Another major class of plant-borne antioxidants is the carotenoids… a family that includes beta-carotene, which gives orange carrots and red-yellow peppers their bright colors.
The carotenoid clan includes the yellowish antioxidants in leafy greens like spinach, chard, and kale, called xanthophylls (zan-tho-fills).
The xanthophylls we get from leafy greens (lutein and zeaxanthin) concentrate in the retina, where they help perform and protect key vision functions.
But one long-overlooked, highly promising member of the xanthophyll family is found only in red- and orange-hued fish and shellfish.
We're talking about astaxanthin, which is produced by certain kinds of algae, and lends its red-orange hue to the small crustaceans that eat them, and to wild Pacific salmon, which feed upon those tiny shellfish.
Wild Pacific salmon are the richest human food source of astaxanthin by far, with all five commercial species—sockeye (red), king (chinook), silver (coho), chum (keta), and pink—providing ample amounts.
Because sockeye salmon feed mostly on small astaxanthin-rich crustaceans, these aptly nicknamed “red” salmon provide more astaxanthin than the other species do.
As we'll explain (see “Astaxanthin in wild and farmed salmon”, below), farmed and wild salmon contain different kinds of astaxanthin.
And wild sockeye has as much as four times as much of the compound, all of it occuring in the natural form used in the new trial and prior studies.
Clinical trial adds to astaxanthin's cardiovascular promise
Past research has found that supplemental astaxanthin can lower blood pressure and artery damage in rats, while human studies indicate that supplemental astaxanthin can lower blood pressure, ease blood flow, and reduce dangerous oxidation of cholesterol.
Now the recently published results of a Japanese clinical study link astaxanthin to improvements in key markers for cardiovascular health... and they support earlier indications that it boosts a hormone that deters accumulation of highly unhealthful belly fat (Yoshida H et al. 2009).
Researchers at Jikei University conducted a three-month, placebo-controlled trial in 61 people aged 25-60, with normal-to-high triglyceride levels (120-200mg/dl).
They were assigned to take capsules that contained either no astaxanthin at all (placebo pills) or delivered astaxanthin doses of 6mg, 12mg, or 18mg per day.
Compared with the placebo group, blood tests showed that the people who took 12mg or 18mg per day showed significantly reduced 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.
As the authors wrote, “This first-ever randomized, placebo-controlled human study suggests that astaxanthin consumption ameliorates [improves] triglyceride and HDL-cholesterol in correlation [tandem] with increased adiponectin [levels] ...”
Astaxanthin in wild and farmed salmon: Not created equal
Most of the studies conducted to date have used a supplemental astaxanthin product extracted from fresh-water algae (Haematacoccus pluvialis).
Those supplements contain the same form of astaxanthin found in wild salmon, so it seems reasonable to presume that equivalent intakes, whether from supplements or wild salmon, would yield similar bodily effects.
If anything, salmon should be the superior source because it provides astaxanthin as part of a full package of synergistic nutrients—omega-3s, vitamin D, and astaxanthin—in a combined abundance found in no other food.
Farmed salmon get astaxanthin as a feed additive, both because consumers will not buy white- or grey-fleshed salmon, and because astaxanthin is essential for salmon's growth and overall health.
A minority of farmed salmon get chow that contains the natural form derived from algae, but most farms feed their fish the cheaper synthetic astaxanthin made from petrochemicals.
Astaxanthin comes in various forms, and chemists can tell farmed salmon from wild salmon by looking for the unnatural forms (isomers) created when astaxanthin is synthesized from petroleum.
To date, there is no evidence that the unnatural forms of astaxanthin in farmed salmon deliver health benefits comparable to those seen with the natural forms.
And wild salmon is far richer in astaxanthin, compared with farmed fish.
Astaxanthin levels in wild Pacific salmon can be four times higher than in farmed salmon.
Tissue levels in the flesh of farmed Atlantic salmon range from about four to 10mg per kilogram (2.2 pounds), but an FDA study found an average of about 14mg per kg in silver (coho) salmon and about 40mg per kg in sockeye (red) salmon (Turujman et al 1997).
In other words, a six-ounce piece of farmed Atlantic salmon averages 0.75 to 1.65mg of astaxanthin, while the same amount of wild sockeye salmon provides 6.75mg of astaxanthin, or four to nine times as much... all of it in the form found in nature.
