Fructose, a sweet poison and a primary factor in gastrointestinal illness, obesity and mental disorders.
But isn’t fruit a natural part of our diet?
Yes it is.
However we consume more fruit today than at any time in human history and this can be a problem for some.
Our earliest ancestors, before 3 million years ago, lived in trees and ate their food raw –primarily fruits, succulents, leaves, some nuts, occasional insects, small lizards and very occasionally small mammals and birds. They could be considered frugivorous omnivores. When survival pressures over a couple of million years forced them to live primarily on land, they evolved their diet toward plants such as underground tubers, roots and those fruits growing close to the ground, while adding more and more flesh foods into their diet. During the Paleolithic era (the period spanning about 2.6 million years ago to the beginning of the agricultural revolution) our hunter-gatherer ancestors in north-east Africa ate mainly flesh foods (crustaceans, fish, land animals) and yams, with back-up foods including legumes, soft seeds and nuts. Honey, eggs and seasonal fruits and berries were occasional condiments while wild vegetables, herbs and water weeds were medicinal foods. This is the diet humans optimised through the use of tools and cooking.
Traditional Australian Aborigines are the best modern example of what our ancestral hunter-gatherers ate. Much of Australia has had similar environments to those in north-east Africa over the past 3 million years and some Aborigines were classical hunter-gatherers right up to the early 1960s. Fewer than 15 species of native fruit were traditionally eaten throughout the whole of Australia, and most of these needed to be prepared first. Many were restricted to healthy young adults and were not given to children or old people. Sugarbag (native honey) was a treat.
Today there are more than 250,000 species of plants in the world yet we consistently eat fewer than 100 different types of these and many we have to heat and or soak before they are edible. Most are poisonous.
With the agricultural revolution and increased trading throughout the world, once rare fruits have become common place. Our modern technology and trading efficiency mean most of us now eat too much fructose from fruit, table sugar and high fructose corn syrup.
What makes fructose bad for our health?
Apple
The problem is linked to the amount of fructose we eat, not that fruit is necessarily bad for humans.
Different fruits have different quantities of fructose. Eating fruit when it is unripe (green) and eating too much is liable to create digestive upsets. There is an old saying: “An apple a day keeps that doctor away, two apples a day will make you pay”. This folklore suggests people should limit their daily intake of fruit so they don’t experience intestinal discomfort. But a modern misinterpretation of this saying (without the second line), is that if one apple a day keeps the doctor away, it must give health and thus several servings of fruit should be even better.
But fructose is difficult to digest. There are eight essential sugars (including glucose, fucose, maltose, galactose and xylose) that are quickly and simply absorbed into the body, raising the blood sugar concentrations within several minutes. Fructose is not one of these and was once recommended as a good food for people with diabetes mellitus and hypoglycaemia because it raises blood sugar more slowly. But it is now known that the slow rising of blood sugar is due to a lengthy ‘multi-step enzymatic phosphorylation’ process that our bodies have to undertake to denature fructose to glucose for absorption into the body. Digesting fructose is difficult and takes time, especially if a person is not totally healthy.
Fructose malabsorption (sometimes called Dietary Fructose Intolerance) is the inability of the small intestine to generate sufficient fructase enzymes (fructose-1-phosphate aldolase) to partially convert fructose into smaller molecular fragments for transportation into the body and on to the liver where it is converted into glucose. The production of fructase is an individual ability which varies with age and health. If the body cannot produce enough fructase, the fructose cannot be converted for passage into the body. It then progresses onto the colon where bacteria feed on it and produce hydrogen, carbon dioxide and methane gasses. These gases create enormous pressure in the intestine causing bloating, pain, diarrhoea and flatulence. The bacteria also form short chain fatty acids and restrict the colon from re-absorbing water. This keeps fluids in the colon and makes bowel motions loose and watery. Approximately half of the world’s population are unable to absorb 25 grams of fructose at one sitting. About three-quarters of the world’s population are unable to absorb 50 grams in one meal.
There is no recognised cure for fructose malabsorption. For those people with this problem, good health is only achieved by restricting fruit, sugar, and grain foods (which also contain fructans) in their diet. This is a food volume-related illness. People with coeliac, atypical coeliac, pseudocoeliac, latent and silent coeliac disease, gluten intolerance, non-coeliac gluten sensitivity, ulcerative colitis, Crohn’s disease, and other gut diseases, have a high probability of also having both fructose malabsorption and lactose intolerance.
This is just the tip of the fructose iceberg-
See our next blog on fructose– Fructose Intolerance: is the sweet stuff making you sick? to find out more about this dangerous chemical. Discover the role of fructans, the link between fructose and obesity, and the connection between fructose and mental illness.