How do plant-based diets impact glucose levels?

This article describes how to optimize your glucose levels while on a plant-based diets using a continuous glucose monitor (CGM).


Article highlights

  • Plant-based diets have surged in popularity, but their impact on glucose levels differs person to person, so testing with CGMs is key to optimizing metabolic health.
  • Smaller portions of grains and starchy vegetables can help minimize glucose spikes from plant foods.
  • Cutting out refined sugars and grains prevents glucose spikes; even "healthy" foods can have added sugars.
  • Adding fat and protein to carbs helps blunt glucose spikes, so pair fruit with nuts or nut butter.
  • Testing your personalized responses to specific plant foods with a CGM rather than relying on general advice allows you to craft the optimal plant-based diet.

Being able to walk down your local supermarket and fill your cart with cashew-based ice cream, gluten-free, vegan pizza, almond milk, and “meatless” meat a decade ago wasn’t very likely.

Today, it’s reality. Plant-based diets and their many variations have grown significantly in popularity over the past decade– and for good reason.

Market research company Mintel found that 31% of Americans practice meat-free days, and 58% of adults drink non-dairy milk. In response, many national chains have started to offer plant-based alternatives.

The wide variety of publicly available options have encouraged even more people to explore the many wonderful options available. Google Trends notes that the query for “plant-based” and many of its variations hit a peak in January 2020, supporting the notion that people are more curious about plant-based diets than ever before.

“The truth is, we don’t need any added sugars in our diet for health, and certainly not if we are striving for improved metabolic fitness.”

Why? Many people are in pursuit of a more functional and healthier lifestyle. A report by International Food Consultants Baum + Whiteman notes that about 83 percent of U.S. consumers studied started incorporating plant-based foods into their diets to improve their health and nutrition, while 62 percent do so specifically for weight management.

Whether you’re plant-based, vegetarian, pescatarian, or flexitarian, it’s important to take a peek “under the hood.” Your metabolic awareness can start with something as simple as using a continuous glucose monitor to understand how your unique body responds to food.

Better yet, you can fine-tune your plant-based diet to get more balanced glucose levels, which is an essential step in the pursuit of a personalized optimal diet. While a diet rich in plant foods is associated with longevity and reduced risk of many diseases, it can be an extra benefit to know the plant foods you’re choosing aren’t causing an unforeseen glucose spike. What might a CGM-informed plant-based diet look like?

Let’s explore.

What does it mean to be “plant-based”

Let’s settle on what we mean by plant-based to avoid any confusion.

Plant-based diets focus on foods derived from plants, but you don’t need to go to Harvard to guess that much. That means grains (oats, barley, quinoa), vegetables, legumes, nuts, seeds, fruits, spices, and herbs are good to go.

However, just because it’s plant-based doesn’t mean it’s necessarily ideal for glucose levels or overall health though; these diets can still include refined sugar, ultra-processed grains, refined vegetable oils, and other additives. What’s more, everyone responds differently to carbohydrates, so while a potato might cause a huge glucose spike in one individual, it may have very little effect on another. This is important information to know.

With a plant-based diet, animal products such as eggs, milk, cheese, and meat are off the list.

How do plant-based diets impact glucose levels?

Plant-based diets can impact everyone differently, as everyone is unique and will have a different glucose response to every food type. What spikes Person A’s glucose levels could have a minimal effect on Person B’s.

Some people fear that plant-based diets will actually worsen metabolic function because low-carb protein sources like meat and cheese may be replaced by higher-carbohydrate grains, starchy vegetables, and fruits. However, given that everyone processes food differently, it’s impossible to know how particular foods affect your glucose levels unless you test. The key is crafting a comprehensive diet plan and combining food and lifestyle activities to ensure the glucose levels stay as stable and healthy as possible. This process of crafting a diet to be most metabolically friendly is especially simple with glucose monitoring to guide you.

How to optimize your glucose levels with plant-based diets

Test out smaller serving sizes

Consuming extra-large portions of anything with significant carbohydrate content is likely to spike your glucose levels more than a standard or smaller serving size, regardless of whether those carbs are coming from something plant-based or not.

Smaller portion sizes are a simple way to see how your body responds to a fixed amount of carbohydrates– plant-based or not.

