I’m new here, I don’t post allot on the forums but I have been researching nutrition (self taught) for 20 years, since I was 13. I have tried many diets for health reason, some worked better than others. The main health problems I have had was Glutan and Dairy allergies (only cows dairy) and this caused major problems in my digestive system before identified. So when I gave up these things in 2006 that was the biggest improvement I saw, at the same time I gave up all factory farmed animal products in general. So I have tried Candida diets, high protien diet, raw super-food (with some animal products) cooked vegan, HCRV (with some cooked) and have tried 8-1010, I could never handle more than 3 days! I would just feel so weird but it was always this ideal to aspire to. At the same time I did think it was a bit radical especially since I mean seriously, garlic? chilli? cmon? and don’t take my salt away I may pass out form low blood pressure-seriously. I have two friends studying nutrition and its very science based and I love the science but yes when subjecting myself to this 30bananas stuff I would try and make it fit somehow, I guess I was never truly convinced but it still had quite a deep effect on me and my diet. When I was consuming very high fruit and training harcore it would feel awesome but I have been recovering from chronic tendonitis for 6 months (I have had it a year-low protein anyone?) and was finding the high fruit and vegan diet very difficult to maintain. I have always felt best on a balance whole food diet, plant based with some animal products, I don’t want to be too extreme anymore, I still like raw foods, fruit, juicing, I like it all. I am even more aware of ethical and environmental impact now. I want to know the truth about diet and health and ethics.
Anyway this may clear up some things for some people, I found it on LFRV.
I have had several requests for links that explain the different problems involving fructose metabolism. So, I have decided to post them all here instead of sending out individual responses. This is not intended to discourage anyone from continuing with a fruit-based diet if you feel good eating such a diet. This post is for people who have been trying a fruit-based diet and have been experiencing problems that they cannot figure out. I am deeply grateful to my friend Gretchen (sweetfruitlover) for unearthing all of this information and sharing it with me. She may have solved the biggest medical mystery of all time: ME!!
The first issue has to do with an enzyme called fructokinase, which is the first enzyme involved in fructose metabolism (if I understand correctly). Different people produce different amounts of this enzyme. If you produce a lot of this enzyme, you will breakdown the fructose you eat much faster and more efficiently than someone who produces less of this enzyme. In this case, more is not better, becuase uric acid is produced as a by-product.
Uric acid is linked to all of the health problems that fall under the category of Syndrome X or Metabolic Syndrome: high blood pressure, high LDL cholesterol, low HDL cholesterol, high triglycerides, insulin resistance (Type II Diabetes), and obesity. There is one family being studied in Switzerland in which many members of the family do not produce any fructokinase, and they appear to suffer no negative consequences as a result. Interestingly, none of these individuals has any of the metabolic abnormalities mentioned above, so it may actually be an advantage for them.
Those who produce the most fructokinase enzymes are at a much greater disadvantage in a society that consumes a high-fructose diet (i.e the United States). The fructose from fruit is less damaging than the fructose in refined foods because it contains vitamin C and pottassium which both help us to eliminate uric acid from our bodies. Plus, it comes packaged in fiber which helps to slow down its digestion.
However, uric acid is ALWAYS produced as a by-product of NORMAL fructose metabolism. It has been postulated that this was valuable at one time in our evolutionary history because uric acid does many of the same things as vitamin C and is also a very powerful anti-oxidant. But this is a case where some might ne extremely helpful, while a lot could be very, very, bad.
For as long as humans have been humans, we have never lived off a high-fructose diet, either as fruitarians or as junk-food consumers, until the present. This does not mean we should all stop eating fruit, but eating 30 bananas in a day may not be such a great idea.
The other thing I wish to point out here is that free fructose is more damaging than bound fructose. When fructose is in its free form as is the case in high fructose corn syrup or fruits like watermelon, apples, or pears, it is metabolised much more quickly, than when it is in it’s bound form attached to glucose in a sucrose molecule, as it is in table sugar or the majority of other fruits.
