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Food, Health, and Eco-news
Hidden Heart-Helpers in Fatty Fish
Omega-3s get more attention, but fatty fish has two other heart-helpers 03/07/2019 By Michelle Lee with Craig Weatherby

Fatty fish like salmon and sardines are the richest source of omega-3 fatty acids.

Among commonly consumed species in America, the fattiest wild fish include salmon, sardines, albacore tuna, sablefish (black cod), and mackerel.

While skipjack and tongol tuna — used in most canned “light” tuna — and yellowfin (ahi) tuna offer significant amounts of vitamin D, fat, and omega-3s, albacore beats them by wide margins.

Of course, there’s very good evidence that seafood-source omega-3s — DHA and EPA — support heart, brain, mood, eye, and metabolic health.

But among other beneficial nutrients — such as magnesium and selenium — fatty fish offer two especially heart-healthy ones, in addition to omega-3s.

The dynamic duo in question are astaxanthin and vitamin D — both of which offer broad menus of health benefits.

And recent findings by research teams from Iran and Norway bolster prior evidence of their cardiovascular benefits.

Astaxanthin is a potent, carotenoid-class antioxidant, which wild salmon — the only substantial food source — acquire by eating krill, shrimp, and zooplankton, which get it from the algae they eat.

Vitamin D, the essential, hormone-like nutrient, abounds only in wild salmon and certain other fatty fish — the best food sources by far.

Before reviewing the new Iranian and Norwegian studies, let’s quickly review what’s known about the heart benefits of vitamin D.

Vitamin D and heart disease: The background
Dr. Erin Michos of Johns Hopkins Medicine is both a cardiologist and a vitamin D expert.

As she says, the available evidence shows that low vitamin D levels raise our risks for heart attacks, congestive heart failure, strokes, high blood pressure, and diabetes.

And, as far back as 2012, Danish researchers persuasively affirmed the heart-health value of vitamin D, in what was the largest and most reliable study.

Importantly, the Danish team tested blood samples to specify people's vitamin D levels… a far more reliable approach than the more common reliance on extremely crude estimates based on people’s answers to diet/lifestyle questionnaires.

The authors compared participants’ vitamin D levels to the participants’ health records over the ensuing nearly 30 years — and the results linked low vitamin D levels to these risks:

  • 57% higher risk of early death
  • 64% higher risk of heart attack
  • 40% higher risk of ischemic heart disease
  • 81% higher risk of death from heart disease

For more on that landmark study, see Vitamin D Heart-Health Link Affirmed.

And we reported on a later study from Ohio State University, which may help explain vitamin D’s cardiovascular benefits.

Novel scans using nanosensors revealed that vitamin D does three things that should boost overall cardiovascular health:

  • Stimulates release of nitric oxide (which relaxes arteries).
  • Acts as a potent antioxidant/anti-inflammatory agent in artery linings.
  • Helps restore damage caused by high blood pressure, atherosclerosis, and diabetes.

For more on that important finding, see Big Heart News, Good and Bad.

Now, epidemiological research from Norway’s University of Bergen (UiB) links vitamin D to reduced risk of death among people with cardiovascular disease.

Norwegian study suggests vitamin D can help deflect cardiovascular deaths
The study began in 2000 and followed 4,114 patients with cardiovascular diseases (average age 62) over the course of 12 years.

And the apparent benefit was an eye-opener: Patients who maintained higher-than-average vitamin D levels were up to 30% less likely to die from heart-related causes.

According to lead author Jutta Dierkes, “We discovered that the right amount of vitamin D reduces the risk of death substantially. However, too much or too little increases the risk.”

People with levels higher than 100 nmol/l (40 ng/mL) were at greater risk of death from heart disease, while those with levels below 42 nmol/l (17 ng/mL) were at greater risk of death from any cause and death from heart disease.

The advice offered by two credible authorities put those vitamin D levels in perspective:

  • The U.S. Institute of Medicine recommends a minimum of 50 nmol/l (20 ng/mL)
  • Leading vitamin D researcher Michael F. Holick, Ph.D., M.D., and many other experts advise a minimum of 75 nmol/L (30 ng/mL).

