Monday, December 23, 2013

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Saturday, December 14, 2013

ADA Position Statement On Nutrition Therapy For Diabetes: Fat

The American Diabetes Association (ADA) recently published their new Position Statement on nutrition therapy for people with diabetes:
Nutrition Therapy Recommendations for the Management of Adults With Diabetes, Diabetes Care, Published online ahead of print, 9 October 2013.
This post focuses on fat. Previous posts focused on carbohydrate and protein. The carbohydrate post summarized the grading system that the ADA used to rate their evidence.

Keeping with their recommendations for carbohydrate and protein, the panel did not designate a particular amount of fat to consume. They noted that people with diabetes eat about 36-40% of their calories from fat - an observation, not a recommendation.

For people without diabetes, the Institute of Medicine states that an acceptable amount of fat to consume (acceptable macronutrient distribution range or AMDR) is 20-35%, and that there is "evidence for increased obesity and its complications [e.g. heart disease] at high intakes of fat." Echoing this, the ADA said:
"Individuals with diabetes should be encouraged to moderate their fat intakes to be consistent with their goals to lose or maintain weight."
Here are the ADA's grades for total fat intake:
Evidence is inconclusive for an ideal amount of total fat intake for people with diabetes; therefore, goals should be individualized. Grade C

Fat quality appears to be far more important than quantity. Grade B
Regarding fat quality, the ADA recommended substituting saturated fat with monounsaturated and polyunsaturated fat: "PUFAs and MUFAs are recommended substitutes for saturated or trans fat."
In people with type 2 diabetes, a Mediterranean-style, MUFA-rich eating pattern may benefit glycemic control and CVD risk factors and can therefore be recommended as an effective alternative to a lower-fat, higher-carbohydrate eating pattern. Grade B
Nuts and olive oil are good sources of monounsaturated fat.

Omega-3 fatty acids are polyunsaturated fatty acids or PUFAs. The panel preferred omega-3-rich food over omega-3 supplements:
Evidence does not support recommending omega-3 (EPA and DHA) supplements for people with diabetes for the prevention or treatment of cardiovascular events. Grade A

As recommended for the general public, an increase in foods containing long-chain omega-3 fatty acids (EPA and DHA) (from fatty fish) and omega-3 linolenic acid (ALA) is recommended for individuals with diabetes because of their beneficial effects on lipoproteins, prevention of heart disease, and associations with positive health outcomes in observational studies. Grade B

The recommendation for the general public to eat fish (particularly fatty fish) at least two times (two servings) per week is also appropriate for people with diabetes. Grade B
About saturated fat, they said:
The amount of dietary saturated fat, cholesterol, and trans fat recommended for people with diabetes is the same as that recommended for the general population. Grade C
They note that the general population should be aiming for less than 10% of calories from saturated fatty acids (SFAs) and less than 300 mg cholesterol/day:
"The Dietary Guidelines for Americans, 2010 recommends consuming less than 10% of calories from SFAs to reduce [cardiovascular disease (CVD)] risk. Consumers can meet this guideline by replacing foods high in SFA (i.e., full-fat dairy products, butter, marbled meats and bacon, and tropical oils such as coconut and palm) with items that are rich in MUFA and PUFA (i.e., vegetable and nut oils including canola, corn, safflower, soy, and sunflower; vegetable oil spreads; whole nuts and nut butters, and avocado).

CVD is a common cause of death among people with diabetes. As a result, individuals with diabetes are encouraged to follow nutrition recommendations similar to the general population to manage CVD risk factors. These recommendations include reducing SFAs to less than 10% of calories, aiming for less than 300 mg dietary cholesterol/day, and limiting trans fat as much as possible."

