Not all carbohydrates hit the bloodstream the same way. The rate at which a carb source raises blood glucose, the glycemic index, determines how much insulin the body has to produce, how quickly energy arrives, and how hard the subsequent drop is. For a product used daily, often as a meal replacement, that rate matters.
What GI actually measures
GI is a scale from 0 to 100, calibrated against pure glucose. The higher the number, the faster a carb source raises blood glucose. A spike followed by a rapid drop is the familiar mid-morning or mid-afternoon crash. Sustained, moderate glucose release is steadier energy.
Source |
Glycemic Index (Approx.) |
| Glucose | 100 |
| Maltodextrin |
85–105 [1]
|
| White bread | ~75 |
| White rice | ~72 |
| Oats (rolled) | ~55 |
| Barley malt extract | ~45–55 |
| Whole barley grain | ~25–28 [2] |
| Lentils | ~29 |
High-GI sources like white rice or refined sugar deliver energy fast and drop fast. Very low-GI sources like whole lentils or raw barley release glucose slowly, but in a shake format they introduce texture, grittiness, and mixability problems that make them impractical.
Barley malt extract sits in the middle: medium GI, derived from a grain with one of the most studied low-GI profiles in the literature, and processable into a form that works in a liquid formulation.
Why barley?
Barley's glycemic properties are driven by beta-glucan, a soluble fiber that forms a viscous gel in the digestive tract and slows the absorption of glucose into the bloodstream. Research indicates that barley beta-glucan attenuates post-prandial glycemic response by influencing the activities of glucose transporters like GLUT2 and SGLT1 [3]. Whole barley grain has a GI of ~25–28, among the lowest of any common grain, almost entirely because of its beta-glucan content.
Barley malt extract is a more processed derivative. The malting process partially breaks down the grain's complex starches into maltose and shorter-chain carbohydrates, which raises the GI relative to whole grain. But it retains meaningful beta-glucan content and provides something whole grain barley can't in this format: consistent solubility, a clean malt flavor that integrates with cocoa, and a carb profile that delivers energy over time rather than in a single spike.
It also avoids the two extremes. High-GI sources like refined sugar or maltodextrin used as a primary carb input produce a spike and a drop. Very low-GI sources that work purely on slow digestion tend to have texture and palatability trade-offs that compound over daily use.
Glycemic Index, with Full Context
GI is measured in isolation, with only the carb source consumed. In practice, nothing is eaten in isolation.
Protein, fiber, and fat all slow gastric emptying and attenuate the glycemic response of whatever carbohydrate is consumed alongside them. This is well-established in the literature on mixed meals. Studies show that adding protein to a carbohydrate meal elicits physiologically significant reductions in the glucose area under the curve (AUC) [4].
Adding soluble fiber amplifies that effect further, as the combination of higher dietary protein and fiber intakes has been shown to modulate postprandial glucose and insulin levels effectively [5].
Each serving of Soma contains 40g of protein and 21g of fiber. Both are present in the same serving as the barley malt extract. The protein alone would blunt the glycemic response of a medium-GI carb source. The fiber reinforces that, both through FOS from chicory (a prebiotic fiber that isn't absorbed as glucose at all) and through the residual beta-glucan in the barley malt extract itself.
The effective glycemic response of a Soma serving is considerably lower than the GI of the barley malt extract in isolation would suggest [6].
On maltodextrin
Maltodextrin appears in Soma's ingredient list. As a primary carbohydrate source, it would be a problem: GI of ~85–105, little nutritional value, used in volume to bulk out cheap formulations.
That's not its function here. Maltodextrin in Soma is present in trace quantities as a processing aid, a carrier for the enzyme blend and a tool for consistent mixability across batches. It contributes negligibly to the carbohydrate content of the serving, and to the overall serving size. The primary carb source is the Smart Carbs + Prebiotic Fiber system: barley malt extract and FOS from chicory.
References
1. "Hofman, D. L., et al. (2016). "Maltodextrins: Production, Properties and Usage." Critical Reviews in Food Science and Nutrition. Maltodextrin typically has a GI ranging from 85 to 105, higher than table sugar."
2. University of Sydney Glycemic Index Research Service (GI Database). Whole grain barley consistently ranks among the lowest GI grains, typically between 25 and 30.
3. "Zhong, Y., et al. (2021). "Beta-Glucan From Barley Attenuates Post-prandial Glycemic Response by Influencing the Activities of GLUT2 and SGLT1." Frontiers in Nutrition. This study details the molecular mechanism by which barley fiber slows glucose uptake."
4. "Journal of Nutrition (2024). "The Effect of Adding Protein to a Carbohydrate Meal on Postprandial Glycemic Response." Meta-analysis confirming that adding plant or dairy protein significantly reduces post-meal glucose spikes."
5. "Amankwaah, A. F., et al. (2017). "Effects of Higher Dietary Protein and Fiber Intakes at Breakfast on Postprandial Glucose." Nutrients. Evidence that the synergy of protein and fiber is a major contributor to stable blood glucose levels."
6. "Kim, J. S., et al. (2019). "Effect of nutrient composition in a mixed meal on the postprandial glycemic response in healthy people." Nutrition Research and Practice. Confirms that the GI of a mixed meal is lower than its individual components when protein and fiber are present."