Some say seaweed improves fertility? Or do the estrogen receptors in seaweed act against improved fertility? Should one consume seaweed if you are planning a family or pregnant? The short answer is there appears to be no reason not to eat seaweed as part of a balanced diet, but this ignores that various researchers have seen some responses as seaweed as a functional food. I.e. Seaweed is food. But seaweed has some properties that are drug-like; such as having preventative breast cancer properties, or dysmenorrhea reduction.
With no definitive answers, how do we answer this question from various customers, some of whom are planning a family and wondering if seaweed as a food is good or has some risks.
- Seaweed is a nutritious vegetable with good levels of nutrients and vitamins.
- So what about the potential for seaweed to affect menstruation, and estrogen regulation in females.
- Is there any potential impact for males?
Evidence For or Against?
Seaweed is a functional food. It is just food.
- If you have seafood allergies, avoid seaweed as the potential to have some seafood passengers included in seaweed.
- Some foods are advised to be avoided during pregnancy to protect the embryo. E.g. Australian advice  is for pregnant women to avoid soft cheeses, pate, raw or partially cooked eggs. In other countries advice may differ on food consumed.
Seaweed has proven health benefits – both from a nutrition and functional food qualities. Here are some of the benefits identified relevant to fertility.
- We have found no evidence in the literature that societies with high consumption of seaweed (Japan, China, Korea, Philippines, Welsh) have any reduction in fertility. Some societies consumed seaweed for millennia.
- Epidemiological US studies show longer period cycles result in lower cancer rates and healthier offspring in females.
- Breast cancer. Previous studies by Jane Teas suggests seaweed may change some estrogen markers and she proposed in  and  that changes from seaweed may reduce breast cancer.
- Endometriosis studies by Skibola showed improvement in reproductive health, reduction dysmenorrhea and endometriosis  and in a followup study showed seaweed was a protective mechanism against phyto-estrogens. 
- Seaweed is a very active anti-oxidant. It is also effective against osteoarthritis conditions. 
- Seaweed changed gut microbiome in animals  and focus is now on the bacteria – gut – brain continuum.
- In both animal  and human studies  patients consuming seaweed had a reduction in hypertension. Some have tried to isolate a specific compound, but have not been successful.
- Animal studies have shown reduction in fatty liver and heart inflammation  
- Seaweed is nutritious – is the improved nutrition by way of a daily serve of fibre or some of the minerals and vitamins part of the issue. Good nutrition of minerals and vitamins is essential. Seaweed has good levels – some approaching 20% or more of RDI. Details are here for minerals and vitamins.
- Feeding rabbits with 2% seaweed to doe rabbits improved their kindling rate, litter size, and their offspring ratio 
- Seaweed improved spermatozoa counts in mice affected by malarial pesticides . Improvements in male fertility may be important and whether levels of zinc or other nutrition may improve male fertility is unclear.
- Pacific Seamoss reduced dysmenorrhea and menorrhagia in company pilot trials. This work will be repeated.
Seaweed Improves Fertility Summary
In summary, there is more positive than negative research findings to date. Seaweed is a traditional food in many cultures. Diet, health and wellbeing are complex in this area of fertility. Simply, people feel better on seaweed, it provides lots of good fibre, minerals, vitamins, protective against breast cancer, anti-inflammatory and limited data suggests it restores normal menstruation. And been eaten in many cultures for millennia without any downsides.
Proposed mechanisms are not yet defined but research is being undertaken by a number of groups globally.
 Foods to Avoid in Pregnancy Pregnancy Birth & Baby
 Teas, J et al 2013 The consumption of seaweed as a protective factor in the etiology of breast cancer: proof of principle. J Appl Phycol 25 771-779 DOI:10.1007/s10811-012-9931-0 (Click for Abstract)
 Wanyonyi, S; du Preez, R; Brown, L; Paul, N; Panchal, S 2017 Kappaphycus alvarezii as a Food Supplement Prevents Diet-Induced Metabolic Syndrome in Rats. Nutrients (9) 11 DOI:10.3390/nu9111261 (Click for Abstract)
 Makkar, H. P. S., Tran, G., Heuzé, V., Giger-Reverdin, S., Lessire, M., Lebas, F., & Ankers, P. (2016, February 1). Seaweeds for livestock diets: A review. Animal Feed Science and Technology. Elsevier. https://doi.org/10.1016/j.anifeedsci.2015.09.018
 Okab, AB, Samara, EM et al 2013 Effects of dietary seaweed (Ulva lactuca) supplementation on the reproductive performance of buck and doe rabbits, Journal of Applied Animal Research, 41:3, 347-355, DOI: 10.1080/09712119.2013.783479
 Pringgenies, D, Ghofur, A, Azizah R, Ridho A. 2013 Effect of Red Seaweed (Euchema cottonii) Powder Administration To The Quantity and Quality of Spermatozoa of Allethrin-Exposed House Mice Managing Aquatic Resources in Blue Economy eprints.undip.ac.id
 Skibola, C.F. The effect of Fucus vesiculosus, an edible brown seaweed, upon menstrual cycle length and hormonal status in three pre-menopausal women: a case report. BMC Complement Altern Med 4, 10 (2004). https://doi.org/10.1186/1472-6882-4-10
 Skibola, C.F, Curry, J.D, VandeVoort, C, Conley A, Smith, M.T. Brown Kelp Modulates Endocrine Hormones in Female Sprague-Dawley Rats and in Human Luteinized Granulosa Cells. 2005 The Journal of Nutrition, Volume 135, Issue 2, Pages 296–300, https://doi.org/10.1093/jn/135.2.296
 du Preez, R. et al. Carrageenans from the Red Seaweed Sarconema filiforme Attenuate Symptoms of Diet-Induced Metabolic Syndrome in Rats. Mar. Drugs 18, 97 (2020).
 Myers SP, O’Connor J, Fitton JH, et al. A combined phase I and II open label study on the effects of a seaweed extract nutrient complex on osteoarthritis. Biologics. 2010;4:33-44. Published 2010 Mar 24. doi:10.2147/btt.s8354
This is to present our understanding to date from information published in the literature by others. This does not constitute medical advice and you should seek advice from your physician.
This is a brief review and our understanding of published information. The information is certainly worthy of further study due to the importance in society for reproduction. When natural reproduction is difficult, many face high cost and trauma.