Saturday, November 23, 2013

High Dietary Acid Load May Raise Risk For Type 2 Diabetes

Fruits and vegetables, such as the winter squashes shown,
can help reduce dietary acid load.
A large prospective study found that the higher a woman's dietary acid load, the greater her risk for type 2 diabetes:

Dietary Acid Load And Risk Of Type 2 Diabetes: The E3N-EPIC Cohort Study, Diabetologia, Published online 11 November 2013

Researchers from France followed 66,485 women teachers for 14 years. The women were part of the E3N-EPIC cohort. They were sectioned into 4 groups or quartiles, corresponding to the acid load of their diet. Those in the highest quartile, consuming foods with the most acid-forming potential, had a 56% increased risk of developing type 2 diabetes compared to those in the lowest quartile.

Interestingly, women with normal body weight (BMI less than 25) had the highest risk - a 96% increased risk for developing type 2 diabetes (top quartile compared to bottom). Overweight women (BMI 25 and over) had a 28% increased risk. However, this could indicate that the association between an acid-forming diet and diabetes is independant of body weight.

Given the long follow-up, researchers were able to rule out reverse causation, that is, the possibility that diabetes led to acidosis.

The researchers concluded:
"We have demonstrated for the first time in a large prospective study that dietary acid load was positively associated with type 2 diabetes risk, independently of other known risk factors for diabetes. Our results need to be validated in other populations, and may lead to promotion of diets with a low acid load for the prevention of diabetes. Further research is required on the underlying mechanisms."

Is Insulin Resistance The Mechanism?

Cross-sectional studies have shown that a high dietary acid load is associated with insulin resistance. Acidosis may interfere with binding of insulin to its receptors, or may result in decreased insulin secretion:
"The induction of mild acidosis by the administration of ammonium chloride results, in humans, in reduced insulin sensitivity, as assessed by the gold standard technique, the euglycaemic clamp. Furthermore, metabilic acidosis decreases the binding of insulin to its receptors in rats, suggesting that metabolic acidosis may promore insulin resistance. Finally, in experimental studies, acid/base alterations are associated with decreased insulin secretion."
"Type 2 diabetes incidence and glucose intolerance have been shown to be higher in people with a lower urinary pH [more acidic] than in those with a higher urinary pH."

What Is An Acid-Forming Diet?

An acid-forming diet has the potential to drive body fluids to a lower, or more acidic pH. (The body works to maintain blood in a tight, slightly alkaline pH range of 7.35 to 7.45.)

In this study, two equations were used to estimate the acid-forming potential of a diet:

Potential Renal Acid Load (PRAL):
PRAL = 0.49 Protein (g/d)* + 0.037 Phosphorus (mg/d) - 0.021 Potassium (mg/d) - 0.026 Magnesium (mg/d) - 0.013 Calcium (mg/d)

Net Endogenous Acid Production (NEAP):
NEAP = 54.5 Protein (g/d) / Potassium [mEq/d) − 10.2

* Protein is used as an estimate for sulfate.1 Protein is made up of amino acids. Of the 20 common protein-sourced amino acids in food, only 2 contain sulfur: methionine and cysteine.

Of note in these equations, foods high in protein (especially proteins high in methionine and cysteine) and to a lesser degree phosphorus have a high acid-forming potential. Foods high in potassium and magnesium have a low acid-forming potential. (Remer et al. found that eliminating calcium from the equation improved prediction of acid effect.1)

You can estimate the acid-forming potential of a food by substituting actual values into the equations. A database such as NutritionData can supply these values.

Here are a few examples. (Numbers with a plus sign are acidic; numbers with a minus sign are alkaline.)

2 ounces cheddar cheese:
PRAL = 0.49 (14) + 0.037 (286) - 0.021 (54.8) - 0.026 (15.6)
PRAL = +16 (very acidic)

3 ounce beef tenderloin, broiled:
PRAL = 0.49 (23) + 0.037 (180) - 0.021 (290) - 0.026 (19.6)
PRAL = +11 (very acidic)

2 slices whole wheat bread:
PRAL = 0.49 (8) + 0.037 (113) - 0.021 (139) - 0.026 (46)
PRAL = +4 (weakly acidic)

1 medium banana:
PRAL = 0.49 (1) + 0.037 (30) - 0.021 (487) - 0.026 (37)
PRAL = -10 (very alkalizing)

