A guide to impact carbs, sugar alcohols and detecting hidden carbs

Have you ever picked up a low calorie or low carb snack, checked out the nutritional information and thought to yourself “this seems too good to be true”? Well in most cases, your intuition was right, and unfortunately, they’re not true at all!

Whilst products heralding a low-carb content or minimal calories may hold strong appeal for those of us watching our weight, monitoring our carb intake or tracking our macros, all too often the claims plastered on the packaging of popular health-food items are hiding sneaky hidden truths. Like many of you, we’ve seen lots of exciting new low carb bars and snacks pop up recently, but when we added up the calories by macro nutrients into apps such as MyFitnessPal … the calories just don’t add up! So what is going on? Let’s start by checking out this example:

‘Low-carb protein bar’ per the manufacturer’s label

'Low carb' Nutrition Information Panel

‘Low carb’ Nutrition Information Panel

Now, Fat is 9 calories per gram, protein is 4 calories per gram and carbohydrates are 4 calories per gram. Therefore, the amount of calories coming from each macro listed looks like this when broken down:

12.9 x 9 = 116 calories from fat.
45 x 4 = 180 calories from protein.
4 x 4 = 16 calories from carbohydrates.

Add these all together, and we get a calorie total of 312 calories – not the 370 calories listed!
That’s almost 60 calories unaccounted for – an ambiguous nightmare for those of us trying to monitor what we’re putting into our bodies! So where are these calories coming from and why don’t the numbers add up?

Here’s why

Net carbs vs. total carb counts. Nutritional information labels on food products in Australia often include dietary fibre as a separate line within the total carb count, giving an accurate estimation of the carbs that can actually be digested. However, certain brands or imported products may deduct this fibre count from the carb count altogether, and print only a “Net Carb” line as calculated below:

Total Carbs – Dietary Fiber = Total Net Carbs

Knowing the net carbs of a product may indicate the amount of carbohydrate that will have an effect on blood sugar levels and is therefore very handy to know when trying to limit the amount of carbs we’re consuming. However, within this value for ‘net carbs’ often hides the culprit behind the contribution of those extra calories we detected in the food label earlier. Enter the world of sugar alcohols.

Sugar alcohols

Sugar alcohols get their name from their molecular structure, which is a hybrid between a sugar molecule and an alcohol molecule. Biochemically speaking, sugar alcohols are structurally similar to sugar, but are either poorly digested (e.g., maltitol), or are so benign that they are not actually metabolized (e.g., erythritol).1

Generally speaking, sugar alcohols (also called Polyols) contain fewer calories, have lower impact on insulin levels and are considered safe for those with diabetes – attributes which make this class of ingredients easy candidates to jam-pack into many ‘low-carb’ alternatives. Indeed, sugar alcohols allow food manufacturers in some countries to alter the value they state for ‘Carbohydrates’ on their nutritional panel, however not different sugar alcohols have varying GI’s and thus varying levels of  impact carbohydrates. For this reason, it’s important to understand exactly how much of the sugar alcohol you are consuming, will behave like a true carbohydrate in your body. Below we list the most common sugar alcohols, their GI (glycemic index), calories per gram, and estimated ‘net’ or ‘impact’ carbohydrates as a percentage.

See how all but erythritol are actually metabolized to some extent by our bodies? That’s why they should never not be totally deducted from the carb count, or omitted from the nutritional information completely panel if they have been deducted.

GI, Cal/Gram and % Metabolized Table of Polyols

GI, Cal/Gram and % Metabolized Table of Polyols

Source: Livesey, op. cit., pp. 179, 180. Taken from Mendosa.com

We must note here however that the net carb content of polyols above is purely an estimate as it varies between individuals, and there is a direct correlation to the polyol’s glycemic index. As complex as it sounds, it’s actually quite simple… if the product can raise your blood glucose levels, then it is being (alebeit partially) digested as a carbohydrate. If the polyol (such as erythritol) has zero GI, then there is no available or digestible carbohydrate.

Let’s run through a typical scenario using a standard protein bar. The bar says it has a total of 5.2 g of carbohydrate. Great, that sounds pretty low carb doesn’t it? But then there is a line for Maltitol (7.2g) and Gylycerol (7.6g). So in theory there’s a potential for 5.2 + 7.2 + 7.6 g of carbs = 20g carbs? Well not quite.  If only 35% of the maltitol is digestible and almost none of the glycerol is, then in reality the equation looks more like this:

5.2 + (7.2*35%) +0 = 7.72 g NET  /  Digestible carbs

So as you can see… Polyols are no ‘get out of jail free’ card and no silver bullet for low carbers unless you only consume erythritol and / or glycerol. So if you’re low carbing and regularly eating snacks full of sugar alcohols and not losing weight – this could be why. Cut them out for 2 weeks and you may find the weight starts falling off again.

As for food labels, be very wary. By simply deducting them entirely from the carb count, food manufacturers are being extremely misleading in the nutritional information they’re providing – leading many of us to over-consume carbohydrates despite being assured that we’re picking a “low-carb” option.

So how can we avoid this trap? Equipped with the knowledge above, it’s easy for you to add up total calories based on the macronutrient nutrition information per 100g yourself.

The first step is to see if your product contains sugar alcohols. If it does, does the nutritional panel list them separately to disclose their content? Great, now you can figure out the net carbs based on the trick we just showed you. If it doesn’t list them, we can go back to the example provided at the beginning, where we had up to 60 calories unaccounted for.

Ingredients: Branded® protein blend (42%) [whey protein isolate, calcium caseinate, whey protein concentrate, milk protein concentrate, creatine monohydrate, L-glutamine, glycine, emulsifiers (soy lecithin, 471)], protein milk chocolate (23%) [maltitol, cocoa butter, milk solids, soy protein isolate, cocoa liquor, emulsifier (soy lecithin), flavour], water, glycerol, emulsifier (soy lecithin),  flavours, sorbitol, cocoa powder,  preservative (202), sweetener (955).

As we guessed, the bar has sorbitol and maltitol, along with glycerol – which we saw earlier has the highest carb count per gram of all common sugar alcohols!

If the food manufacturer were to properly disclose the contribution of these sugar alcohols to the bar, the nutritional panel would look like this:

As we can see, the bar has 8.9g of maltitol, which when multiplied by 2.1cal/g = 17.8 calories, a whopping 9.7g glycerol, which when multiplied by 4 = 38.8 calories and 1.7g of sorbitol, which when multiplied by 2.6 = 4.42 calories. So all up, these sugar alcohols are contributing roughly 18 + 38 + 4 calories = the very 60 calories we were missing from the start!

So here’s our take home message: while sugar alcohols might be better for your diet than actual sugar, not all of them are not “calorie-free” or entirely “low-carb”.

Get to know your polyols and start checking labels. Your safest bet is to limit your intake of foods containing the higher GI / digestible ingredients in large amounts, and become savvy with how you CAN track them when you do eat them, so that you can more accurately account for their contribution to your daily carb intake and don’t allow diet sabotage!

As always, knowledge is power.

Side note: For those wondering where “Erythritol” pronounced ‘ee-rith-re-toll’ (the ingredient used in our Noshu donuts) falls into this world of sugar alchohols and carb counting – be assured that Erythritol is the only natural, plant based sugar alcohol which has negligible calories, is not absorbed at all by the body and has virtually no impact on blood sugar levels. Phew!

1.    http://www.builtlean.com/2012/10/08/sugar-alcohol/
2.    http://www.mendosa.com/netcarbs.htm

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