Note: This article was originally posted on April 9, 2019, and was updated and reposted on March 24, 2026.
Introduction
People often think of sugar as being fundamentally different from starch, but starches are actually just long chains of glucose molecules—much like a strand of pearls. Understanding this helps us make more informed choices about what we eat and how those choices affect our blood glucose levels.
Sugars – not all the same
Monosaccharides (meaning “one sugar”) are simple sugars that are not attached to anything, and can be thought of like individual pearls. Simple sugars include;
- glucose
- fructose
- galactose
Disaccharides are made up of two sugar molecules joined together (“di” means two) and include;
- sucrose (table sugar): glucose + fructose
- lactose (sugar in milk): glucose + galactose
- maltose (malt sugar): glucose + glucose
Oligosaccharides contain 3–10 sugar molecules strung together and are found in beans, peas, and lentils, and include;
- Raffinose = galactose + glucose + fructose
- Stachyose = galactose + galactose + glucose + fructose
Humans cannot digest oligosaccharides; however, our gut bacteria can ferment them [1][5].
Polysaccharides contain hundreds or thousands of sugar molecules of different types. Humans can also not digest certain polysaccharides, including cellulose and hemicellulose, which are types of fiber. These can help slow digestion and, as a result, can slow the rise of blood sugar [1].
- When all the sugars in a polysaccharide are glucose, it is called a starch.
Starch
Starches are long chains of glucose molecules, strung together like a strand of pearls.
- Starch is found in grains, including wheat, corn, rice, oats, millet, and barley, as well as tubers such as potatoes, yams, sweet potatoes, and cassava.
There are two types of starches
- Amylose: Long, unbranched chains – found in oats and legumes
- Amylopectin: Long, branched chains – found in short-grain rice, potatoes, white bread, and corn products
Amylopectin is digested more easily than amylose, so foods such as cornstarch, which are high in amylopectin, are digested much faster than wheat starch, which has more amylose [1].
Digestion of Starchy Foods
When we eat starchy foods such as pasta or rice, amylase, which is a digestive enzyme released in our saliva, begins to act like a pair of scissors. It breaks the strands of glucose, releasing each molecule of glucose for energy. Since the pearls are entirely glucose, blood sugar (glucose) can spike quickly.
The process continues in the stomach, where the high-acid environment temporarily halts digestion. It then resumes in the small intestine, where pancreatic amylase breaks the starch into the disaccharide maltose (two glucose molecules).
These individual glucose molecules (monosaccharides) are absorbed into the small intestine and transported to the liver, where they are stored as glycogen. When glycogen stores are full, excess glucose is converted to fat [1][2].
Carbohydrates and Type 2 Diabetes
Unlike protein and fat, there is no biological requirement for humans to consume carbohydrate-based foods, provided they eat sufficient amounts of protein and fat [3]. These can be used by the body to produce glucose for the brain through a process called gluconeogenesis. While I don’t recommend that people avoid eating carbohydrate foods, it is essential that those with pre-diabetes, diabetes, or insulin resistance be knowledgeable about how different types of carbohydrates affect their blood sugar.
“Eating to your meter” encourages people to test how specific foods affect their blood sugar [4], which is a key component of personalized nutrition [6].
Final Thoughts
Starches are just long chains of glucose molecules, like a strand of pearls, and are easily split into their individual glucose molecules during digestion, resulting in a rapid and large spike in blood sugar. For those with diabetes, it is essential to monitor the effect these foods have and ensure they are eaten in small enough portions and paired with other foods that moderate the blood glucose spike they cause.
Personalized nutrition focuses on customizing your diet—the types of foods, portion sizes, and timing to meet your specific health needs. This is at the heart of the routine services I offer.
More Info
If you would like more information, you can learn about me and the Comprehensive Dietary Package that I offer.
To your good health!
Joy
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References
- Chapter 4, Carbohydrates: Simple Sugars and Complex Chains, http://samples.jbpub.com/9781284064650/9781284086379_CH04_Disco.pdf
- Rappaport B. Metabolic factors limiting performance in marathon runners. PLoS Comput Biol. 2010;6(10). doi:10.1371/journal.pcbi.1000960 [https://journals.plos.org/ploscompbiol/article?id=10.1371/journal.pcbi.1000960]
- National Academies Press. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. 2005; Chapter 6, pp. 265–275. [https://www.nationalacademies.org/projects/HMD-FNB-18-P-119/publication/10490]
- Zeevi D, Korem T, Zmora N, et al. Personalized Nutrition by Prediction of Glycemic Responses. Cell. 2015;163(5):1079-1094. [https://pubmed.ncbi.nlm.nih.gov/26590418/]
- Holesh, J. E., Aslam, S., & Martin, A. (2024). Physiology, Carbohydrates. StatPearls Publishing.
- Menni, C., et al. (2025). Precision Nutrition: The Role of the Microbiome and Postprandial Glucose. Nature Communications.
Joy is a Registered Dietitian Nutritionist and owner of BetterByDesign Nutrition Ltd. She has a postgraduate degree in Human Nutrition, is a published mental health nutrition researcher, and has been supporting clients’ needs since 2008. Joy is licensed in BC, Alberta, and Ontario, and her areas of expertise range from routine health, chronic disease management, and digestive health to therapeutic diets. Joy is passionate about helping people feel better and believes that Nutrition is BetterByDesign©.