Fortunately, the optimal upper and lower vitamin D levels identified in the Norwegian study fit American experts’ blood-level recommendations.

It’s challenging to recommend a universally applicable vitamin D intake level, because the amount needed to maintain each person’s blood level will vary with their sun exposure, dietary vitamin D (from fatty fish and supplements), body mass index, and overall health.

It’s best to have your levels tested by a nutrition-savvy physician who can help you determine your ideal daily supplemental dose — if any — and get your levels retested a few months later.

Fish fit the vitamin D bill; Sockeye salmon stand out
As we said, fatty fish are the best food sources of vitamin D, by a very wide margin.

By way of comparison, virtually all milk sold in the U.S. is fortified with 115-124 IUs of vitamin D per 8-oz serving.

Among fish, wild sockeye salmon rank as the richest source, with a single 3.5 ounce serving surpassing the US RDA of 600 IU by about 15 percent.

These are the average levels in a 3.5 oz (100 grams) serving of various fish:

  • Sockeye salmon 690 IU
  • Albacore tuna 540 IU
  • Silver salmon 440 IU
  • King salmon 240 IU
  • Sardines 300 IU
  • Chub Mackerel 370 IU
  • Sablefish 170 IU
  • Pacific Halibut 160 IU
  • Yellowfin tuna 75 IU
  • Pacific cod 20 IU

Wild salmon beats farmed salmon by a mile for vitamin D 
Boston University researchers tested vitamin D levels in cooked farmed Atlantic salmon versus cooked wild Pacific salmon (species not identified).

And wild salmon had four times the amount of vitamin D —a whopping 988 IU of vitamin D per 3.5oz serving, or almost two-thirds more than the U.S RDA of 600 IU.

That difference could stem both from the stark dietary differences between farmed and wild salmon, and from the fact that farmed salmon have considerably higher levels of total fat.

While farmed and wild salmon used to offer comparable levels of omega-3s, levels of omega-3s have been dropping in farmed salmon due to dietary changes. (For more on that development, see Farmed Salmon Get More Lice, Lose Omega-3s.)

But farmed salmon contain many more saturated fats and omega-6 fatty acids, which raises their total fat content well above that of most wild salmon.

Vitamin D is concentrated in fat, so when you cook farmed salmon they release a great deal more fat into the pan, along with loads of vitamin D.

For more on that study, see Wild Salmon Affirmed as Top Vitamin D Source.

Astaxanthin lowered heart and diabetes risks in Iranian clinical trial
Astaxanthin — pronounced asta-zan-thin — is the pigment that gives salmon its gorgeous red-orange-pink color.

Last year, researchers from two Iranian universities studied the effects of supplemental astaxanthin in adults with diabetes.

Their placebo-controlled trial lasted eight weeks and measured astaxanthin’s effects on blood sugar regulation, oxidation of blood fats, insulin sensitivity, and body fat levels.

The 44 participants were given either 8mg of astaxanthin or a placebo, once a day for eight weeks.

At the end of the trial period, the astaxanthin group showed five benefits:

  • Lower body fat levels
  • Lower blood pressure
  • Better blood sugar control
  • Lower blood levels of triglycerides
  • Lower blood levels of bad “LDL” cholesterol

As the Iranian team noted, prior research showed that the effects of astaxanthin on fat metabolism and antioxidant defenses were better than those of vitamins E or C.

Earlier Japanese clinical trial found cardiovascular benefits from astaxanthin
Back in 2010, we reported on the encouraging results of a placebo-controlled Japanese clinical trial that tested astaxanthin’s effects on cardiovascular and metabolic health.

Researchers at Jikei University conducted a three-month, placebo-controlled trial in 61 people aged 25-60, with normal-to-high triglyceride levels.

The participants took either a placebo pill or one of three different daily doses of astaxanthin: 6mg, 12mg, or 18mg.

