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Fish, omega-3s, and diabetes
11/12/2004
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New nutritional options for prevention and treatment

by Randy Hartnell


November is American Diabetes Month, so we’d like to offer some of the latest information on fish and omega-3s in the prevention and treatment of diabetes and related cardiovascular conditions.


There is little doubt that fish and omega-3s can help prevent and treat the cardiovascular dysfunctions associated with diabetes. In addition, dietary fish may help prevent impaired glucose tolerance—one of the diet- and lifestyle-related metabolic imbalances known collectively as “syndrome X,” which can lead to diabetes.


And, omega-3s may even benefit long-time diabetes patients.


Here’s the story, in full, including a heartening account of one diabetics experience with omega-3s.


Diabetes: A growing scourge

Of the estimated 18.2 million people in the United States who have diabetes, nearly one-third (5.2 million) are unaware of their disease. Every year, some 1.3 million new cases are diagnosed among people aged 20 years or older.


Diabetes is a leading killer of Americans, yet it is under-reported as a cause of death.  Among deceased diabetics, only 35-40 percent of death certificates note the presence of the disease, while only 10-15 percent list diabetes as the underlying cause of death.  Despite under-reporting, diabetes still ranked as the sixth leading killer in the U.S. in 2000, with some 213,000 deaths attributed to the disease.  Overall, the risk for early death among people with diabetes is about 2 times that of people without diabetes.


Although the causes and triggers of diabetes remain a mystery, genetics and lifestyle factors—such as obesity and lack of exercise—appear to play the key roles. Diabetes often goes undiagnosed, because many of its symptoms are subtle or commonplace. However, early detection of diabetes can help decrease the chance of developing complications.


The American Diabetes Association (ADA) advises people to watch for these possible signs of diabetes, any of which should lead you to contact your physician:

  • Frequent urination
  • Excessive thirst
  • Extreme hunger
  • Unusual weight loss
  • Increased fatigue
  • Irritability
  • Blurry vision

Omega-3s in diabetes prevention and treatment

Eating fish frequently appears to be safe and beneficial for diabetics, and some studies indicate that dietary fish may protect against the development of impaired glucose tolerance—an early warning sign of diabetes. Although omega-3s do not seem to improve insulin resistance—the core problem in diabetes—they appear to offer valuable benefits.


In fact, there is some evidence that fish oil or supplemental omega-3s (specifically, the EPA found only in fish oil) may help prevent some of the adverse effects of diabetes, from oxidation, inflammation, and hypertension to kidney and blood vessel damage. For example, the authors of four relevant studies on the effects of marine omega-3s (EPA and DHA) in diabetes came to these conclusions:

  • “…EPA-E [the ethyl ester form of omega-3 EPA used in clinical trials] has significant beneficial effects on diabetic neuropathy and serum lipids as well as other diabetic complications such as nephropathy and macroangiopathy.”
  • “…EPA-E administration improved increased albumin [protein] excretion in NIDDM [type II diabetes] patients with nephropathy and its effects on albuminuria [excessive protein in urine] sustained for at least 12 months after the start of treatment.”
  • “The present study documented the existence of a state of increased oxidative stress in type 2 diabetics. Significant beneficial effects of low dose omega-3 fatty acids substitution for PUFA-6 [omega-6 fatty acids, as in corn or safflower oil] were observed not only on oxidative stress parameters but also on blood pressure and metabolic profile.”
  • “Supplementation with omega-3 fatty acids has beneficial effects on serum [blood] triglycerides, HDL-cholesterol, lipid peroxidation and antioxidant enzymes, which may lead to decreased rate of occurrence of vascular complications in diabetes.”

Bob’s story: keeping diabetes’ damage at bay

Robert Jeffcott is an old friend who has had diabetes for more than 20 years.  Bob believes that the omega-3s in wild salmon and sockeye oil have slowed the progression of his disease. Because of the circulatory and immune-suppressing effects of diabetes, Bob—who is 71 years old—has had foot surgery several times, to remove areas of damaged tissue.


However, despite being semi-disabled, Bob says that he is doing better than fellow diabetics diagnosed about the same time. He tells me that he’s experienced lower blood pressure, improved circulation (due to the blood thinning properties of omega-3s), and a strengthened immune system, which helps fight minor infections that can quickly become major ones, like the gangrene that requires foot surgery and amputations among some older diabetics.


