I have always known tomatoes to be a healthy food for just about everyone, but I wanted to know more specifically what kind of role these beauties play in the culinary world of a diabetic. In my research I came across this very informative and comprehensive article written by Registered Dietician Julia Zakrzewski on Signos.com.
How Do Tomatoes Affect Blood Sugar?
By Julia Zakrzewski, RD - Signos Health & Nutrition Writer
Science-based and reviewed
Published: September 7, 2022
Tomatoes are low in sugar and are packed with nutrients, making them a blood-sugar-friendly food. The bright red fruit is rich in lycopene, vitamin C, and potassium, which contribute to heart health and immune function.
All fresh tomatoes are low in sugars and because they fall
low on the glycemic index, don’t usually have a significant impact on blood
sugar levels. In fact, they are actually high in potassium and lycopene, which
can help improve blood sugar.
Keep reading to find out why these nutrients are important for your health, and how you can incorporate both fresh and canned tomatoes into your daily diet.
Glycemic Index of Tomatoes
Fresh tomatoes are non-starchy vegetables that contain very few sugars and have a very low glycemic index (GI) score. It is estimated the GI is 15 for a 5oz tomato.
Do All Tomatoes Have the Same GI?
There are hundreds of different varieties of tomatoes. The
most popular ones you may recognize include:
- Roma
- Heirloom
- Beefsteak
- Cherry
- Grape
Different types of tomatoes lend themselves to different
preparations and uses. Because of their size, cherry and grape tomatoes are
better suited for salads or an easy snack. Beefsteak and heirloom tomatoes are
larger and a bit sturdier, so they can hold up on a sandwich. Roma tomatoes are
naturally sweeter and are best used for canning or sauces.
The USDA nutrient database lists similar carb content across
the fresh tomato varieties and a similar GI scores across the board. So
whether you are using your fresh tomatoes in a salad or turning them into a
sauce, know your blood sugars should remain stable.
Will Fresh Tomatoes Raise Your Blood Sugar?
It is unlikely that fresh tomatoes will raise your blood
sugar. A low GI score is an indicator that the food will slowly digest in your
system and have a delayed effect on your blood sugar levels.
But, tomatoes are not a significant source of fiber. They
only offer approximately 1-2g of fiber per 100g serving. Pairing tomatoes with
other vegetables, like dark leafy greens or avocado, can help increase your
total fiber intake during your meals, which plays a key role in slowing down
your glucose metabolism and absorption.
Will Canned Tomatoes Impact Blood Sugar Levels?
Canned tomatoes are still low in starch and will also have a
low GI score. This means they should not impact your blood sugar levels,
either.
Sometimes canned tomatoes are prepared with herbs and
spices. Commonly used canned tomato-based products, like sauces, have large
amounts of added sugars. Sugars are used to balance the acidity of tomatoes,
making them sweeter. If you see sugar on the ingredient list, put the can down
and look for a sugar-free option. Added sugars are more likely to raise blood
sugar levels.
Always try to buy unflavoured canned vegetables whenever possible.
Glycemic Index of Tomato-Based Foods
Fresh tomatoes are a key ingredient for other foods. Here is
a list of popular tomato-based products and their GI score:
- Tomato sauce (Marinara): 23
- Unsweetened tomato juice: 38
- Canned tomato soup: 38
Tomato paste and condiments, such as ketchup, do not have
assigned GI scores. These items are usually referred to as miscellaneous sauces
that are used to enhance the flavor of foods instead of being a full
meal.
An entire bottle of ketchup can have high sugar content (again, check your labels!). But if you monitor your portion sizes, you would only be consuming 3g of sugar per tablespoon. You can control how much sauce you add to your meals and monitor your sugar intake.
When buying tomato sauce, look for a short, clean ingredient
list with no added sugar.
Nutrients in Tomatoes
Tomatoes constitute mostly of water and they contain
essential vitamins including:
Vitamin C: supports immune function and promotes protein
synthesis. Both of these mechanisms reduce your risk of disease.
Potassium: helps to regulate cardiac function and can help
lower blood pressure. People with lower blood levels of potassium may be at a
higher risk for type two diabetes.
Lycopene: is an antioxidant that gives tomatoes their red
color. It is being researched for its potential role in weight
management.
A 2019 study tested the potential weight loss benefits of
lycopene supplements on obese mice. The results indicated a positive
correlation between lycopene supplements and observed weight loss. While human
trials need to be completed, it is a promising area of research.
Unflavored canned tomatoes and tomato juice products all carry similar nutrient profiles. The most significant difference between products is the fiber content. Tomato juice has much lower fiber compared to canned and fresh tomatoes.
