Over the last couple of years, certain seeds have come to be seen as superfoods. Chia and flax seeds are two well-known examples.

Both are incredibly rich in nutrients, and both have been linked to health benefits such as a healthier heart, lower blood sugar levels and protection against certain types of cancers (1, 2).

But many people wonder which of the two seeds is actually the healthiest. This article looks at the science-based evidence behind each to answer this question.

What’s the Difference Between Chia Seeds and Flax Seeds?

Chia seeds are little, oval-shaped seeds originating from the Salvia hispanica plant, more commonly known as the chia plant. They are sometimes called salba seeds, are usually bought whole and come in black or white varieties.

Chia seeds are native to Mexico and Guatemala, and were likely used as a staple food in ancient Aztec and Mayan diets (3).

In comparison, flax seeds are flatter and slightly bigger than chia seeds. Also known as linseeds, they are generally brown or golden, can be bought whole or ground and are thought to originate from the Middle East.

Chia seeds taste pretty bland, whereas flax seeds have a slightly nuttier flavor. However, both seeds are easily incorporated into a variety of dishes.

Summary: Both chia and flax are types of seeds. Chia seeds are smaller and blander tasting, whereas flax seeds are larger and nuttier in flavor.

Nutrition Comparison

Both chia and flax seeds are rich in a variety of nutrients.

This table compares the two, listing the amounts of major nutrients per 1-ounce (28-gram) portion, or around 3 tablespoons (4, 5, 6).

Flax seedsChia seeds
Carbs8 grams12 grams
Fiber8 grams11 grams
Protein5 grams4 grams
Fat12 grams9 grams
Omega-3 fatty acids6,400 mg4,900 mg
Omega-6 fatty acids1,700 mg1,600 mg
Manganese35% of the RDI30% of the RDI
Thiamine31% of the RDI11% of the RDI
Magnesium27% of the RDI30% of the RDI
Phosphorus18% of the RDI27% of the RDI
Copper17% of the RDI3% of the RDI
Selenium10% of the RDI22% of the RDI
Iron9% of the RDI12% of the RDI
Zinc8% of the RDI7% of the RDI
Calcium7% of the RDI18% of the RDI
Potassium7% of the RDI1% of the RDI

As you can see, both seeds contain a good amount of protein and omega-3 fats, although flax seeds have a slight upper hand when it comes to these two nutrients.

Flax seeds also contain significantly more manganese, copper and potassium.

Chia seeds contain slightly fewer calories and more fiber. They also contain 1.5–2 times more of the bone-strengthening minerals calcium and phosphorus, as well as slightly more iron.

Summary: Both seeds are very nutritious. If you’re looking for the most omega-3s, pick flax seeds. If you’re seeking the highest amount of fiber and bone-strengthening minerals, opt for chia seeds.

Both May Lower the Risk of Heart Disease

Both chia and flax seeds contain good amounts of alpha-linolenic acid (ALA), a type of plant-based omega-3 fat.

ALA is considered essential because it’s a type of fat that your body cannot produce. This means that you can only get it through your diet.

Interestingly, several studies have linked ALA to a lower risk of heart disease (7).

For instance, one large review of 27 studies observed that high ALA intakes may be linked to as much as a 14% lower risk of heart disease (8).

Another study of 3,638 people in Costa Rica reported that those who consumed the most ALA also had a 39% lower risk of heart attacks compared to those who consumed the least.

According to the researchers, the lowest risk of heart attacks was seen at intakes of around 1.8 grams of ALA per day (9).

Several studies have also looked at the benefits of flax or chia seeds on blood pressure and cholesterol levels, two risk factors for heart disease.

Eating around 1 ounce (35 grams) of chia seeds and chia flour per day may lower blood pressure by 3–6 mm Hg in people with diabetes, and by up to 11 mm Hg for those with high blood pressure (10, 11).

Similarly, eating around 1 ounce (about 30 grams) of flax seeds per day may help reduce blood pressure by 7–10 mm Hg in the general population, and by as much as 15 mm Hg in participants with high blood pressure (12).

Other studies have shown that flax seed-enriched diets reduced levels of “bad” LDL cholesterol by up to 18%, and triglyceride levels by up to 11% (13, 14).