As Bob told me, “The doctors are kind of incredulous. I’ve been scheduled for surgery a few times, before they realized my toes were doing okay. I take two to three sockeye oil capsules a day, and eat wild salmon at least three times a week, and I’m convinced that this is what has helped keep me going. I also think that the omega-3s have helped me avoid the depression that can easily overtake someone in my condition. I really believe that omega-3s can make a big difference in the lives of diabetics… they sure have in mine.”


NOTE: Diabetics should be aware that supplemental omega-3s have, in some (not all) studies, worsened blood sugar control initially.  This effect seems to be a temporary, self-correcting phenomenon, but diabetics should monitor their blood sugar closely—under a physician’s guidance—when first taking omega-3 supplements.


The Heart-Diabetes Connection

We know that people who eat a lot of fish—like the Japanese and Greenland’s Inuit Eskimos—enjoy lower rates of diabetes.  And, while there is no proof that diets high in fish or marine omega-3s can prevent or treat diabetes, there is ample evidence that diets high in fish or supplemental omega-3s can improve key cardiovascular functions and reduce key risk factors for heart disease.


Heart disease is one of the most threatening “side effects” of diabetes, and this is why the ADA recommends two to three servings of fish per week—advice that echoes similar guidelines published by the American Heart Association.  As we reported in last month’s issue of Vital Choices [http://www.imakenews.com/vitalchoiceseafood/index000064200.cfm] three new studies lend even more weight to the mountain of evidence indicating that people can reduce their risk of heart disease by eating fish frequently.


In fact, ways to reduce diabetics’ risk of heart disease is one of the ADA’s primary education goals during the 2004 American Diabetes Month campaign. As the ADA noted in a recent press release:


“According to [the results of] a national study published in the January 2004 issue of the Journal of the American Medical Association, only 7.3 percent of people with diabetes met recommended guidelines for all three risk factors—blood glucose, cholesterol and blood pressure levels. Additional research released at the ADA’s 64th Annual Scientific Sessions in June indicate that only one-third of people with diabetes meet the ADA’s goals for LDL ("bad") cholesterol, and that nearly half of all people with diabetes have uncontrolled high blood pressure.”


There is good evidence that fish helps people with diabetes reduce their risk of a heart attack. In April 2003, researchers at the Harvard School of Public Health found that women with diabetes who ate fish 1 to 3 times a month reduced their risk of coronary heart disease by 30 percent, while those who ate fish 5 or more times per week reduced their risk by over 60 percent.


Omega-3s reduce heart risks in diabetes and “syndrome X”

A recent U.S. government-sponsored review of the scientific literature held good news for people who have either diabetes or the cluster of negative physiological indicators known as “syndrome X” or “metabolic syndrome,” which include these:

  • Excessive fat tissue in and around the abdomen (“central obesity”)
  • A blood fat imbalance—mainly high triglycerides and low HDL cholesterol—that fosters plaque buildups in artery walls (atherogenic dyslipidemia)
  • Insulin resistance or glucose intolerance (The body can’t properly use insulin or blood sugar)
  • A tendency toward excessive blood clotting, known as a pro-thrombotic state (Indicated by high fibrinogen or plasminogen activator inhibitor [–1] in the blood)
  • Elevated blood pressure (130/85 mmHg or higher)
  • Pro-inflammatory state (e.g., elevated high-sensitivity C-reactive protein in the blood)

Syndrome X indicates increased risk for both diabetes and heart disease.


In their literature review, the researchers analyzed the results of 18 studies involving people with type II diabetes or syndrome X. They found that “marine” omega-3 fatty acids—the kind found only in fish, shellfish, and human breast milk—exert a favorable effect on blood levels of triglycerides. The researchers also found that marine omega-3s help, in their words, to “…improve large artery endothelium-dependent dilation in subjects with hypercholesterolemia...”  In other words, marine omega-3s help to keep arteries from narrowing in people with high cholesterol levels.