For those who are interested, agave is almost 95% pure free form fructose and honey is about 75% pure free form fructose. One study found that vegetarians had higher levels of AGEs (advanced glycosilated endproducts) than non-vegetarians and the researchers concluded that it was because the vegetarians ate significantly more honey (i.e. fructose) than the non-vegetarians, and I would venture to say that they ate more fructose contain foods in general since fructose is in ALL fruits AND vegetable to one degree or another.
It is my guess that successful long-term fruitarians like Anne Osborne, Julie Suiter, Kveta Martinec, and Jeff Atwell must produce fewer fructokinase enzymes than average. Anne has told me that the uric acid levels in her blood were at the low end of normal. In the United States, uric acid levels averages 2.5 to3.5 in the 1920s. In 1990, the average was between 5.5 to 6.5, and it is believed to be even higher today.
All of the above information comes from The Sugar Fix by Dr. Richard Johnson which is a book I highly recommend. Gretchen has told me that Fructose Exposed by Dr. Frank Lyons is also very good and well worth reading. I have order a copy, but have not yet received it and, therefore cannot give a personally testamonial for it.
Dr. Robert Lustig’s video lecture (1.5 hours in length) about the perils of consuming too much fructose is also very good.
His conclusion is that the only people who can really benefit from fructose are athletes because it does a better job at maintaining cellular hydration than does glucose alone under physical stress.
There is a disorder known as Fructose Malabsorption or FM. It is believed to affect 30% of the general population to one degree or another and to be the primary cause of Irritable Bowel Syndrome in 80% of cases. The symptoms are mainly gastrointestinal in nature and include: gas, bloating, vomiting, diarrhea, and constipation, as well as depression, brain fog, and fatigue.
According to the Wikipedia page on FM:
Fructose malabsorption, formerly named “dietary fructose intolerance,” is a digestive disorderin which absorption of fructose is impaired by deficient fructose carriers in the small intestine’senterocytes. This results in an increased concentration of fructose in the entire intestine.
This condition is common in patients identified to be suffering symptoms of irritable bowel syndrome, although occurrence in these patients is not higher than occurrence in the normal population. Conversely, patients with fructose malabsorption often fit the profile of those with irritable bowel syndrome. A small proportion of patients with both fructose malabsorption andlactose intolerance also suffer from celiac disease.
Fructose is absorbed in the small intestine without help of digestive enzymes. Even in healthy persons, however, only about 25-50g of fructose per sitting can be properly absorbed. Persons with fructose malabsorption may absorb less than 25g per sitting (NB: Amount is arbitrarily determined according to investigation of fructose absorption in many individuals). In the large intestine, fructose that hasn’t been adequately absorbed osmotically reduces the absorption of water and is metabolized by normal colonic bacteria to short chain fatty acids and the gases hydrogen, carbon dioxide and methane. This abnormal increase in hydrogen is detectable with thehydrogen breath test.
The physiological consequences of fructose malabsorption include increasing osmotic load, providing substrate for rapid bacterial fermentation, changing gastrointestinal motility, promoting mucosalbiofilm and altering the profile of bacteria. These effects are additive with other short-chain poorly absorbed carbohydrates such as sorbitol. The clinical significance of these events depends upon the response of the bowel to such changes; they have a higher chance of inducing symptoms in people with functional gut disorders than asymptomatic subjects. Some effects of fructose malabsorption are decreased tryptophan, folic acid and zinc in the blood.
Restricting dietary intake of free fructose and/or fructans may provide symptom relief in a high proportion of patients with functional gut disorders.
Foods that should be avoided by people with fructose malabsorption include:
- Foods and beverages containing greater than 0.5g fructose in excess of glucose per 100g and greater than 0.2g of fructans per serving should be avoided. Foods with >3g of fructose per serving are termed a ‘high fructose load’ and possibly present a risk of inducing symptoms. However, the concept of a ‘high fructose load’ has not been evaluated in terms of its importance in the success of the diet.