Cut out refined grains and sugars

Generally speaking, any food in its unrefined form will cause less of a glucose spike. In studies that have compared eating the same caloric amount of whole grains (least processed), coarse flour (more processed), and fine flour (most processed), they have found a linear increase in glucose and insulin elevation as the grain becomes more processed.

If a nutritional label has a non-zero value next to “Added sugars,” it’s not an ideal choice for optimizing metabolic fitness. Even innocuous items like protein bars can have as much as 15 or more grams of “added sugar.” Additionally, products labeled “low-sugar” or ”low glycemic” can still be full of added sugars. The truth is, we don’t need any added sugars in our diet for health, and certainly not if we are striving for improved metabolic fitness. These added sugars can be in obvious foods like soda and candy bars but can also be in less obvious foods like ketchup, salad dressing, and pasta sauces.

People have reported that grain-rich diets tend to spike their glucose significantly. So, if you’d like to put this to the test, try eliminating or limiting your consumption of rice, rye, quinoa, oats, millet, corn, bulgur, buckwheat, or barley. To test the impact, see how your body responds to 50g of each individual grain and track your glucose levels from fasting levels to the peak.

Test out starchy vegetables like potatoes, yams, and squash to see how you respond

The same logic above applies here. Sweet potatoes and squash are fairly carbohydrate-dense and can spike glucose levels, so try them out and monitor your glucose levels. Some research shows that cooling and reheating starchy vegetables can minimize their glycemic impact by increasing resistant starch concentrations.

Consider adding fat and protein to fruit

Fruits contain sugar, so it’s possible that certain fruits can cause a high glucose elevation. Try different fruits out and see how different varieties affect your levels. You can also experiment with adding fat and protein to the fruit to minimize the glucose spike, with additions like nut butters and chia seeds.

In one study, consumption of 23 grams of protein and 17 grams of fat 25-30 minutes before carbohydrate ingestion significantly decreased post-meal glucose elevation in nondiabetic individuals and those with insulin resistance.

Similarly, eating fat alone in conjunction with a carbohydrate load will decrease the post-meal glucose spike. Research shows that eating 3 ounces of almonds with a meal of carbohydrate-rich food leads to significantly lower post-meal glucose spikes than when a carb source is eaten alone. Similar trends were seen when participants were served 1 and 2 ounces of almonds, but the biggest effects were seen with 3 ounces of almonds (~40g of fat).

Additionally, you can experiment with lower-sugar fruits. For example, a single mango has 45 grams of sugar per fruit– more than 2 full peaches, an orange, and 100 grams of blackberries combined.

  • Strawberries: only about 8 grams of sugar in 8 medium-sized strawberries
  • Peaches: around 13 grams of sugar in a medium-sized peach.
  • Blackberries: between 4 to 5 grams of sugar per 100 grams
  • Lemons and limes: you’re probably not likely going to take a bite out of a lemon or lime anytime soon. With only 2 grams of sugar per fruit, lemons and limes give you a pretty big flavor for glucose level bang for your buck. Simply add lemon or lime into sparkling water or over a salad to get some extra flavor.
  • Honeydew melon: a slice of honeydew melon has around 11 grams of digestible sugar.
  • Orange: a medium-sized orange has about 14 grams of digestible sugar.
  • Grapefruit: half a medium-sized grapefruit has about 11 grams of sugar.
  • Avocados: Ha, bet you thought this was a vegetable! These low-sugar high-healthy fat treats are actually fruits and are nearly sugar-free.

Many Levels customers have also found that eating fruit with fat (almond butter or tahini drizzled on top, or fruit in a chia pudding) has minimized their glucose spikes.

Final Thoughts – Finding how your body responds to foods

Swapping out high-glycemic foods with low-glycemic alternatives will generally help lower glucose levels, but what works for someone else might have a different effect on you.

For example, some people may say that corn, beets, and excessive carrot consumption spikes them, whereas others note minimal impact.

There are many ways to lower glucose easily by making small changes in lifestyle, but it all depends on your individual unique responses. The objective data provided by continuous glucose monitors can take out much of the guesswork from the glucose spike equation.

It’s important to keep in mind that being conscious of your glucose levels shouldn’t be viewed as a limitation in your dieting. Building your metabolic awareness can help structure your eating habits so you can eat more of what you want and still stay within the metabolic health range.