Sources

  • American Diabetes Association. Good Fats and Bad Fats http://www.diabetes.org/diabetes-cholesterol/faqs-fat.jsp
  • American Diabetes Association. National Diabetes Fact Sheet http://www.diabetes.org/diabetes-statistics.jsp
  • American Heart Association, Inc. “What is the metabolic syndrome?” http://www.americanheart.org/presenter.jhtml?identifier=534
  • Goodfellow J, Bellamy MF, Ramsey MW, Jones CJ, Lewis MJ. Dietary supplementation with marine omega-3 fatty acids improve systemic large artery endothelial function in subjects with hypercholesterolemia. J Am Coll Cardiol. 2000 Feb;35(2):265-70.
  • Jain S, Gaiha M, Bhattacharjee J, Anuradha S. Effects of low-dose omega-3 fatty acid substitution in type-2 diabetes mellitus with special reference to oxidative stress--a prospective preliminary study. J Assoc Physicians India. 2002 Aug;50:1028-33.
  • Kasim SE. Dietary marine fish oils and insulin action in type 2 diabetes. Ann N Y Acad Sci. 1993 Jun 14;683:250-7. Review.
  • Kesavulu MM, Kameswararao B, Apparao Ch, Kumar EG, Harinarayan CV. Effect of omega-3 fatty acids on lipid peroxidation and antioxidant enzyme status in type 2 diabetic patients. Diabetes Metab. 2002 Feb;28(1):20-6.
  • Luo J, Rizkalla SW, Vidal H, Oppert JM, Colas C, Boussairi A, Guerre-Millo M, Chapuis AS, Chevalier A, Durand G, Slama G. Moderate intake of n-3 fatty acids for 2 months has no detrimental effect on glucose metabolism and could ameliorate the lipid profile in type 2 diabetic men. Results of a controlled study. Diabetes Care. 1998 May;21(5):717-24.
  • MacLean CH, Mojica WA, Morton SC, et al. Effects of Omega-3 Fatty Acids on Lipids and Glycemic Control in Type II Diabetes and the Metabolic Syndrome and on Inflammatory Bowel Disease, Rheumatoid Arthritis, Renal Disease, Systemic Lupus Erythematosus, and Osteoporosis. Summary, Evidence Report/Technology Assessment: Number 89. AHRQ Publication Number 04-E012-1, March 2004. Agency for Healthcare Research and Quality, Rockville, MD. http://www.ahrq.gov/clinic/epcsums/o3lipidsum.htm
  • McVeigh GE, Brennan GM, Cohn JN, Finkelstein SM, Hayes RJ, Johnston GD. Fish oil improves arterial compliance in non-insulin-dependent diabetes mellitus. Arterioscler Thromb. 1994 Sep;14(9):1425-9.
  • Nosari I, Cortinovis F, Lepore G, Maglio ML, Pagani G. [Use of omega-3 in diabetic patients] Clin Ter. 1994 Mar;144(3):213-21. Review. Italian.
  • Okuda Y, Mizutani M, Ogawa M, Sone H, Asano M, Asakura Y, Isaka M, Suzuki S, Kawakami Y, Field JB, Yamashita K. Long-term effects of eicosapentaenoic acid on diabetic peripheral neuropathy and serum lipids in patients with type II diabetes mellitus. J Diabetes Complications. 1996 Sep-Oct;10(5):280-7.
  • Pelikanova T, Kohout M, Valek J, Kazdova L, Base J. Metabolic effects of omega-3 fatty acids in type 2 (non-insulin-dependent) diabetic patients. Ann N Y Acad Sci. 1993 Jun 14;683:272-8.
  • Prince MJ, Deeg MA. Do n-3 fatty acids improve glucose tolerance and lipemia in diabetics? Curr Opin Lipidol. 1997 Feb;8(1):7-11. Review.
  • Shimizu H, Ohtani K, Tanaka Y, Sato N, Mori M, Shimomura Y. Long-term effect of eicosapentaenoic acid ethyl (EPA-E) on albuminuria of non-insulin dependent diabetic patients. Diabetes Res Clin Pract. 1995 Apr;28(1):35-40.
  • Vessby B, Boberg M. Dietary supplementation with n-3 fatty acids may impair glucose homeostasis in patients with non-insulin-dependent diabetes mellitus. J Intern Med. 1990 Aug;228(2):165-71.
  • Woodman RJ, Mori TA, Burke V, Puddey IB, Watts GF, Beilin LJ. Effects of purified eicosapentaenoic and docosahexaenoic acids on glycemic control, blood pressure, and serum lipids in type 2 diabetic patients with treated hypertension. Am J Clin Nutr. 2002 Nov;76(5):1007-15.

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