4 Potential Side Effects of Eating Too Many Flaxseeds

Flaxseeds are small, nutrient-dense seeds that contain fiber, plant protein, and heart-healthy fats. While they’re linked to multiple health benefits, research suggests that consuming them in large quantities may have some potential risks to be aware of.

1. Allergic Reaction

While a true allergic reaction to flaxseeds is relatively rare, it’s possible to develop one after consuming or coming into contact with them.

Research suggests that reports of flaxseed allergy are being documented more frequently, both after ingestion and after exposure to the skin. In some cases, this may lead to:

Severe allergic reactions, with symptoms such as difficulty breathing or swelling of the face and throat, require immediate emergency medical attention. For milder reactions, like a minor skin rash, see a healthcare provider as soon as possible.

2. Potential Toxicity

Experts recommend avoiding the consumption of raw or unripe flaxseeds, as they may contain toxic compounds.

Flaxseeds contain naturally occurring anti-nutrients and toxic compounds, including cyanogenic glycosides and phytic acids. It’s unknown if these are safe for human consumption in the long term. Some evidence warns that these toxic compounds could lead to potentially serious side effects or life-threatening health risks impacting the nervous, respiratory, and endocrine systems if consumed in large doses.

However, consuming ground flaxseed may prevent this potential toxicity, as the heating processes from roasting, boiling, or baking may inactivate these toxic compounds.

3. Drug Interactions

Flaxseeds (and flaxseed oil) have the potential to interact with certain medications, such as anticoagulant or antiplatelet drugs, both of which are used to prevent blood clotting.

Blood-thinning medications are designed to slow the blood clotting process in the body, and research shows that flaxseed contains blood-thinning properties. Mixing the two may lead to excessive bleeding or bruising.

Consult with a healthcare provider first if you’re taking any prescription medication before consuming flaxseed or flaxseed oil regularly.

4. Digestive Side Effects

While flaxseeds are a solid source of soluble and insoluble fiber, which are key for maintaining regular bowel movements and avoiding constipation, too much fiber can lead to unwanted side effects.

To avoid uncomfortable digestive symptoms like bloating, gas, stomach pain, or diarrhea, experts recommend adding flaxseed into your diet gradually and at lower doses. Consuming a large amount of fiber quickly can be rough on your digestive system if you’re not accustomed to it, and consuming higher doses of flaxseed can produce these side effects.

Flaxseed Nutritional Information

If you’re considering safely adding flaxseed into your diet, here’s how one tablespoon (tbsp) of whole flaxseeds stacks up nutritionally:

• Calories: 55
• Protein: 1.9 grams (g)
• Total fat: 4.4 g
• Carbohydrates: 3 g
• Fiber: 2.8 g
• Calcium: 26 milligrams (mg)
• Choline: 8 mg
• Magnesium: 40 mg
• Phosphorus: 66 mg
• Potassium: 84 mg
• Sodium: 3 mg
• Folate: 9 micrograms (mcg)

Tips for Consuming Flaxseeds

It’s generally safe for most healthy adults to consume flaxseeds in moderation (such as 1-2 tablespoons of ground flaxseeds per day) in the short term, or for up to six months. Some tips for incorporating these seeds into your diet and preventing any potentially serious side effects include:

• Adding flaxseeds to yogurt, cereal, smoothies, salads, soups, or using them as a substitute for breadcrumbs.
• Grinding whole flaxseeds to make a homemade flaxseed powder allows you to retain the most nutrients, rather than buying a bag at the grocery store.
• Using flaxseeds (mixed with water) as an egg substitute in baking for vegan or vegetarian diets.
• Avoiding flaxseed if you’re pregnant or breastfeeding, as there’s not enough data on how it could impact those groups.

Note that flaxseed supplements contain flaxseed oil, rather than whole flaxseeds.