Limited research suggests that kelp may support weight loss and thyroid function, but more studies are needed to verify this. While kelp is very nutritious, the evidence for other benefits is limited. In addition, eating too much kelp could have negative effects.

Kelp is a large type of seaweed that grows in shallow oceans in areas called kelp forests. There are about 30 kelp varieties.

One hundred grams (g) of raw kelp contains 43 calories and 0.56 g of fat. It also contains various vitamins and nutrients, including:

  • vitamin K
  • vitamin A
  • calcium
  • iron
  • magnesium

Kelp is thought to have various health benefits, including relating to weight loss and thyroid health. In fact, it’s already present in many common things, from toothpaste to ice cream.

But does eating it really provide such health wonders? Read on to learn about what recent research says about kelp and what conclusions we can make based on the findings.

Kelp contains the natural fiber alginate, which can act as a fat blocker, stopping the absorption of fat in the gut. Does this mean that eating kelp can help you lose weight? According to research, there’s no clear answer.

A 2021 study examined the effects of kelp powder on weight loss in 50 Japanese individuals with a body mass index (BMI) of 25 to 30, which is considered overweight. One group took the powder for 8 weeks, while the other group took a placebo.

Male participants who took kelp powder saw a decrease in body fat percentage. There were no major changes in female participants.

That said, this study only explored fat loss and not weight loss. In addition, we can’t extrapolate from this study that eating kelp (raw or cooked) as part of your diet would have the same effect in females or males.

There are also few studies with humans showing similar findings.

In a 2022 animal study on giant kelp (Macrocystis pyrifera), researchers looked at how consuming kelp affected weight in mice fed a high fat diet. Researchers found that adding kelp did not help the mice lose any gained weight.

For this reason, more research with humans is needed to understand the effects of kelp on weight loss and obesity.

Language matters

In this article, we use “male” and “female” to refer to someone’s sex as determined by their chromosomes and “men” and “women” when referring to their gender (unless quoting from sources using nonspecific language).

Sex is determined by chromosomes, and gender is a social construct that can vary between time periods and cultures. Both of these aspects are acknowledged to exist on a spectrum, both historically and by modern scientific consensus.

Kelp also contains iodine, which plays a crucial role in producing thyroid hormones and managing metabolism, among other effects.

A deficiency in this vital mineral can contribute to various diseases and disorders, such as thyroid conditions and autoimmune diseases.

However, even people who eat seaweed regularly don’t get most of their iodine from this food. For most people, the primary dietary source of iodine is table salt.

While eating kelp could help reduce the chance of having iodine deficiency, there’s no evidence that eating kelp can directly help you treat or reduce the chance of developing any of these conditions.

It’s also possible to consume too much iodine, which can have negative effects on your health. In a 2021 study that examined kelp and weight loss, researchers used iodine-reduced kelp powder to ensure the safety of the study participants.

Kelp may have some additional benefits. Like other seaweeds, it contains antioxidants like carotenoids and polyphenols. Antioxidants suppress the negative effects of free radicals, which are unstable molecules that can damage your cells.

Research from 2021 suggests that kelp may be linked to a lower chance of developing:

  • heart disease
  • type 2 diabetes
  • digestive tract issues
  • bone-related conditions

That said, while seaweed, in general, has been more widely studied, there’s not much research on kelp specifically. Newer studies on humans are needed to replicate these findings.

It’s best to consume kelp in its natural form. That’s because, like other supplements, kelp supplements aren’t regulated by the Food and Drug Administration (FDA). There’s no way to know they’re safe or what the effects of any other ingredients might be.

In addition, although kelp’s high iodine content appears beneficial, there are risks. For adults, the FDA recommends a dietary intake of 150 micrograms (mcg) of iodine per day.

One pound of raw kelp can contain up to 2,500 mcg of iodine, so make sure you’re reading your packages and monitoring how much you eat. In theory, eating too much iodine could lead to iodine poisoning.

In addition, eating a lot of kelp could potentially lead to hyperthyroidism (overactive thyroid). In one medical literature case, a 70-year-old woman presented with symptoms of the condition after taking medications containing kelp for 3 months.

This doesn’t mean you shouldn’t eat kelp. It’s a nutritious food that can be a regular part of your diet. But like with any food, it’s a good idea to eat it in moderation and generally eat a balanced diet.

Sure, kelp makes a great seaweed salad and goes well with sushi. But there are many more ways to incorporate a healthy dose of kelp into your diet. These include:

  • Get your noodle fix, low carb style: Try swapping out your pasta for this low carb alternative, or use kelp to create a tasty kelp noodle salad.
  • Impress with chips and dip: Seaweed snacks are crunchy morsels of umami flavor. While these chips can be found at most grocery stores, you can also make your own.
  • Season with seaweed: Kelp seasonings are available in convenient shakers. They add a great flavor to stir-fries, marinades, and even popcorn.
  • Make a soup: One of the most common ways to use kelp is in soups. Whether you’re making a kelp stock or miyeok-guk (seaweed soup), kelp-infused soups are an excellent way to get a bowl full of nutrients. A bowl of miyeok-guk is also a Korean birthday tradition.
  • Power with powder: An easy way to start eating kelp is to buy convenient kelp powder. This nutrient-dense powder can be used in a variety of recipes. Add it to your favorite morning smoothie, or mix it into your salad.
  • Spice up a healthy dessert: Mix things up by making sea-inspired desserts. Try this recipe for kelp carrot cake, whip up seaweed pudding, or bake some seaweed salt-speckled cookies.

Some limited research suggests kelp might help with fat loss and maintaining healthy thyroid function, but studies with humans are required to confirm these findings. Despite being a highly nutritious food, the evidence for other potential benefits is also not yet conclusive.

Furthermore, consuming excessive amounts of kelp could potentially lead to iodine poisoning, especially if you already regularly consume the mineral from other sources like table salt. Eating kelp is healthy, but it’s best to do so in moderation.