When preparing for a PET scan, it is important to follow your doctor’s instructions about what you can and cannot eat beforehand. The main reason for dietary restrictions before a PET scan is to avoid high blood sugar, which can cause interference with the images. There are some vegetables that are generally considered safe to eat in the day or two leading up to your scan.
Quick Answers
Here are quick answers to some common questions about eating vegetables before a PET scan:
- Leafy greens like spinach and lettuce are usually fine to eat.
- Cruciferous vegetables like broccoli and cauliflower are typically okay.
- Root vegetables like carrots and sweet potatoes are generally allowed.
- Low-sugar fruits like tomatoes, cucumbers, and avocados are often permitted.
- Starchy vegetables like corn, peas, winter squash should be avoided.
- Always check with your doctor for specific instructions on what you can eat.
Why Dietary Restrictions Before a PET Scan?
PET (Positron Emission Tomography) scans involve injecting a radioactive tracer into the body. This tracer accumulates in areas with high metabolic activity, including cancerous tumors. The PET scanner detects the radiation from the tracer to create 3D images of the body.
In order to get clear images, it is important to have relatively low and stable blood sugar levels before a PET scan. High blood sugar can cause interference as the tracer is absorbed and used by tissues differently. For this reason, doctors recommend restricting carbohydrate intake from starchy foods, sweets, and sugary drinks in the 24-48 hours prior to a PET scan.
Non-Starchy Vegetables
Most non-starchy vegetables are acceptable to eat before a PET scan. These types of veggies are relatively low in carbohydrates and sugars, so they won’t significantly impact blood glucose levels. Some good options include:
- Leafy greens – Spinach, lettuce, kale, chard, etc.
- Cruciferous vegetables – Broccoli, cauliflower, Brussels sprouts, cabbage, bok choy, etc.
- Root vegetables – Carrots, turnips, parsnips, beets, radishes, etc.
- Asparagus
- Celery
- Onions and garlic
- Eggplant
- Cucumbers
- Tomatoes
- Peppers – bell peppers, chili peppers, etc.
- Summer squash – zucchini, yellow squash, etc.
- Green beans
These vegetables all contain 5 grams of carbohydrates or less per 1/2 cup cooked serving. As long as you stick to reasonable portion sizes, they are unlikely to have significant effects on blood glucose levels.
What About Starchy Vegetables?
Starchy vegetables are higher in carbohydrates and natural sugars. It’s best to avoid these types of veggies before a PET scan, including:
- Corn
- Potatoes
- Sweet potatoes
- Yams
- Plantains
- Parsnips
- Pumpkin
- Winter squash – acorn squash, butternut squash, etc.
- Peas
- Beans – pinto beans, kidney beans, black beans, etc.
A 1/2 cup serving of these starchy veggies contains around 15-30 grams of carbohydrates. Eating them in the 1-2 days before your PET scan could potentially impact the accuracy of the test.
Fruits and Vegetables to Avoid
In addition to starchy vegetables, you’ll also want to avoid eating most fruits before a PET scan. Fruits tend to be high in natural sugars that can rapidly increase blood glucose levels. Steer clear of:
- Bananas
- Grapes
- Berries – strawberries, blueberries, raspberries etc.
- Pineapple
- Mango
- Apples
- Pears
- Watermelon
- Cherries
- Dried fruits
- Juices – orange, apple, grape, etc.
Some lower sugar fruits like avocados, tomatoes and cucumbers may be allowed in moderation. Check with your medical team about specific fruits to avoid.
Sample 1-Day Meal Plan
Here is a sample low-carb, 1-day meal plan with PET scan-friendly vegetable choices:
| Meal | Foods |
|---|---|
| Breakfast | Scrambled eggs with onions and peppers |
| Lunch | Tuna salad lettuce wraps with celery sticks |
| Dinner | Grilled chicken with roasted Brussels sprouts and carrots |
| Snacks | Cucumbers with hummus, celery with nut butter |
This provides a good mix of protein and low-carb veggies from the allowed list. Make sure to stay hydrated by drinking plenty of water and avoiding sugary drinks.
Key Tips
Here are some key tips to keep in mind when choosing vegetables to eat before your PET scan:
- Stick to non-starchy vegetables – leafy greens, cruciferous veggies, etc. Stay away from starchy options like corn, peas, potatoes.
- Avoid most fruit – the natural sugars can interfere with PET scan results.
- Enjoy low-sugar fruits sparingly – tomatoes, cucumbers, avocados are lower risk.
- Read labels on packaged foods and avoid added sugars.
