Seafood and Vitamin D

Fish as A Natural Source of Vitamin D

Vitamin D

"Summer Sunshine" by **Mary** is licensed under CC BY-NC-SA 2.0

Vitamin D – the sunshine vitamin

What’s not to like?

Vitamin D is purported to fight disease, reduce depression, and help with weight loss.[1]   Described as The Death D-fying Vitamin in a recent Mayo Clinic Proceedings editorial,[2]  Vitamin D controls calcium absorption and skeletal development, influences energy metabolism, immune function and much more.[3] 

What it is

Vitamin D is both a nutrient we eat (it is naturally present in some foods and added to some fortified foods and drinks) and a hormone our bodies produced when ultraviolet rays from sunlight strike the skin and trigger vitamin D synthesis.[4], [5]  Called the sunshine vitamin because it’s produced when skin is exposed to sunlight, vitamin D is also present in some foods and can be taken as a supplement.[6]   Vitamin D is a fat-soluble vitamin, which means it dissolves in fat and tends to accumulate in the body.[7]  There are two dietary forms of vitamin D:

  • Vitamin D3 (cholecalciferol). Found in some animal foods, like fatty fish and egg yolks.
  • Vitamin D2 (ergocalciferol). Found in some plants, mushrooms, and yeasts.

D3 (cholecalciferol) seems to be almost twice as effective at increasing blood levels of vitamin D as D2 (ergocalciferol).[8]

What it does

Vitamin D is a hormone that helps to regulate blood calcium and phosphate levels to support bone health, muscles, and immune system.  Vitamin D has been shown to reduce the risk of viral, microbial, and respiratory diseases.[9]   Research often shows health benefits in individuals who have higher levels of vitamin D.  Clinical trials, however, do not demonstrate that taking supplements will lower the risk of various diseases.  Here is what we can say about the effects of vitamin D from research on people who have higher vitamin D serum levels… Vitamin D:[10]

  • May lower risk of osteoporosis and of hip and non-spine fractures
  • May increase muscle strength, which helps prevent falls
  • May lower risk of colon, pancreatic, prostate, and other cancers (the jury is still out on this) and/or may improve survival if cancer develops
  • May help keep arteries flexible and relaxed, which helps control high blood pressure
  • May have lower inflammation which may in turn lower cardiovascular disease
  • Is associated with lower rates of multiple sclerosis, rheumatoid arthritis, Type 2 diabetes[11]
  • May assist with weight loss – in one study, people who took a daily supplement of calcium and vitamin D were able to lose more weight than those taking a placebo supplement (this may be attributed to a decrease in lipid intake because of a calcium-specific appetite control).[12]

Conversely, vitamin D deficiency is linked to a number of health concerns (osteoporosis, multiple sclerosis, chronic fatigue syndrome, depression, type 2 diabetes, heart disease, and cancer), however, an association does not mean that low vitamin D causes these conditions, or that taking a vitamin D supplement will adequately prevent or treat them.  Currently, there are clinical trials studying correlations between Vitamin D and COVID-19.[13]  Recent studies have suggested that low levels of vitamin D are linked to higher rates of muscle injury and function in the high performance athlete. [14] In addition, low levels of vitamin D have been linked to poor male sexual function.[15]  

Vitamin D Surfing

"Surfing is for old Guys" by moonjazz is licensed under CC BY-NC-SA 2.0

How much do you need?

The Institute of Medicine revised its recommended daily allowance in 2011, increasing the both the RDA and the safe upper limit (see the table below).  The Endocrine Society says that adults may need 2,000 IU per day to ward off vitamin D deficiency and no toxicity symptoms have been documented at the 2,000 IU level in over-the-counter supplements.[16], [17]   

Institute of Medicine Recommended Dietary amount of Vitamin D[18]



Safe Upper Limit

Up to age 70

600 IU

4,000 IU

Over 70

800 IU

4,000 IU


While healthy adults without symptoms of deficiency do not necessarily need to have their vitamin D levels tested, it may be useful to find out whether you have an insufficiency or deficiency.  Getting your blood level of vitamin D checked by your doctor can ensure that you are getting an adequate amount.  Your blood level should be greater than 30 nanograms per milliliter.[19]  Here are some factors that may influence your levels:[20]