Can Tomatoes Reduce Insulin Resistance?
Your pancreas produces a hormone called insulin, which is
responsible for clearing sugars out of your bloodstream.
Insulin
resistance means your insulin hormone is no longer able to efficiently
clear sugars and your blood glucose levels can rise.
Researchers have been studying the link between tomatoes and
blood sugar improvements in people with diabetes since the 1990s. Scientists
have found bioactive compounds in fresh and cooked tomatoes that reduce
oxidative stress related to diabetes.
Oxidative stress is when the free radicals in your body
outnumber the antioxidants. Free radicals are harmful to your health and an
abundance of these molecules increases the risk of developing different
diseases.
Although the data is promising, no studies exist yet on the
link between tomatoes and blood sugar control in people without diabetes.
Potassium and Insulin Secretion
Some observational studies have demonstrated that lower
potassium levels may increase your risk of diabetes. This is because potassium
channels affect pancreatic beta cells, which are involved with insulin
production and secretion.
Your body regulates your blood potassium levels through
biochemical signaling, but the resources must be replenished. Eating
potassium-rich foods, such as fresh or cooked tomatoes, is recommended to help
you satisfy your potassium requirements.
Other Health Benefits of Tomatoes
Phytochemicals are natural chemical compounds found in
different plant-based foods, including tomatoes. It’s speculated that
phytochemicals can decrease your risk of developing certain types of
cancer.
In 2021 a large-scale meta-analysis reviewed all
high-quality studies that investigated any link between phytochemical intake
and colon cancer incidence.
The data showed a positive link that people who ate a diet
rich in phytochemicals had decreased incidence of colon cancer compared to
people who consumed fewer phytochemical-rich foods.
How to Add More Tomatoes to a Healthy Diet
Tomatoes are versatile and can be eaten on their own or
mixed into your favorite dishes. Pair them with protein-rich or fiber-rich
foods to delay digestion and minimize any impact on your blood sugars. Try
these tomato-forward ideas:
Tomato slices on a grilled cheese sandwich, made with whole
grain bread.
Sautée tomatoes and spinach into your breakfast omelet.
Tomato salad with three different varieties and colors, and
add legumes for protein.
Stock your pantry with canned (no sugar added)
tomatoes.
Add canned tomatoes and tomato paste to your next soup or
chili dish.
Swap out fruit juice for unflavoured tomato juice.
As you explore adding more tomatoes into your cooking, consider choosing specific varieties for your dishes.
Try This Famous Tomato Salad
A famous tomato salad, that aligns with the Mediterranean diet,
is the Caprese salad. It has simple instructions and is blood-sugar
friendly:
- Cut 1-2 ripe tomatoes into slices
- Cut 8oz fresh mozzarella into ¼” slices
- A handful of fresh basil leaves
- 2 tablespoons each of olive oil and balsamic glaze to dress the salad
Layer your ingredients in a repeating pattern: tomato, mozzarella, and basil. Repeat the pattern until you have used all your ingredients. Drizzle olive oil and balsamic glaze over your salad. You can add a pinch of salt and fresh ground pepper if you want.
Are There Downsides of Eating Tomatoes?
People who suffer from acid reflux or who are recovering
from an ulcer are advised to limit their intake of tomato products. The high
ascorbic acid in tomatoes can aggravate symptoms and worsen feelings of
heartburn.
This recommendation includes all tomato products, including
tomato sauces, salsas, and tomato juice drinks.
Can You Eat Too Many Tomatoes?
There is no scientific literature to suggest how many
tomatoes are safe to eat in a day. You should listen to how your body responds
to tomatoes and make a decision that feels right for you.
Are Green Tomatoes Safe to Eat?
There are two circumstances when you would encounter a green
tomato: the first is an unripe red tomato, and the second would be a variety of
tomato that grows green with stripes.
Both of these are safe to eat, but the unripened tomato will
lack flavor and nutrients.
A true green tomato has a tart flavor that offers more
crunch than a regular red tomato. Green tomatoes are normally cooked before
eating and used in salsa, or they are breaded and fried.
While fried tomatoes are delicious, they are also higher in
fats and carbs. You can try making them in the airfryer or grilling them
instead.
Tomatoes and Blood Sugar: Key Takeaways
Tomatoes are nutritious, and they are loaded with essential
vitamins and antioxidants. They have low sugar content and should not cause
your sugar levels to increase.
You can rely on fresh tomatoes or canned options in your
diet. Choose unflavored canned options whenever possible and always read the
ingredients before buying.
If you suffer from acid reflux you should wean back on
tomatoes until your symptoms subside.
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Have a great week, everyone, and thank you for your support!
Blessed be… and happy cooking!
Chef Michael R