Why is oatmilk so high in sugar? The surprising truth about production

November 6, 2025 •

4 min read

According to one popular brand's nutritional information, a single serving of its plain oatmilk can contain around 7 grams of sugar, a figure that often surprises consumers. This naturally leads to the question: why is oatmilk so high in sugar, especially when it is marketed as a health-conscious, plant-based alternative to dairy milk?

Quick Summary

Commercial oat milk's sweetness comes from an enzymatic process that breaks down complex oat starches into simple sugars like maltose. This process significantly elevates the beverage's sugar content and glycemic index. This phenomenon occurs even in unsweetened versions and differs greatly from other plant-based milks.

Key Points

Enzymatic Hydrolysis: Commercial oat milk is made using enzymes that break down oat starches into simple sugars like maltose during production.
Maltose is the Main Sugar: This enzymatic process creates maltose, a high-glycemic sugar, which explains the naturally sweet taste of oat milk.
Impact on Blood Sugar: The resulting simple sugars cause a quicker spike in blood sugar compared to whole oats, even in 'unsweetened' versions.
Not all Plant Milks are Equal: Oat milk tends to have a higher sugar content and glycemic index than unsweetened almond or soy milk.
Read the Nutrition Label: Always check the nutrition facts for total carbohydrates and sugars, as 'unsweetened' on the front may not tell the whole story.
Balance Consumption: Pairing oat milk with protein and fat can help slow the absorption of sugar and mitigate blood sugar spikes.

The Oat Milk Processing Paradox

At first glance, it seems logical that oat milk, a product made from a wholesome grain, would be low in sugar. Oats themselves are a complex carbohydrate, rich in fiber and known for their ability to promote steady energy release. The disconnect arises during the commercial manufacturing process. Unlike simply blending oats and water at home, large-scale production relies on enzymes to create the desired consistency and flavor.

The Role of Amylase Enzymes

This central part of the manufacturing process is known as enzymatic hydrolysis. It involves adding a specific type of enzyme, such as alpha-amylase, to the oat and water slurry. The function of this enzyme is to break down the long chains of complex carbohydrates (starch) found in the oats. This enzymatic action converts the starches into simpler, more easily digestible sugars, most notably maltose.

Starch Breakdown: Complex starches are too large for our bodies to absorb quickly. The enzymes act as a catalyst to break these down into smaller, simpler sugar units.
Maltose Creation: Maltose, a disaccharide, is the primary sugar created during this process. It has a high glycemic index (GI), even higher than table sugar (sucrose) in its pure form.
Natural Sweetness: This conversion of starch to sugar is the key reason commercial oat milk tastes inherently sweet and creamy, even if no additional sugars or sweeteners are listed on the ingredients panel. This is also why many brands can declare no added sugar, despite the final product containing a significant amount of sugar.
Smoother Texture: The enzymatic breakdown also helps to prevent the oat milk from becoming slimy or gritty, giving it the smooth, desirable mouthfeel consumers prefer.

Impact on Blood Sugar and Digestion

The sugar created during this process—largely maltose—is quickly absorbed by the body, which can lead to a more significant and rapid spike in blood sugar compared to consuming whole oats. For individuals managing blood sugar levels, such as those with diabetes, or anyone looking to avoid energy crashes, this is an important consideration. A splash of oat milk in coffee is unlikely to cause a major issue, but larger servings, like in a smoothie or a bowl of cereal, can have a noticeable impact.

Oat Milk vs. Other Milk Alternatives


Feature	Oat Milk	Almond Milk (Unsweetened)	Cow's Milk (2% Fat)
Sugar Content (per cup)	7–16g (varies)	1–2g	~12g (lactose)
Primary Sugar Type	Maltose (created via enzymes)	Negligible	Lactose (naturally occurring)
Fiber Content (per cup)	~2g	~1g	0g
Glycemic Index	Moderate-High (69)	Low (30s)	Low (30s)
Protein Content (per cup)	~3–4g	~1g	~8g

Making a Smarter Choice

Consumers can take several steps to make a more informed choice when selecting oat milk or other dairy alternatives. The first is to always read the nutritional label, paying close attention to the total carbohydrate and sugar counts, not just the ingredients list. Flavored versions often have even more sugar added beyond the enzymatic conversion.

