Do Overnight Oats Have Antinutrients? The Full Breakdown

December 15, 2025 •

3 min read

According to a study cited in The American Journal of Clinical Nutrition, soaking oats can significantly reduce phytic acid, an antinutrient that hinders mineral absorption. So, do overnight oats have antinutrients? Yes, but preparing them correctly minimizes their impact.

Quick Summary

Overnight oats contain antinutrients like phytic acid, but soaking reduces these compounds, improving digestibility and mineral absorption compared to raw oats.

Key Points

Oats contain antinutrients: Oats naturally contain antinutrients like phytic acid, tannins, and oxalates, which can slightly hinder mineral absorption.
Soaking reduces antinutrients: The overnight soaking process significantly reduces phytic acid content, making minerals like iron, zinc, and calcium more available for the body to absorb.
Health benefits outweigh concerns: For most healthy individuals consuming a balanced diet, the numerous health benefits of oats, such as high fiber and heart health, far outweigh the concerns over antinutrients.
Soaking enhances digestion: Soaking breaks down complex starches, which improves digestibility and can be especially beneficial for those with sensitive stomachs.
Nutrient absorption can be optimized: Adding an acidic medium like lemon juice or pairing oats with Vitamin C-rich fruits can further enhance mineral absorption.
Cooked vs. overnight: Soaking for overnight oats may be more effective at reducing phytic acid than quick cooking, while also preserving heat-sensitive nutrients.

The Antinutrients Found in Oats

Antinutrients are natural compounds in many plant-based foods, including grains like oats. Oats contain phytic acid, tannins, and oxalates, which are linked to the plant's defense mechanisms. For most people eating a balanced diet, the benefits of oats outweigh potential antinutrient concerns.

The Phytic Acid Effect: Binding Minerals

Phytic acid is the primary antinutrient in oats of concern, located in the bran. It can bind to minerals like iron, zinc, calcium, and magnesium in the gut, potentially reducing their absorption. This effect is more notable for those with diets high in unprocessed grains or existing mineral deficiencies. However, phytic acid also has antioxidant properties and may help regulate blood sugar.

Other Compounds: Tannins and Oxalates

Oats also contain smaller amounts of tannins and oxalates. Tannins can interfere with protein and mineral absorption, while oxalates can bind calcium. These are generally not a concern for healthy individuals with varied diets.

The Mitigating Power of Soaking

Soaking, as used in overnight oats, significantly reduces antinutrient levels. This process activates natural enzymes like phytase, which breaks down phytic acid, making minerals more available. Soaking doesn't eliminate phytic acid completely but greatly reduces it.

Soaking also aids digestion by breaking down complex starches. It increases resistant starch, beneficial for gut bacteria, though this fermentation might cause bloating in sensitive individuals.

Enhancing the Soaking Process

To further reduce antinutrients, especially as oats have low natural phytase:

Use an acidic medium: Adding yogurt, kefir, lemon juice, or apple cider vinegar helps break down phytic acid.
Add a high-phytase grain: A small amount of freshly-ground rye or buckwheat can enhance phytic acid reduction.

Overnight Oats vs. Cooked Oats

The choice between overnight and cooked oats depends on preference, but preparation leads to nutritional differences.


Feature	Overnight Oats	Cooked Oats
Preparation	No heat, soaked overnight.	Cooked with heat.
Antinutrient Levels	Soaking significantly reduces phytic acid.	Heat deactivates some inhibitors but may be less effective for phytic acid than long soaking.
Texture & Taste	Creamy, chewy, cool; flavors blend.	Soft, warm, mild oat flavor.
Nutrient Integrity	Preserves heat-sensitive nutrients.	Some heat-sensitive nutrient reduction possible.
Glycemic Index	Tend to be lower due to soaking and resistant starch.	Higher, especially instant oats.

Maximizing Nutrient Availability

Enhance the nutrition of overnight oats with these tips:

Pair with Vitamin C: Fruits like berries or citrus boost non-heme iron absorption.
Add Protein and Healthy Fats: Ingredients like nuts or seeds balance the meal and help offset minor antinutrient effects.
Choose Less Processed Oats: Rolled or steel-cut oats generally offer more nutrients and a lower glycemic index than instant varieties.
Consider Sprouting or Fermenting: These methods are more effective at breaking down antinutrients but require more effort. Sprouted oat products are also available.

Weighing the Benefits: Oats as a Healthy Choice

Oats are highly nutritious, rich in fiber (beta-glucans), antioxidants, and essential minerals. The fiber supports heart health, blood sugar control, and a healthy gut. For most healthy adults, soaking for overnight oats sufficiently addresses antinutrient concerns. Enjoy oats as part of a varied diet.

Conclusion: Making an Informed Choice About Overnight Oats

Overnight oats, like other whole grains, contain antinutrients, primarily phytic acid. Soaking overnight is an effective way to reduce these compounds, improving digestion and mineral absorption. For most people, the substantial health benefits of oats outweigh the minimal impact of remaining antinutrients. Adding an acidic ingredient or Vitamin C-rich fruits can further improve nutrient availability. Enjoy overnight oats as part of a balanced diet.

Explore the Health Benefits of Oat Beta-Glucan in this meta-analysis

Frequently Asked Questions

The main antinutrient found in overnight oats is phytic acid (phytate), which is a compound that can bind to minerals and hinder their absorption in the digestive tract.

No, soaking does not completely eliminate antinutrients, but it is a very effective way to significantly reduce them, particularly phytic acid. Other methods like fermenting or sprouting can further reduce levels.

Not necessarily. While cooking can break down some antinutrients and enzyme inhibitors, overnight soaking is often more effective at reducing phytic acid levels. Each method has slightly different benefits for nutrient preservation and digestibility.

For most healthy people on a balanced diet, eating overnight oats will not cause a mineral deficiency. Any slight inhibition of mineral absorption is usually not a concern. Individuals with existing deficiencies or heavily reliant on grains might need to be more mindful of preparation.

To maximize absorption, try soaking the oats with an acidic medium like yogurt or lemon juice, and pair your meal with a source of Vitamin C, such as fresh berries, to enhance iron uptake.

Some sources recommend draining and rinsing the oats after soaking to wash away dissolved antinutrients. However, other methods suggest it is not necessary, especially when using an acidic medium to break down the compounds effectively. You can choose the method you prefer.

Soaking oats makes them easier to digest by breaking down complex starches. However, the increased resistant starch from soaking can cause bloating or discomfort for very sensitive individuals. If you experience issues, starting with a small portion is recommended.