Fish oil helps prevent prediabetes from progressing to diabetes

Type 2 diabetes is a serious disease that is spreading at epidemic proportions. Many people have prediabetes without knowing it, with signs such as frequent hunger, apple-shaped obesity, insulin resistance, elevated cholesterol, and high blood pressure. Diet and lifestyle play a major role, and according to a study published in Research, fish oil supplementation may reduce the risk that people with prediabetes will go on to develop type 2 diabetes. In their article, the authors take a closer look at how the active omega-3 fatty acids in fish oil - EPA and DHA - help regulate insulin sensitivity, blood glucose, and other metabolic disturbances. In addition, simple dietary changes may further improve blood sugar control and weight management.

Globally, type 2 diabetes is among the leading chronic diseases and is associated with numerous symptoms and premature death. According to the International Diabetes Federation (IDF), nearly 600 million adults worldwide have diabetes, with type 2 diabetes accounting for about 90 percent of cases. At the same time, approximately 40 percent of the adult population in the United States has prediabetes, and a similar trend is seen in Europe. Prediabetes - also referred to as metabolic syndrome - develops gradually as a result of insulin resistance, a condition in which the hormone insulin functions poorly and the cells’ ability to take up blood sugar (glucose) is impaired. This leads to elevated blood glucose and insulin levels, triggering a range of metabolic disturbances, including abdominal obesity, high cholesterol, and high blood pressure. The condition is also characterized by chronic inflammation and oxidative stress, which increase the risk of vascular damage, atherosclerosis, and cardiovascular disease.
Although numerous studies have shown that diet and lifestyle play a major role in the development of prediabetes and type 2 diabetes, the role of fish oil has remained controversial. Fatty fish and fish oil contain the biologically active omega-3 fatty acids EPA and DHA, but the underlying mechanisms by which fish oil affects blood sugar regulation have not been fully understood. For this reason, the researchers behind the new study set out to investigate the issue more closely.

Fish oil regulates blood sugar through multiple mechanisms

The researchers first analyzed data from the UK Biobank, a large British health database that has collected extensive information on diet, lifestyle, and health over many years. The study included nearly 50,000 participants with prediabetes, about one-third of whom regularly took fish oil supplements. During a follow-up period of nearly nine years, 3,385 participants developed type 2 diabetes. However, those who took fish oil supplements had a nine percent lower risk of developing the disease.
The therapeutic effect of fish oil is largely attributed to its ability to regulate variants of the protein GLUT4 (glucose transporter type 4), which is stored inside cells. When cells require energy, GLUT4 is transported to the cell membrane, allowing insulin to increase the uptake of blood glucose into the cells. This improves insulin sensitivity and leads to more efficient utilization of glucose.
The researchers then conducted studies in mice to further examine the metabolic effects of fish oil on blood sugar using various analytical methods. These studies showed that EPA and DHA can improve glucose metabolism in prediabetes through several mechanisms, including:

• Transport of GLUT4 to muscle cell membranes
• Increased synthesis of glycogen, the body’s primary carbohydrate storage form in the liver and muscles
• Improved aerobic (oxygen-dependent) metabolism of carbohydrates and fats
• Enhanced creatine function, which supports anaerobic (oxygen-independent) energy metabolism

When carbohydrate metabolism improves, it has a positive effect on blood glucose and insulin levels. In this way, fish oil supplementation may reduce the risk that people with prediabetes will develop type 2 diabetes. The researchers also found that EPA had a stronger effect than DHA on blood sugar regulation.
The beneficial effect of fish oil on blood glucose remained significant even after adjusting for confounding factors such as age, sex, smoking, alcohol intake, dietary habits, and medication use.
It is also worth noting that fish oil may help prevent prediabetes in the first place through the mechanisms described above. In addition, fish oil counteracts chronic inflammation and oxidative stress, which - as noted - raise the risk of cardiovascular disease and are key drivers in the development of many chronic conditions.

Additional advice for preventing prediabetes and type 2 diabetes

Ultra-processed foods, including excessive amounts of refined carbohydrates and seed oils rich in omega-6 fatty acids, are a major contributor to the rising prevalence of prediabetes and type 2 diabetes. As part of prevention and treatment, it may therefore be beneficial to prioritize a whole-food, plant-forward diet with an emphasis on adequate protein, healthy fats, and dietary fiber. Supplementation with vitamin D and/or chromium may also be considered, as these nutrients influence blood sugar regulation through different mechanisms. You can read more about this in the following articles:

• There is a link between vitamin D deficiency and insulin resistance, diabetes, and overweight

• Chromium’s role in blood sugar regulation, diabetes, and cardiovascular disease

References:

Li, H et al. Marine N-3 Fatty Acids Mitigate Hyperglycemia in Prediabetes by Improving Muscular GLUT4 Translocation and Glucose Homeostasis. Research 2025.