Tomatoes and Blood Sugar: Navigating the Glycemic Index

Tomatoes are an extremely versatile fruit that can add a fresh, tangy zest to any dish or meal. These plump, sweet, and juicy fruits are often enjoyed in everything from salads to soup, salsa, pasta sauce, and curries. 

They’re also great sources of vitamin A, C, and K, contain many healthy minerals, and have a high water content, meaning they’re great for hydration. But is this sweet and tangy fruit safe for individuals who are watching their blood sugar to eat regularly?

In this article, we’ll explore the connection between tomatoes and blood glucose levels, insulin response, and other health effects that tomatoes may have.

Tomatoes and Blood Sugar: What the Science Says

Raw tomatoes are composed almost entirely of water and are low in carbohydrates. According to the nutritional data from the USDA, only three to five percent of a tomato is carbohydrate content and that number includes the natural sugars found in tomatoes. 

As a result, eating a tomato—in your salad, for instance—shouldn’t lead to an increase in blood sugar levels. A recent meta-analysis of research on tomatoes, found that there was no significant effect of tomato consumption on fasting blood glucose levels. But what about the phytochemicals and other nutrients in tomatoes? Can these actually lead to a decrease in blood glucose.

Unfortunately, not much research has been done on this subject. However, a small randomized control trial involving healthy women pointed to lower blood glucose concentrations in people who consumed 200 grams of tomato juice or tomato 30 minutes before eating a small serving of carbohydrates.

It’s difficult to draw large conclusions from this study due to its extremely small study population (25 women). So, although it may suggest that the tomato can have anti-hyperglycemic effects, more wide-reaching research is likely still needed to confirm its findings.

Do Different Tomato Varieties Have Different Effects?

While it’s true that different varieties of tomato have distinct nutrient compositions, most types of fresh, raw tomatoes will have similar nutritional value. Fresh tomatoes are considered a low GI food with a score of 30. According to the USDA, grape tomatoes have slightly more carbohydrate content than roma tomatoes per 100 gram serving: 5.51 grams to 3.84 grams. 

Sun-dried tomatoes, however, have much less water content and consequently much higher proportions of calories, carbohydrates, and other nutrients. In general, dried fruits may impact your glucose more dramatically than whole, raw fruits, so portion size is important to consider when adding sun-dried tomatoes to your plate.

Fresh vs. Canned Tomatoes

When we compare fresh and canned tomatoes, much of the nutritional content appears to be the. The key difference lies in the sodium content, which is added during the canning process.

So if you prefer using canned tomatoes over the ripe fruit, look for options that don’t have salt added during processing. The table below gives an overview of the nutritional differences between fresh and canned tomatoes.

What About Tomato Juice?

Similarly to fresh tomatoes, tomato juice has very little carbohydrate content. However, juices will almost always impact your glucose more significantly than whole fruits, so it’s best to choose whole fruit whenever possible.

You’ll also want to check the nutritional label to make sure that your serving of tomato juice is sparse in carbs and does not contain added salt.

In the table below, you can see how different methods of consuming tomatoes can affect their nutrient composition.

Tomatoes and Type 2 Diabetes

So what does this all mean for individuals with type 2 diabetes?In essence, the low carbohydrate content in fresh tomatoes suggests that these fruits shouldn’t cause a drastic increase in blood sugar. 

Some studies seem to suggest that an antioxidant called lycopene (found in tomatoes) can positively affect blood glucose levels in individuals with diabetes, however more research is still needed to determine how strong the impact is.

However, another study published in the International Journal of Food Sciences and Nutrition found that there were no significant differences in blood glucose levels among diabetic participants who consumed 200 grams of raw tomato daily for eight weeks during the study period.

Due to conflicting results across various studies, it’s hard to determine how much, if any, effect tomatoes can have on blood sugar levels. More research is still needed to determine how tomatoes may be beneficial for individuals with diabetes.

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Lycopene and Diabetes 

Tomatoes have several important nutrients, one of which is called lycopene, and has been linked to preventing chronic diseases such as cancer and cardiovascular disease.