- Foods with high fructose-to-glucose ratio. Glucose enhances absorption of fructose, so fructose from foods with fructose-to-glucose ratio <1, like bananas, is readily absorbed, whereas foods with fructose-to-glucose ratio >1, like apples and pears, are often problematic regardless of the total amount of fructose in the food.
- Foods rich in fructans and other Fermentable Oligo-, Di- and Mono-saccharides and Polyols (FODMAPs), including artichokes, asparagus, leeks, onions , and wheat-containing products, including most beers, breads, cakes, biscuits, breakfast cereals, pies, pastas, pizzas, and somenoodles.
- Foods containing sorbitol, present in some diet drinks and foods, and occurring naturally in somestone fruits, or xylitol, present in some berries, and other polyols (sugar alcohols), such as erythritol, mannitol, and other ingredients that end with -tol, commonly added as artificial sweeteners in commercial foods.
Foods with a high glucose content ingested with foods containing excess fructose may help sufferers absorb the excess fructose.
The role that fructans play in fructose malabsorption is still under investigation. However, it is recommended that fructan intake for fructose malabsorbers should be kept to less than 0.5 grams/serving, and supplements with inulin and fructooligosaccharide (FOS), both fructans, should be avoided.
Another, far more serious disorder of fructose metabolism is known as Hereditary Fructose Intolerance. This is a very rare genetic disorder that is present in only 1 of 20,000 people, and is more common in people of Northern European ancestry.
This disorder involves the second enzyme in the fructose breakdown process called Aldolase B, which is completely missing. It recessive and requires a gene from both parents. It does appear that some people who are only carriers (meaning they possess only one gene, rather than two) can have impaired fructose metabolism as well, only not as severe.
The primary symptom of this disorder is severe hypoglycemia after the ingestion of fructose containing foods. It was long believed that if you were not diagnosed in infancy with this disorder, you would have died and never mad it to adulthood. But this has proven incorrect as more and more adults are testing positive for it after the age of 30.
A tell tale sign is a life-long strong dislike of purely sweet tasting foods, and a preference for sweet tarts, smarties, and pixy stix (all glucose-based candies). A number of people with this disorder have stated that one or both of their non-HFI parents did suffer from hypoglycemia, but never had the extreme aversion to sweets or the other health problems associated with HFI. So, it is quite possible that carrier produce half the Aldolase B enzyme as non-carriers and, thus, experience a degree of fructose metabolic impairment.
When I found out that hypoglycemia was the main symptom and a very abnormal occurance in normal people, this is what made me sit up and take note. I have been severely hypoglycemic in response to fructose ingestion my entire life. I have complied a list of all of my symptom that suggest and HFI diagnosis in my case here: Why I feel that I may have Hereditary Fructose Intolerance.
It is high unlikely that many of you reading this, will have HFI, though it is conceivable that you could be a carrier and have a partially impaired pathway for fructose metabolism. However, it is quite possible that some of you could have FM to one degree or another. I do wonder if the percentage of people with either of these disorders could be higher in the LFRV community, than the general population, simply because many people are attracted to try this diet BECAUSE they are having some kind of health problem.
For more information on HFI, see these links:
http://hfiinfo.proboards.com/index.cgi (on-line community forum)
Given all of my symptoms, and the fact that I have been so sick for so long, I have decided to get the genetic test offered by Dr. Dean Tolan’s lab at Boston University, as a first step in determining if I do in fact have HFI. If the test is negative, that does not mean I do not have it, but that another more invasive test involving a liver biopsy to analyze the level of Aldolase B enzyme in my liver must be done.
My doctor has agreed to order the test for me, and I spoke with Dr. Tolan this morning to make arrangements. They only run the test when they have 4 samples to do, so it will probably be about 6 weeks before I know anything further about my own situation. In the meantime, I am eating a low to no fructose diet and am feeling better already, so I feel like I am definitely on the right track here one way or the other.
I hope all this information has been helpful. If you have anymore questions, please feel free to post a question here or contact me directly by email at email@example.com