New to DFI, need some guidence...

[charlie]

From my understanding sugars are broken down, as sandra says in the mouth and intestines, but not absorbed into the blood until the large intestines and this is where the problem starts. With DFI they are lacking the protein carrier to pull the fructose through the villae wall of the intestine into the blood from where it is transported to the liver for further destruction so it sits and ferments in the large bowel and causes gas and bloating.
With HFI they are lacking the enzyme that is in the liver to break the final stage of the fructose absorbtion, it therefore sits in the liver and acts as a toxin but some gets passed through to the kidneys and toxins there too as it is still in the blood.

That is a very basic overview but that is also why it is so hard to treat with replacements as it would almost have to be intravenous, anything eaten would be destroyed before it gets to the relevant organ.

[meaniejean]

Exactly, Charlie. DFI is a transport issue, HFI an enzyme issue.

[anastazya]

Charlie...I am trying to come up with a way to test for FM in HFI patients. There is nothing that says you can't have both.

[meaniejean]

The way to test for FM in HFI patients is the same as with anyone else - just WAY more dangerous - the oral fructose breath test. The problem is testing for HFI in FM patients (because enough fructose might not make it to the liver for HFI to cause a dramatic drop in blood sugar especially in those who have residual amounts of aldolase produced) - and this is done with IV fructose load (bypasses the malabsorption problem) - again, VERY dangerous - liver biopsy is probably the safest method.

But really, there would be no need to test for FM in an HFI, since obviously HFI is serious enough to prescribe strict fructose avoidance.

If you have both FM and HFI, a breath test will cause increase in hydrogen (or methane) excretion AND changes in blood work (though the blood work changes may not be as dramatic as they might be in someone without FM).

-Sandra

[charlie]

I'm with Sandra on this one, I'm not sure I quite follow why you would test for both as if you have HFI you wouldn't want to risk the damage fructose would do surely? The only difference on the diet is that some DFI have problems with fructans too. Therefore the safest option is to remove from your diet fructose and then if still having problems take out wheat too. Your body will soon give a answer.

I'm sure you probably can have both but I don't see the need for further tests - or am I just being thick?

[anastazya]

Charlie...it's to help figure out what you should and shouldn't try to eat. The biggest problem is that you keep trying foods that make you sick. If you know that you have both then you can adjust your diet accordingly. Saves the trial and error of foods we do now.

Sandra...I am wondering if there are false negatives out there with HFI patients due to the lack of fructose going into the system. If you body isn't breaking it down, the transportation of fructose doesn't happen on a large enough scale to have any hydrogen/methane released. That would show a negative. But, if the HFI patient had the fructose that was already broken down (what our bodies would have done naturally if we didn't have HFI) then there should be no symptoms of HFI (since it is my understanding that it's the toxic form of fructose that causes symptoms). The fructose would be at a level that the transportation system could work and then would be able to tell if the HFI patient also has FM.

The normal FM test only works if the patient is breaking down fructose properly. If someone can't break down fructose...there is no way to test for FM.

[meaniejean]

Actually, it is the opposite. The FM test works fine with HFIers. Here's why.

In fructose malabsorption (very simplified version): you drink the fructose solution, it passes into your small intestine and cannot be absorbed. It then passes into your large intestine where the fructose feeds normal bacteria and hydrogen (or methane) is produced by the bacteria feeding on the unabsorbed fructose. Breath test is positive. Fructose is not able to enter blood stream because it passes right through the body (though some amount may still enter the blood stream depending upon the degree of malabsorption).

In HFI (once again, the simplified version) - you drink the fructose solution, it is absorbed through the small intestine (because unlike malabsorption, you are able to normally absorb the fructose), it enters the bloodstream, makes its way to the liver to be processed. But, you are missing aldolase B so the fructose metabolism is stalled at this step and toxic substrates build up in your system. And then you pass out or try to gnaw off your arm due to crazy hypoglycemic crisis ... ; )

If you have malabsorption AND HFI: You drink the solution, most of it goes straight through you as in the first example (and hydrogen/methane are produced), the rest makes its way into the bloodstream. Your liver tries to process the fructose but cannot without aldolase B, so again, toxins build up. This would produce both HFI symptoms, but probably not to the extent of the second example (without concomitant fructose malabsorption) and a positive breath test.

