Kelp vs. Spirulina - Which is Better?

Kelp is an underwater plant, often confused for seaweed. It belongs to the brown algae family.

It is used as a dietary supplement and is rich in vitamins A, B1, B2, B12, C, K, polysaccharides, magnesium, potassium, iodine, zinc, calcium, carbohydrates etc.

Care should be taken to purchase kelp growing in unpolluted waters for otherwise it could contain toxins like arsenic.

The high iodine content can benefit those with thyroid problems. Since the nutrients are available naturally, they body can easily assimilate them.

About Spirulina

Spirulina is also an underwater plant which belongs to the blue-green algae family. It contains both phycocyanin (blue) and chlorophyll (green) pigmentation.

Although microscopic, Spirulina can grow to 0.5mm in height. It grows well in fresh, warm, alkaline waters. The physical configuration of the plant which grows in swirling, microscopic strands gave rise to the name ‘spirulina’ which is Latin for ‘spiral’ or ‘helix’.

Spirulina and kelp are distantly related.

Spirulina contains 65-71% essential amino acids and is considered a ‘complete protein’. Compare this to beef, considered a high protein food which contains only 22% protein.

Spirulina has a photosynthesis conversion rate of 8-10%, which is much higher than land plants like soybeans. Apart from this, spirulina also has high concentrations of Vitamin B12, chelated minerals, natural plant rhamnose sugars, enzymes and trace elements.

A great advantage of spirulina is that since it grows in high temperatures and alkaline waters, it is more hygienic as fewer pollutants can thrive in such waters. It is also able to better maintain its nutritional value and have longer shelf life.

Nutritional Comparisons of Kelp and Spirulina

  • Calories: For a 1 tbsp quantity of spirulina (the average content in most supplements) we get 20 calories. Of these, we get 5 calories of fat, 9 of protein and 6 of carbohydrates.   A single ounce of kelp provides us with 12 calories. This contains 10 calories of carbohydrates and the rest is fat.
  • Carbohydrates: 1 tbsp spirulina contains 1.8g carbohydrates. This is split between 0.5g complex carbohydrates and the rest is shared between dietary fiber and sugars.  A single serving of kelp contains 9.57g carbohydrates, 1.68g protein and 1.3g dietary fiber.
  • Fats: Spirulina contains 0.5g total fats in a single serving. This includes 0.2g saturated (bad) fats which are harmful to the body and produce unhealthy LDL cholesterol. The right ratio should exist between healthy and unhealthy fats in a good food profile.  Kelp has a lower fat content (0.2g) preserving with saturated fats accounting for just 0.1g. It contains heart-healthy
    omega fatty acids – omega-3 (2.2mg) and omega-6 (5.6mg).
  • Protein: You can get 4g protein from every serving of spirulina. This gives us 8% of our daily requirements according to the USDA. Hence spirulina is considered a complete protein providing the body with all required amino acids that it cannot produce on its own. The protein content in spirulina is much higher than that found in most plant proteins.
  • Vitamins: 10% of our daily requirement of riboflavin and thiamine are provided by a single serving of spirulina. It also gives us 1-2% RDA of vitamins A, K, E, C, B3, B12, B6, and folate. Kelp provides us with an excellent source of various minerals. A single serving of kelp gives us 23% DV vitamin K and 13% DV folate. It also provides us with 32.5IU vitamin A and small quantities of choline, pantothenic acid, vitamin E, C and niacin.
  • Minerals: We get 21% DV of copper, 7% manganese, 11% iron from every serving of spirulina. It also provides us with 1% zinc, calcium, phosphorous and selenium and 3% of potassium, sodium and magnesium.  A single ounce of kelp contains 8.9mg potassium and 16.8mg calcium. It has high quantities of sodium (65mg) which is 3% DV. This is why kelp is often substituted for table salt. Other minerals contained in kelp include iron, magnesium, copper, zinc and manganese.

Benefits of Kelp and Spirulina

Both kelp and spirulina are rich in nutrient content and are known to possess many health benefits.

They increase energy levels, improve liver function, boost immunity levels, possess anti-inflammatory benefits, help reduce the risk of heart disease, AIDS, cancer, help with weight-loss programs, protect cells from damage due to exposure to heavy metals and X-rays.

Specific benefits provided by spirulina are as a remedy for bad breath. This is due to its high chlorophyll content. It also helps in the treatment of chronic sinusitis and gum diseases.

Kelp specifically helps treat thyroid related disorders due to the high levels of iodine found in it. Those with under-active thyroid could be prescribed kelp to improve thyroid functioning.

Both kelp and spirulina are available as powders, liquids, tablets or capsules. The dosage used depends on whether they are being used as a general supplement or to treat specific illnesses. Always consult a doctor when taking these supplements.


Be careful not to overdose on kelp or spirulina. To avoid stomach upsets, take both with food. Excess kelp can cause an iodine overdose and worsen thyroid problems. Reduce the dosage or stop taking the supplement if you experience severe side effects.

Both kelp and spirulina are excellent dietary supplements. They can be eaten raw or dried and added to various recipes. Since both contain different quantities of nutrients, we could combine them to and enjoy a complete nutritional diet.

2 thoughts on “Kelp vs. Spirulina - Which is Better?”

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.