Why do I feel dizzy after eating natto?

According to research, the enzyme nattokinase in natto can thin the blood and may lower blood pressure. For some individuals, this, along with other factors like histamine intolerance or a soy allergy, explains why they might feel dizzy after eating natto.

Quick Summary

Several factors can cause dizziness after consuming natto, including the blood-thinning effect of nattokinase, general post-meal low blood pressure, histamine intolerance, or a soy allergy. Managing portion size, hydration, and meal composition can help mitigate these symptoms.

Key Points

• Nattokinase Effects: The enzyme nattokinase in natto can lower blood pressure, which may cause dizziness, especially if you already have low blood pressure or are on medication.

• Postprandial Hypotension: Dizziness after a meal can be a general condition where blood pressure drops after eating, and can be exacerbated by natto.

• Histamine Intolerance: As a fermented food, natto is high in histamine, and an inability to break this down can cause symptoms like dizziness.

• Soy Allergy: Since natto is made from soy, an allergic reaction is possible and can cause dizziness, especially in severe cases.

• Management Steps: To alleviate dizziness, sit or lie down, drink water, and eat smaller, more frequent meals to prevent rapid blood pressure changes.

• Seek Medical Advice: If dizziness persists or is severe, consult a healthcare professional to rule out underlying conditions or allergies.

Understanding the Causes of Dizziness After Eating Natto

Natto, a traditional Japanese food made from fermented soybeans, is celebrated for its health benefits but can cause adverse reactions in some individuals. The sensation of feeling dizzy or lightheaded after eating natto can be unsettling, but it's often linked to several distinct physiological responses. These range from the effects of a specific enzyme in the food to more general post-meal bodily adjustments.

Nattokinase and its Effect on Blood Pressure

Natto contains a potent enzyme called nattokinase, which is a powerful agent for heart health, known for its ability to dissolve blood clots and act as a natural blood thinner. While beneficial for many, this same property can cause problems for others. For those with naturally low blood pressure (hypotension) or people on blood pressure medication, the additional blood pressure-lowering effect of nattokinase can cause blood pressure to drop too low, resulting in dizziness or fainting spells. In these cases, the effect is directly linked to natto's unique components.

Postprandial Hypotension

Postprandial hypotension is a common condition that affects many, especially older adults. It describes a drop in blood pressure that occurs after a meal. During digestion, the body diverts a significant amount of blood flow to the stomach and small intestine. Normally, the heart and blood vessels compensate by increasing heart rate and constricting vessels elsewhere to maintain overall blood pressure. If this compensatory response is inadequate, blood pressure can fall, leading to lightheadedness or dizziness. While not unique to natto, a large meal or consuming certain foods can exacerbate this effect.

Histamine Intolerance

As a fermented food, natto is a source of histamine. For people with histamine intolerance, the body struggles to break down histamine effectively, leading to a buildup that can trigger various symptoms, including dizziness, headaches, and a rapid heart rate. A histamine reaction is essentially a non-allergic sensitivity to histamine-rich foods. This condition, often linked to Mast Cell Activation Syndrome (MCAS), can cause systemic effects and is a plausible explanation for post-natto dizziness in sensitive individuals.

Soy Allergy

Natto is a soy product, and soy is a common food allergen. Allergic reactions to soy can range from mild to severe, including anaphylaxis. While abdominal pain and hives are more common, severe allergic reactions can cause a significant drop in blood pressure and lead to dizziness, confusion, and fainting. It's crucial to differentiate a true allergy, which involves an immune system response, from a digestive intolerance. A rare, delayed-onset natto allergy has also been documented, associated with prior exposure to certain marine organisms.

Reactive Hypoglycemia

Though less common with natto specifically, reactive hypoglycemia is a potential cause of dizziness after any meal. This occurs when the body over-produces insulin in response to a meal, causing blood sugar levels to drop too low after digestion. The resulting drop in glucose can lead to dizziness. While natto contains carbohydrates, this is a more likely cause when combined with high-sugar foods or in individuals with pre-existing conditions like diabetes.

Comparison of Potential Causes for Natto-Induced Dizziness

Feature	Nattokinase Effects	Postprandial Hypotension	Histamine Intolerance	Soy Allergy	Reactive Hypoglycemia
Mechanism	Blood-thinning enzyme lowers blood pressure excessively.	Blood rerouted for digestion without proper compensation.	Body cannot break down histamine from fermented food.	Immune system overreacts to soy protein.	Body produces too much insulin, dropping blood sugar.
Symptom Onset	Within hours of consumption.	30-60 minutes after eating, especially large meals.	Can vary, sometimes delayed.	Within minutes to two hours.	Up to 4 hours after eating.
Risk Factors	Pre-existing low blood pressure, taking blood pressure medication.	Older adults, high blood pressure, diabetes, Parkinson's.	Reduced DAO enzyme activity, genetic predisposition.	Confirmed soy allergy, sometimes linked to seafood exposure.	Diabetes, prediabetes, stomach surgery.
Associated Symptoms	Fainting spells.	Nausea, vision changes, chest pain.	Headaches, flushing, GI issues.	Hives, swelling, difficulty breathing.	Sweating, shakiness, anxiety.

