“Low-Carbohydrate” Food Facts and Fallacies

In Diabetes


Ten years ago, weight-conscious Americans jumped on the fat-free bandwagon.
Supermarket shelves were replete with products touting
“reduced-fat” and “fat-free” labels, which implied
that these products were healthier and lower-calorie alternatives to standard
“high-fat” fare. Yet, in the same 10-year time interval, Americans
have continued to struggle with ever-expanding waistlines, gaining an average
of 1 lb/year.1 The
prevalence of type 2 diabetes has risen
simultaneously.2

Thirty-eight percent of our population is currently attempting to lose
weight.3 The latest
trend in the highly lucrative, yet often fickle, diet industry is a resurgence
of low-carbohydrate, high-protein, high-fat diets. Findings of a February 2004
survey by A.C. Nielsen, a leading market information company, revealed that
17.2% of households included someone on a low-carbohydrate diet. Slightly
more, 19.2%, included someone who had tried a low-carb diet but had
quit.4 This current
diet trend directly counters the decade-old focus on low-fat diets and
implicates carbohydrates as the culprit in America’s obesity problem.

In response to the low-carb resurgence, food manufacturers have rapidly
revised food products and package claims to seemingly reduce the carbohydrate
content of their products and increase consumer demand for them. Restaurant
menus have incorporated purportedly low-carb entrees to accommodate demand for
low-carb meals away from home. Aggressive marketing schemes imply that these
products are healthier alternatives to standard high-carb fare and that they
promote weight loss. For individuals with diabetes who are counting
carbohydrates or attempting to lose weight, the current marketplace can be a
source of a great deal of misinformation, cause considerable confusion, and
possibly affect glycemic control.

Confusing Labeling Terminology

Many food manufacturers have created their own terminology for carbohydrate
content that they claim has minimal effect on blood glucose. They suggest that
consumers subtract carbohydrate contributed from sugar alcohols, fiber, and
glycerin from the total carbohydrate value on the Nutrition Facts panel of
packaged foods to determine the “net carbs,” “impact
carbs,” “effective carbs,” or “net effective
carbs” of these foods. While these terms sound slightly different, they
are used by manufacturers to mean essentially the same thing.

However, this calculation can substantially underestimate the actual
carbohydrate value in many products and may result in insulin errors for
people using carbohydrate counting to determine their insulin dosages. In
addition, individuals with type 2 diabetes following a low-carb regimen for
weight loss may erroneously interpret these “disappearing carbs”
to mean “disappearing calories,” as well.

Currently, there are no Food and Drug Administration (FDA) regulations for
the use of carbohydrate claims on food package labels, as there are for claims
about fat, such as “low-fat,” “reduced-fat,” and
“fat-free.” Several organizations, including the Grocery
Manufacturers of America, have petitioned the FDA to establish regulations for
carbohydrate content claims. The FDA is working on guidelines for defining
“low,” “reduced,” or “free” carbohydrates
and for the use of the term “net” in relation to carbohydrate
content of food, based on recent recommendations by its Obesity Working
Group.

The U.S. Department of Agriculture (USDA) Food Safety and Inspection
Service has implemented an interim policy that provides guidelines for the use
of such labels on products within its jurisdiction, such as meat and poultry.
The USDA permits manufacturers to use the terms “net carbs,”
“impact carbs,” and “net effective carbs,” provided
such claims are truthful, not misleading, and supported by calculations shown
on the label.5

The net effect of this labeling lingo is confusion and a host of inquiries
to which health care professionals must respond.

How Do Manufacturers Lower the Carbohydrate Content of Foods?

A few creative chefs have replaced some naturally occurring carbohydrate
with healthy lower-carbohydrate alternatives, such as making low-carbohydrate
mashed “potatoes” with pureed cauliflower. But for the most part,
food manufacturers are lowering the grams of carbohydrate in processed foods
by altering the portion size or replacing naturally occurring carbohydrate
with ingredients that are higher in protein, fat, or other types of
carbohydrate. Examples include:

  1. substituting soy flour, soy protein, or wheat protein for refined flour

  2. adding fiber from wheat bran, oat bran, corn bran, inulin, or polydextrose
    as a bulking agent

  3. adding high-fat ingredients, such as nuts and oils

  4. replacing sugar with sugar alcohols, such as maltitol, lactitol, or
    sorbitol, or nonnutritive sweeteners, such as sucralose or acesulfame
    potassium

Are the Terms “Net Carbs,” “Impact Carbs,”
and “Net Effective Carbs” Truthful?

Fiber and sugar alcohols (including glycerin) currently must be included in
the total carbohydrate value shown in foods’ Nutrition Facts panel. To appeal
to the low-carb market, food manufacturers are subtracting these values from
the total carbohydrate grams to yield a lower-carbohydrate value termed
“net carbs,” “impact carbs,” “effective
carbs,” or “net effective carbs”
(Figure 1). The intent of these
claims is to convince consumers that the products are beneficial to a low-carb
diet because with their minimal effect on blood glucose, increases in insulin
levels and consequent weight gain will not occur.

