The glycemic index is a scale that relates to how quickly or slowly a given food will cause your blood glucose level to rise. Foods low on the glycemic index (GI) scale tend to cause a slow, steady rise in blood sugar. Meanwhile, foods high on the glycemic index cause more significant spikes in blood glucose levels.
Low GI foods tend to foster weight loss, while foods high on the GI scale may contribute to weight gain.⁶ ⁷ That said, high GI foods can help with energy recovery after exercise or offset hypoglycemia.⁸ Long-distance runners and other endurance athletes favor foods that are high on the glycemic index for this reason. Conversely, people with diabetes and prediabetes may choose to concentrate on low-GI foods to help them control their blood sugar.
Sugars are the simplest form of carbohydrates, known as monosaccharides and disaccharides. Monosaccharides include glucose, fructose, and galactose (milk sugar). Disaccharides, such as sucrose, maltose, and lactose, are made up of two monosaccharides put together. The term ‘sugar’ typically refers to the disaccharide sucrose, a combination of glucose and fructose made naturally in all green plants via photosynthesis.¹ ⁹
Regular, healthy sugar intake is important for your body’s proper functioning, with glucose being the preferred source of energy for most of our cells. Your brain alone, for instance, uses up half of all your sugar energy (but can fall back on ketones when necessary).¹⁰ ¹¹ However, too much or too little sugar can be harmful; it’s been linked to hypoglycemia (usually from going too long without eating enough),¹² acne,¹³ dental problems such as cavities,¹⁴ and even metabolic conditions like obesity and diabetes.¹⁵ When sugar, whether artificial or natural, isn’t used up as energy, your body stores it as fat.² Learning the differences between natural and added sugars is critical in learning how to manage your sugar intake, as they can affect your body in different ways.
Fruits, vegetables, and dairy products all contain natural sugars. A banana or glass of milk will provide fructose or lactose, but you’re also getting fiber and nutrients such as vitamins and protein. These natural forms of sugar are paired with nutrients, like protein and fiber, that slow their absorption and keep your blood sugar (glucose levels) stable over longer periods. This keeps your energy levels steady and staves off a sugar rush or crash.
Added sugars are found in processed and prepared foods, such as sweetened beverages, cereals, snack foods, candy, jams, curds, desserts, pastries, and other baked goods.³ Foods that are high in added sugars are processed much more quickly by the body. They’re also often high in calories and low in fiber and nutrients, so you still might not feel very full after eating them, even if they have a meal’s worth of calories. Added sugars are more likely to cause big spikes and drops in your blood sugar; the crash after eating or drinking something high in added sugars can make you feel hungrier and cause you to overeat. Due to their high caloric density and high sugar content, they can cause damage to your body’s metabolic systems — such as through weight gain or insulin resistance.
Sugary drinks such as juice, soda, and even certain coffee drinks are responsible for a lot of the added sugar in the American diet. These beverages can contain up to 65 grams of added sugar. Often, this added sugar is high-fructose corn syrup, which is a popular and cheap sweetener.³
Along with knowing the difference between natural and added sugars, learning about the caloric density of sugar, how to read food labels, the glycemic index of foods, and daily percentage values is also important in managing sugar intake.
