Soy Drink or Oat Drink? Protein and Sugar

Published: 11 October 2026

Short answer: If you want a drink that replaces the protein in milk, choose soy. In a 2026 study of plant drinks sold in Turkey, soy drinks had a median of 1.95 g of protein per 100 mL, against 0.80 g for oat drinks. In the same study, oat drinks were higher in energy and sugar, partly because the oat starch is broken down into sugars during production. For both, the most important line on the carton is not the plant but the fortification: calcium, vitamin B12 and vitamin D are only there if the manufacturer added them.

The studies behind this comparison

The most local data comes from a study published in May 2026 in Frontiers in Nutrition by Ekici and Bas. They recorded the labels of 56 plant drinks from 10 brands sold in supermarkets in Turkey in October and November 2025, including 11 oat drinks and 4 soy drinks.

Because the soy group was small, two European studies are useful alongside it, and they point the same way. A 2023 analysis in Nutrients covered 249 plant drinks from 27 brands across Europe. A 2022 Swiss study measured the composition of 36 plant products in the laboratory, including 7 soy and 4 oat drinks.

Protein: soy is far ahead

In the European survey, soy drinks had a median of 7.8 g of protein per 250 mL glass and oat drinks 2 g. In the Swiss analysis, cow’s milk and soy drinks had more than 3% protein, while most other plant drinks had 1% or less; the authors write that these “cannot be considered good protein sources”.

Quality differs too. Protein quality is measured with a score called DIAAS, which reflects both the amino acids a protein contains and how well they are digested. In the Swiss study, soy was the only plant drink with a DIAAS above 100% for children over three, adolescents and adults.

Sugar and energy: oat drinks are sweeter

In the Turkish study, oat drinks had the highest median energy of all plant sources, 192 kJ (about 46 kcal) per 100 mL, and the highest median sugars, 3.30 g. Soy drinks had 125 kJ (about 30 kcal) and 2.55 g of sugars.

Part of this sugar is not added. Oat drinks are usually made with enzymes that break oat starch down into more soluble carbohydrates; the authors note that this can give the drink a naturally sweeter taste and a higher energy density. The European survey describes the same effect: in oat and rice drinks, “not all the sugars are necessarily added”.

The product type mattered more than the plant. Across all 56 drinks, unsweetened products had a median of 0.20 g of sugars per 100 mL, against 3.10 g for plain or original versions and 3.00 g for barista versions. The authors conclude that formulation was more strongly reflected in the products’ Nutri-Score than the plant source.

Fat and fibre

In the Turkish study, oat drinks had a median of 0.60 g of fibre per 100 mL and soy drinks a median of 0 g. Oats contain beta-glucan, a soluble fibre; the authors of a 2026 meta-analysis note that the amount in oat drinks varies substantially with processing. In the European survey, soy drinks contained more fat than oat drinks, mostly polyunsaturated. In the Swiss analysis, omega-3 fats were found in substantial amounts only in soy drinks and cow’s milk.

Fortification: read the carton, not the plant

Neither soy nor oats naturally provides the calcium and vitamin B12 found in milk. In the European survey, 76% of non-organic plant drinks and yogurt alternatives taken together were fortified with calcium, and 64% of the non-organic drinks had added vitamin B12. Organic products lacked these added nutrients because of legal restrictions on fortification. Calcium-fortified drinks provided a median of 300 mg of calcium per 250 mL, similar to low-fat milk. Our fortified plant drink checklist explains what to look for on the label.

Under Turkey’s labelling rules, these products are called “drink”, not “milk”; our article on vegan food labels in Turkey explains the rule.

Cholesterol and blood pressure

A 2026 network meta-analysis in Advances in Nutrition pooled 14 randomised trials with 543 participants; 13 of them tested soy drink. Replacing 500 mL of cow’s milk a day with soy drink may lower LDL cholesterol by 0.47 mmol/L and may also lower blood pressure. Oat drink may slightly lower total cholesterol, but only two trials tested it. Most trials lasted only 4–6 weeks, and the authors rate the evidence as low or very low certainty. They found no major differences when plant drinks were compared with each other, so heart health is not a strong reason to choose one over the other; protein, sugar and fortification matter more. See also does going vegan lower cholesterol?

Who should be careful

Soy allergy. The Swiss authors cite earlier research finding that 14% of people with cow’s milk allergy are also allergic to soy protein; they should avoid soy drinks.
Children. Craig and Fresán (2021) note that drinks with less than 5 g of protein per serving (about one glass) are not ideal for growing children. Oat drinks fall well below this. Ask your paediatrician which drink suits your child.
Babies. In the UK, unsweetened, calcium-fortified plant drinks are considered suitable as a main drink only for children older than 12 months. They do not replace breast milk or infant formula.

How to choose

For protein, choose soy.
Look for “no added sugar” (on Turkish labels, “ilave şeker içermez” or “şekersiz”). With oat drinks, also check the sugars line, because sugars from the oats themselves still appear there.
Check calcium, B12 and vitamin D in the nutrition table. If they are missing, cover these nutrients elsewhere; our B12 guide explains how.

Oat drink is a reasonable choice if you prefer its taste and get your protein from other foods, such as legumes. If the drink is meant to replace milk in your diet, a fortified, unsweetened soy drink comes closest.

Sources

Ekici M, Bas M. Nutritional quality of plant-based beverages in Türkiye: application of the updated nutri-score algorithm. Front Nutr 2026;13:1832771.
Medici E, Craig WJ, Rowland I. A Comprehensive Analysis of the Nutritional Composition of Plant-Based Drinks and Yogurt Alternatives in Europe. Nutrients 2023;15(15):3415. (Two of the authors have links to the Alpro Foundation and Alpro (Danone).)
Walther B, et al. Comparison of nutritional composition between plant-based drinks and cow’s milk. Front Nutr 2022;9:988707.
Wallerer S, et al. Impact of Plant-Based Drinks on Cardiometabolic Outcomes: A Systematic Review and Network Meta-analysis. Adv Nutr 2026;17(3):100595.
Craig WJ, Fresán U. International Analysis of the Nutritional Content and a Review of Health Benefits of Non-Dairy Plant-Based Beverages. Nutrients 2021;13(3):842.

Editor: Anıl Güler, Pharmacist
Last reviewed: 11 October 2026