1 large sweet potato, baked in skin (about 1 cup):
PRAL = 0.49 (4) + 0.037 (108) - 0.021 (950) - 0.026 (54)
PRAL = -15 (very alkalizing)

Foods containing animal protein tend to be the most acid-forming. In general:

  • Dairy - Acidic
  • Meats (beef, poultry, pork, seafood) - Acidic
  • Grains (wheat, rice, corn) - Weakly Acidic
  • Beans and legumes - Slightly Alkaline to Slightly Acidic
  • Fats and Oils - Neutral
  • Fruits - Alkaline
  • Vegetables - Alkaline
1 Dietary Potential Renal Acid Load And Renal Net Acid Excretion In Healthy, Free-Living Children And Adolescents, American Journal of Clinical Nutrition, 2003

Sunday, November 17, 2013

How Much Protein Should A Person With Diabetes Eat?

The American Diabetes Association (ADA) recently published their new Position Statement on nutrition therapy for people with diabetes:
Nutrition Therapy Recommendations for the Management of Adults With Diabetes, Diabetes Care, Published online ahead of print, 9 October 2013.
This post focuses on protein. (A previous post focused on carbohydrate. That post summarized the grading system they used to rate their evidence.)

The panel did not designate a particular amount of protein to consume, either in grams or percentage of calories, other than noting that people with diabetes eat about 45% of their calories from carbohydrate, 36-40% from fat, and 16-18% from protein:
Evidence suggests that there is not an ideal percentage of calories from carbohydrate, protein, and fat for all people with diabetes. Grade B

Macronutrient distribution should be based on individualized assessment of current eating patterns, preferences, and metabolic goals. Grade E
Diabetes is the most common cause of kidney failure in the US. Even when a person's diabetes is controlled, they can still develop chronic kidney disease.

One job of the kidney is the removal of excess nitrogen or nitrogenous waste. Protein is the primary source of nitrogen in our diet. (The other macronutrients - fat, carbohydrate, and fiber - do not, by themselves, contain nitrogen. However, natural foods usually contain a combination of macronutrients.)

About protein consumption, the National Institutes of Health, NIDDK, say:
"In people with diabetes, excessive consumption of protein may be harmful. Experts recommend that people with kidney disease of diabetes consume the recommended dietary allowance for protein, but avoid high-protein diets. For people with greatly reduced kidney function, a diet containing reduced amounts of protein may help delay the onset of kidney failure."
The ADA panel said:
For people with diabetes and no evidence of diabetic kidney disease, evidence is inconclusive to recommend an ideal amount of protein intake for optimizing glycemic control or improving one or more [cardiovascular disease] risk measures; therefore, goals should be individualized. Grade C

For people with diabetes and diabetic kidney disease (either micro- or macroalbuminuria), reducing the amount of dietary protein below usual intake is not recommended because it does not alter glycemic measures, cardiovascular risk measures, or the course of GFR* decline. Grade A
There appears to be some disagreement in these recommendations. Do people with diabetes and kidney disease reduce their protein intake or not? The best course of action may be to have kidney function checked regularly and individualize protein intake based on those measurements.

The term "protein" conjures meat and other animal-based foods. However, plant-based foods also provide protein. Here is what the ADA panel said about soy:
"For individuals with diabetic kidney disease and microalbuminuria, changing the source of protein to be more soy-based may improve [cardiovascular disease] risk factors but does not appear to alter proteinuria."
They cited the following 2 studies as a basis for that statement, both of which found that intake of soy protein improved serum cholesterol levels and markers of kidney function, including proteinuria, "and may be beneficial for type 2 diabetic patients with nephropathy [kidney disease]":
Isolated Soy Protein Consumption Reduces Urinary Albumin Excretion and Improves the Serum Lipid Profile in Men with Type 2 Diabetes Mellitus and Nephropathy, Journal of Nutrition, August 2004