The American Heart Association recommends limiting added sugar intake for all ages. One teaspoon of sugar weighs about four grams and equals about 16 calories. Here are the daily recommendations for men, women, and children:¹⁶ ¹⁷
Children should also be limited to less than eight ounces of sugary drinks per week. For individuals with existing health conditions such as diabetes, these limits might be even more strict.³
Knowing how much added sugar you can safely consume is one thing, but navigating the nutrition labels on foods is another. In 2016, the FDA mandated changes to the nutrition labels of packaged foods and drinks. This went into effect in 2021, and the label now features added sugar content under the total sugars section.⁴
The label also features the percent Daily Value (% DV), which calculates how much of a nutrient contributes to the daily recommended allotment. The daily value of added sugar is 50g per day in a standard 2,000 calorie diet. For example, if one serving of a brand of cookies contains 25g of added sugars, the daily value would show as 50%. If you consume a serving of these cookies, you’ve eaten half the recommended daily amount of added sugar. Knowing this can make it easier to adjust your sugar consumption that day to ensure it doesn’t go over 50g.⁴
If you have a stricter limitation on added sugar, you’ll need to make more adjustments. To keep things simple, 5% DV or less of added sugar is considered low, and 20% DV and above is considered high, making it even easier to choose the right snack or drink based on your health needs.⁵
Sugar goes by even more names than the scientific classifications we’ve already mentioned. Here are some ingredients that sound different (or maybe even healthy) but in reality are just added sugars:³
The following chart provides GI levels for more than 60 foods derived from comprehensive analyses of more than 2,100 food items from journals published in 2008 and 2021.¹⁸ ¹⁹ For this chart, keep in mind that all values reflect the mean glycemic index determined by researchers — there’s always the possibility for some of the same foods to have a higher or lower GI depending on certain factors, like cooking methods. As an example, the 2021 journal authors note that cereal products might show a wide disparity in glycemic index values due to varying manufacturing methods.¹⁹
|Food||Mean glycemic index score (scale of 0-100)|
|White wheat bread††||73|
|Whole wheat/whole meal bread||75|
|Rice, Long grain, white, boiled*||62|
|Unleavened wheat bread||70 ± 5|
|Brown rice, boiled||68 ± 4|
|Couscous†||65 ± 4|
|Wheat roti||62 ± 3|
|Udon noodles||62 ± 8|
|Rice noodles†||53 ± 7|
|Specialty grain bread||53 ± 2|
|Chapati||52 ± 4|
|Spaghetti, whole meal||50|
|Corn tortilla||49 ± 6|
|Instant oat porridge||82|
|Wheat flake biscuits||71|
|Millet porridge||67 ± 5|
|Porridge, rolled oats||58|
|Fruit and fruit products|
|Pineapple, raw||82 ± 4|
|Mango, raw†||51 ± 5|
|Banana, raw†||47 ± 5|
|Strawberry jam/jelly||51 ± 10|
|Peaches, canned†||43 ± 5|
|Orange, raw†||43 ± 3|
|Apple, raw†||44 ± 5|
|Potato, instant mash||84|
|Potato, boiled||78 ± 4|
|Pumpkin, boiled||64 ± 7|
|Sweet potato, boiled||46|
|Potato, french fries||64 ± 6|
|Taro, boiled||72 ± 5|
|Vegetable soup||48 ± 5|
|Dairy products and alternatives|
|Rice milk||86 ± 7|
|Ice cream, reduced- or low-fat||36|
|Yogurt, fruit||41 ± 2|
|Milk, full fat||37|
|Chickpeas||28 ± 9|
|Kidney beans||36 ± 4|
|Soya beans||16 ± 1|
|Rice crackers/crisps||87 ± 2|
|Soft drink/soda||59 ± 3|
|Glucose||107 ± 7|
Some data are the mean ± SEM (standard error of the mean).
† Average of all available data.
†† Low-GI varieties were also identified.
Remember that glycemic index values are based on aggregated research, as individuals may respond with slight differences when exposed to the same foods. It’s also true that a wide range of variables influences the glucose content of natural foods; even two apples grown on the same tree and harvested simultaneously can have unequal distribution of sugar between them.
Glycemic index values are also based on a 100-gram serving size (about 0.2lbs) which isn’t always reasonable or applicable to the portions you’d normally eat of certain foods.²⁰ The preparation methods of foods is another factor that can alter GI levels; potatoes and other tubers, for instance, have a lower GI after being baked and cooled.²¹ One way to lower the glycemic impact of a high GI food is to eat it alongside protein, fiber, and fat; this can reduce the effect it has on your blood sugar.²² ²³
GI values are still helpful for anyone looking to maintain healthy blood sugar levels or provide targeted benefits in conjunction with exercise or the treatment of specific diseases. But information on both glycemic index and glycemic load (a formula that combines GI and portion size into a single number) has its limits, and you should speak with your doctor about any drastic changes to your diet before you begin to experiment.²⁰
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 The Department of Health, State Government of Victoria, Australia. (2022). Sugar. Better Health Channel.
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 Sagili, V. S., Chakrabarti, P., Jayanty, S., Kardile, H., & Sathuvalli, V. (2022). The Glycemic Index and Human Health with an Emphasis on Potatoes. Foods (Basel, Switzerland), 11(15), 2302.
 Giuntini, E. B., Sardá, F. A. H., & de Menezes, E. W. (2022). The Effects of Soluble Dietary Fibers on Glycemic Response: An Overview and Futures Perspectives. Foods (Basel, Switzerland), 11(23), 3934.
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