. By the 1950s, for example, the average American consumed about 25–30 pounds (11–14 kg) of added sugar annually. By the late 1990s, this figure had climbed to 76 pounds (34 kg) per year (so it's not surprising that obesity has increased). While it has since decreased slightly to an estimated 60 pounds (27 kg) per year, it's still at least twice the amount consumed back when people ate mostly home-cooked meals, and very little processed foods. Even table sugar (sucrose) is a major source of fructose. Sucrose is a disaccharide made up of 50% glucose and 50% fructose. When consumed, sucrose is broken down into equal parts of glucose and fructose by enzymes in the digestive system. In a typical Western diet, table sugar is estimated to account for 25-50% of total fructose intake. The variability depends on the proportion of HFCS vs. sucrose used in sweetened foods and drinks, the consumption of natural sources like fruits, and regional dietary preferences and processed food use. The takehome message is clear. "An apple a day" can no longer be relied on to keep the doctor away. As a group, fruits typically contain the highest fructose levels, followed by certain vegetables. Dairy products and whole grains contain very little fructose (unless sweetened). That said, most people are probably getting the lion's share of their fructose intake from high fructose corn syrup, simply because it's in so many products. But as we're well aware, we're not most people. And most of us are on a very restricted diet in order to control our MC symptoms. Because of that, our intake of processed foods should be minimal. And most of us have to restrict our sugar intake (excess sugar can promote leaky gut). That suggests that in many cases, fruit may be our primary source of fructose. So while we shouldn't avoid fruit (unless we have been diagnosed with cancer), we shouldn't to go hogwild about eating it, either. Moderation is almost always the best policy. Note that fructose does not cause cancer. The research discussed in this article does not show the fructose increases the risk of developing cancer, it only shows that fructose increases the rate at which cancer grows once it originates. Therefore, the findings suggest that patients with cancer or those at high risk should minimize dietary fructose intake, although in view of its prevalence in processed foods, this is challenging. However, we have demonstrated that we can control our microscopic colitis (MC) symptoms by making certain challenging diet changes, so it's obvious that avoiding virtually any foods or food ingredients can certainly be done if we're serious about avoiding those food sensitivities. The research also suggests that targeting healthy liver cells' metabolism (instead of tumor cells directly) might offer a novel strategy for cancer treatment. Future clinical trials may explore dietary or pharmacological interventions to limit fructose's role in tumor growth. And note that apples are rated as having the highest fructose level. Apples have an interesting history. Fossil evidence suggests that the earliest ancestors of apples evolved around 50 million years ago during the Eocene epoch, long before humans existed. Early humans (Homo sapiens, appearing about 300,000 years ago) encountered apples as a wild fruit during their evolutionary journey. Apples provided early humans with a source of energy, vitamins, and hydration, which likely contributed to their dietary diversity and survival. The relationship between humans and apples became more significant during the agricultural revolution (about 10,000 years ago) when humans began to domesticate plants and animals. While I believe in science, I also believe in the foods with which we evolved. We evolved eating venison, for example, and every one of us can tolerate venison as a safe source of protein. We didn't evolve eating wheat (it became a part of the human diet about 10,000 years ago, during the Neolithic period), and that's why some people (including all MC patients) canot tolerate wheat. Evolution is a powerful tool that has shaped our digestive system and our immune system. But more than that, our paleo ancestors evolved eating whole foods. High fructose corn syrup (HFCS) was never a part of their diet. That's why, after carefully reviewing this research, I still eat apples. And I'll continue to eat apples in the future. I'm a firm believer that our food is our medicine, so if I should receive a cancer diagnosis at some point in the future, I'll definitely stop eating apples, and avoid all other sources of fructose in my diet, in order to starve the cancer. Until that day, though, I'll continue to enjoy the benefits of fresh fruit. The fructose content of various foods is listed below, for reference: High-fructose fruits
Moderate-fructose fruits
Low-fructose fruits
Dried fruits Dried fruits have a higher fructose concentration due to the removal of water:
Fruit juices The fructose content of most fruit juices varies depending on the type of fruit and how the juice is processed. Here are the approximate fructose content listings of some of the common fruit juices:
Vegetables Vegetables generally contain much less fructose than fruits, though the amount varies depending on the type of vegetable. High-fructose vegetables (>3g per serving) These vegetables are still lower in fructose than most fruits but are among the higher-fructose vegetables.
Legumes and other starchy vegetables Legumes like peas and beans are low in fructose, while some starchy vegetables contain slightly more Dairy products Milk and most dairy products contain very little or no fructose because their primary sugar is lactose, not fructose. Grains Grains generally contain very little fructose compared with fruits, as they are primarily composed of starches (complex carbohydrates). However, small amounts of fructose can be present in grains, particularly in processed forms or when combined with sweeteners like high-fructose corn syrup. Whole grains in their natural, unprocessed forms have negligible fructose content:
Special consideration: corn Corn contains small amounts of natural fructose, but when processed into high-fructose corn syrup (HFCS), it becomes a significant source of fructose in processed foods. References 1. Washington University in St. Louis. (2024, Secember 4). Research reveals how fructose in diet enhances tumor growth. Medical Xpress, Retrieved from https://medicalxpress.com/news/2024-12-reveals-fructose-diet-tumor-growth.html?utm_source=nwletter&utm_medium=email&utm_campaign=daily-nwletter 2. Fowle-Grider, R., Rowles, J. I., Shen, I., Wang, Y., Schwaiger-Haber, M., Dunham, A. J., . . . Patti, G. J. (2024). Dietary fructose enhances tumour growth indirectly via interorgan lipid transfer. Nature, Retreived from https://www.nature.com/articles/s41586-024-08258-3#citeas
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