|March 11, 2024

The Complete Bulletproof Guide to Gluten and Grains

By Bulletproof Staff
Reviewed by Theresa Greenwell for Scientific Accuracy on 02/20/2024

The Complete Bulletproof Guide to Gluten and Grains
  • Many types of grains cause inflammation for gluten-sensitive and celiac people.
  • Does rice have gluten? Is oatmeal gluten-free? Discover which grains you should avoid if you have a gluten sensitivity.
  • Besides gluten, many grains contain mold and pesticides that are detrimental to your health.

The Bulletproof Diet doesn’t include a lot of grains. Why? Grains do not always contribute to healthy eating, and many have a high carb content. That said, not all grains are created equal.

There is a vast difference in nutritional value between whole grains and refined grains. Whole grains offer health benefits like micronutrients, dietary fiber and phytochemicals.[1] Examples of whole grains include barley, farro, quinoa, brown rice and bulgur. By comparison, refined grains, like white rice, white flour and white bread, don’t offer as many nutrients for your body to use.[2]

Here’s an in-depth breakdown of how gluten and grains affect your biology based on scientific evidence. Have a read-through to help you decide if foods that contain gluten are right for you.

Phytic acid keeps you from absorbing nutrients

Many grains contain phytic acid, a natural compound in food also known as an “anti-nutrient.” When you eat phytic acid-rich foods, it can bind to minerals in the digestive tract, forming phytate complexes. This binding process can reduce the bioavailability of these minerals, making them harder for your body to absorb. And so, you may not be getting as much iron, zinc and calcium from the grains you eat.[3]

The phytic acid will also bind to those three nutrients in any other veggies you eat alongside grains. Brown rice, wild rice and whole wheat have high levels of phytic acid. Brazil nuts and almonds are high in it, too.

You may run into nutrient deficiencies if you eat phytic acid-rich foods with most of your meals.[4] Phytic acid is also a bigger concern for vegetarians – it binds to iron and zinc in other vegetables, but not the forms in meat. So, if you do eat something high in phytic acid, pair it with grass-fed beef or another high-quality meat if your diet allows.

If you do eat foods rich in phytic acid, cooking, sprouting, fermenting, pickling or soaking overnight in water can help break it down. Another way to limit phytic acid foods in your diet is by avoiding eating large quantities in one sitting. For example, instead of eating two cups of quinoa for lunch, swap one cup of grain with a cup of cooked vegetables.

Phytic acid does have some redeeming qualities. It has proven beneficial effects on human health as a source of antioxidants, for example.[5] But you can get antioxidants from many other sources that don’t interfere with nutrient absorption, like colorful veggies.


When food passes through your GI tract, it bumps against the lining of your gut and causes minor damage. Usually, your cells repair things before the damage can cause any problems. Your gut stays sealed and intact.

Lectins interfere with that process. They’re sticky proteins that bind to the lining of your gut and prevent that routine healing process.[6] The damage leads to low-grade intestinal distress. This may explain why undercooked beans and grains, both high in lectins, cause digestive discomfort for so many people.[7]

Limited animal studies suggest that lectins may contribute to gut permeability.[8] But these studies use raw legumes (which we rarely consume) or isolated lectins. Properly cooking food containing lectins reduces the lectin activity and makes it safe to eat.[9]

Lectin sensitivity varies between individuals. Some people can eat lectins and never see a problem. Others run into inflammation, acne, joint pain and stomach issues.[10] If you’re curious about your own sensitivity, try eating lectin-filled nightshade vegetables in isolation. For example, sample some tomatoes, eggplant or peppers on their own. Then, see how you feel afterward.

Gluten, agglutinin, and other grain proteins

Gluten is a popular topic in the nutrition world these days. People diagnosed with celiac disease have an autoimmune disorder triggered by consuming gluten. They can manage their condition by cutting gluten from their diets. But is there such a thing as gluten sensitivity?

Gluten sensitivity, also known as non-celiac gluten sensitivity (NCGS), is a condition in which individuals experience symptoms like those of celiac disease when consuming gluten, but without the autoimmune response and damage to the small intestine seen in celiac disease. The diagnosis is relatively new and somewhat controversial, as it lacks specific biomarkers and diagnostic tests.[11]

Some researchers say gluten itself causes inflammation and intestinal damage in non-celiac people.[12] Others say it’s the short-chain fermentable carbs in wheat causing gut issues and that gluten is a scapegoat.[13] Or it could be agglutinin, a part of wheat germ that triggers inflammation.[14]

Or, according to the very latest research, it could be amylase-trypsin inhibitors. These are proteins that contribute to allergies, asthma, irritable bowel syndrome and arthritis.[15]

Researchers don’t agree on how gluten affects your gut. But during the past few years, more people have chosen a gluten-free diet to counter health-related concerns. For some, gluten may cause fatigue, bloating and digestive issues.[16] Cutting out grain can help avoid these side effects.

Grains get moldy

Grain crops can have problems with mold.[17] Mold produces mycotoxins, which are poisonous substances of which the worst ones are aflatoxins. Aflatoxins have been linked to many human diseases throughout the world.[18] Aflatoxins are considered unavoidable contaminants of grains. Countries try to limit aflatoxins by regulating and monitoring their presence in food.

