1

votes

Is fructose biologically necessary ?

Answered on September 12, 2014
Created September 21, 2012 at 7:41 PM

I have read on here that our immune system, our testes, and certain glycolytic activities (from intense exercise to possibly complex, system II thought) all require glucose. The Jaminet's see it as a nutrient in a way that fructose is not. Glucose can be made endogenously via gluconeogenesis. What about fructose? Is there any biological necessity for it?

IS there some great benefit that I/one is missing out by not consuming fruit/fructose? Anecdotally, I have gone long periods without a any fruit or nightshades (only consuming them in the spring/summer and not in large amounts), so very minimal fructose, and I get a fairly comprehensive physical including blood work bi-annually too, which have been coming back well for the some time now ( I get a lot things checked- from glucose tolerance test, a hormonal panel, a blood lipid panel, and other things like creatinine, BUN, vitamin B12, vitamin D, etc). Objective measures aside, subjectively I feel better with starchy/glucose based foods for carbs over fruit/sucrose/fructose based foods.

C3bc92e6b5eba45dc55f43ac3c70cc25

on September 22, 2012
at 03:47 PM

I Google fructose spend metabolism. A few animal studies came up, fructolysis plays a big role in spermatozoa survival under anaerobic & aerobic metabolism. Still doesn't answr your Q. It's pretty cool seeing how spring time,mating season,fruit, fructose fueling sperm sort of ties in.

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on September 22, 2012
at 02:19 PM

So what you are saying is if one were to choose where to get their carb sources from, glucose ones would be preferable to fructose based ones, correct?

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on September 22, 2012
at 02:18 PM

AgingHippie- That's not a useful answer. And since when is asking a question synonymous with obsessing?

336c383a3c4d28652d7ab888c79108a3

(614)

on September 22, 2012
at 12:41 AM

If "I feel better with starchy/glucose based foods for carbs over fruit/sucrose/fructose based foods." THEN eat starchy/glucose based foods for carbs AND STOP WORRYING - the stress will kill you!

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on September 22, 2012
at 12:00 AM

ha. Yes I think it is and have wondered about that too. I guess measuring ejaculate volume in summer vs winter would be one way to test, but that's a science experiment I will leave for some other more adventurous soul.

3846a3b61bc9051e4baebdef62e58c52

(18635)

on September 21, 2012
at 11:27 PM

And yes fructose does use other pathways that may negatively impact the liver....not so much in the case of a couple pieces of fruit as a 64oz big gulp obviously.

3846a3b61bc9051e4baebdef62e58c52

(18635)

on September 21, 2012
at 11:24 PM

Also liver is where the glucose to keep your blood sugars stable when not eating come from first if I remember correctly. Its also important in the conversion of T3.....but you can get liver glycogen through gluconeogenesis (i.e. protein and fat) just as well as anything, and startch refills liver glycogen even if it is at a slightly reduced rate compared to fructose. There is no need for fructose.

3846a3b61bc9051e4baebdef62e58c52

(18635)

on September 21, 2012
at 11:23 PM

Also liver is where the glucose to keep your blood sugars stable when not eating come from first if I remember correctly. Its also important in the conversion of T3.....but you cant get liver glycogen through gluconeogenesis just as well as anything, and startch refills liver glycogen even if it is at a slightly reduced rate compared to fructose. There is no need for fructose.

3846a3b61bc9051e4baebdef62e58c52

(18635)

on September 21, 2012
at 11:18 PM

Its a carb....so easy answer is no.

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on September 21, 2012
at 10:30 PM

Yes I know you did...this is similar, but not the same.

64433a05384cd9717c1aa6bf7e98b661

(15236)

on September 21, 2012
at 10:14 PM

liver glycogen is used to make glucose to raise/maintain your blood sugar levels. Muscle glycogen isnt used for gluconeogenesis.

194d8e8140425057fe06202e1e5822a7

(3979)

on September 21, 2012
at 09:54 PM

Wow, I asked a very similar question a couple hours ago: http://paleohacks.com/questions/151076/carbs-not-evil-simple-carbs-evil#axzz276hf7btG

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on September 21, 2012
at 08:54 PM

Since you are trying to lean out, you may want to actually reduce fruit consumption, not increase it. Also, you are right that fruit is good for intestinal motility, but I find that just adding shredded red onion to salads works just as well at keeping me regular. Results may vary.

