Why Are Oats Not Considered Healthy?

October 18, 2025 •

3 min read

According to research, oats contain phytic acid, an 'anti-nutrient' that can inhibit the absorption of essential minerals like iron and zinc. This, among other factors, contributes to the growing debate over why oats are not considered healthy in all circumstances and for all individuals.

Quick Summary

This article explores the potential downsides of consuming oats, including antinutrients, risk of gluten contamination, processing impact, and digestive issues for sensitive individuals.

Key Points

Antinutrients: Phytic acid in oats can bind to minerals like iron and zinc, hindering their absorption, a problem particularly for those with grain-heavy diets.
Digestive Issues: The high fiber content in oats can cause gas and bloating, especially in individuals with sensitive digestive systems or those unaccustomed to high fiber intake.
Blood Sugar Impact: Highly processed instant oats have a high glycemic index and can lead to rapid blood sugar spikes, unlike less-processed steel-cut oats.
Gluten Contamination: Non-certified oats are susceptible to cross-contamination with gluten-containing grains during processing, posing a risk for people with celiac disease.
Over-processing and Additives: Many pre-packaged and flavored oat products are laden with added sugars and artificial ingredients, negating their health benefits.
Heavy Metal Concerns: There have been reports of heavy metal contamination in some oat products, with certain levels raising potential health concerns for vulnerable groups.

For years, oats have been lauded as a breakfast staple and a pillar of a healthy diet. Rich in fiber, vitamins, and minerals, they have been promoted for their heart-protective and cholesterol-lowering properties. However, a closer look reveals several aspects that challenge this 'superfood' status, leading many to question why oats are not considered healthy for everyone.

The Problem of Antinutrients

Oats contain compounds known as antinutrients, primarily phytic acid (or phytate). Phytic acid can bind to essential minerals like iron, zinc, calcium, and magnesium in the digestive tract, reducing their absorption. While this is usually not an issue for those with varied diets, it can be a concern for individuals who rely heavily on grains. Traditional methods like soaking, sprouting, or fermenting can reduce phytic acid levels.

The Risk of Gluten Contamination

Although naturally gluten-free, oats can be problematic for people with celiac disease or gluten sensitivity due to cross-contamination. This can occur during farming, transport, or processing in facilities that also handle gluten grains. Individuals with gluten sensitivities should choose oats certified as 'gluten-free' to avoid contamination. A small number of people with celiac disease may also react to avenin, a protein in oats similar to gluten.

Blood Sugar Spikes from Processing

The glycemic impact of oats depends heavily on processing. Steel-cut oats, being less processed, help regulate blood sugar, whereas instant or quick oats are absorbed quickly, potentially causing blood sugar spikes. Adding sugars or syrups to oatmeal exacerbates this effect.

Comparing Different Oat Types


Feature	Steel-Cut Oats	Rolled Oats	Instant Oats
Processing	Minimally processed, chopped groats	Steamed and flattened flakes	Pre-cooked, dried, and rolled thinly
Cooking Time	Longest, 20-30 minutes	Medium, 5-10 minutes	Shortest, 1-3 minutes
Glycemic Index	Low-moderate	Moderate	Moderate-high
Texture	Chewy, hearty	Soft but with some texture	Mushy, soft
Nutrient Impact	Least processed, retains most nutrients	Good source of nutrients	Least nutritious due to processing
Blood Sugar Effect	Slower, more stable increase	Moderate increase	Rapid spike

Digestive Discomfort and Other Issues

The high fiber content of oats can lead to digestive problems like bloating and gas, especially when fiber intake is increased too quickly. Slow introduction and increased fluid intake may help, but for some, discomfort persists. High-fiber foods can also be an issue for those with gastroparesis.

Concerns have also been raised about potential heavy metal contamination in some oat products, which can come from the soil. While levels are often within safety limits, long-term exposure is a consideration. Many processed oat products also contain unhealthy additives like preservatives, artificial flavors, and added sugars. Opting for less-processed oats and natural toppings is recommended.

How to Maximize the Benefits and Minimize the Downsides

While concerns exist, oats can still be a nutritious part of a diet for many. To make the healthiest choice:

Choose steel-cut or rolled oats over instant.
Soak oats to reduce phytic acid.
Use healthy toppings like nuts and berries instead of sugar.
Maintain a balanced diet with various food sources for nutrients.
If sensitive to gluten, always choose certified gluten-free oats.

Whether oats are a healthy choice is personal. Understanding these potential drawbacks and adjusting preparation can help you decide if they fit your diet.

Visit the NIH to read more about the inhibitory effect of oats on iron absorption.

Frequently Asked Questions

Phytic acid is a natural compound in oats that acts as an 'anti-nutrient' by binding to minerals like iron, zinc, and calcium. This process can reduce the body's ability to absorb these nutrients effectively.

To reduce phytic acid, you can soak your oats overnight in water, ideally with a splash of an acidic medium like lemon juice or apple cider vinegar. This process activates enzymes that help break down the phytic acid.

While oats are naturally gluten-free, they are often contaminated with gluten from wheat, barley, or rye during processing. Individuals with celiac disease must purchase oats specifically labeled and certified as 'gluten-free' to ensure they are safe.

Steel-cut oats are the least processed and have the lowest glycemic index, leading to a slower and more stable increase in blood sugar compared to instant or rolled oats.

Yes, for some people, especially those unaccustomed to a high-fiber diet, the high soluble fiber content in oats can cause digestive discomfort like gas and bloating. It is recommended to introduce oats slowly and increase fluid intake.

Instant oatmeal is highly processed and often contains added sugars and artificial ingredients. This processing increases its glycemic index, which can cause faster blood sugar spikes compared to less-processed varieties.

Yes, some studies have detected heavy metals like cadmium in certain oat products, though often below standard safety limits. Long-term exposure, especially for sensitive populations like infants, is a concern.