So, no false negative for those with HFI. Actually, it is possible to get a false POSITIVE breath test with HFI or FDPase deficiency if your body enters a state of acidosis. There is no malabsorpion, but the acidosis can cause hydrogen to be released through your lungs.

[ukbill]

Only one very important problem here!

The FM test will knock an HFI'er sideways and make them extremely ill. and for some months following the test!

For a child with an already compromised liver it could be fatal!

I know I had 150G fructose intravenously (it should have been 15 g) on my challenge test as an adult with no liver damage (before the test) It took me 6 to 9 months before i was anything like stable again.

I believe the FM test is 150g fructose in a solution?

This could easily Kill an HFI child!

I cannot say how bad it was for me as an adult but the doctors were in a flat panic as I went into a coma I remember them asking me what they could do!

I could not answer as my tongue had swollen and was too big to allow me to speak and they were a long way away up the end of a long dark tunnel looking down at me.

FH test is NOT safe for HFI'ers! EVER!

[meaniejean]

Exactly, ukbill. It look Calvin a couple of months to recover. It was so sad. I started talking jibberish after my test for no apparent reason. It was a bit scary. Dizzy for weeks.

However, they do not give 150g of fructose - they give 1 g/kg body weight but they cap it at either 20g or 25g depending upon the laboratory. Still plenty enough to do some major damage - especially in children. This is an oral test for FM, not IV.

From what I read, if they were going to do it to diagnose HFI it would be 1 g/kg body weight (oral, not IV) - but no cap. Seems a little backwards really, but I'm assuming it has something to do with "normal" fructose metabolism thresholds. I don't know what the IV amounts are supposed to be, but I'm almost certain they are nowhere near 1 g/kg body weight!

They do the 20-25g cap for FM because even non-malabsorbers would malabsorb larger amounts of fructose to some extent. They need to separate pathological malabsorption from functional malabsorption.

So, yes, potential HFIers beware! Horrible, horrible test!

IV 150g - you are lucky to be alive, ukbill - that could kill a "normal" person!!!

[ukbill]

You know I'm not surprised..

It kicked the proverbial poo out of me for some time.

The doctors then wanted to do a liver biopsy on me.. but my step father, a retired Doctor, said not to.. I think he was worried in case they botched that test as badly..

Although he would never criticise another Doctor ( He was Old School) I think he was baddly shaken my the effect on me of the tests.

The first day in Hospital they gave me 150g Sucrose intravenously.. so I had 75g Fructose that day as well, before the big test the next day.

After the Sucrose was given the Blood sugar tests showed a rapid rise in blood sugar for the first 20 min (the Glucose burning off) up to 11 mol / litre, then the Fructose hit and my blood went vertically down below 2.5 mol / litre which is the minimum level of detection (in 1981) if I remember right.

When the crash hit .. It hurt really bad.. but I avoided loosing consciousness that time, which was a pity as I really wanted the pain to stop.

I remember I could not stop my legs from thrashing about, they had a mind of their own. It tooka bout 2 hours for the worst of the reaction to die down.

Of course then I knew nothing of the damage to my liver of the toxins caused by the breakdown products form Fructose. I thought until recently that I could eat anything so long as I did not eat enough to get a reaction.. and I could balance out some foods containing Fructose with lots of Carbs. and Protein.. Which is true but the toxins are doing the damage "behind the scenes" so to speak.

It was Not a good two days, or 6 months following.

For any Doctor reading this..

For an adult of 95Kg with HFI trust me 15g is fine for the test.

You will get the result you need, and scaled down to suit the weight of a child will work too.