Hyperinsulinemia or high blood insulin levels affects many disorders. Some of these diseases are metabolic syndrome (a disease characterized by hypertension, abnormal blood cholesterol, obesity, and insulin resistance), polycycstic ovary syndrome (a disorder in which the ovaries are enlarged and contain many fluid-filled sacs/cysts), obesity, (accumulation of excess body fat), insulinoma (tumor in the pancreas), and excessive insulin use, (in type 1 – where the pancreas do not produce insulin so insulin has to be injected, or in type 2 diabetes where the pancreas continues to manufacture insulin, sometimes at higher than normal levels).
Insulin is a hormone produced by the pancreatic beta cells. It’s functions are to:
- counter the combined actions of hyperglycemic hormones: glucagon, epinephrine/adrenaline, cortisol, adrenocorticohormone/ACTH, growth hormone, and thyroxine – hormones that increase blood sugar levels.
- maintain low blood glucose levels thereby regulating glucose metabolism
- stimulate lipogenesis (fat synthesis)
- reduce lipolysis (fat breakdown)
- increase amino acid transport into cells
- modulate the transcription of numerous genes altering the cell content of many mRNAs
- stimulate growth, DNA synthesis and cell replication; effects that it holds in common with insulin-like growth factors (IGF) and relaxin- an insulin-like hormone.
Insulin is a vital hormone. However, because of its effects on blood sugar concentration, too much can be dangerous, especially to organs that depends on glucose for its primary fuel source like the central nervous system. Free fatty acids cannot cross the brain-blood barrier although the brain can use ketones.Uncontrolled low blood sugar caused by hyperinsulinemia can lead to seizures, mental retardation, and permanent brain damage. The normal fasting blood insulin level range is 5-20 mcU/ml (mcU/ml means microunit per milliliter). Tappell and colleagues found that eating 30 grams (1/4 cup) of walnuts per day can favourably change the fasting insulin levels of overweight type 2 diabetics. To conduct the study, they recruited 50 overweight adults with type 2 diabetes aged 54 -58 yrs. None were on insulin injections. Participants were instructed to a low fat diet (about 2,000 calories with 30% fat) for one year. The subjects were divided into 2 groups; a control group and a “walnut” group – those who consumed 30 g of walnuts per day.
Results: The “walnut“ group showed significantly greater lower fasting levels of insulin than the control group, during the first three months. Both groups showed a 1-2 kg loss on the diet, and lower levels of serum triglyceride (the storage form of fat in the body). The researchers concluded that dietary fats can be manipulated with whole foods like walnuts to produce reductions in fasting insulin levels, and its salutary effects on insulin is attributed to walnuts’ polyunsaturated fat content (omega-3 fatty acid). Their investigation was published in the European Journal of Clinical Nutrition.
Origin, Geographic, and Nutritional Content of Walnuts
Black Walnut (Juglans nigra) or Eastern Black Walnut or American Walnut is a native of the deciduous forests of the eastern United States and Ontario, Canada. It is a large tree that may grow up to 125 feet, and live over 100 years. The walnut fruit is a drupe-like furrowed nut encased in a thick yellowish-green husk. A drupe is a fruit in which an outer fleshy part (or skin) surrounds a shell (the pit of stone). The meat is edible, sweet, oily and high in protein.
One quarter cup (30 g) of walnuts contains:
- Calories: 163 calories
- Omega 3 fatty acid: 2.27 g
- Omega 6 fatty acid:
- Protein: 3.81 g
- Carbohydrates: 3.4 g
- Total Fat: 16.30 g
- Saturated Fat: 1.53 g
- Monounsaturated Fat: 1.53 g
- Polyunsaturated Fat: 12 g
- Vitamin A: 10.25 International Units (IUs)
- Vitamin B1/Thiamin: 0.09 mg
- Vitamin B2/Riboflavin: 0.04 mg
- Vitamin B3/Niacin: 1/23 mg
- Vitamin B6: 0.13 mg
- Biotin: 4.75 mcg (micrograms)
- Folate: 24.50 mcg
- Vitamin E: 1.10 IUs
- Vitamin K: 0.68 mcg
- Pantothenic Acid: 0.14 mg
- Calcium: 26 mg
- Copper: 0.40 mg
- Iodine: 2.25 mg
- Iron: 0.73 mg
- Magnesium: 40 mg
- Phosphorus: 87 mg
- Potassium: 110 mg
- Selenium: 1.15 mcg
- Sodium: 0.50 mg
- Zinc: 0.77 mg
Tappell LC et al. “Long-term effects of increased dietary polyunsaturated fatty acid fats from walnuts on metabolic parameters in type 2 diabetes” European J of Clinical Nutrition 2009;63:1008-1015
Kasim-Karakas S. Omega-3 Fatty Acids and Insulin Resistance CRC Press, Boca Raton, FL 2000
Storlien LH et al. “Dietary Composition and Insulin Action in Animal Models” British J Nutrition 2000;83(Supp 1): S85-S90
National Library of Medicine (NLM) and the National Institute of Health (NIH) Medical Encyclopedia
Whitney EN & Rolfes SR Understanding Nutrition, Ninth Edition Wadsworth, CA 2002