Another option is to consider unsweetened alternatives like almond or soy milk, which typically have lower glycemic indices and less sugar. For those who prefer oat milk, pairing it with protein or fat in a meal can help slow down the absorption of its sugars, mitigating the blood sugar spike.

The “Added Sugar” Labeling Debate

For a time, some brands labeled their oat milk with 0 grams of added sugar, since no extra sucrose was added during production. However, the FDA now considers sugars that are created from a grain through enzymatic hydrolysis to be “added sugars” for labeling purposes. This has led to more transparent labels that show a sugar content higher than some consumers might expect from an unsweetened product. This change helps consumers see the real nutritional profile of the beverage they are purchasing.

Conclusion

The sweetness of oat milk is a direct result of its commercial production process, which utilizes enzymes to break down the natural starches in oats into simple sugars like maltose. While this provides a creamy texture and pleasant taste, it also results in a higher sugar content and glycemic index compared to whole oats or some other plant-based milks. By understanding this process and reading labels carefully, consumers can make informed choices to manage their sugar intake and overall health. Opting for unsweetened varieties and balancing consumption with other foods can help mitigate the effects of its sugar content on blood glucose levels.

How to choose a lower-sugar oat milk brand

When shopping for oat milk, focus on unsweetened versions and check the nutrition facts panel. Compare the total carbohydrate and sugar content per serving among different brands, as these numbers can vary. While all brands use the enzymatic process, some may have lower resulting sugar content. Look for options with fewer total carbohydrates if blood sugar is a primary concern. You can also make your own simple oat milk at home to control all ingredients. For more tips on comparing different plant-based milks, check out this guide from Shape Magazine, which details various alternatives and their nutritional pros and cons.

Frequently Asked Questions

Yes, even 'unsweetened' oat milk contains sugar. The sweetness comes from the enzymatic process used during manufacturing, which breaks down the oats' natural starches into simple sugars like maltose. No sucrose or other sweeteners are added, but the sugar is naturally created during processing.

The sugar in oat milk, predominantly maltose, is easily digested and can cause a more rapid increase in blood sugar levels than the complex carbohydrates in whole oats. For most people, moderate consumption is fine, but those monitoring blood sugar, like diabetics, should be mindful of serving size and pairing it with other foods.

Oat milk's creamy texture is largely a result of the starches and fibers in the oats. During production, the enzymatic process and homogenization create a smooth, emulsified liquid. Many brands also add vegetable oil to achieve an even richer, barista-style consistency.

Oat milk generally has a higher glycemic index (GI) than dairy milk and other plant-based options like almond or soy milk. While oat milk's GI is around 69, dairy milk and unsweetened nut milks are typically in the 30s. This means oat milk can impact your blood sugar more significantly.

Homemade oat milk can have less sugar, depending on the method. Simple blending and straining of oats and water does not use the enzymes that convert starch to maltose, resulting in a less sweet product. However, without enzymatic treatment, the texture is often more starchy or slimy and can separate quickly.

The sugar in oat milk is primarily maltose, created during processing from the oats' starch. The sugar in cow's milk is lactose, which is a different type of sugar naturally present in dairy. The body processes these sugars differently, with the lactose in dairy milk generally causing a more gradual blood glucose response due to the milk's protein content.

To minimize the blood sugar impact, opt for unsweetened varieties and consume oat milk in moderation. Pairing it with a source of protein or healthy fat, such as in a smoothie with protein powder or alongside eggs, can help slow down the digestion and absorption of its sugars.