Fibromyalgia Diet: Monosodium Glutamate & Aspartame

Do certain foods seem to make your fibromyalgia symptoms worse? What about better?

Young mother grocery shopping with little daughter and choosing for organic baby food in the supermarket
d3sign / Getty Images

A lot of people with this condition look for dietary methods to help alleviate symptoms, and you can find a lot of stories online about people who say they've gotten a lot better by eating more of X or less of Y.

But what does medical science tell us about the relationship between our diets and our symptoms? Possibly more than you think. We've learned a significant amount in recent years that can help us shape our eating habits. At the very least, current research can give us an idea of where to start looking.

Something you may want to consider is the impact of something called excitotoxins, which put your brain at risk. The two primary excitotoxins are glutamate and aspartate, which can get into your diet through monosodium glutamate and aspartame.

The Blood Brain Barrier in Fibromyalgia

Before looking at excitotoxins, it helps to understand a little bit about your brain.

Fibromyalgia is considered a neurological condition because of several known abnormalities in the central nervous system, including dysregulation of multiple chemical messengers called neurotransmitters.

When talking about the impact of food on a neurological aspect of illness, you have to consider the blood brain barrier (BBB). The job of the BBB is to keep things out of the brain that aren't supposed to be there, or that should be regulated by the brain's own systems rather than subject to what's going on in the rest of the body.

Theoretically, the food you eat should have a relatively small impact on the brain. However, because of a known aspect of fibromyalgia, our brains may be especially vulnerable to diet.

In your cells, there's something called substance P. Its job is to send pain messages from the cells to your brain. People with fibromyalgia have been found to have about three times more substance P than other people.

And here's the important thing about substance P: Research shows that it makes the BBB more permeable, so things may slip through that normally wouldn't—and shouldn't.

Monosodium Glutamate and Aspartame in Fibromyalgia

So far, we don't have conclusive evidence that any one particular thing is bad for everyone with fibromyalgia. What we do have is a growing knowledge of the condition and how certain substances may interact with it.

Much of the research focus has been on a couple of food additives:

  1. Monosodium glutamate (MSG)
  2. Aspartame

MSG is a common food additive that enhances flavors. It's also a naturally occurring amino acid. The second word in its name—glutamate—is the possible problem.

In your central nervous system, glutamate is a neurotransmitter (chemical messenger). It has the important job of exciting neurons (brain cells), which helps you focus and learn new information. However, too much excitement is a bad thing for neurons.

If you've got too much glutamate, it'll keep exciting the neurons until it kills them. It does this by acting on a part of the cell called an NMDA receptor, which is believed to be involved in both pain and depression.

Aspartame is a sugar substitute marketed as NutriSweet and Equal, among other names. When your body breaks it down, one of the products you're left with is aspartate, which also stimulates (and can toxically over-stimulate) the NMDA receptor. (Aspartate is a natural part of many foods, and it's unclear whether aspartame-derived aspartate acts differently in your body than aspartate found in regular foods.)

For this reason, glutamate and aspartame are called excitotoxins. Unlike other cells in your body, neurons aren't replaceable—your body can't make new ones to replace those that die.

Fibromyalgia is believed to include higher-than-normal levels of glutamate in some regions of the brain. But is it possible that dietary glutamate and aspartate contribute to this high level or make it worse?

In a healthy person, the BBB should keep these things out of the brain, but with a potentially compromised BBB, they may very well creep in.

In 2016, the journal Pain Management published a review of studies on fibromyalgia and diet. The review cites multiple studies that show a link between glutamate/aspartate and pain as well as research showing high glutamate levels in the brain and cerebrospinal fluid.

Several studies have examined the role of glutamate, aspartame, and other excitotoxins in the diet. Most have found that eliminating them helped alleviate symptoms, while adding them back in increased symptoms. A few people were noted to have recovered completely simply because of this dietary change.

One study, published in Rheumatology International, found no correlation, but its participants eliminated only MSG and aspartame, meaning they may still have been eating other excitotoxins.

Eliminating Excitotoxins

The Pain Management review states that the only way to know whether you have a problem with excitotoxins in your diet is by completely cutting them out. That generally means eating whole foods and avoiding anything with additives.

Watch for aspartame in any products that are called:

  • Diet
  • Sugar-free
  • Reduced-calorie

Aspartame may also be in less obvious places, such as:

  • Yogurt
  • Cereal
  • Bread

When MSG is added to food, it has to be listed as an ingredient. However, glutamate is naturally occurring in some foods, including:

  • Soy sauce
  • Fish sauces
  • Worcestershire sauce
  • Aged cheeses such as sharp cheddar and parmesan
  • Gelatin
  • Hydrolyzed protein
  • Autolyzed yeast extract
  • Protein concentrates
  • Protein isolates

Other potentially problematic ingredients include non-specific ingredients that may include MSG, such as:

  • Spices
  • Seasoning
  • Flavoring
  • Natural flavoring

The review suggests only using only table sugar or honey as a sweetener while testing an excitotoxin-free diet. It says most study participants have seen a difference in how they feel after a week or less but recommends a one-month testing period.

Micronutrients: Fighting Excitotoxins

Some micronutrients can block or lessen the effects of excitotoxins. Increasing them in your diet or taking them as supplements may help prevent the damage they can do.

These include:

Most of these nutrients have been studied for fibromyalgia and been found to be at least somewhat effective at alleviating symptoms. If you're interested in taking them, be sure to discuss this with your physician—too much of some of these supplements, like Vitamin E and B6, can cause toxicity.

Starting an Anti-Excitotoxin Diet

Before you add supplements or try an excitotoxin-elimination diet, be sure to talk to your healthcare provider. Testing for nutritional deficiencies may help you identify the most important supplements or foods to add. Be sure to discuss your overall health and dietary needs so you can safely approach the changes you want to make.

Until you're familiar with what foods contain excitotoxins, it may help to have a list printed out or saved on your smart device so that you can reference it at the grocery store. Be sure to educate anyone who shops or prepares food for you as well.

It's hard to know exactly what you're eating at a restaurant, so you may want to stick to home-prepared meals during your testing period.

Keep in mind that dietary changes aren't likely to take away all of your symptoms, and it may take time to see any results.

A Word From Verywell

An elimination diet like this isn't easy. It takes a lot of planning, thought, and changes to the way you cook. When you're struggling with chronic pain, fatigue, and cognitive dysfunction, it can seem insurmountable.

Try to keep in mind the diet is a temporary process that could help you feel a lot better in the long run. If possible, recruit family members or friends to help you so that you don't fall back on convenience foods on bad days.

And if you slip up and eat some things you shouldn't? Don't beat yourself up. Consider it an opportunity to see how those foods made you feel, and try to be better about it tomorrow.

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

By Adrienne Dellwo
Adrienne Dellwo is an experienced journalist who was diagnosed with fibromyalgia and has written extensively on the topic.