Resistant Starch: Benefits, Best Sources & Supplements

Resistant starch is a type of carbohydrate that “resists” digestion in the small intestine and travels to your colon, where it feeds your good gut bacteria.

Health disclaimer: This article is for general information only and isn’t medical advice. Any doses mentioned are amounts used in research or listed on product labels, not a personal recommendation. Supplements and medications can cause side effects and interact with other drugs or health conditions, so check with your doctor or pharmacist before starting anything new, especially if you’re pregnant, breastfeeding, on medication or managing a health condition. Stop and get medical help if you have a reaction. See our full medical disclaimer.

What Resistant Starch Actually Is

Resistant starch escapes digestion, reaching the colon intact, where bacteria ferment it into short-chain fatty acids, including butyrate, the preferred fuel for colon cells (Baptista et al., 2024).

The Benefits

Feeds your gut bacteria — may promote beneficial bacteria and butyrate, though study results are mixed (review).
Fuel for your colon — butyrate is the main energy source for the cells lining the colon.
Better blood sugar — can blunt spikes after meals (review) and improved insulin sensitivity in a small trial (Robertson et al., 2005).
Fullness and appetite support.

The Best Sources (Food First)

Cooked-then-cooled potatoes, rice, and pasta. Cooling cooked starches actually creates resistant starch.
Green (unripe) bananas and green banana flour.
Cooked and cooled legumes — beans, lentils, chickpeas.

How to Add It Without Bloating

Start small and ramp up slowly. Going from zero to a big dose overnight causes gas and bloating while your bacteria adjust.

Types of Resistant Starch

There are five recognised types, each found in different foods (Baptista et al., 2024):

Type 1: trapped in whole grains, seeds and legumes, protected by fibrous walls.
Type 2: found in raw potatoes, green (unripe) bananas and some raw starches.
Type 3: forms when starchy foods like potatoes, rice and pasta are cooked and then cooled. Reheating keeps much of it.
Type 4: chemically modified starches added to some processed foods.
Type 5: starch bound with fat, formed in some cooking processes.

The Cook-and-Cool Trick

Cooking rice, potatoes or pasta, then cooling them in the fridge overnight, increases their resistant starch. You can eat them cold, as in potato or pasta salad, or reheat them, and much of the resistant starch remains. Leftovers aren’t just convenient; they may be slightly better for your gut and blood sugar. In one study, cooked white rice that was chilled for 24 hours and then reheated had more resistant starch, and caused a smaller blood sugar rise, than freshly cooked rice (Sonia et al., 2015).

Blood Sugar and Fullness

Resistant starch acts more like fibre than ordinary starch. It can lower the blood sugar rise after meals (Baptista et al., 2024) and may improve insulin sensitivity in some people (Robertson et al., 2005). Some studies also suggest it helps people feel full for longer. These effects are modest, not dramatic, but they add up over time.

Who Should Be Careful

People with IBS: resistant starch ferments in the gut and can cause gas and bloating. Start slowly or skip it if it worsens symptoms.
People on diabetes medication: improvements in blood sugar could affect medication needs; monitor and talk to your doctor.
Anyone with a restricted diet for medical reasons should check with a dietitian.

Common Questions

Is green banana flour or potato starch worth buying? They’re concentrated sources, but food first is a good rule. If you try them, start with a teaspoon and increase slowly.

How much do I need? There’s no official target. Studies often used 15 to 30 g a day, but adding a few food sources consistently is a reasonable goal.

Does it help weight loss? It may help with fullness, but it’s not a weight-loss solution by itself.

When to See a Doctor

See a doctor if you have ongoing bloating, pain, changes in bowel habits or weight loss rather than adjusting your diet alone.

The Bottom Line

Resistant starch is a prebiotic powerhouse — it feeds good bacteria, produces butyrate, and helps blood sugar and fullness. Ramp up slowly to skip the bloat.

Informational only, not medical advice.

References

Baptista NT, Dessalles R, Illner AK, et al. Harnessing the power of resistant starch: a narrative review of its health impact and processing challenges. Frontiers in Nutrition. 2024.
Sonia S, et al. Effect of cooling of cooked white rice on resistant starch content and glycemic response. Asia Pacific Journal of Clinical Nutrition. 2015.
Robertson MD, et al. Insulin-sensitizing effects of dietary resistant starch and effects on skeletal muscle and adipose tissue metabolism. American Journal of Clinical Nutrition. 2005.