Explanation of ScienceGuy's deliberately obscure post:
Some proteins in your body have "decorations" of long chains of polysaccharides. Polysaccharide is just a fancy way of describing a molecule made up of a bunch of sugar molecules like glucose or fructose, linked together. These sugar chains are essential in allowing your body to recognize, sort, and otherwise deal with these proteins. Think of them as "tags" on the proteins. They're very important.

HOWEVER.

Key point that ScienceGuy left out: the body is perfectly capable of MAKING most of the sugars he's talking about FROM fats and amino acids. In other words, if your body needs sugars and they're not available, it gets busy with the organic chemistry. So while adding the rarer sugars like mannose and xylose to your diet may help, it's not absolutely necessary. Possibly after more research has been done, it may be worth it to add the foods high in the rarer sugars during specific episodes (mannose during UTIs, for example. It's found in aloe vera) or while in maintenance. Strawberries, for example, are high in xylose. If this becomes the Next Big Thing, there will be dietary guides all over the place, and it'll be easy to pick the low-glycemic-index stuff.

But beware the pseudoscientific antilowcarbing! He gave himself away in the first sentence.