Figure 1.
Figure 1.

Low-carb food package label.

But is this labeling misleading? Do these alternative carbohydrate values
have a minimal impact on glycemia?

Sugar alcohols/polyols

Sugar alcohols, or polyols, are hydrogenated carbohydrates that are used in
foods primarily as sweeteners and bulking agents.
Table 1 provides a list of
commonly used sugar alcohols or polyols and their caloric values. Sugar
alcohols provide 0.2–3.0 kcal/g, rather than the usual 4 kcal/g from
completely absorbed carbohydrate, because they are incompletely absorbed in
the small intestine. FDA regulations require that food manufacturers count
polyols as 2 kcal/g or use the specific kcal/g value determined by the FDA for
a single-sugar
alcohol.6 Because of
their incomplete absorption, consumption of polyols can cause flatulence or a
laxative effect in varying degrees in some individuals.

Table 1.

Calories in Common Polyols

Despite claims by many food manufacturers, sugar alcohols do
affect the postprandial blood glucose response in individuals both with and
without diabetes.7
In some studies, specific sugar alcohols elicited a lower glycemic response
than glucose, fructose, and/or
sucrose.7,8
In addition, a recent study showed maltitol syrup to have a significantly
greater glycemic effect than other sugar
alcohols.9

The glycemic effect of sugar alcohols may vary because of the type and
amount of sugar alcohol consumed or because of individual responses. The
American Diabetes Association nutrition recommendations state: “There is
no evidence that the amounts likely to be consumed in a meal or day will
result in significant reduction in total daily energy intake or improvement in
long-term
glycemia.”10
The following general
guidelines1114
are frequently used for counseling individuals with diabetes in carbohydrate
counting (Figure 2):

  1. Subtract half of the grams of total sugar alcohols (polyols) listed from
    the total carbohydrate value.

  2. Many sugar-free products that contain sugar alcohols, such as sugar-free
    hard candy and gum, would fall into the “free foods” category,
    with < 5 g of carbohydrate or < 20 kcal/serving, making it unnecessary
    to count the carbohydrate from the sugar alcohol.

Figure 2.
Figure 2.

Guidelines for including dietary fiber and sugar alcohols (polyols)
in carbohydrate
counting.
13,14

Individuals with diabetes who adjust their insulin based on carbohydrate
intake would be most likely to benefit from this information. However, many
educators are finding the need to address the topic with other patients who
have type 2 diabetes simply because of their interest in the carbohydrate
information on food packages.

Glycerin(e)/glycerol

Glycerin (sometimes spelled glycerine), or glycerol, is a sweet, syrupy
liquid that is about 75% as sweet as sucrose. It is chemically categorized as
a polyol with 4.32 kcal/g. The FDA classifies glycerin as a Generally
Recognized as Safe food additive. As a food additive, glycerin is used in a
variety of products, including nutrition or energy bars, because of its
ability to retain moisture, and reduced-fat frozen desserts, to prevent
formation of ice crystals. Many nutrition bars have > 9 g of glycerin in a
single-serving bar.

According to the FDA, synthetic glycerin is produced by the hydrogenolysis
of carbohydrates15
and must be included in the grams of total carbohydrate listed in the
Nutrition Facts panel. If the label has a statement regarding sugars, the FDA
requires the glycerin content per serving to be declared as sugar
alcohol.16 Some
food manufacturers disagree with the classification of glycerin as a
carbohydrate and have been omitting it from their calculations.

The metabolic fate of glycerin has yet to be determined, but it is believed
to be converted into glucose primarily via
gluconeogenesis.17
The effect of glycerin on blood glucose levels in individuals with diabetes is
unknown.

Dietary fiber

The term dietary fiber includes a wide variety of food components, each
having different physiological effects. Dietary fiber is not digested and
absorbed in the small intestine like glucose. Fiber is fermented in the large
intestine to produce fatty acids, which are then absorbed and used as energy.
Foods rich in hemicelluloses and pectins (generally known as soluble fiber),
such as fruits and vegetables, are more completely fermentable than foods rich
in celluloses (insoluble fiber), such as
cereals.18 Although
the energy derived from fermented fiber varies among individuals, the
estimated energy yield from fiber is between 1.5 and 2.5
kcal/g.18 Although
fiber does contribute to calories, its effect on blood glucose is likely
minimal. For individuals with diabetes who desire this level of detail,
practitioners may suggest subtracting the total grams of dietary fiber from
the grams of total carbohydrate on the Nutrition Facts panel. The effect is
probably insignificant if the amount of dietary fiber is < 5
g.13,14

Do Products Billed as “Low-Carb” Support a Healthy Weight
Loss Regimen?

Food products, whether manufactured or naturally occurring, must be
evaluated within the context of the dietary goals they are intended to
support. Therefore, it is essential to evaluate products advertised as
“low-carb” with regard to the contribution they make to weight
loss or maintenance and overall health.