Only a handful of studies have examined the effect of chia seeds on blood cholesterol levels, most of which have failed to report any cholesterol-lowering benefits (15, 16, 17).

That said, chia seeds contain just slightly less ALA than flax seeds, so they may be expected to have similar heart-protective effects. Therefore, more studies may simply be needed to confirm this effect.

It’s worth noting that, due to their high omega-3 content, both flax and chia may have blood-thinning effects. Individuals on blood-thinners should consult their doctors before adding large amounts of these seeds to their diets (18, 19, 20).

Summary: Both chia and flax seem to have benefits for reducing blood pressure. They may also have similar cholesterol-lowering properties, although more studies on chia seeds are needed.

Both Help Lower Blood Sugar Levels

Both flax and chia seeds contain good amounts of fiber, which has been linked to a lower risk of developing type 2 diabetes (21, 22, 23).

Fiber helps guard against type 2 diabetes by slowing down how fast carbs are digested and how quickly sugar is absorbed into the blood. This leads to a more gradual rise in blood sugar levels after a meal (24).

In other words, fiber helps prevent blood sugar spikes. This stabilizes blood sugar levels and offers some protection against type 2 diabetes. In fact, several studies have linked regularly eating flax and chia seeds to this protective effect.

For instance, studies in people with type 2 diabetes report that taking 1–2 tablespoons of flax seed powder per day may reduce fasting blood sugar by 8–20%. These effects were seen after as little as one to two months (25, 26).

Similarly, animal studies show that chia seeds may help stabilize blood sugar levels and reduce insulin resistance, both of which may help reduce the risk of developing type 2 diabetes (27, 28, 29, 30).

Human studies have also found that eating bread made with chia seeds may lead to smaller spikes in blood sugar than eating more traditional breads (31, 32).

Chia seed intake was also more effective than wheat bran, another fiber-rich food, at reducing levels of hemoglobin A1C — a marker of blood sugar control (10).

Summary: Eating either flax or chia seeds each day appears to help lower blood sugar levels.

Flax Seeds May Be Slightly More Effective at Reducing the Risk of Certain Cancers

Both chia and flax seeds may help protect you against cancer in several ways.

For starters, they’re both rich in fiber, a nutrient generally linked to a lower risk of certain types of cancers (33).

Insoluble fiber, the predominant type in both chia and flax seeds, may be linked to a lower likelihood of developing colon or breast cancer (21, 34, 35, 36).

Both seeds also contain antioxidants, which help the body reduce its levels of free radicals. Free radicals are cell-damaging molecules that can contribute to aging and diseases such as cancer (1, 37, 38).

However, when it comes to antioxidant levels, flax seeds may have the upper hand. That’s because they contain up to 15 times higher levels of lignans, a specific type of cancer-fighting antioxidant, compared to chia seeds (39).

For this reason, flax seeds may be slightly more effective than chia seeds at preventing cancers from developing.

Several observational studies support the notion that eating flax seeds on a regular basis can lower the risk of developing certain cancers.

For instance, one review found a link between the antioxidants found in flax seeds and a lower risk of breast cancer, especially in postmenopausal women (40).

Furthermore, one study in over 6,000 women reported that eating flax seeds regularly appeared to reduce the risk of developing breast cancer by up to 18% (41).

A small study in men observed that those given around 1 ounce (30 grams) of ground flax seeds each day, as part of a low-fat diet, had lower prostate cancer markers. This may suggest a reduced risk of prostate cancer (42).

Few studies have looked at the effects of chia seeds on the risk of cancer. Due to their lower antioxidant levels, chia seeds may be slightly less effective than flax at guarding against cancer.

However, more studies are needed before strong conclusions can be made.

Summary: Both chia and flax seeds are good sources of fiber, which may reduce the risk of certain cancers. However, flax seeds contain significantly higher levels of cancer-fighting antioxidants, giving them a slight upper hand.

Flax Seeds May Be Slightly More Effective at Reducing Hunger and Appetite

Chia seeds and flax seeds are both great sources of fiber, which can help reduce hunger and cravings (42, 43).

