But a growing body of evidence suggests that they may help deter diabetes.
Humans need to consume small amounts of omega-3 and omega-6 fatty acids.
Both are essential to our cells, and to critical aspects of brain function, metabolism, and immune-system health.
Omega-3s vs. diabetes: The story so far
The protective potential of omega-3s is supported by epidemiological studies, most of which link higher omega-3 intakes to lower diabetes risk … see “Omega-3s Linked to Lower Diabetes Risk”.
But there’s more to the story, which involves America’s extreme, historically unprecedented dietary “omega imbalance”.
The average American eats far too many omega-6 fatty acids, from the vegetable oils used in home and commercial kitchens.
In contrast, most Americans don’t get enough omega-3 fatty acids to enable and maintain optimal health …in part because of their over-consumption of competing omega-6 fatty acids.
And that imbalance appears to promote diabetes, as we reported in “Omega-6/Omega-3 Imbalance Pushes Heart/Diabetes Perils”.
Why would people’s relative intakes of omega-3 and omega-6 fatty acids affect their diabetes risk?
MetS drives diabetes risk
Having higher omega-3s levels in your cells – and a higher ratio of omega-3s to omega-6s – in your cells tends to deter a major risk factor for diabetes, called Metabolic Syndrome or MetS.
MetS is defined as having three or more of a half-dozen unhealthful signs:
- Abdominal obesity (excessive fat tissue in and around the abdomen).
- High blood triglycerides, low HDL cholesterol and high LDL cholesterol: a state that fosters plaque buildups in artery walls.
- Elevated blood pressure.
- Insulin resistance or glucose intolerance (the body can’t properly use insulin or blood sugar).
- Pro-thrombotic state that promotes dangerous clots (e.g., high fibrinogen or plasminogen activator inhibitor–1 in the blood).
- Pro-inflammatory state (e.g., elevated C-reactive protein in the blood).
MetS is now believed largely responsible for the epidemics of cardiovascular disease and diabetes exploding throughout the world.
Omega-3s stimulate helpful “starvation hormone”
Two of the undesirable traits that define MetS – abdominal obesity and insulin resistance – may be deterred by a hormone called adiponectin.
And long-term human studies link higher levels of adiponectin to lower risks of type 2 diabetes and heart disease.
Among other things, adiponectin our cells’ sensitivity to insulin – loss of which causes diabetes – and plays a critical role in regulating fat storage.
When adiponectin levels are high, the body stores excess fat in fat cells (adipocytes), to protect against possible starvation during lean times … hence its nickname, the “starvation hormone.”
Fat deposited because of the actions of adiponectin lie primarily in the subcutaneous tissue located, as the name implies, under the skin.
As a person accumulates more fat, adiponectin levels decline and the body begins storing fat in the abdomen, heart, liver and muscle tissues … where it can cause inflammation and pave the way for heart disease and diabetes.
For more on this topic, see “‘Starvation Hormone’ Helps Metabolic Health” and other articles in the Omega-3s & Metabolic Health section of our news archive.
Studies published over the past few years suggest that higher intakes of fish and/or supplemental fish-source omega-3s raise adiponectin levels and benefit related markers for good metabolic health (Neale EP et al. 2013; Lefils-Lacourtablaise J et al. 2013; Younan SM et al. 2013; Mostowik M et al. 2013)
In a recent controlled clinical trial, the participants who took omega-3 capsules developed higher adiponectin levels, among other diabetes-related benefits … see “Omega-3s Reduced Diabetes Risk Markers”.
Now, a “meta-analysis” of the medical literature by scientists at the Harvard School of Public Health adds weight to the idea that fish and their omega-3s may help deter diabetes.
Harvard study supports omega-3s vs. diabetes
The new literature review comes from a team led by Jason Wu, Ph.D., of the Harvard School of Public Health (Wu JH et al. 2013).
As he said, “By reviewing evidence from existing randomized clinical trials, we found that fish oil supplementation caused modest increases in adiponectin in the blood of humans.” (ES 2013)
The reviewers analyzed the results from 14 randomized, placebo-controlled clinical trials involving 1,323 people:
- 682 took fish oil capsules
- 641 took placebo capsules (mostly olive or sunflower oils)
Those in the groups taking fish oil developed higher adiponectin levels, which increased by an average of 0.37 mcg/mL.
However, the effect of fish oil on adiponectin levels differed across the trials, which suggests that fish oil may raise adiponectin levels more significantly in some people.
“Although higher levels of adiponectin in the bloodstream have been linked to lower risk of diabetes and coronary heart disease, whether fish oil influences glucose metabolism and development of type 2 diabetes remains unclear,” said Wu.
“However,” he added, “[the] results from our study suggest that higher intake of fish oil may moderately increase blood level of adiponectin, and these results support potential benefits of fish oil consumption on glucose control and fat cell metabolism.” (ES 2013)
Funding for the meta-analysis came from The National Institutes of Health’s National Heart, Lung and Blood Institute.
- Lefils-Lacourtablaise J, Socorro M, Géloën A, Daira P, Debard C, Loizon E, Guichardant M, Dominguez Z, Vidal H, Lagarde M, Bernoud-Hubac N. The Eicosapentaenoic Acid Metabolite 15-Deoxy-δ(12,14)-Prostaglandin J3 Increases Adiponectin Secretion by Adipocytes Partly via a PPARγ-Dependent Mechanism. PLoS One. 2013 May 29;8(5):e63997. doi: 10.1371/journal.pone.0063997. Print 2013.
- Mostowik M, Gajos G, Zalewski J, Nessler J, Undas A. Omega-3 Polyunsaturated Fatty Acids Increase Plasma Adiponectin to Leptin Ratio in Stable Coronary Artery Disease. Cardiovasc Drugs Ther. 2013 Apr 14. [Epub ahead of print]
- Neale EP, Muhlhausler B, Probst YC, Batterham MJ, Fernandez F, Tapsell LC. Short-term effects of fish and fish oil consumption on total and high molecular weight adiponectin levels in overweight and obese adults. Metabolism. 2013 May;62(5):651-60. doi: 10.1016/j.metabol.2012.10.014. Epub 2012 Nov 26.
- The Endocrine Society (ES). Fish Oil Supplements May Help Fight Against Type 2 Diabetes. May 22, 2013. Accessed at https://www.endocrine.org/news-room/current-press-releases/fish-oil-supplements-may-help-fight-against-type-2-diabetes
- Wu JH, Cahill LE, Mozaffarian D. Effect of fish oil on circulating adiponectin: a systematic review and meta-analysis of randomized controlled trials. J Clin Endocrinol Metab. 2013 Jun;98(6):2451-9. doi: 10.1210/jc.2012-3899. Epub 2013 May 23.
- Wu JH, Micha R, Imamura F, Pan A, Biggs ML, Ajaz O, Djousse L, Hu FB, Mozaffarian D. Omega-3 fatty acids and incident type 2 diabetes: a systematic review and meta-analysis. Br J Nutr. 2012 Jun;107 Suppl 2:S214-27. doi: 10.1017/S0007114512001602. Review.
- Younan SM, Rashed LA, Abd El Aziz OM. Cardioprotective Modulation of Cardiac Adiponectin and Adiponectin Receptors by Omega-3 in the High-Fat Fed Rats. Chin J Physiol. 2013 Apr 30;56(2). doi:pii: CJP.2013.BAA069. 10.4077/CJP.2013.BAA069. [Epub ahead of print]