  • Where you live. People living at the Equator get the most sunshine year-round and the farther you move from the equator, the less you get (especially in winter).
  • Air quality. Carbon particles can interfere with UVB rays from the sun, diminishing vitamin D production.
  • Use of sunscreen. Sunscreen may affect your ability to absorb sunlight – but that’s not a good enough reason to stop using sunscreen.
  • Skin color. People with dark skin tend to require more UVB exposure than light-skinned people to generate the same amount of vitamin D.
  • Weight. Being obese is correlated with low vitamin D levels and that being overweight may affect the bioavailability of vitamin D.
  • Age. Older people have lower levels of the substance in the skin that UVB light converts into the vitamin D precursor
  • Gastrointestinal conditions. Some health conditions interfere with absorption of vitamin D.
  • Depression management.  Studies show that vitamin D may ease symptoms in people with clinical depression.[21]

There appears to be a strong link between lower rates of certain diseases in populations that live in sunnier climates or have higher serum levels of vitamin D,  but clinical trials that give people vitamin D supplements to affect a particular disease are still inconclusive.[22]

Salmon Vitamin D

"wild salmon grilled on a cedar plank" by woodleywonderworks is licensed under CC BY 2.0

Food vs. supplements

The Dietary Guidelines for Americans says that we should get most of our nutrients from foods that contain vitamins, minerals, dietary fiber, and other substances that benefit health.  Seafood is a good source of vitamin D, especially Chilean sea bass, salmon, tuna, mackerel, and sardines, although many other fish and shellfish provide a generous percentage of RDA.  Sea bass is especially high in vitamin D, providing approximately 225 IU per 100g (3.5 oz).[23] 

Other foods that are high in calcium include spinach, kale, okra, collards, soybeans, and white beans.[24]  If you are not getting enough vitamin D from your regular diet, you can include fortified foods (e.g, fortified milk, cereal, yogurt, orange juice, etc.) and/or dietary supplements. 

Fish is one of the best sources of dietary vitamin D and can deliver vitamin D-rich fish right to your door! 



While vitamin D supplementation at the over-the-counter level of 2,000 IUs has not shown any adverse effects, please talk with your health care provider about any complementary health approaches you use (including vitamin D supplements).



 [1]  Healthline Editorial Team. The benefits of Vitamin D. Reviewed by Debra Rose Wilson, updated April 7, 2020.

[2]  Holick, M.F. (2018). The Death D-fying Vitamin. Mayo Clinic Proceedings, 93(6)679-681.

[3]  Katz, D. (2018) Preventive medicine:  Vitamin D supplements: of scandal, sunlight, skin in the game. New Haven Register, Sept. 9, 2018.





[8]  Gunnars, K. (2019).  Vitamin D 101 – A detailed beginner’s guide.



[11]  Torborg, L. (2019) Mayo Clinic Q and A:  Vitamin D – too much or too little can lead to health problems.

[12]  Major, G., Alarie, F., Doré, J., & Tremblay, A. (2008). Calcium plus vitamin D supplementation and fat mass loss in female very low-calcium consumers: Potential link with a calcium-specific appetite control. British Journal of Nutrition, 101(5), 659-663.



[15]  Tirabassi, G., Sudano, M., Salvio, G., Cutini, M., Muscogiuri, G., Corona, G., and Balercia, G. (2018) Vitamin D and Male Sexual Function: A Transversal and Longitudinal Study, International Journal of Endocrinology, 2018, 8 pp.

[16]  Anding, R.H. (2020). When was the last time you had your vitamin D checked?

[17]  Atkins, A. (2019) How much vitamin D do you really need? Oprah Magazine.


[19]  Anding, R.H. (2020). When was the last time you had your vitamin D checked?


[21]  Gunnars, K. (2019).  Vitamin D 101 – A detailed beginner’s guide.




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