Understanding the Methods: How to measure fructans? for dietary analysis

According to a study published in Frontiers in Nutrition, fructans can significantly impact individuals with irritable bowel syndrome (IBS), making accurate measurement crucial for effective dietary management. Understanding how to measure fructans? involves exploring complex laboratory assays and personal diagnostic tools to inform dietary choices and research.

Quick Summary

Several laboratory methods, including enzymatic assays (AOAC 999.03) and HPAEC-PAD, accurately quantify fructan content in foods by measuring released sugars. For individuals, a hydrogen breath test indicates intolerance by detecting fermentation byproduct gases.

Key Points

• Lab vs. Personal Measurement: Laboratory analysis measures the chemical content of fructans in food, while a personal hydrogen breath test measures an individual's intolerance or malabsorption.

• Enzymatic-Spectrophotometric Assay (AOAC 999.03): This method uses specific enzymes to break down fructans and removes other sugars before a colorimetric reaction to quantify the total fructan content in food.

• HPAEC-PAD Chromatography: A more advanced laboratory technique, HPAEC-PAD separates and quantifies different chain lengths of fructans, providing a detailed profile of the fructans in a food sample.

• Hydrogen Breath Test for Intolerance: The standard diagnostic tool for individuals, this test measures breath hydrogen and methane to indicate if a consumed fructan has been fermented by gut bacteria.

• Informing Dietary Choices: Lab data informs general food content, while a personal breath test provides actionable insights into an individual's specific digestive response to fructans.

• Challenges in Quantification: Measuring fructans can be complex due to the presence of other carbohydrates and the varying chain lengths of fructan molecules.

The Importance of Fructan Measurement

Fructans are a type of carbohydrate known as a prebiotic, meaning they feed beneficial bacteria in the gut. However, for individuals with conditions like IBS, their rapid fermentation in the large intestine can lead to significant gastrointestinal distress, including bloating, gas, and abdominal pain. Accurately measuring fructan levels is therefore critical for:

• Dietary Management: For individuals on a low-FODMAP diet, knowing the precise fructan content in foods is necessary to manage symptoms effectively.
• Nutritional Research: Scientists quantify fructans to understand their health benefits, how food processing affects their levels, and their overall impact on human digestion.
• Food Industry: Food manufacturers measure fructans to accurately label products, especially those marketed as low-FODMAP or high in dietary fiber.

Laboratory Methods for Quantifying Fructans in Food

For a detailed, quantitative analysis of fructan content in food products, specialized laboratory techniques are required. These methods involve several steps, typically including extraction, hydrolysis, and detection.

Enzymatic-Spectrophotometric Assay (AOAC Method 999.03)

This widely recognized method is based on the principle of hydrolyzing fructans into their constituent monosaccharides, followed by a colorimetric measurement.

1. Sample Extraction: Fructans are water-soluble, so a sample of the food is first extracted using hot water to isolate the fructans.
2. Removal of Interfering Sugars: Enzymes are used to break down other sugars like sucrose and starch into glucose and fructose. These free sugars are then chemically reduced to sugar alcohols using alkaline borohydride, so they do not interfere with the final measurement.
3. Fructan Hydrolysis: The extracted fructans are then hydrolyzed into glucose and fructose using a specific fructanase enzyme mixture.
4. Spectrophotometric Measurement: The newly released glucose and fructose are measured using a spectrophotometer after a colorimetric reaction with para-hydroxybenzoic acid hydrazide (PAHBAH). The amount of fructan is calculated based on the quantity of released sugars.

High-Performance Anion-Exchange Chromatography with Pulsed Amperometric Detection (HPAEC-PAD)

This technique offers high sensitivity and the ability to analyze the chain-length distribution of fructans, providing more detailed information than colorimetric methods.

• Sample Preparation: Similar to other methods, the process begins with extracting fructans from the sample. Interfering free sugars are often removed enzymatically.
• Chromatographic Separation: The extracted fructans are separated based on their molecular size and charge using an anion-exchange column. HPAEC-PAD can resolve a wide range of fructan chain lengths, from small fructooligosaccharides (FOS) to long-chain inulin.
• Detection: The separated fructans are detected using pulsed amperometry, which measures the electrical current generated as the carbohydrates are oxidized at an electrode surface.
• Degree of Polymerization: By using a combination of mild acid hydrolysis and HPAEC-PAD, researchers can also determine the average degree of polymerization ($DP_{av}$) of the fructans.

Measuring Personal Fructan Intolerance

For individuals experiencing digestive symptoms, the goal is not to measure the fructan content of food but to diagnose intolerance. This is most commonly done via a hydrogen breath test.

