Exploring the sense and nonsense of food and health

From Fish to Nuts – Controlling Diabetes

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Diabetes Facts:

  • In contrast to the 2007 National Diabetes Fact Sheet, which used fasting glucose data to estimate undiagnosed diabetes and prediabetes, the 2011 National Diabetes Fact Sheet uses both fasting glucose and A1C levels to derive estimates for undiagnosed diabetes and prediabetes. These tests were chosen because they are most frequently used in clinical practice.
  • Among U.S. residents ages 65 years and older, 10.9 million, or 26.9 percent, had diabetes in 2010.
  • About 215,000 people younger than 20 years had diabetes—type 1 or type 2—in the United States in 2010.
  • About 1.9 million people ages 20 years or older were newly diagnosed with diabetes in 2010 in the United States.
  • In 2005–2008, based on fasting glucose or hemoglobin A1C (A1C) levels, 35 percent of U.S. adults ages 20 years or older had pre-diabetes—50 percent of adults ages 65 years or older. Applying this percentage to the entire U.S. population in 2010 yields an estimated 79 million American adults ages 20 years or older with pre-diabetes.
  • Diabetes is the leading cause of kidney failure, nontraumatic lower-limb amputations, and new cases of blindness among adults in the United States.
  • Diabetes is a major cause of heart disease and stroke.
  • Diabetes is the seventh leading cause of death in the United States.

Two recent studies investigated specific diet components – one nut intake and one fish intake on the risk of developing diabetes and controlling blood glucose levels.

Nuts as a Replacement for Carbohydrates in the Diabetic Diet.

OBJECTIVE Fat intake, especially monounsaturated fatty acid (MUFA), has been liberalized in diabetic diets to preserve HDL cholesterol and improve glycemic control, yet the exact sources have not been clearly defined. Therefore, we assessed the effect of mixed nut consumption as a source of vegetable fat on serum lipids and HbA1c in type 2 diabetes.

RESEARCH DESIGN AND METHODS A total of 117 type 2 diabetic subjects were randomized to one of three treatments for 3 months. Supplements were provided at 475 kcal per 2,000-kcal diet as mixed nuts (75 g/day), muffins, or half portions of both. The primary outcome was change in HbA1c.

The mixed nuts were a combination of raw almonds, pistachios, walnuts, pecans, hazelnuts, peanuts, cashews, and macadamian nuts.  The mixed nut group had the greatest improvement in blood glucose control when measured by the glycosylated hemoglobin (Hb1c) test.  They also had a significant decline in LDL (“bad” cholesterol).  The other two groups had no significant improvement in Hb1C, but the muffin-nut mixture significantly reduced LDL cholesterol in the blood.

Dr. Jenkins, the lead author of they study said: “Those receiving the full dose of nuts reduced their HbA1c (the long-term marker of glycemic control) by two thirds of what the FDA recognizes as being clinically meaningful for therapeutic agents.  Furthermore, neither in the current study nor in previous reports has nut consumption been associated with weight gain.”

D. J. A. Jenkins, C. W. C. Kendall, M. S. Banach, K. Srichaikul, E. Vidgen, S. Mitchell, T. Parker, S. Nishi, B. Bashyam, R. de Souza, C. Ireland, R. G. Josse. Nuts as a Replacement for Carbohydrates in the Diabetic Diet. Diabetes Care, 2011; DOI: 10.2337/dc11-0338

Dietary Fish Linked to Lower Risk for Type 2 Diabetes in Men

The second study was a prospective study to see if there was an association between fish intake and type 2 diabetes in Japanese adults.  22, 921 men and 29, 759 women aged 45-70 years old non-diabetics completed a survey and a food frequency questionnaire (147 food items).  Over a 5-year period, 971 new cases of type 2 diabetes were self-reported (572 men and 399 women).  Fish intake as significantly associated with a reduced risk for the development of type 2 diabetes in men but not for women.

Previous studies have linked the presence of environmental contaminants to an increased risk of diabetes.  The authors proposed that the women in this study had a higher body fat mass, which can accumulate these contaminants and possibly negate the benefits of fish intake on glucose control.

There were some obvious limitations in this study, the authors noted.  There was a lack of data concerning the cooking methods of the fish or the contamination level of the fish consumed.  There was only a one time dietary recall and all the data was self-reported as often found in diet studies of this type.

Nevertheless, study results often find gender differences.  If this is truly the case in this study, it suggests that one-diet-fits-all approach is not always the answer.  Future diet recommendations will hopefully be able to be more individualized and personalized to take into consideration the variety of confounding biological factors affecting diet and health.

American Journal of Clinical Nutrition; Published online July 20, 2011.


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