What to Do If You Feel Dizzy After Eating Natto

If you experience dizziness after eating natto, it is important to take immediate steps to manage the symptoms and ensure your safety. Here's a helpful list of actions:

• Sit or lie down immediately: This is the most important step to prevent falling or fainting, especially during the 30-60 minute window after eating when postprandial hypotension is most likely to occur.
• Drink water: Staying well-hydrated before and during meals can increase blood volume and help counteract a drop in blood pressure.
• Rest and elevate your legs: Lying down with your legs raised above your heart can help improve blood flow to the brain.
• Eat smaller, more frequent meals: Eating large meals can trigger more pronounced blood pressure drops. Opting for smaller, more regular meals can reduce the digestive load.
• Keep a food journal: Track your meals to identify if natto or other foods consistently trigger dizziness. This can help pinpoint if it's a specific food sensitivity or a general eating pattern issue.

Prevention and Long-Term Management

For long-term management, consider these strategies:

1. Reduce Portion Size: Start with a very small amount of natto to see how your body reacts. If dizziness occurs, reduce your portion or avoid it entirely.
2. Adjust Diet: Limit the intake of high-sugar or simple carbohydrate foods with your meal. Complex carbohydrates and protein are digested more slowly and are less likely to cause a rapid blood sugar or blood pressure shift.
3. Consult a Doctor: If symptoms are persistent, severe, or accompanied by other concerns like breathing difficulties, it's essential to consult a healthcare professional. They can rule out underlying conditions like blood pressure issues, diabetes, or allergies.
4. Identify Other Sensitivities: If histamine intolerance is suspected, a low-histamine diet trial might be recommended under medical supervision.
5. Re-evaluate Medications: If you take blood pressure medication, discuss your symptoms with your doctor, as your medication or dosage might need adjustment, particularly if nattokinase is a factor.

Conclusion

Feeling dizzy after eating natto can be attributed to several factors, with nattokinase's blood-pressure-lowering effect and histamine content being common culprits. Other possibilities include general postprandial hypotension or a rarer soy allergy. Understanding the root cause is key to effective management. By implementing strategies such as eating smaller meals, staying hydrated, and consulting a healthcare professional for persistent symptoms, you can better navigate and address this unique dietary response. Ultimately, paying attention to your body's signals is the best way to enjoy natto and other fermented foods safely.

Harvard Health offers additional information on postprandial hypotension.

Frequently Asked Questions

Is it normal to feel dizzy after eating natto?

While not a universal experience, feeling dizzy after eating natto is not unheard of and can be linked to several specific factors, such as the nattokinase enzyme, histamine levels, or general post-meal blood pressure drops.

Can the nattokinase in natto cause dizziness?

Yes, nattokinase can cause dizziness. It is an enzyme that thins the blood and lowers blood pressure. For people with naturally low blood pressure or those taking blood pressure medication, this effect can be strong enough to cause dizziness or lightheadedness.

Does natto contain a lot of histamine?

As a fermented food, natto is a source of histamine. For individuals with histamine intolerance, consuming natto can lead to a buildup of histamine, which can cause symptoms including dizziness and headaches.

Can a soy allergy be the reason for dizziness after eating natto?

Yes, a soy allergy could be the cause. Natto is made from fermented soybeans, and in severe allergic reactions, a significant drop in blood pressure can occur, leading to dizziness, confusion, and fainting.

How can I prevent feeling dizzy after eating natto?

You can try eating smaller portions of natto, staying hydrated by drinking water, especially before meals, and sitting down for 30-60 minutes after eating. Eating fewer simple carbs might also help prevent blood sugar fluctuations.

Is it safe to eat natto if I'm taking blood thinners?

If you are on blood-thinning medication, you should be cautious with natto or nattokinase supplements. The enzyme has its own blood-thinning effects, and combining it with other medications could increase the risk of excessive bruising or bleeding. Always consult a doctor first.

Could it be a general post-meal blood pressure drop?

Yes, postprandial hypotension is a general condition where blood pressure drops after a meal. This occurs as blood is diverted for digestion and is more common in older adults or those with certain medical conditions, and can be influenced by the type and size of the meal.