Despites these findings, one 10-year study involving 35,783 women found little evidence for an association between tomato-based food products and the risk of type 2 diabetes.

While lycopene can be beneficial for individuals with diabetes, recent studies have yet to confirm the ability of lycopene in tomatoes to lower your risk of developing this condition. 

Antioxidant Effects of Lycopene

While there isn’t much evidence for positive glycemic effects of tomatoes, it seems they may still have some benefit for individuals with diabetes.

Some studies suggest that lycopene may reduce oxidative stress in both healthy individuals and those with diabetes, indicating that this antioxidant may improve some negative effects associated with type 2 diabetes.

Other research, however, which looked at the long-term effect of cooked tomatoes on levels of antioxidants, lipids, and glucose in the blood, concluded that while tomato lycopene may have therapeutic potential as an antioxidant, there was no significant lipid lowering effect.

Possible Link With Insulin Resistance

Tomatoes have been observed to have an anti-hyperglycemic effect in some early studies that comes from a linolenic acid derivative found in tomatoes and other foods.

The 13-oxo-OTA compound, which is found in tomatoes, Mandarin oranges, and bitter gourd, may play an important role in the management of glucose metabolism disorders, possibly via insulin resistance pathways. 

It’s also been found that the dried peels of fruits and vegetables (including tomatoes) may also have a beneficial impact on blood sugar. A study conducted on mice has shown that dried tomato peel may have a positive impact on glucose tolerance as well as on insulin resistance. 

However, as these results have still not been observed in humans, more research is still needed to confirm this link. Remember that portion sizes are important when consuming dried fruits, as they generally tend to be higher in sugar and can also lead to glucose spikes in some cases.

Other Potential Positive Effects

Apart from effects on blood sugar, tomatoes may be beneficial for reducing cardiovascular risk associated with type 2 diabetes. Tomatoes have also been shown to have anti-cancer properties, and may help support skin health and immune response.

While there may not be much direct evidence that eating tomatoes can lead to better blood glucose control, this fruit remains to be a tasty, nutritious option to add to your meals due to its low carbohydrate content and versatile flavor.

Don’t Like Tomatoes? Try These Alternatives

If you don’t like the taste or texture of tomatoes, or if you’d rather swap out tomatoes for another tasty alternative, there are a few substitutions you can add for similar flavors and health benefits.

Tamarind paste 

Tamarind paste is both sweet and sour, making it a great option for cooking. This paste can also serve as a close substitute for tomatoes in some recipes, as it’s full of antioxidants and has been found to have a positive effect on blood sugar levels.

Olives

You may try adding different varieties of olives to your cooking as a substitute for tomatoes, since they have a similar umami flavor profile. 

Olives are high in fiber, vitamin E, and can have anti-inflammatory properties, making them a great option to add to your dish.

Beetroot

Cooking beetroot until soft, and then peeling and pureeing them is a great way to get a similar consistency and color to tomatoes in your recipe. 

Beetroot is full of antioxidants, may help regulate glucose levels, and can also help lower blood pressure.

Carrots and Vinegar 

For some added zest, you can cook carrots until they soften and add a little vinegar for the consistency and tartness of tomatoes. Carrots are high in antioxidants, contain lots of vitamins, and can support healthy glucose and cholesterol levels.

Are There Possible Downsides of Eating Tomatoes?

While tomatoes are a nutritious fruit with lots of health benefits, there are a few things you may want to keep in mind when eating them.

Pesticides

Pesticides are often used in the cultivation of tomatoes and many other fruits and vegetables, which can remain on their skin after harvest. Since tomato skins are consumed along with the flesh, there is a minor risk of pesticide ingestion. 

To avoid this or minimize its occurrence, choose organically grown tomatoes and wash them well before eating.

Unripe tomatoes 

Unripe green tomatoes contain a chemical called tomatine, an alkaloid that’s mildly toxic to humans. The tomatine content in tomatoes lessens as the tomatoes mature, making red tomatoes safe to eat.

Some researchers recommend limiting green tomato intake when possible due to its potential harmful effects.