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So many factors influence how and what we eat. We eat to celebrate. We eat foods that matter to us and our cultures. We choose foods that taste good and feel good for us. Our personal health can also play a part in our decisions about what to eat.

For people with ankylosing spondylitis, there is no one best diet. But there is ongoing interest in finding out whether certain foods or ways of eating can help or make things worse.

Ankylosing spondylitis (AS) is a kind of arthritis that causes inflammation between the vertebrae in the spine.

Typically, your immune system works to target and destroy any bad guys that get into your body. This is great for fighting bacteria, viruses, and other infections. But sometimes your immune system might attack healthy parts of your body. This immune reaction can cause damage.

In AS, the damage happens mainly in the spine, but other joints and parts of the body can also be affected. AS has long been associated with gastrointestinal issues.

Studies show that many people with AS also have a vitamin D deficiency, which may worsen symptoms of this condition.

In a small 2020 study, nearly a quarter of the 118 participants with AS showed signs of iron deficiency anemia. Anemia may worsen with AS.

Research suggests that people with AS are at greater risk of inflammatory bowel disease (IBD). People with IBD are also more likely to develop AS.

Ongoing research seeks to better understand the link between different autoimmune diseases. People with one inflammatory condition seem to be more likely to develop another.

Researchers have studied changes in the levels and location of gut microbiota, looking for the key to their role in autoimmune conditions. But they haven’t yet figured out the exact basis of changes to immune function from the gut.

There is not enough evidence to recommend a specific way of eating when you have AS.

Until more research is done, we can’t say for sure which foods may help manage the condition. But some foods may play a part in reducing inflammation or preventing complications of AS.

Fruits and vegetables

If people have been nagging you to eat your vegetables for most of your life, we apologize. But veggies live up to the hype.

Studies show that diets high in fruits and vegetables may be beneficial for people with inflammatory conditions and may help reduce symptoms while improving overall health. But research in people with AS is still limited.

AS can increase the risk of heart disease, so it’s a good idea to eat in a way that keeps your heart happy. Try to eat a variety of fruits and veggies and keep it interesting by including both raw and cooked vegetables.

Calcium sources

AS can increase the risk of osteoporosis and bone fractures, especially in the spine. Over time, inflammation can cause bony growths in between the vertebrae.

To keep your bones healthy and strong, it’s important to make sure your diet includes enough calcium. If you have trouble consuming enough calcium-rich foods, you can talk with your doctor about a supplement.

Sources of calcium include:

  • milk
  • calcium-fortified orange juice or milk alternatives such as soy, almond, or oat beverages
  • yogurt
  • cheese
  • canned salmon or sardines
  • white beans, soybeans, or baked beans
  • almonds
  • tofu made with calcium

Vitamin D is another important nutrient for bone health. People with AS are at a much greater risk of vitamin D deficiency. Most will need to supplement vitamin D since there are not many food sources of this vitamin.

The recommended dose will depend on your health, your blood levels, and where in the world you live.

Healthy fats

Fats give flavor and texture to foods. They also make meals more filling. Certain types of fats, such as the unsaturated omega-3 fats concentrated in fatty fish, may help reduce inflammation in the body and improve other aspects of health as well.

Some research suggests that high dose supplementation with omega-3s may benefit those with inflammatory conditions, but research in people with AS is still limited.

Sources of unsaturated fats include:

  • fish
  • avocado and avocado oil
  • nuts, including walnuts, almonds, peanuts, and pecans
  • seeds, including sesame, hemp, and flaxseed
  • olives and olive oil
  • peanut oil

There’s not enough evidence to recommend avoiding any specific foods when you have AS.

Past studies have tried to find connections between a person’s symptoms and their diet, looking at parts of the diet such as intake of carbohydrates, fiber, and types of fats. But none of the studies could conclude that a certain way of eating would improve AS.

Findings from older studies in people with AS suggest that certain foods — such as meat, coffee, sweets, sugar, chocolate, citrus fruits, and apples — may worsen symptoms in some people.

This doesn’t mean diet doesn’t matter — it just means that there’s no research to support specific diet recommendations. Future research may find something different.

Some people with AS experience ongoing digestive symptoms like diarrhea, gas, bloating, and heartburn. Dietary changes may help reduce these symptoms.

If you’re curious about how certain foods affect how you feel, try keeping a food and symptom journal. It may help you notice some patterns.

A food and symptom journal can include details such as:

  • timing of meals and snacks
  • what you had to eat and drink
  • how you felt, including any specific symptoms
  • anything else significant from that day — sleep, stress levels, activities

Sometimes friends, family members, or people you barely know may give you unsolicited diet advice. It can be frustrating to get advice you haven’t asked for.

There doesn’t seem to be much evidence to support AS-specific diets. But here are some diets you may have heard about.

Low starch diet

Some studies have explored whether a diet low in starchy foods — like bread, potatoes, pasta, rice, and cereals — could help with AS. The theory is that a low starch diet could reduce the number of inflammatory bacteria in the gut, but research does not yet support this idea.

An ongoing clinical trial is trying to find out whether a low starch diet may be helpful for AS.

Gluten-free diet

There is interest in finding out whether people with AS do better on a gluten-free diet. As with the low starch diet, this theory is focused on how gluten may change the gut bacteria. So far, there is no evidence that a gluten-free diet is helpful.

A clinical trial is underway to look into this further.

Nightshade vegetables

Some people feel that eating fewer nightshade vegetables — like potatoes, peppers, and tomatoes — helps reduce their inflammation. But there is no evidence that these veggies make inflammation worse.

Cutting out nightshade vegetables can reduce the variety in your diet, and there’s probably no reason to avoid them.

If you take biologics to help manage AS, you know that these meds can suppress your immune system. This means food safety is extra-important.

It’s best to avoid undercooked or unpasteurized foods. Also, make sure all meat is cooked to a safe temperature, and avoid cross-contamination by using different cooking surfaces and utensils for raw foods and cooked foods.

There is no one perfect diet for all people with AS. There are many reasons why we eat the way we do, and there’s not enough evidence to recommend a specific diet to help with the symptoms of AS. Ongoing research is investigating whether a gluten-free or low starch diet may help.

If you think certain foods trigger symptoms for you, do some detective work. A food and symptom journal can help you identify patterns. A registered dietitian may be able to help you navigate food choices.