Sugar and the immune system

This is going to come off as extremely ignorant, but I know very little about health science, so here goes.

I was just in a nutrition-oriented work session where the speaker mentioned a number of things I’d never heard before. The one that stood out for me was her statement that sugar paralyzes the immune system for anywhere from 6 to 8 hours. She did not mention what level of sugar intake was required for this to happen.

I just did a cursory Google search and found a number of sites that mention this same information (although I saw ranges of paralysis time from minutes to several hours), but I didn’t see any medical sites I recognized that mentioned this. Is this just common knowledge? Is it the subject of scientific studies? Is it debated in the medical community? Or is it considered quackery? I truly have no idea. I appreciate any light you can shed on this.

That’s just stupid.

Ducks say what?

(With the complicated potential exception for uncontrolled diabetics, but that has to do more with cellular damage caused by high blood glucose, mostly to the blood vessels and nerves, not, as far as I know, to the immune system directly.)

Eighty percent of your immune system lives in your gut. Those billions of micro flora eat what is put in your stomach. You eat a lot of sugar, it favors the micro flora that get their groceries from sugar, at the expense of the micro flora that obtain their groceries from other sources. This would create an out-of-balance immune system, which is not good, but paralyzing the immune system is a bit harsh.

What micro flora don’t eat sugar? Everything eats sugar. (Okay, that might be a wee bit hyperbolic, but only a wee bit.)

And dietary sugars are absorbed in the small intestine. The GALT (all those immune cells you’re talking about) is in the large intestine. There shouldn’t be a lot of sugars left at that point. Undigestible (to humans) cellulose and polysaccharides, sure. Those are digested by bacteria in the large intestine. But those are in beans and corn and vegetables, not in Big Gulps and Milky Way bars.

80% by what metric?

Our cells run on sugar (glucose).

Verdict? Quack Quack.

Your gut bacteria are not your immune system. They are good to have there, but they do not play any very significant role in fighting off infections.

This is pretty boilerplate quackery that seems to be one of the newer claims of the woo crowd.

I wonder if the OP is referring to advanced glycation end-products, which result when sugars (mainly glucose, although it isn’t as reactive as other sugars like fructose, but is far more common in the body) react with proteins and other structural elements in the body and impair their function and are thought to play a major role in aging (appropriately, they are abbreviated as AGEs). And yes, this includes inflammatory processes, so that may be where the OP is getting that part from, although it isn’t something that happens in minutes or hours.

Here’s one study that suggests sugar consumption might temporarily impair immune system functioning:

She did briefly discuss AGEs, but I’m fairly certain it was not in that context. I can’t claim that I was completely paying attention then, though, because I think that was the point of the lecture when I was puzzling over her earlier comments about her healthy and fit friend dying of cancer caused by stress.

Interesting. Maybe that’s where all these nutrition folks are coming from.

So, “phagocytic capacity of neutrophils” . . . looks like that means that your white blood cells get lazy after a shot of glucose, and don’t ingest microbes as quickly for a couple of hours. Ah, according to wiki, neutrophils are only 50-70% of an average person’s white blood cells. So, the study indicates that half of your white blood cells get lazy for a couple of hours.

(“Paralyzed” implies a stun or damage effect that is not addressed in the study. Since the study does not address why the neutrophils slow their ingestion, “blissed out” or “satiated” would be equally unsupported guesses.)

I’m not going to try to get up to speed on how big a part of your immune system the white blood cells are, but a quick readthrough leaves me with the impression that they’re mostly after large microorganisms, maybe the sort that can come through cuts? They also notify other parts of the immune system that something’s up. The study did not address their ability to signal.

Your neutrophils are not your whole immune system, there are a lot of other elements to that. They’re not even all of your white blood cells. So, no, your immune system does not turn off for an hour or two after eating a candy bar.

(The abstract says that the “greatest effects” were within one to two hours, and that the average number of engulfed microorganisms that could be counted inside a neutrophil* was “significantly below the fasting control values” for 5 hours. Note that ‘significantly’ here could simply mean ‘measureably’ and ‘statistically determined to not be the result of data noise’. It does not necessarily imply a large effect, only a reliable one. We’d need the whole article to see if the effect beyond two hours was more than a trace effect.)

  • What did you do today, Mommy?

Oh, I squished some white blood cells on microscope slides and counted the contents of their guts.

Did you discover something?

Yes. I determined a statistically significant correlation.

Good. I know you like finding those.

God, I wish that were true. I have horrible allergies to all kinds of crazy things and break out in hives all the time. If only my immune system could be suppressed for 8 hours just by downing a Butterfinger…

There is no such thing as your “immune system”, it doesn’t exist as a single thing that can be targeted an affected.

What your body has is multiple levels of protection, that are generally referred to as the “immune system”.

Your liver, spleen, lymphatic system, white blood cells, antibodies, etc. There is no possible thing that could shut all of your ‘system’ down for several hours. These things are working independantly of each other to protect your body from harm.

The term ‘immune system’ is just a collective description of this process.To say that there is one thing that can turn the system on or off is just woo.

Then it sinks into the mass of all that gum you’ve ever swallowed and you’re done for! :eek:

One thing that catches my eye is that starch didn’t have any effect, which is a bit odd because starches are digested into sugar, not surprising since starch is made up of glucose. While it is true that it has to go through the whole digestion process, unlike simple sugars (but even sucrose and lactose need to be split first), the end result is the same, as indicated by the glycemic index of foods like bread and potatoes (which are actually worse than pure sugar, except glucose, when measured by glycemic index).

It is worth re-emphasizing Michael’s very important and well taken points.

Within minutes after ingesting essentially any (digestible) carbohydrate - bread, rice, pasta, table sugar, etc., - it is converted to glucose in the gut (and is then absorbed). So, except for the rate of absorption, it doesn’t matter in what form you ingest carbohydrate - it will all be absorbed as glucose (i.e. “sugar”).

So, unless our immune systems are paralyzed from breakfast to bedtime and to a couple of hours before the next day’s breakfast, this notion of “sugar paralyzing the immune system” is complete and utter horse shit.

(and the same thought process applies to the many other claims about the deleterious effect of eating sugar)

What about the ten pounds of red meat we all have in our guts?