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on September 21, 2012
at 08:53 PM

Also, since you are trying to lean out, you may want to avoid fruit. While beneficial for digestion, I find that red onions shredded onto salads has a similar affect. Results may vary.

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on September 21, 2012
at 08:29 PM

...oh nevermind- fructose just has to get converted by the liver to glucose before it can be stored as glycogen. I think I get it.

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on September 21, 2012
at 08:28 PM

thhq- asking does not necessarily mean one is obsessing. If you must know I asked upon a whim after someone made a comment on a previous answer of mine that got me thinking. Thanks though (?).

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on September 21, 2012
at 08:22 PM

THanks thhq I recognize that. But asking does not imply obsessing.

Medium avatar

(10611)

on September 21, 2012
at 08:20 PM

No of course fructose is not biologically necessary. Neither is meat. Vegans are the proof of that. Seriously, why obsess over it? It makes paleo look like an eating disorder. As if paleos could pick and choose. As if.

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on September 21, 2012
at 08:12 PM

I also read this book by one Dr. Bernstein forever ago and he favors glucose because he said it is ubiquitous in all foods, unlike fructose, which is distinctly found in fruit. He says glucose is preferred by our cells. He even says to avoid nightshades becasue of the fructose content.

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on September 21, 2012
at 08:10 PM

I thought fructose could not be stored as muscle glycogen? Is that just factually incorrect?

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on September 21, 2012
at 08:09 PM

I also would not favor fruit for leaning out...I'd actually avoid it. I do notice that fruit makes for speedy digestion, but what I do is add shredded red onion to salads and that keeps me regular just as well. Results may vary.

3ce6a0d24be025e2f2af534545bdd1d7

(26217)

on September 21, 2012
at 08:07 PM

Right. But the same could be said for external sources of glucose. It is odd that the body can convert fructose to glycogen more efficiently that glucose...

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on September 21, 2012
at 08:07 PM

Right but what benefit does liver glyogen have? Isn't muscle glyogen preferable for an athlete who engages in glycolytic work?

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on September 21, 2012
at 08:06 PM

Right- exogenously we can live with out carbs, enogenously we cannot live without glucose, can we? But from what I gather it does not seem like there is any need for fructose.

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on September 21, 2012
at 08:03 PM

LOL. I avoid foods that give me digestive distress, and one of those foods is fruit with a high fructose/glucose ratio. So I avoid things like apples and pears. When I do eat fruit it is pretty much only fresh figs (my favorite) or blueberries. If you are farting a lot, I would change your diet as I take it as a bad sign. However, cows eat their natural diet of grass and apparently produce methane fairly efficiently.

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5 Answers

2
32f5749fa6cf7adbeb0b0b031ba82b46

(41747)

on September 21, 2012
at 11:58 PM

As far as I know, we don't use fructose in the body, so it's not biologically necessary. Glucose is used everywhere, thus biologically necessary. It's so essential to biology that we humans can biosynthesize it if glucose starved (intentional use of the word starved, zero carb is not natural.)

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on September 22, 2012
at 02:19 PM

So what you are saying is if one were to choose where to get their carb sources from, glucose ones would be preferable to fructose based ones, correct?

2
C4f1a0c70c4e0dea507c2e346c036bbd

on September 21, 2012
at 07:58 PM

Do you fart less from glucose over fructose? I've been eating a lot of fruits lately to try to lean out more and get a better poo. My gas is becoming awful in quantity.

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on September 21, 2012
at 08:03 PM

LOL. I avoid foods that give me digestive distress, and one of those foods is fruit with a high fructose/glucose ratio. So I avoid things like apples and pears. When I do eat fruit it is pretty much only fresh figs (my favorite) or blueberries. If you are farting a lot, I would change your diet as I take it as a bad sign. However, cows eat their natural diet of grass and apparently produce methane fairly efficiently.

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on September 21, 2012
at 08:53 PM

Also, since you are trying to lean out, you may want to avoid fruit. While beneficial for digestion, I find that red onions shredded onto salads has a similar affect. Results may vary.

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on September 21, 2012
at 08:09 PM

I also would not favor fruit for leaning out...I'd actually avoid it. I do notice that fruit makes for speedy digestion, but what I do is add shredded red onion to salads and that keeps me regular just as well. Results may vary.

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on September 21, 2012
at 08:54 PM

Since you are trying to lean out, you may want to actually reduce fruit consumption, not increase it. Also, you are right that fruit is good for intestinal motility, but I find that just adding shredded red onion to salads works just as well at keeping me regular. Results may vary.

