Understanding the PET Scan and Your Pre-Scan Diet
A Positron Emission Tomography (PET) scan is an imaging test that reveals how your tissues and organs are functioning by measuring metabolic activity. The most common type, an FDG-PET scan, uses a radioactive sugar tracer (fluorodeoxyglucose) that is injected into your bloodstream. Because cancer cells and other diseased tissues often have a higher metabolic rate, they absorb more of this sugar and appear brighter on the scan. The purpose of the pre-scan diet and fasting is to lower your body's natural blood sugar (glucose) levels so that the injected radioactive tracer is not diluted by competition with dietary sugars. This ensures the tracer is effectively taken up by the targeted cells, producing high-quality and reliable images. If your blood sugar is too high at the time of the scan, the quality can be compromised, potentially leading to a rescheduled appointment.
Why is Hummus Banned from the Pre-Scan Diet?
Hummus is typically made from chickpeas (garbanzo beans), tahini (sesame seed paste), olive oil, lemon juice, and seasonings. The primary reason it is forbidden before a PET scan is its high concentration of carbohydrates from the chickpeas.
The Chickpea Carbohydrate Issue
For 24 hours leading up to an FDG-PET scan, a low-carbohydrate, high-protein diet is required. Chickpeas are legumes, and many scanning centers explicitly list beans and other legumes as foods to avoid. They contain significant amounts of carbohydrates that can cause your blood sugar to rise. This directly compromises the effectiveness of the radioactive sugar tracer used in the scan. Furthermore, some varieties of hummus can contain added sugars or other ingredients that are also forbidden. Even plain hummus is not suitable, as the base ingredient is the main concern.
Fasting is Non-Negotiable
In addition to the 24-hour diet, you must enter a period of total fasting for at least 6 hours before the scan, during which only plain water is permitted. This means that even if a very low-carb meal were acceptable, it must be consumed well outside of this strict fasting window. Therefore, consuming hummus right before your scan is doubly forbidden.
Allowed vs. Forbidden Foods: A Comparison
To help you plan your meals, here is a comparison of typical food choices for the 24-hour pre-scan diet.
| Allowed (High Protein, Low-Carb) | Forbidden (High-Carb, Sugars) |
|---|---|
| Meats, fish, and eggs | Grains (bread, pasta, rice, cereal) |
| Non-starchy vegetables (spinach, broccoli, cauliflower, green beans, mushrooms) | Starchy vegetables (potatoes, corn, peas, carrots) |
| Hard cheese and butter | Dairy (milk, yogurt, ice cream) |
| Nuts (excluding sweetened varieties) | All fruits and fruit juices |
| Water, diet soda, sugar-free drinks | Sugary drinks (soda, juice, sweet tea) |
A Sample Low-Carb Meal Plan
For the 24 hours leading up to your scan, consider a meal plan that adheres strictly to the low-carbohydrate, high-protein guidelines. Remember to stop eating completely at least 6 hours before your appointment, only drinking plain water.
- Evening Before: Grilled chicken breast with steamed broccoli and asparagus, seasoned with salt and pepper.
- Morning of (if scan is in the afternoon, minimum 6 hours before): Scrambled eggs with a small amount of cheese and spinach.
- Hydration: Throughout the entire prep period, drink plenty of plain water.
Conclusion: Prioritize Scan Accuracy
In summary, the question of "Can I have hummus before a PET scan?" has a clear answer: no. The reason is rooted in the scientific principle of the FDG-PET scan, where high carbohydrate intake from foods like hummus can interfere with the diagnostic process. Adhering to the specified low-carb, high-protein diet for 24 hours, followed by a strict 6-hour fasting window, is essential for minimizing false readings and ensuring the highest quality images for your doctor's evaluation. Always consult with your doctor or the imaging center for specific instructions tailored to your condition, as some specialized cardiac PET scans have different requirements. For more detailed information on PET scan preparation, resources from reputable institutions can be found online. Dana-Farber Cancer Institute
What to Do Instead of Eating Hummus
Instead of eating hummus, focus on approved high-protein, low-carbohydrate options. Enjoy sources like plain grilled chicken, turkey, or fish. Non-starchy vegetables such as leafy greens, cucumber, and mushrooms are also excellent choices. These foods will help keep your blood sugar stable and your stomach full without compromising the accuracy of your test.