Soy Protein Intake, Cardiorenal Indices, and C-Reactive Protein in Type 2 Diabetes With Nephropathy, A longitudinal randomized clinical trial, Diabetes Care, April 2008
Lastly, the following recommendation by the ADA stands out:
In individuals with type 2 diabetes, ingested protein appears to increase insulin response without increasing plasma glucose concentrations. Therefore, carbohydrate sources high in protein should not be used to treat or prevent hypoglycemia. Grade B

* GFR is Glomerular Filtration Rate, a measure of kidney function. Higher numbers are better. A normal, healthy kidney has a GFR above 90 (the unit is mL/min/1.73m2) with no protein, such as albumin, found in urine.

Friday, November 15, 2013

Increasing Red Meat Consumption Increases Risk For Type 2 Diabetes In 3 Large Cohorts

Following the theme of yesterday's post, Large Prospective Study Supports Link Between Meat Consumption And Diabetes, below is a study from this summer which found that increasing the amount of red meat eaten - by just a half serving or a few ounces a day - increases the risk for type 2 diabetes:

Changes in Red Meat Consumption and Subsequent Risk of Type 2 Diabetes Mellitus: Three Cohorts of US Men and Women, JAMA Internal Medicine, July 2013

Researchers followed 149,143 participants of 3 Harvard-based prospective cohorts - the Health Professionals Follow-Up Study, the Nurses’ Health Study, and the Nurses’ Health Study II. After adjustment (for age, family history, race, marital status, initial red meat consumption, smoking status, physical activity, alcohol intake, total energy intake, and diet quality), they found that:
"Increasing red meat intake during a 4-year interval was associated with an elevated risk of [type 2 diabetes] during the subsequent 4 years in each cohort."

"Increasing red meat intake of more than 0.50 servings per day was associated with a 48% elevated risk [of type 2 diabetes] in the subsequent 4-year period.

"Reducing red meat consumption by more than 0.50 servings per day from baseline to the first 4 years of follow-up was associated with a 14% lower risk during the subsequent entire follow-up."
They concluded:
"Our results confirm the robustness of the association between red meat and [type 2 diabetes] and add further evidence that limiting red meat consumption over time confers benefits for [type 2 diabetes] prevention."
People change their eating behavior over time. Studies that measure food intake at one point in time, usually at baseline or the beginning of a study, fail to account for these changes. In these 3 cohorts, diet was updated every 4 years.

Thursday, November 14, 2013

Large Prospective Study Supports Link Between Meat Consumption And Diabetes

Here's another study that provides evidence for a link between meat consumption and risk for type 2 diabetes:

Association Between Dietary Meat Consumption And Incident Type 2 Diabetes: The EPIC-Interact Study, Diabetologia, January 2013

Researchers investigated food intake from 16,835 participants of the InterAct project, "an examination of the interaction of genetic and lifestyle factors on the incidence of type 2 diabetes." The InterAct project, or EPIC-InterAct study, is a large prospective study nested within the EPIC study (European Prospective Investigation into Cancer and Nutrition). InterAct drew participants from 8 countries, accounting for variations in meat consumption across Europe.

After adjusting for confounders, researchers found a significant positive association with type 2 diabetes and each of the following: total meat consumption, red meat consumption, and processed meat consumption. The association was dose-dependent; for every 50 gram increase (about 2 ounces) there was a corresponding increase in diabetes risk. For women, there was also an association between poultry consumption and diabetes.

Their conclusion:
"This prospective study confirms a positive association between high consumption of total and red meat and incident type 2 diabetes in a large cohort of European adults."
In this study, "red meat" was unprocessed and included:
  • Beef
  • Pork
  • Veal
  • Mutton
  • Lamb
  • Goat
  • Horse
  • Hamburgers
  • Meatballs
  • Minced meat

"Poultry" included:
  • Chicken
  • Hen
  • Turkey
  • Duck
  • Goose
  • Rabbit

"Processed meat" included:
  • Bacon
  • Ham
  • Liver
  • Black pudding
  • Chorizo
  • Sausages
  • Corned beef