Can muscle glycogen be fully replenished with any food source that contains glucose?

Question

For example, if one were stranded in a survival situation could they eat only wild edible leafy plants, such as goose grass and dandelions, and eventually fully replenish all of the bodies muscle glycogen, whilst walking long distances and performing labour equivalent to moderate intensity callisthenics?

Answer 1

Yes, it's a process called glycogenesis. Your larger issue is simply about calories. While your body can produce glycogen from spinach (as an example), there's only 105 calories in a pound of spinach. Spinach actually has some protein in it as well, and your body will use gluconeogenesis to convert some of that protein into glucose.

So while from a pure bio-chemistry standpoint your body does this every day, to get ~2,500 calories you would need to eat roughly 24 pounds of spinach. And walking long distances daily is going to consume a lot more than 2,500 calories.

The primary realistic pathway towards what you're thinking here is the aforementioned gluconeogenesis, converting from stored fat to glycogen then glycogenesis to glucose. Back of the envelope math says that 1 pound of stored fat in a human is about ~3,500 calories.

A 180 pound person, averaging 20% body fat, has 36 pounds of fat on them. Once you get under ~4% things can get pretty horrible since fat does other things like insulation and vitamin storage. So leave 4% (7 pounds) of someone's fat in place.

That still leaves you with 29 pounds of fat-energy, or 101,500 calories. At 5,000 calorie days, that's nearly three weeks. It would be an absolutely horrible 3 weeks I wouldn't want to participate in, but I'd rather do that than eat 48 pounds of spinach every day.

Answer 2

In theory, provided you consume enough of something containing carbohydrates then yes, you can replenish muscle glycogen eventually.

It's a little more complicated than that in practice.

For example, 100 grams of raw dandelion provides only 5.7 grams of carbohydrates (when you remove the fiber). Assuming total muscle glycogen depletion (which never completely happens) of 400 grams and assuming that all of those carbs end up as glucose (and they won't). Then you'd have to eat ~7kg of dandelion to restore glycogen.

That's a lot of leafy greens!

If you boiled the dandelion, you actually get less carbs per 100 g (only 3.5 g). Presumably because you lose a bunch to the water (which you might be able to drink).

Anyway, what I'm getting at is that practically speaking leafy greens suck at restoring glycogen. There are many foods that would simply require too much quantity of that food to make it practical.

And yes, it would depend to some degree how much glycogen you utilize doing whatever you're doing. It would also depend on how much of those carbs end up as glucose in the blood to be converted to glycogen in the muscle. Also how much glycogen is in the liver.

About 400 grams of glycogen are stored in muscles and about 100 grams are stored in the liver. All carbs are eventually broken down into glucose, fructose or galactose, but only glucose makes it past the liver without the need for conversion in the liver.

Answer 3

By long distance walking plus callisthenics, you could burn ~5,000 calories per day. To prevent glycogen breakdown (and consequently ketosis), you would probably need to consume at least 10-15% of calories as carbohydrates, that is 125-190 g carbohydrates per day (study 1 ; study 2 - table 2).

The amount of digestible carbohydrates (total carb - fiber) and calories in various foods that can be found in wilderness:

• Dandelion, 100 g = 5.7 g carbs; 45 kcal
• Blueberries, 1,000 g = 121 g carbs; 570 kcal
• Raspberries, 1,000 g = 54 g carbs; 520 kcal
• Chestnuts, 400 g, roasted = 192 g carbs; 980 kcal
• Hazelnuts, 200 g = 34 g carbs, 1256 kcal

From foods you can find in wilderness, berries and chestnuts are high in carbohydrates, and nuts and animal foods are high in calories. Green vegetables are not high in carbohydrates or calories.

In conclusion, to prevent glycogen depletion during a period of heavy physical activity, you may need to consume more than 100 grams of digestible carbohydrates per day. Saying that, you do not need to have glycogen stores or consume carbohydrates to survive and remain active.

Answer 4

Not as efficiently depending on the presentation or arrangement of the glucose molecules, they might be assembled in a more complex form in certain food types (i.e: in larger chains known as polysaccharides).

Generally speaking leafy and cruciferous vegetables are not the #1 way to go when it comes to this carbohydrate since simple glucose (a monosaccharide) also known as "dextrose" is found in fast digesting carb food sources that have a high GI or "Glycemic Index".

Foods types that mostly belong to the "grains and cereals" realm such as white: bread, pasta, and even tubers such as white potatoes, others include highly sweet fruits such as watermelons, pineapples and dates, and finally to be more extreme all the fast food junk such as pretzels, sodas, doughnuts and cupcakes . You can also find fast shooting glucose in other forms for example as candy, and its been said that gummy bears in particular are one of the quickest ways to replenish muscle glycogen, as used by many bodybuilders for post workout recovery.

Also, and since you mentioned a survival situation in the example that requires you probably to stay fed for a long period of time, and adding to that a demanding activity such as calisthenics or physical activity that compares to it, you might want to consider SLOW digesting carbs that keep you fuel for longer since they have a low GI.

Sources of the above mentioned? Black beans, whole wheat everything (pasta, rice, etc), oats, sweet potatoes, legumes and nuts, quinoa, amongst others.