Basu A, Penugonda K. Pomegranate juice: a heart-healthy fruit juice. Nutr Rev. 2009 Jan;67(1):49-56. Review.
Codoñer-Franch P, López-Jaén AB, Muñiz P, Sentandreu E, Bellés VV. Mandarin juice improves the antioxidant status of hypercholesterolemic children. J Pediatr Gastroenterol Nutr. 2008 Sep;47(3):349-55.
Fassett RG, Coombes JS. Astaxanthin, oxidative stress, inflammation and cardiovascular disease. Future Cardiol. 2009 Jul;5(4):333-42. Review.
Ghosh D, Scheepens A. Vascular action of polyphenols. Mol Nutr Food Res. 2009 Mar;53(3):322-31. Review.
Hussein G., et al., 2005b. Antihypertensive potential and mechanism of action of astaxanthin II. Vascular reactivity and hemorheology in spontaneously hypertensive rats. Biol. Pharm. Bull. 28(6):967-971.
Hussein G., et al., 2006a, Antihypertensive potential and mechanism of action of astaxanthin: III. Antioxidant and histopathological effects in spontaneously hypertensive rats. Biol. Pharm. Bull. 29(4):684-688.
Hussein G., et al., 2006b, Astaxanthin, a carotenoid with potential in human health and nutrition. J.Nat.Prod.69(3):443-449
Hussein, G. et al., 2005a, Antihypertensive and Neuroprotective Effects of Astaxanthin in Experimental Animals. Biol. Pharm. Bull. 2005; 28(1): 47-52.
Karppi J, Rissanen TH, Nyyssönen K, Kaikkonen J, Olsson AG, Voutilainen S, Salonen JT. Effects of astaxanthin supplementation on lipid peroxidation. Int J Vitam Nutr Res. 2007 Jan;77(1):3-11.
Kawashima A, Madarame T, Koike H, Komatsu Y, Wise JA. Four week supplementation with mixed fruit and vegetable juice concentrates increased protective serum antioxidants and folate and decreased plasma homocysteine in Japanese subjects. Asia Pac J Clin Nutr. 2007;16(3):411-21.
Li W., et al., Alpha-tocopherol and astaxanthin decrease macrophage infiltration, apoptosis and vulnerability in atheroma of hyperlipidaemic rabbits. Journal of Molecular and Cellular Cardiology 2004; 37: 969-978.
Miyawaki, H. et al. Effects of Astaxanthin on Human Blood Rheology. Journal of Clinical Therapeutics and Medicines 2005; 21 (4):421-429.
Nagaki, Y. et al. The Effect of Astaxanthin on Retinal Capillary Blood Flow in Normal Volunteers. Journal of Clinical Therapeutics and Medicines 2005; 21 (5): 537-542.
Ostertag LM, O'Kennedy N, Kroon PA, Duthie GG, de Roos B. Impact of dietary polyphenols on human platelet function--a critical review of controlled dietary intervention studies. Mol Nutr Food Res. 2010 Jan;54(1):60-81.
Pashkow FJ, Watumull DG, Campbell CL. Astaxanthin: a novel potential treatment for oxidative stress and inflammation in cardiovascular disease. Am J Cardiol. 2008 May 22;101(10A):58D-68D. Review.
Ruel G, Pomerleau S, Couture P, Lamarche B, Couillard C. Changes in plasma antioxidant capacity and oxidized low-density lipoprotein levels in men after short-term cranberry juice consumption. Metabolism. 2005 Jul;54(7):856-61.
Spormann TM, Albert FW, Rath T, Dietrich H, Will F, Stockis JP, Eisenbrand G, Janzowski C. Anthocyanin/polyphenolic-rich fruit juice reduces oxidative cell damage in an intervention study with patients on hemodialysis. Cancer Epidemiol Biomarkers Prev. 2008 Dec;17(12):3372-80.
Wongcharoen W, Phrommintikul A. The protective role of curcumin in cardiovascular diseases. Int J Cardiol. 2009 Apr 3;133(2):145-51. Epub 2009 Feb 23. Review.
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. 2009 Oct 14. [Epub ahead of print]