The Hydrogen Breath Test

This non-invasive test measures hydrogen and methane gases in the breath, which are produced by the fermentation of unabsorbed carbohydrates in the large intestine.

1. The Procedure: After a period of fasting, a patient drinks a solution containing a controlled amount of fructose or inulin. They then provide breath samples at regular intervals over several hours.
2. Interpretation of Results: A significant rise in breath hydrogen or methane levels indicates that the carbohydrate was not fully absorbed and instead fermented by gut bacteria, suggesting intolerance or malabsorption.
3. At-Home Options: Personal breath testers are available for home use, providing convenience. These devices, like those from FoodMarble, can measure hydrogen and methane, allowing individuals to track their personal response to various foods and potentially identify their specific tolerance levels.

Comparison of Fructan Measurement Methods

Feature	Enzymatic-Spectrophotometric (AOAC 999.03)	HPAEC-PAD Chromatography	Hydrogen Breath Test
Purpose	Quantifies total fructan content in food samples.	Quantifies total fructan content and chain-length distribution in food samples.	Diagnoses an individual's intolerance to fructans.
Equipment	Standard lab equipment (spectrophotometer, water baths).	Specialized High-Performance Liquid Chromatography (HPLC) system with a PAD detector.	Specific breath-testing device for hospital or home use.
Cost	Relatively low, especially with commercial kits.	High initial investment for equipment.	Low for a single test, moderate for personal at-home devices.
Information	Provides a total fructan value (single number).	Provides a detailed fructan profile (DP range).	Measures fermentation byproduct gases (indirectly indicating intolerance).
Specificity	High, using specific enzymes for hydrolysis.	Very high, allowing separation of different carbohydrate types.	Dependent on the carbohydrate consumed during the test.
Use Case	Food manufacturing, large-scale quality control.	Research, detailed food composition studies.	Clinical diagnosis, personal dietary management.

Conclusion

Measuring fructans requires different approaches depending on the goal. For precise quantification of the carbohydrate in a food product, laboratories employ rigorous methods like the enzymatic-spectrophotometric assay (AOAC 999.03) and the more advanced HPAEC-PAD. These provide valuable data for nutritional research and food labeling. For individuals seeking to understand their personal sensitivity, a hydrogen breath test, which detects fermentation in the gut, is the standard diagnostic tool. While laboratory methods offer detailed chemical composition, personal breath tests offer practical, real-world insights into individual tolerance. When navigating a diet that restricts fructans, understanding the strengths and limitations of these measurement techniques is key to making informed decisions.

For a detailed overview of the AOAC 999.03 method's evaluation, see the publication on ResearchGate: Measurement of Total Fructan in Foods by Enzymatic/Spectrophotometric Method: Collaborative Study.

Frequently Asked Questions

Can I measure fructan content in food at home?

No, you cannot measure the actual fructan content of food at home. Specialized laboratory equipment and chemical reagents are required. However, you can use a personal hydrogen breath test device at home to test your body's reaction to fructans.

What is the most accurate lab method for measuring fructans?

The most detailed and accurate laboratory method is High-Performance Anion-Exchange Chromatography with Pulsed Amperometric Detection (HPAEC-PAD). It can not only measure total fructan content but also separate and quantify different chain lengths, which affects digestion.

What is a hydrogen breath test for fructans?

A hydrogen breath test measures the levels of hydrogen and methane gas in your breath after consuming a test solution containing fructans. Elevated gas levels indicate that the fructans were not properly absorbed and were fermented by bacteria in your gut, suggesting intolerance.

How do laboratory methods differentiate fructans from other sugars?

Laboratory methods like the AOAC 999.03 assay use specific enzymes to first hydrolyze other carbohydrates like starch and sucrose. These are then reduced chemically before the fructans themselves are hydrolyzed and measured, ensuring high specificity.

Why can fructan content vary in the same food type?

Fructan content in foods can vary significantly based on factors like the food's origin, cultivar, and processing methods. For example, the fructan content in wheat bread varies depending on the type of wheat and baking process.

How do fructan measurements help with a low-FODMAP diet?

For those on a low-FODMAP diet, accurate fructan measurements in foods are essential for making informed dietary decisions. Lab analysis helps determine safe portion sizes and which foods to avoid to minimize symptom triggers.

Is the home hydrogen breath test reliable for measuring fructans?

The home hydrogen breath test is a reliable way to gauge an individual's response to fructans, but it doesn't measure the quantity of fructans in a food. Results depend on following instructions carefully, and clinical testing may offer higher precision due to controlled conditions.

What are some foods high in fructans?

Foods commonly found to be high in fructans include onion, garlic, wheat, rye, and chicory root. The exact content can vary, but these are generally restricted on a low-FODMAP diet.