The results showed that astaxanthin improved key markers for cardiovascular health and raised levels of a hormone that prevents build-up of highly unhealthful belly fat.

Compared with the placebo group, the people who took 12mg or 18mg per day developed significantly lower triglyceride levels, while those who took 6mg or 12mg per day enjoyed significantly higher levels of “good” HDL cholesterol.

In addition, blood levels of adiponectin — a hormone that discourages accumulation of unhealthful belly fat — rose in the people who took 12mg or 18mg of astaxanthin per day.

For more on that study, see Salmon’s Red-Orange Hue Helps Hearts & Fights Belly Fat.

Astaxanthin: A quick primer
More importantly, astaxanthin is a carotenoid-class antioxidant, and therefore related to beta-carotene — the vitamin A precursor that makes carrots orange.

Astaxanthin is found in particular types of algae, which tiny aquatic creatures such as krill eat.

In turn, algae and crustaceans like krill get eaten by certain aquatic animals — especially salmon, lobster, and shrimp — a diet that gives them their rich, vibrant, red-orange-pink colors.

(Likewise, pink flamingos get their striking hue from eating algae and crustaceans rich in astaxanthin.)

In the body, astaxanthin exerts powerful antioxidant effects — due largely to its effects on our genes — thereby protecting cells from disease-promoting free radical damage.

Astaxanthin also comes in capsule form, typically with 4mg (4,000mcg) per capsule.

Omega-3 krill oil contains about 200mcg per capsule (20 times less), while levels in wild salmon and wild salmon oil are somewhat lower than those.


  • Brøndum-Jacobsen P, Benn M, Jensen GB, Nordestgaard BG. 25-hydroxyvitamin d levels and risk of ischemic heart disease, myocardial infarction, and early death: population-based study and meta-analyses of 18 and 17 studies. Arterioscler Thromb Vasc Biol. 2012 Nov;32(11):2794-802. doi: 10.1161/ATVBAHA.112.248039. Epub 2012 Aug 30. PubMed PMID: 22936341.
  • Degerud E, Nygård O, de Vogel S, Hoff R, Svingen GFT, Pedersen ER, Nilsen DWT, Nordrehaug JE, Midttun Ø, Ueland PM, Dierkes J. Plasma 25-Hydroxyvitamin D and Mortality in Patients With Suspected Stable Angina Pectoris. J Clin Endocrinol Metab. 2018 Mar 1;103(3):1161-1170. doi: 10.1210/jc.2017-02328. PubMed PMID: 29325121.
  • Lu Z, Chen TC, Zhang A, Persons KS, Kohn N, Berkowitz R, Martinello S, Holick MF. An evaluation of the vitamin D3 content in fish: Is the vitamin D content adequate to satisfy the dietary requirement for vitamin D? J Steroid Biochem Mol Biol. 2007 Mar;103(3-5):642-4. Epub 2007 Jan 30. PubMed PMID: 17267210; PubMed Central PMCID: PMC2698592.
  • Mashhadi NS, Zakerkish M, Mohammadiasl J, Zarei M, Mohammadshahi M, Haghighizadeh MH. Astaxanthin improves glucose metabolism and reduces blood pressure in patients with type 2 diabetes mellitus. Asia Pac J Clin Nutr. 2018;27(2):341-346. doi: 10.6133/apjcn.052017.11. PubMed PMID: 29384321.
  • Michos E. Vitamin D and the Heart. Johns Hopkins Women's Cardiovascular Health Center, Johns Hopkins Medicine, 13 May 2016.
  • Yoshida H, Yanai H, Ito K, Tomono Y, Koikeda T, Tsukahara H, Tada N. Administration of natural astaxanthin increases serum HDL-cholesterol and adiponectin in subjects with mild hyperlipidemia. Atherosclerosis. 2010 Apr;209(2):520-3. doi: 10.1016/j.atherosclerosis.2009.10.012. Epub 2009 Oct 14. PubMed PMID: 19892350.

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