Why insulin matters

After consuming carbohydrate-rich foods, the pancreas secretes insulin to shuttle glucose into cells. Large, repeated insulin surges can promote fat storage, inhibit fat loss, and contribute to energy crashes, even when the foods appear healthy.

The “insulin index” shows that some nutritious items elicit a stronger insulin response than their glycemic index suggests. It reflects the elevation of insulin in the blood 2 hours after consumption. It is a tool that can be used in combination with glycemic index, to determine the metabolic effect of a particular food on the organism.

Below are everyday foods often labelled as “healthy” that can still produce a notable insulin rise, especially if eaten in generous portions or without protein and fat for balance.

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1. "High fibre" Breakfast cereals

Fibre within certain cereal slows down the absorption of glucose in the blood, and reduces the glycemic index compared to regular cereal. However, a study found that consumption of high-fibre cereal does not benefit the insulin levels of healthy individuals. As a result, the GI may appear normal, but the insulin index remains high for both high fibre and regular cereal.

Tip: Opt for full-fat yogurt with blueberries as a topping instead of cereal.

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2. Fruit smoothies

Blending breaks down cell walls, speeding glucose absorption. A 500 ml banana-berry smoothie can contain more than 40 g of free sugars, producing insulin excursions similar to a medium-sized cola.

Tip: Eat a whole fruit, and combine it with cheese to slow down glucose absorption.

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3. Dried fruit

Raisins, dates, and apricots have a higher sugar density than fresh fruit. 100g of raisins contain 4 times more sugar than the same weight of grapes.

Tip: Avoid dried-fruit; opt for fresh, organic, whole fruits instead, and keep portions small.

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4. Ripe bananas

As bananas ripen, starch converts to sugar. A large ripe banana (~25 g net carbs) can raise insulin almost twice as much as a greenish one of the same size.

Tip: Choose slightly green bananas or replace with a low GI food such as strawberries.

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5. Low-fat flavoured yogurt

Low fat yogurts are often filled with flavourings, sweeteners, and preservatives. Added fruit purées can push total sugars to 20 g per pot. Insulin area-under-curve is ~24 % higher than with full-fat, unsweetened yogurt of equal calories (Wanders et al., 2020).

Tip: Opt for plain full-fat yogurt and add your own berries.

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6. Whole-wheat bread

Whole-wheat bread has a similar insulin index to white bread.

Tip: Choose sourdough bread; fermentation breaks down sugar and reduces the spike. Consume it with a side of protein and fat such as cheese and eggs.

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7. Commercial Honey

Commercial blends of honey sold in the supermarket and marketed as natural, have been show to stimulate high insulin and glucose responses. More specifically, studies show that pure high-quality honey has a smaller insulin index than commercially-available blends.

Tip: Choose a locally-sourced good-quality honey. Use up to 1 teaspoon per-day; enjoy the flavour, not the volume.

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8. Oat milk lattes

Unsweetened oat beverages contain ~7 g rapidly absorbed maltose per 240 ml. Although they seemingly have less sugar than whole milk, they have a higher glycemic index because they are highly processed.

Tip: Swap for unsweetened coconut milk or whole sheep/goat milk.

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Practical take-aways

• Balance macros. Adding protein, fat, or fibre slows gastric emptying, reducing peak insulin.
• Watch portion size. Even healthy carbohydrates raise insulin proportional to dose.
• Use whole forms. Intact grains and whole fruit trigger smaller responses than their puffed or blended counterparts.
• Cool-and-reheat starches. Cooling promotes resistant starch that lowers insulin demand.

Persistent fatigue, cravings, or stubborn weight may improve when these insulin drivers are moderated and paired wisely.

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References

_{Ciok J, Dzieniszewski J and Lang (2004). Glycemic and Insulinemic Responses to Six Cereal Products in Healthy Adults. Central European Journal of Public Health, 12(3), pp.134–140.}

_{Goletzke, J., Atkinson, F.S., Ek, K.L., Bell, K., Brand-Miller, J.C. and Buyken, A.E. (2016). Glycaemic and insulin index of four common German breads. European Journal of Clinical Nutrition, 70(7), pp.808–811. doi:https://doi.org/10.1038/ejcn.2016.9.}

_{Holt, S.H., Miller, J.C. and Petocz, P. (1997). An insulin index of foods: the insulin demand generated by 1000-kJ portions of common foods. The American Journal of Clinical Nutrition, 66(5), pp.1264–1276. doi:https://doi.org/10.1093/ajcn/66.5.1264.}

_{Jayashree Arcot, Janette Brand Miller and Rural Industries Research And Development Corporation (Australia). Honeybee Research And Development (Program (2005). A preliminary assessment of the Glycemic index of honey : a report for the Rural Industries Research and Development Corporation. Barton, A.C.T.: Rural Industries Research And Development Corporation.}

_{Phillips, K. M., McGinty, R. C., Couture, G., Pehrsson, P. R., McKillop, K., & Fukagawa, N. K. (2021). Dietary fiber, starch, and sugars in bananas at different stages of ripeness in the retail market. PloS one, 16(7), e0253366. https://doi.org/10.1371/journal.pone.0253366}

_{Shkembi, B. and Huppertz, T. (2023). Glycemic Responses of Milk and Plant-Based Drinks: Food Matrix Effects. Foods, 12(3), p.453. doi:https://doi.org/10.3390/foods12030453.}

_{Yahia, E.M., Carrillo-López, A. and Bello-Perez, L.A. (2019). Chapter 9 - Carbohydrates. [online] ScienceDirect. Available at: https://www.sciencedirect.com/science/article/pii/B9780128132784000099.}

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