Soda & Diet Soda: Nutrients, What Research Shows and Safety

Soda, also called soft drink or pop, is a sweet fizzy drink. The regular kind is sweetened with sugar or syrup. The "diet" kind is sweetened with low- or no-calorie sweeteners instead. Many people drink it for the taste, the bubbles or the caffeine, and many switch to diet soda hoping to cut sugar without giving up the habit. This page looks at both kinds as drinks, says what pooled studies and official bodies found, and says plainly where the evidence is weak. It does not cover flavored sparkling water without sweeteners, which is a different product. [1] [2] [4]

Read this first

• A regular soda is mostly sugar and water. USDA lists about 151 kcal and 38 g of carbohydrate in a 12 fl oz can of a caffeinated pepper-type soda. [1] The CDC calls sugar-sweetened drinks a leading source of added sugars in the American diet. [4]
• A diet soda has no calories in the USDA data, and USDA lists no sugar in the diet cola it measured. [2]
• Caffeine is in many sodas. USDA lists about 37 mg in the regular can and about 39 mg in the diet can. [1] [2] The FDA says about 400 mg a day is an amount not generally linked to negative effects in most healthy adults. [13] The NHS advises no more than 200 mg a day in pregnancy. [14]
• The evidence in one line: pooled studies link sugar-sweetened soda to weight gain and to type 2 diabetes, and to tooth erosion. For diet soda the picture is unsettled: it may help some people cut calories, but WHO advises against sweeteners for weight control, and observational links to disease are hard to interpret. [6] [7] [9] [10] [15]
• If you have PKU (phenylketonuria, a rare inherited condition), the FDA says to avoid or restrict aspartame, and labels must say the product contains phenylalanine. [12]

What is in it (USDA values)

Two USDA FoodData Central items (SR Legacy) are used. The regular soda is a caffeinated pepper-type soda (item 173209). The diet soda is a low-calorie cola or pepper-type drink sweetened with sodium saccharin (item 171876). [1] [2] USDA household portions are used for the serving: 12 fl oz (368 g) for the regular item and 12 fl oz (355 g) for the diet item. Soda made with other sweeteners will differ, so check the label.

The % Daily Value for carbohydrate (FDA 2016 Daily Value 275 g) works out to about 14% in a regular can. Sodium is about 2% of the 2,300 mg Daily Value in either can, and phosphorus about 3%. Other vitamins and minerals are at or near zero in both items. [1] [2] USDA lists no separate "total sugars" value for the regular item, so the table shows carbohydrate; for a sugar-sweetened soda the Nutrition Facts label on your can lists sugars and added sugars. The serving figures are the 100 g values multiplied by the serving weight.

Soda also contains acids (such as phosphoric or citric acid), flavorings and sometimes colors. Our USDA file does not list them, so we do not describe their amounts.

What research says

What the pooled studies cannot show. These are mostly observational studies of what people reported drinking. People who drink diet soda often differ from those who do not, and some may have switched because they already gained weight. [7] [9]

How much is a normal serving

The USDA household portions are 12 fl oz (about 355 to 368 g) for a can and 16 fl oz for a bottle. [1] [2] That is information, not a prescription. For sugar, WHO recommends that free sugars make up less than 10% of daily energy (about 50 g for a 2,000-calorie diet), and says 5% or less may bring extra benefit. [3] One regular can has about 38 g of carbohydrate in the USDA item, so one can may use up much of a day's allowance if that carbohydrate is nearly all sugar; check your label. The CDC says to choose water over sugary drinks. [4] [5]

Safety, allergy and medicines

• Caffeine. A 12 fl oz caffeinated soda typically has 23 to 83 mg, depending on the product. [13] In pregnancy, the NHS advises no more than 200 mg of caffeine a day from all sources. [14] The FDA says the Dietary Guidelines advise avoiding caffeinated drinks for children under 2, and that experts advise against energy drinks for children and teens. [13] Many sodas are caffeine-free, so read the label.
• Aspartame. In 2023 the International Agency for Research on Cancer classified aspartame as "possibly carcinogenic to humans" (Group 2B), based on limited evidence. The expert committee JECFA (FAO/WHO) found no reason to change its acceptable daily intake of 0 to 40 mg per kg of body weight, and WHO said an adult of 70 kg would need to drink more than 9 to 14 cans a day of a diet soft drink with 200 to 300 mg of aspartame to exceed it, with no other sources. [11] The FDA disagrees with the IARC classification, has no safety concerns at approved use, and lists its own acceptable daily intake as 50 mg per kg. [12]
• Saccharin (in the diet item USDA measured): FDA says the bladder cancer seen in rats was not relevant to humans, and the National Toxicology Program removed it from its list of potential carcinogens in 2000. [12]
• Phenylketonuria. People with PKU should avoid or restrict aspartame; labels must say the product contains phenylalanine. [12]
• Children. The AHA advised in 2018 against prolonged use of low-calorie sweetened drinks by children, with water as the best choice. [10] The CDC says the Dietary Guidelines recommend no added sugar for children younger than 11. [4] [5]
• Teeth. Frequent sipping of any acidic or sugary drink keeps teeth exposed longer; the studies we read were observational or lab-based. [15] A 2026 study of tooth-surface pH found a non-alcoholic soft drink had the lowest starting pH of the drinks it tested, and that pH recovered within 10 to 15 minutes. [18]
• Allergy and medicines. The sources we read did not link plain soda to a food allergy or a medicine interaction. Colors or flavorings can differ by product; check labels.
• Kidney disease, diabetes and pregnancy. Regular soda adds sugar without protein or fiber; diabetes and kidney advice differs by person, so ask a clinician. The sources we read did not give specific kidney-disease advice for soda.
• Emergency. For trouble breathing or swelling of the face or throat after any food or drink, call 911 (or your local emergency number).

Choosing, storing and food safety

• Read the Nutrition Facts for sugars, added sugars and caffeine; labels differ more than the single USDA items suggest.
• Look for "caffeine-free" if you want to avoid caffeine.
• If you drink soda, a smaller portion and less often is the simplest change; water is the baseline drink. [4] [10]
• We did not read a source on storage of opened cans or bottles.

Related pages

• Caffeine and sugar in drinks: a quick comparison
• Caffeine in foods and drinks: official limits
• Mineral and sparkling water
• Water
• Energy drinks
• Added sugars, sodium and saturated fat on labels