However, they contain different levels of soluble fiber, a type particularly effective at reducing hunger and controlling appetite.

Soluble fiber tends to become sticky when mixed with water, slowing down digestion and increasing feelings of fullness.

This type of fiber is also known to trigger hormones involved in controlling hunger, which may further reduce appetite (42, 44).

Up to 40% of the fiber from flax is soluble. In contrast, only 5% of the total fiber in chia is soluble. For this reason, flax seeds may be slightly more effective at reducing hunger and appetite than chia seeds (21, 36).

In one study, participants given a drink containing the amount of soluble fiber found in approximately 1 ounce (28 grams) of flax seeds reported lower feelings of hunger and overall appetite than those given a control drink (45).

In another, men given a flax seed-containing meal reported feeling fuller and less hungry than those given no flax seeds (43).

Only one study could be found on the fullness effects of chia seeds.

Researchers gave participants bread containing different amounts of chia seeds. The breads with the most chia seeds reduced appetite 1.5–2 times faster than those with the least (31).

Overall, both flax seeds and chia seeds seem to reduce hunger and appetite. However, due to their higher soluble fiber content, flax seeds may be slightly more effective at doing so.

However, more studies directly comparing the two are needed.

Summary: Flax seeds contain more soluble fiber than chia seeds, which may make them slightly more effective at reducing hunger and appetite. However, more studies are needed.

Both Improve Digestion

Digestion is a critical function your body performs every day, helping you break down the foods you eat and absorb their nutrients.

Poor digestion can make it more difficult for your body to get all the nutrients it needs, and can produce some unpleasant side effects.

Constipation and diarrhea are two of the most common side effects of poor digestion, and affect as many as 27% of people (46, 47).

Thanks to their high fiber content, flax and chia seeds may help relieve both constipation and diarrhea (48).

As mentioned earlier, there are two types of fiber: soluble and insoluble.

  • Soluble fiber: Dissolves in water, forming a gel in the gut. It can slow down the passage of food, promoting feelings of fullness (24).
  • Insoluble fiber: Does not dissolve in water and passes through the gut without changing much. This type of fiber adds bulk to your stools and may speed the passage of food through your gut (49).

Found in both chia and flax seeds, insoluble fiber helps add bulk to stool, and acts as a laxative, reducing constipation (50).

On the other hand, the gel-forming properties of soluble fiber, which is found mostly in flax seeds, can help digestive waste bind together, reducing diarrhea (51).

Summary: Both flax and chia seeds contain insoluble fiber, which helps relieve constipation. Flax seeds contain more soluble fiber, which may help reduce diarrhea.

How to Eat Chia and Flax Seeds

Both flax and chia seeds are incredibly versatile and very easy to introduce into your diet. Both taste relatively bland, so you can add them to almost anything.

They can be sprinkled on top of yogurts or incorporated into smoothies, porridge or baked goods. Both can also be used to thicken sauces or as egg substitutes in many recipes.

Regarding how much to eat, most of the benefits listed above were seen with 1–2 tablespoons (10–20 grams) of seeds per day.

It’s worth noting that, although both can be consumed whole, there are advantages to consuming them ground.

Whole flax seeds can go through your gut without being absorbed, because their outer shell is hard for the intestines to break down. Eating them ground can help increase the absorption of the nutrients they contain.

Chia seeds are often consumed whole. However, new studies show that the nutrients they contain may also be better absorbed when chia seeds are ground (17).

Due to their high fat content, both types of seeds should ideally be stored in the refrigerator or freezer to prevent them from going rancid. For this reason, also make sure to consume them promptly.

Summary: Both chia and flax seeds are incredibly versatile and an easy addition to most dishes. Both should be consumed ground for the most health benefits.

The Bottom Line

Chia and flax seeds are both very nutritious. Both also offer similar benefits for heart health, blood sugar levels and digestion.

However, flax seeds do appear to have a slight advantage, especially when it comes to reducing hunger and appetite, as well as lowering the risk of certain cancers.

Plus, they’re often less expensive.

Yet, ultimately, the differences between the two seeds remain small. Either flax seeds or chia seeds would be a great addition to your diet.