- Portion control matters – even allowed veggies can raise blood sugar in large amounts.
- Consult your doctor if you have any questions about what to eat before your PET scan.
The Purpose of Dietary Restrictions
It may be inconvenient to alter your diet for a medical test, but there are good reasons behind the dietary rules for a PET scan. By limiting carbohydrate intake from certain vegetables and fruits, you can help ensure the images come out clear and useful for detecting any issues.
Blood glucose appears similar to the radioactive tracer used in PET scans. High blood sugar levels make it harder for the scanner to distinguish between the two. This can reduce the accuracy of the test results.
Following your doctor’s recommendations helps set you up for the best possible PET scan. Any mild hunger or cravings will be temporary. The insights gained from accurate PET images are well worth the short-term dietary changes.
How Blood Glucose Affects PET Scan Results
PET scans detect radiation from injected radioactive tracers like fluorodeoxyglucose (FDG). This substance accumulates in areas with high metabolic activity, including cancer tumors, inflammation, and infection.
However, high blood glucose competes with FDG for uptake by cells. The higher your blood sugar levels, the less FDG is absorbed by relevant tissues. This makes the PET scan images less distinct and clear.
Blood glucose above 150-200 mg/dL (8-11 mmol/L) is generally considered high enough to interfere with PET scan accuracy. Anything over 200 mg/dL can cause significant issues with obtaining useful images.
Preparing for Your Scan
Here are some steps you can take to prepare for a PET scan and help ensure optimal results:
- Talk to your doctor in advance about dietary guidelines and restrictions.
- Avoid sweets, sugary drinks, pasta, rice, bread, and starchy veggies for 1-2 days beforehand.
- Stick to non-starchy vegetables, eggs, meat, fish, nuts, seeds, oils, and non-starchy dairy.
- Verify you can drink plain water – some centers say no food or drink 6+ hours prior.
- Check your blood glucose before arriving for the scan if you have diabetes.
- Arrive early to drink water and use the restroom – you’ll lie still during the scan.
- Wear comfortable clothing without metal fasteners near the scan area.
Preparing both your diet and logistics will help your PET scan go smoothly. A bit of planning goes a long way towards getting the accurate information needed for your health management.
Interpreting PET Scan Results
Your medical team will analyze the PET images, along with other diagnostic tests and scans you may undergo. This is not something you can interpret on your own. However, voicing any questions or concerns you have about the results to your doctor is important.
Based on the PET scan findings, your doctor may recommend additional imaging, biopsies, or changes to your treatment plan. PET scans are often used to look for signs of cancer returning after treatment or spreading to new areas in the body.
Your doctor will explain what the results mean for your health situation. Don’t be afraid to ask for clarification if certain aspects are confusing. Understanding the results will help you be proactive about your healthcare.
Frequently Asked Questions
Can I eat salads before a PET scan?
Yes, salads made with PET-friendly vegetables are good meal options before a PET scan. Focus on leafy greens like spinach, lettuce, arugula, etc. Top with a few sliced veggies like cucumbers, tomatoes, carrots, broccoli, and avocado for healthy fat. Avoid starchy additions like corn, beans, peas, potatoes.
What if I accidently ate something with sugar?
Talk to your doctor if you accidentally consumed a high-sugar food or drink before your PET scan. They may recommend rescheduling the test if it was a significant amount of carbohydrates. For small slip-ups, drinking extra water can help flush out excess blood glucose.
Can I drink coffee before my PET scan?
Most centers allow plain black coffee before a PET scan since it has minimal carbs. Avoid adding cream, milk, or sugar. Check with your testing facility – some want you to avoid all food and drinks for 6+ hours beforehand.
What about vegetable juice or tomato juice?
Despite seeming healthy, vegetable and tomato juices tend to be high in natural sugars. Your best bet is to avoid them before your PET scan. Stick to plain water instead of any sweetened beverages.
Is honey allowed?
No, honey should be avoided in the day or two leading up to your PET scan. Despite being natural, honey contains a lot of concentrated sugars that can spike your blood glucose. Stick to non-starchy vegetables and be wary of sauces containing honey.
The Bottom Line
Preparing with a low-carb diet in the day or two before your PET scan is important for getting accurate results. Enjoy plenty of leafy greens, cruciferous vegetables, asparagus, celery, eggplant, and other low-sugar produce. Avoid sweets, fruit, starchy vegetables, and sugary drinks.
Always follow your doctor’s specific recommendations on what you can eat and drink before your PET scan. A bit of short-term dietary restriction will pay off with the critical insights gained from optimal PET scan images.
