A couple of months ago I started to take note that the perceived sweetness of foods isn't always correlated with its sugar content. One stark example was yogurt, where yogurts that tasted mostly plain or even tart would sometimes have higher sugar content than yogurts that were appreciably sweet.

Unfortunately, I don't have any great examples to show at the moment.

I was munching on one of these: Kirkland Protein Bars which got me thinking about this topic again. The bars are fairly sweet, but the product claims to only have 1 gram of sugar and it doesn't have any artificial sweeteners.

I understand that serving size is a confounding factor, especially given that I don't have any good examples to show on hand, but from what I recall, the serving sizes for the yogurts were comparable.

TL;DR: is there a strong correlation between how our tongues perceive sweetness and the stated sugar content? Are there other ingredients that can contribute to sweetness without contributing to the net sugar content?


3 Answers 3


Different sugars have different relative sweetness (in %) (Elmhurst College):

  • Sucrose: 100
  • Fructose: 140
  • High fructose corn syrup (HFCS): 120-160
  • Glucose: 70-80
  • Lactose: 20

Relative sweetness of some non-sugar sweeteners (NutrientsReview):

  • Aspartame: 180
  • Acesulfam potassium: 200 (in some diet colas)
  • Stevia: 300
  • Saccharin: 400
  • Sucralose: 600

Plain yogurt (100 g) contains 4.7 g sugars, but mostly lactose, which is not sweet. (NutritionData, milk composition)

Kirkland Protein Bars contains stevia (300% sweetness) (link - read at the bottom of the Nutrition Facts), which explains its sweetness. Stevia is a natural non-sugar sweetener.

Perceived sweetness can increase with the food temperature (ScienceDirect) and salt content (a study in mice). Liquid and solid foods with the same sugar content can have different perceived sweetness (ScienceDirect). And there are sweet taste enhancers...(ChemistryWorld)

  • Thanks Jan! This is exactly the info that I was looking for.
    – dant
    Apr 16, 2018 at 17:42
  • So, yes, relative sweetness is a thing, but at the same time, HFCS is only twice as sweet as glucose, so at 1g of sugar, it's still not going to make a protein bar taste terribly sweet when there's normally more like 20g of sugar in a sweet protein bar like that.
    – Cascabel
    Apr 18, 2018 at 20:40
  • I edited; yes, Kirkland Protein Bars contain stevia, which has 300% sweetness.
    – Jan
    Apr 19, 2018 at 6:57

The linked protein bars are sweetened using stevia, a sugar substitute that's extracted from plants, but like artificial sweeteners, isn't actually sugar, so it's not going to show up in nutrition facts. It's on the ingredient list for both:

protein bar ingredients

Hard to say about the yogurt. Could have been one or more of many reasons:

  • stevia or some other sweetener you missed
  • differences in acidity (which counters sweetness)
  • other flavors that make us perceive sweetness more easily (even salt works)
  • other flavors that we associate with sweetness
  • For yogurt he says that tastes less sweat than expected from sugar content. That's simply due to lactose.
    – Jan
    Apr 19, 2018 at 7:00
  • @Jan But it was comparing two yogurts, not just an expectation based on amount of sugar.
    – Cascabel
    Apr 19, 2018 at 13:48
  • 1
    Yes, I aggree. Most of this mystery can be probably explained by non-sugar sweeteners.
    – Jan
    Apr 19, 2018 at 13:50
  1. Was there salt in the bar? Salt can bring out and intensify sweetness like in chocolate lava cake (sea salt tops) or on pineapple (typically Asian norm).

  2. The other possibility are the many varied natural sweeteners that may be in the bar.

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