Carrageenan is a controversial ingredient that's found in a wide variety of products.
It's used as an additive in many foods, including ones marketed as organic or healthy, such as almond milk and yogurt.
While some claim that carrageenan causes everything from cancer to diabetes, the FDA considers it safe for consumption.
So is carrageenan actually bad for you? This article examines the evidence.
Carrageenan is a food additive that's extracted from Chondrus crispus, a type of edible, red seaweed.
Food manufacturers use it to help thicken and stabilize foods, resulting in improved texture and an extended shelf life.
There are two types of carrageenan — degraded and undegraded — that have very different chemical structures.
The main difference between the two is that the degraded type is processed in an acidic solution, while the undegraded type is not.
Degraded carrageenan, which is also known as "poligeenan," is not used in food. It's often used in studies to cause inflammation and has been classified as "possibly carcinogenic" by the World Health Organization (1).
However, undegraded carrageenan is often used as an additive in foods.
There has been a lot of concern about its potential health effects on everything from insulin resistance to inflammation.
Nevertheless, despite persistent controversy and calls to ban it, it has been granted GRAS (Generally Recognized As Safe) status since 1959 (2).
Summary: Carrageenan is an additive that's used to thicken and stabilize foods. The undegraded form is commonly used by food manufacturers, and it's generally recognized as safe by the FDA.
Carrageenan is found in many food products. Common sources include (3):
- Ice cream
- Cottage cheese
- Infant formula
- Dairy alternatives (almond, soy and coconut milk)
- Processed meats
- Frosting base mix
- Nutritional supplements
- Prepared meals
- Coffee creamer
- Salad dressing
Even foods labeled "organic" can still contain carrageenan. While the National Organic Standards Board recently voted to remove it from the list of approved ingredients in organic products, the USDA will have the final say.
In addition to food, carrageenan is present in several household products. It can be found in toothpaste, shampoo and even shoe polish (2).
In medicine, it has been used as a laxative and treatment for stomach ulcers (2).
Summary: Carrageenan can be found in a wide variety of everyday foods, household products and medications.
Chronic inflammation, on the other hand, can lead to the development of chronic disease in the long term (5).
Some evidence suggests that carrageenan can trigger inflammation by increasing the secretion of proinflammatory cytokines, a type of immune cell that regulates inflammation (6).
One test-tube study used it to treat intestinal cells and reported an increase in inflammatory markers and inflammation (7).
Another study had similar findings, showing that it set off an immune response in human colon cells (8).
However, when carrageenan is consumed as a food additive, it may not have significant inflammatory effects.
A 2014 review noted that it can have an effect on the immune system when administered intravenously, but not when consumed in the diet (9).
Summary: While some studies have shown that carrageenan can trigger inflammation, it's likely that the findings don't apply to dietary intake.
Some studies show that carrageenan may cause negative changes in your digestive system.
One animal study showed that it can promote the growth of abnormal tube-like glands in the colon, which are known as aberrant crypt foci.
The formation of these glands is one of the earliest changes leading to the development of colon cancer (10).
Another animal study analyzed the effects of a diet consisting of 5% carrageenan in guinea pigs, rabbits, rats, squirrel monkeys, ferrets and hamsters.
The researchers found that administering carrageenan over 3–5 weeks caused intestinal ulcers in guinea pigs and rabbits, but not in the other species (11).
However, other studies have shown that the amount of carrageenan found in the typical diet does not cause intestinal ulcers. When consumed in moderate amounts (under 5% of total diet), it has not been shown to cause adverse effects (12).
More research is needed to determine the effects in humans, as well as how intravenous carrageenan differs from the food-grade variety.
Overall, it seems that moderate amounts in the diet are generally safe.
Summary: Some studies have shown that carrageenan can cause intestinal ulcers and promote the growth of abnormal cells in the colon. These effects are likely limited to high doses in the diet.
While degraded carrageenan is classified as "possibly carcinogenic," the undegraded, food-grade variety is not.
Nevertheless, some research has suggested that even undegraded carrageenan can accelerate the development of cancer, especially when paired with a known carcinogen.
In one animal study, rats were fed either a diet consisting of 15% undegraded carrageenan or no carrageenan. They were also given a type of carcinogen to induce colon cancer.
The group fed carrageenan had a higher rate of tumors than the control group, suggesting that it can promote the formation of cancer cells (13).
Another study showed similar findings. Rats were given a diet consisting of 6% carrageenan over 24 weeks and exposed to a carcinogen. Compared to the control group, the rats receiving carrageenan had a 35% increase in colorectal tumors (14).
Dietary carrageenan has also been shown to increase the production of thymidine kinase, an enzyme that is used as a marker for colon cancer (15).
However, other studies have found no relationship between carrageenan and the development of cancer.
For example, one study in rats fed carrageenan for a 90-day period found no signs of lesions in the digestive tract (16).
So while carrageenan itself could possibly enhance the progression of cancer, it's likely only in the presence of other carcinogens and when consumed in high amounts.
Summary: Several studies have shown that carrageenan can accelerate cancer formation in the presence of known carcinogens. However, current evidence on this is limited to animal studies.
Your body breaks down foods into glucose to be used as energy. It then secretes insulin, the hormone that's responsible for distributing glucose to your cells.Insulin resistance develops when your body can't use insulin as effectively, causing a build-up of glucose and insulin in your blood.
Over time, this can lead to problems like diabetes.
Some studies show that carrageenan could contribute to insulin resistance and glucose intolerance.
In one study, rats were given drinking water containing carrageenan and then tested for glucose tolerance. The researchers found that insulin and glucose levels were significantly higher in the carrageenan group than the control group (17).
Another study gave mice either a carrageenan-containing diet, a high-fat diet or a combination of both for one year.
Mice that had been treated with carrageenan had more severe glucose intolerance than the high-fat diet alone. The high-fat, carrageenan diet had a significant effect on blood sugar levels, glucose tolerance and even lipid levels (18).
Research is still lacking when it comes to the effect of carrageenan on insulin levels in humans, so it's unclear just how applicable the results of these studies are.
A healthy diet paired with exercise and a moderate intake of processed foods that contain carrageenan is the best way to prevent insulin resistance and keep blood sugar levels steady.
Summary: Some animal studies have found that carrageenan could cause insulin resistance and glucose intolerance, especially when paired with a high-fat diet.
Studies show that carrageenan can cause some negative health effects.
However, most of the studies used much higher amounts than what's seen in the typical diet and were test-tube or animal studies.
Therefore, it's unclear how the effects might translate to humans.
If you're consuming carrageenan in moderation, there's no need to worry. Amounts comprising under 5% of your diet are unlikely to have significant health effects (12).
But if you want to err on the side of caution and limit your intake, start at the grocery store. Don't just assume that products marked as "organic" or "healthy" are carrageenan-free, as these are often some of the most common sources.
Instead, try reading the ingredient lists when grocery shopping and use this handy shopping guide to find brands that don't use carrageenan.
You can also reduce your intake of processed foods. Not only will this reduce your intake of carrageenan — it will also improve your diet overall.