What Temperature Destroys Vitamin B1? Understanding Thiamine's Heat Sensitivity

January 7, 2026 •

3 min read

Research has shown that vitamin B1 is one of the most thermolabile, or heat-sensitive, of all the B vitamins. While there is no single temperature that instantly destroys vitamin B1, prolonged exposure to heat during cooking and food processing can cause significant degradation.

Quick Summary

Thiamine degrades gradually with heat, not at a single point. Its destruction is influenced by temperature, cooking time, and pH level. Proper cooking methods can minimize nutrient loss.

Key Points

Heat Sensitivity: Vitamin B1 (thiamine) is highly sensitive to heat and degrades over time with exposure to high temperatures.
Water Solubility: As a water-soluble vitamin, thiamine leaches into cooking water, with significant loss occurring when the water is discarded after boiling.
pH Factor: Thiamine is most stable in acidic conditions (below pH 6.0) and rapidly destroyed in alkaline environments (above pH 7.0).
Boiling vs. Steaming: Boiling is particularly destructive, while steaming and microwaving are better for preserving thiamine due to shorter cooking times and minimal water usage.
Pressure Cooking: This method uses intense heat and pressure, leading to near-complete decomposition of thiamine.
Cumulative Effect: It's not a single temperature, but the combination of temperature, time, and cooking environment that determines the extent of thiamine loss.
Storage Matters: Proper storage, avoiding light, heat, and moisture, is also crucial for preventing thiamine degradation before cooking.

The Heat Sensitivity of Thiamine

Thiamine, commonly known as vitamin B1, plays a crucial role in metabolism, converting food into energy for the body. As a water-soluble vitamin, it is particularly vulnerable to degradation from heat, light, and oxidation. The idea that a single temperature 'destroys' vitamin B1 is an oversimplification; rather, it is a process of degradation that accelerates with higher temperatures and longer cooking times. For instance, a study on milk processing showed different levels of thiamine loss based on temperature and duration, with higher temperatures and longer times leading to greater loss.

The Impact of pH on Thiamine Stability

Beyond heat, the pH of the cooking environment is a major factor in thiamine's stability. Thiamine is more stable in acidic conditions, specifically at a pH below 6.0. Conversely, in alkaline conditions (pH above 7.0), such as when baking soda is used, thiamine is rapidly destroyed. This means that the other ingredients in a dish can either protect or accelerate the degradation of vitamin B1, regardless of the temperature used.

How Different Cooking Methods Affect Thiamine Levels

Because thiamine is both water-soluble and heat-sensitive, the method of cooking has a profound impact on how much of the vitamin is retained in your food. Water-based cooking, like boiling, can cause a significant portion of the thiamine to leach out into the cooking water, which is often discarded. Cooking methods that minimize water use and time, or use very high temperatures for very short periods, tend to preserve more of the vitamin. Food processing techniques, such as ultra-high temperature (UHT) processing for milk, can also lead to significant thiamine losses, sometimes as high as 40-50%.

Cooking Methods Comparison


Cooking Method	Relative Thiamine Loss	Explanation
Boiling	High	Thiamine leaches into the water and is discarded. High heat also accelerates degradation.
Steaming	Low	Minimal water contact and shorter cooking times preserve more thiamine.
Microwaving	Low	Rapid heating and minimal water use lead to better retention.
Roasting/Baking	Moderate to High	High, dry heat over an extended period can cause considerable degradation.
Pressure Cooking	High	The combination of high heat and pressure can cause near-complete thiamine decomposition.
Stir-Frying	Low to Moderate	Quick cooking with minimal water and heat exposure can preserve nutrients, though high fat content is a factor.

Practical Tips for Retaining Vitamin B1

To maximize your dietary intake of thiamine, consider incorporating these cooking and preparation strategies:

Choose the Right Method: Opt for steaming, microwaving, or quick stir-frying instead of boiling whenever possible.
Use Minimal Water: If you must boil, use as little water as possible and consider incorporating the nutrient-rich cooking liquid into a soup or sauce.
Minimize Soaking: Thiamine can also dissolve in soaking water. Drain and rinse foods like legumes and grains quickly before cooking.
Avoid Baking Soda: Do not add baking soda to your cooking, as its alkaline nature will rapidly destroy thiamine.
Cook for Shorter Durations: The longer food is exposed to heat, the more thiamine is lost. Cook for the minimum time required.
Store Properly: Protect thiamine-rich foods from light, heat, and moisture during storage to minimize pre-cooking degradation.

Conclusion: Maximizing Thiamine Intake

Rather than focusing on a single temperature, it is more effective to understand that what temperature destroys vitamin B1 is a function of duration and environment. Thiamine is gradually degraded by heat, and this process is exacerbated by alkaline conditions and prolonged cooking in water. The best approach for preserving this vital nutrient is to choose cooking methods like steaming and microwaving that minimize exposure to heat and water. By adopting these simple culinary habits, you can significantly reduce nutrient loss and ensure a more thiamine-rich diet. For those interested in deeper nutritional data, the Office of Dietary Supplements offers comprehensive information on thiamin.

Frequently Asked Questions

Yes, boiling is one of the most destructive cooking methods for thiamine. This is because thiamine is water-soluble, meaning it dissolves and leaches into the boiling water, which is then often discarded along with the nutrient.

The best methods are those that use minimal water and less heat for shorter durations. Steaming, microwaving, and quick stir-frying are generally recommended to preserve the maximum amount of vitamin B1.

Baking, especially at high temperatures for longer periods, can cause a significant loss of vitamin B1, as seen in studies on bread baking. The high, dry heat over time leads to thermal degradation.

Yes, thiamine is very unstable in alkaline conditions (pH above 7.0). Adding baking soda to cooking water, for instance, can rapidly destroy the vitamin.

Yes, pressure cooking causes significant thiamine loss. The combination of high heat and pressure accelerates the decomposition of the vitamin, and losses are considerable.

Yes, ultra-high temperature (UHT) processing can cause substantial thiamine loss. Research has shown that UHT can reduce thiamine content by 40-50% in milk.

You can minimize loss by cooking with minimal water, using quick-cooking methods, avoiding baking soda, and consuming the cooking liquid if possible. Storing foods properly also helps.

Thiamine is most stable in acidic conditions, specifically at a pH of less than 6.0.

The amount varies greatly depending on the process. Refining grains, for example, can remove a vast majority of thiamine, which is why foods are often enriched.