Soy milk doesn’t cause brain fog on its own. But if you have an allergy or sensitivity, consuming soy may cause symptoms that include brain fog. You can also develop brain fog for other reasons.
Brain fog can have various causes. But drinking soy milk isn’t likely to cause brain fog unless you have an allergy or sensitivity to it.
Brain fog isn’t a medical diagnosis but rather a colloquial term that typically describes symptoms that can include:
- difficulty concentrating
- difficulty thinking
- forgetfulness
- confusion
It can result from certain health conditions and allergies.
Keep reading to learn about the effect of soy allergies or sensitivities on brain fog, whether phytoestrogens in soy may play a role, and other causes of brain fog.
Soy allergies are common in both adults and infants. If you’re allergic to soy and consume it, you may experience symptoms of an allergic reaction. These commonly include:
- abdominal pain
- diarrhea
- nausea and vomiting
- indigestion
- runny nose
- wheezing or trouble breathing
- itchy mouth
- swelling
- confusion
- hives
A severe allergic reaction can lead to anaphylactic shock, which is a life threatening emergency.
It’s possible that some allergies can cause brain fog.
Rhinosinusitis, a common symptom of seasonal allergies, can cause brain alterations that may result in symptoms of brain fog, according to 2021 research. The researchers also pointed out that worsening rhinosinusitis was also associated with other neurological symptoms, including:
- cognitive deficits
- mood changes
- memory issues
- trouble focusing
- worse school performance
- anxiety
- depression
A 2019 review of animal studies suggested that allergies can cause inflammation in certain brain pathways. This inflammation may lead to motor and learning deficits, according to researchers. However, this study was performed in mice. Research in humans on the neurological impacts of soy allergy is still needed.
It’s also important to note that soy milk can contain ingredients other than soy, including additives like emulsifiers. If you experience symptoms after drinking soy milk but not after eating soybeans, it’s possible that another ingredient may be responsible.
If you think you may be allergic to soy or another additive in soy milk, it’s best to talk with an allergist to get an allergy test.
While there isn’t much research on soy sensitivities and intolerances and resulting brain fog, some research suggests that sensitivities to other foods, including gluten, may cause brain fog.
A 2020 proof-of-concept pilot study surveyed people with non-celiac gluten sensitivity and found that many of them experienced headaches and brain fog after consuming gluten.
It’s possible that sensitivity to another food, such as soy, may cause similar symptoms. However, research on this topic is still needed.
If you think eating soy is causing brain fog, it may help to keep a food journal in which you note all of your symptoms and how long after consuming soy you experienced them. You may also decide to avoid soy for a while to determine if that stops your symptoms.
Learn about the differences between food sensitivities, intolerances, and allergies.
Soy has a high concentration of isoflavones, a type of phytoestrogen. Phytoestrogens are plant compounds with chemical structures similar to estrogen, though with a much weaker effect. They’re also antioxidants and can provide some health benefits. They may also support improved brain health.
A 2022 study of phytoestrogen intake among older adults in Sicily suggested that a higher intake of phytoestrogens, especially isoflavones, which are common in soy, lentils, and legumes, was associated with better cognitive status.
The researchers noted that the intake of two specific phytoestrogens, daidzein, and genistein (the main isoflavones in soy), was significantly associated with better cognitive status.
You can develop brain fog in response to many different health conditions.
Brain fog can result from:
- seasonal allergies
- infections, including
- COVID-19 and long COVID
- Lyme disease
- meningitis, encephalitis, and cholangitis
- urinary tract infection (UTI)
- pneumonia
- lack of sleep
- stress and anxiety
- depression
- overworking
- certain medications
- nutritional deficiencies
- hormonal changes, such as during menopause
- chronic pain
- substance use
- stopping substance use
- brain tumor
If you aren’t sure what’s causing your symptoms, it’s worth noting when they appear and talking with a doctor to rule out potential causes. Sometimes, identifying the cause can help prevent future episodes and open up opportunities for treatment.
Read about remedies for brain fog.
Soy milk is unlikely to cause brain fog in people who are not allergic to it. It’s also possible that a food sensitivity to soy could potentially cause brain fog.
Brain fog can also result from other health conditions, including COVID-19 and nutritional deficiencies.
If you aren’t sure why you have brain fog, it’s best to talk with a doctor to determine the cause and best course of treatment.
