The Japanese have the highest life expectancy among people of the G7 countries (United States, United Kingdom, Italy, Germany, France, Canada).¹

Many factors contribute to the increased longevity of Japanese people, but one possible reason could be their high intake of seaweed,² which is served in approximately 21% of their meals.³

Seaweed is a type of algae that comes in many varieties, including green, brown, and red,² which are made into foods such as kombu, nori, and wakame.⁴

Although the amount of nutrients varies based on the specific variety, most seaweed contains nutrients such as vitamins, minerals, fiber, proteins, as well as protective compounds like polyphenols, carotenoids, and omega-3 fatty acids.²

Some types of seaweed—like spirulina⁵ and chlorella⁶—contain all nine essential amino acids, making these varieties an excellent plant-based protein.

One meta-analysis of nine clinical studies concluded that consuming brown seaweed decreased levels of LDL and total cholesterol. The study highlights the role of fucoidans which may regulate lipid metabolism by increasing lipoprotein lipase activity leading to improved lipid profile.⁷

Seaweed contains a compound called fucoxanthin, which has been tied to better blood sugar control.^8,9

A meta-analysis of clinical studies found that consuming brown seaweed significantly improved after-meal blood sugar spikes, HbA1c levels, and homeostatic model assessment of insulin resistance (HOMA-IR).⁹

Seaweed is also one of the highest dietary sources of iodine. Just one serving (about 10 grams) of dried nori (a type of seaweed that is dried and pressed into sheets) contains 232 mcg of iodine, which is 155% of the recommended daily allowance.⁴

Iodine is especially beneficial for thyroid function, which depends on adequate iodine in order to make hormones.⁴

However, because of seaweed’s high iodine content, individuals with thyroid disorders and school-aged children should limit seaweed intake.⁴

Seaweed is a versatile vegetable that can be included in bean dishes, stir fries, and salads, or served on its own as seaweed salad or dried seaweed chips.

References

1. Available at: https://www.statista.com/statistics/1372668/g7-country-life-expectancy/. Accessed January 16, 2025.
2. Cao L, Lee SG, Lim KT, et al. Potential Anti-Aging Substances Derived from Seaweeds. Mar Drugs. 2020 Nov 18;18(11).
3. Zava TT, Zava DT. Assessment of Japanese iodine intake based on seaweed consumption in Japan: A literature-based analysis. Thyroid Res. 2011 Oct 5;4:14.
4. Available at: https://nutritionsource.hsph.harvard.edu/seaweed/. Accessed January 24, 2025.
5. Podgorska-Kryszczuk I. Spirulina-An Invaluable Source of Macro- and Micronutrients with Broad Biological Activity and Application Potential. Molecules. 2024 Nov 15;29(22).
6. Chen C-Y, Lu J-C, Chang Y-H, et al. Optimizing heterotrophic production of Chlorella sorokiniana SU-9 proteins potentially used as a sustainable protein substitute in aquafeed. Bioresource Technology. 2023 2023/02/01/;370:128538.
7. Shin D, Shim SR, Wu Y, et al. How Do Brown Seaweeds Work on Biomarkers of Dyslipidemia? A Systematic Review with Meta-Analysis and Meta-Regression. Mar Drugs. 2023 Mar 30;21(4).
8. Mikami N, Hosokawa M, Miyashita K, et al. Reduction of HbA1c levels by fucoxanthin-enriched akamoku oil possibly involves the thrifty allele of uncoupling protein 1 (UCP1): a randomised controlled trial in normal-weight and obese Japanese adults. J Nutr Sci. 2017;6:e5.
9. Kim YR, Park MJ, Park SY, et al. Brown Seaweed Consumption as a Promising Strategy for Blood Glucose Management: A Comprehensive Meta-Analysis. Nutrients. 2023 Dec 1;15(23).