1
3ce6a0d24be025e2f2af534545bdd1d7

(26217)

on September 21, 2012
at 07:57 PM

The only "advantage" to fructose is that it is sweeter than glucose, and as such people can use less to meet their sweet quotient. Of course I would argue that it is better not to have a sweet quotient. The other advantage is that the calories are absorb quicker by your cells than glucose with a smaller insulin reaction (although that may not be a good thing).

Sugars and/or carbohydrates are not essential nutrients for the body. Humans can live with zero intake of carbohydrates.

That being said, the slow rate of burning fat and GNG production would make living on zero carbs pretty sedentary.

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on September 21, 2012
at 08:29 PM

...oh nevermind- fructose just has to get converted by the liver to glucose before it can be stored as glycogen. I think I get it.

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on September 21, 2012
at 08:06 PM

Right- exogenously we can live with out carbs, enogenously we cannot live without glucose, can we? But from what I gather it does not seem like there is any need for fructose.

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on September 21, 2012
at 08:10 PM

I thought fructose could not be stored as muscle glycogen? Is that just factually incorrect?

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on September 21, 2012
at 08:12 PM

I also read this book by one Dr. Bernstein forever ago and he favors glucose because he said it is ubiquitous in all foods, unlike fructose, which is distinctly found in fruit. He says glucose is preferred by our cells. He even says to avoid nightshades becasue of the fructose content.

3ce6a0d24be025e2f2af534545bdd1d7

(26217)

on September 21, 2012
at 08:07 PM

Right. But the same could be said for external sources of glucose. It is odd that the body can convert fructose to glycogen more efficiently that glucose...

1
64433a05384cd9717c1aa6bf7e98b661

(15236)

on September 21, 2012
at 07:55 PM

Necessary? no, fructose and glucose both get converted during glycolysis to glyceraldehyde 3-phosphate and eventually pyruvate.

It fills up your liver glycogen quicker, so you could argue better recovery from certain exercise or after fasting, etc

3846a3b61bc9051e4baebdef62e58c52

(18635)

on September 21, 2012
at 11:24 PM

Also liver is where the glucose to keep your blood sugars stable when not eating come from first if I remember correctly. Its also important in the conversion of T3.....but you can get liver glycogen through gluconeogenesis (i.e. protein and fat) just as well as anything, and startch refills liver glycogen even if it is at a slightly reduced rate compared to fructose. There is no need for fructose.

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on September 21, 2012
at 08:07 PM

Right but what benefit does liver glyogen have? Isn't muscle glyogen preferable for an athlete who engages in glycolytic work?

64433a05384cd9717c1aa6bf7e98b661

(15236)

on September 21, 2012
at 10:14 PM

liver glycogen is used to make glucose to raise/maintain your blood sugar levels. Muscle glycogen isnt used for gluconeogenesis.

3846a3b61bc9051e4baebdef62e58c52

(18635)

on September 21, 2012
at 11:27 PM

And yes fructose does use other pathways that may negatively impact the liver....not so much in the case of a couple pieces of fruit as a 64oz big gulp obviously.

3846a3b61bc9051e4baebdef62e58c52

(18635)

on September 21, 2012
at 11:23 PM

Also liver is where the glucose to keep your blood sugars stable when not eating come from first if I remember correctly. Its also important in the conversion of T3.....but you cant get liver glycogen through gluconeogenesis just as well as anything, and startch refills liver glycogen even if it is at a slightly reduced rate compared to fructose. There is no need for fructose.

0
C3bc92e6b5eba45dc55f43ac3c70cc25

on September 21, 2012
at 11:51 PM

Isn't fructose found in sperm? Or fuels sperm? Can someone explain that?

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on September 22, 2012
at 12:00 AM

ha. Yes I think it is and have wondered about that too. I guess measuring ejaculate volume in summer vs winter would be one way to test, but that's a science experiment I will leave for some other more adventurous soul.

C3bc92e6b5eba45dc55f43ac3c70cc25

on September 22, 2012
at 03:47 PM

I Google fructose spend metabolism. A few animal studies came up, fructolysis plays a big role in spermatozoa survival under anaerobic & aerobic metabolism. Still doesn't answr your Q. It's pretty cool seeing how spring time,mating season,fruit, fructose fueling sperm sort of ties in.

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