The United States has the most severe mycotoxin contamination on the planet. Here’s a map of mycotoxin contamination in crops, courtesy of agricultural research company Biomin[19]:


On top of that, the United States still uses pesticides that have been banned by the European Union, Brazil and China.[20] These products don’t even mean lower mold levels. We also have the worst mycotoxin regulations of any developed country. Corn and wheat are some of the most susceptible crops.[21]

In other words, American-grown grains are often moldy and likely to be contaminated with pesticides. Not the ideal addition to your health-conscious lifestyle.

Grains spike your insulin levels and cause fat gain

Grains are carb heavy. Whole grain or refined, the carbs you eat will turn into glucose. Your body will store a certain amount as glycogen, but the rest you’ll store as fat. The carbs will also cause your insulin to spike and fall.[22] You may feel hungry every few hours, crave sugar and, if you eat too much, put on some extra weight.[23]

A high-fat, low-carb diet, on the other hand, will give you steady energy for hours while training your body to burn fat.[24] That’s one of the pillars of the Bulletproof Diet (download the Bulletproof Diet Roadmap for free).

That’s not to say you should never eat grains. The Bulletproof Diet recommends a higher-carb day about once a week. If you tolerate them, certain grains can be a good way to get your carbs. Here’s our ranking of individual types of grains, based on best to worst.

White rice

Does rice have gluten? Rice is gluten-free and a good source of carbs. It’s almost pure starch, but there are few nutrients.

Long-grain white rice comes in at about 55 on the glycemic index (table sugar is 100), so it won’t cause your blood sugar to spike much. Short-grain white rice has a higher glycemic rating of about 72. Whichever you choose, you can upgrade the starch in your rice (and make it low carb) by cooking it with coconut oil. Rice is also resistant to mold.

The only issue with rice is that it contains some arsenic, which it absorbed from the soil it grew in. To flush out the arsenic from your rice, rinse it with warm water until the water runs clear.[25] You can cook it with extra water and pour the excess off at the end to decrease the arsenic even more.

Whole grain rice

Whole grain rice has lectins and trypsin inhibitors, but they aren’t heat-stable. By cooking your rice, you can deactivate most of them. Heat won’t get rid of nutrient-sapping phytic acid, though, and whole-grain rice has a lot of it.

Whole grain rice has much more arsenic than white rice, so be sure you rinse it until the water runs clear before cooking.


Quinoa is unusual. It’s a seed, not a grain, and it’s a complete protein, which is rare for a plant. A cup of quinoa has about 39 grams of carbs[26], so eat it in moderation if you’re on a low-carb diet.

It also has prolamins, which may cause issues for people who are sensitive to gluten. But some people with celiac disease can tolerate quinoa.[27] Try it in small quantities and see how you feel afterwards.


Buckwheat is another seed that behaves like a grain. It’s like quinoa in that it has gluten-like prolamin and is high in carbs. But it doesn’t have the complete protein quinoa does.

Oats (gluten free)

If you enjoy oatmeal for breakfast, you may be wondering if oatmeal is gluten-free. The answer is yes.

While all oats are gluten-free, a lot of oats grow next to or on the same land as gluten-containing wheat, rye and barley, and end up contaminated. Gluten-free oats have their own dedicated fields, so if you have a gluten sensitivity, choose these.

Oats may not have gluten, but they do have a similar protein called avenin that can damage your intestinal lining if you’re sensitive to it.[28] Whole-grain oats have a moderate amount of phytic acid and instant oats have a high glycemic index (80). Oat plants are also susceptible to mold.


Rye contains gluten. It’s not as damaging as wheat gluten, but it will still trigger a reaction in you if you’re celiac or sensitive to gluten. Rye also has its own form of agglutinin, the protein that may contribute to digestive issues.[29] Rye also tends to grow mold.

On top of that, rye bread usually has a 2:1 ratio of wheat flour to rye flour. It’s rare that you’d ever eat pure rye without wheat.


As with most other grains on this list, corn contains a gluten-like protein that can damage your gut lining. Corn’s version is called zein. Corn is one of the most genetically modified plants around[30], and it holds a heavy pesticide load.[31]

It’s also often high in mold and mycotoxins.[32] If you do decide to have some corn on occasion, make sure it’s organic.


Then there’s wheat.

Wheat is the worst offender, and not only because of its gluten content. It contains inflammatory agglutinin. It also has FODMAPs, which are sugars that feed bad gut bacteria. Additionally, it contains allergy-inducing amylase-trypsin inhibitors, nutrient-blocking phytic acid and heat-stable lectins that don’t break down when you cook them.

And it gets moldy. Wheat is also susceptible to ochratoxin A, a mold toxin that causes kidney damage in animals.[33] Plus, wheat is high in pesticides.[34]

If you are craving bread, try baking one of our best keto bread recipes. You can enjoy your toast and stay on track with your low-carb diet.

There you have it. By and large, many types of grains don’t have to be a central part of your diet, especially as foods that cause inflammation. Flip the food pyramid on its head. Get most of your calories from quality fats. Load up on organic veggies. Add some wild-caught fish or grass-fed meat. Have a sweet potato now and then.

Fuel your body with good food and it will start working with you, not against you. Need inspiration? Check out our free list of which foods to eat and which to avoid.

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