Table 2 compares a
purportedly low-carb meal to a more traditional meal advocated by many
professional organizations that promote health. Neither menu was devised with
the intent to restrict calories, because caloric restriction is not a point of
focus for many popular low-carb diets. Controlled-carb processed products were
added to the low-carb meal as allowable deviations. When comparing the two
meals, the following legitimate reasons for concern about the low-carb claim
become apparent:

  1. The low-carb meal contains less food volume and potentially less satiety
    value than the traditional meal.

  2. The low-carb meal provides ∼ 520 more calories and ∼ 51 more grams
    of fat than the traditional meal.

  3. Total carbohydrate contained in the low-carb meal is 52 g compared with 83
    g in the traditional meal—a difference of 31 g.

  4. Of the 52 g of total carbohydrate in the low-carb meal, 17 g are claimed to
    be “net carbs.” The other 35 g (27 of which are from the
    controlled-carb products) seem to be negated.

Table 2.

Comparison of a Low-Carb Dinner to a Traditional Dinner

Individuals with diabetes should be advised that use of low-carb products
does not necessarily lead to weight loss or improvements in metabolic
measures.

Implications of the Low-Carb Diet Trend

History tells us that popular diets, like fashion trends, tend to cycle.
The currently fashionable low-carbohydrate diet trend has experienced periods
of more and less popularity during the past 40 years. Unfortunately, this diet
trend promotes misconceptions about carbohydrates and can cause people to
restrict health-promoting nutrients while guiding them to consume liberal
amount of nutrients, especially saturated fat and cholesterol, that can
negatively affect health.

Perhaps the greatest risk of this diet trend is the impact it may have on
eating behaviors of those individuals who have been unable to establish
sensible relationships with food. Manipulations in food manufacturing and
terminology that seemingly allow undesirable nutrients and, by association,
their calories to magically disappear are psychologically appealing to dieters
who are rationalizing how to eat more without having it count.

Individuals with diabetes should be offered sound guidance about how to
interpret truths and mistruths of any diet trend. This is crucial within the
context of the low-carb trend because claims about the glycemic effects of
carbohydrate foods and their contribution to insulin
resistance/hyperinsulinemia and weight gain tend to be a central philosophical
feature. Confusing labeling lingo that has been contrived and printed on
packages of manufactured foods can create unique challenges for individuals
with diabetes who must accurately count grams of carbohydrate to achieve
glycemic control, particularly individuals on intensive insulin therapy.

In truth, the rise in prevalence of overweight and obesity can largely be
attributed to energy imbalance resulting from an increase in energy intake and
decrease in energy expenditure—not to the excessive intake of any single
nutrient.19 Diets
that support severely restricting or omitting any single nutrient without
offering psychosocial support and monitoring of metabolic parameters should be
considered suspect. Severely restricting or omitting carbohydrates can have
potential negative long-term health consequences, especially if healthful
carbohydrate sources, such as fruits, vegetables, whole grains, and dairy
foods, are severely restricted.

Thus, not only amounts, but also sources of carbohydrate
should be a focus of any discussion about meal
planning.7 Highly
processed grains, cereals, and sugars should be replaced with minimally
processed whole grains, fruits, vegetables, and dairy foods for optimal
nutritional benefits. Sweets and sugars should be used with moderation,
especially for those who need to lose weight. When these sensible, but not
headline news–making, guidelines are applied, use of highly processed
and manufactured foods that manipulate carbohydrates becomes unnecessary.

Footnotes

  • Janine Freeman, RD,LD,CDE, is a nutrition specialist at the University
    of Georgia Extension and a diabetes/nutrition consultant in Atlanta, Ga.
    Charlotte Hayes, MMSc, MS, RD, LD, CDE, is a nutrition and exercise consultant
    in Atlanta, Ga.

References

  1. Mokdad AH, Bowman
    BA, Ford ES, Vinicor F, Marks JS, Koplan JP: The continuing epidemics of
    obesity and diabetes in the United States. JAMA286
    : 1195–1200,2001

  2. The evaluation of the energy of certain sugar alcohols used
    as food ingredients
    . Bethesda, Md., Federation of American Societies
    for Experimental Biology, Life Sciences Office, 1994

  3. American Diabetes Association:
    Evidence-based nutrition principles and recommendations for the treatment and
    prevention of diabetes and related complications (Technical Review).
    Diabetes Care 25:148
    –179, 2002

  4. Wheeler ML,
    Fineberg SE, Gibson R, Fineberg N: Metabolic response to oral challenge of
    hydrogenated starch hydrolysates versus glucose in diabetes.
    Diabetes Care 13:733
    –740, 1990

  5. Livesey G: Health
    potential of polyols as sugar replacers, with emphasis on low glycaemic
    properties. Nutr Res Rev 16:163
    –191, 2002

  6. American Diabetes Association: Nutrition
    principles and recommendations in diabetes (Position Statement).
    Diabetes Care 27 (Suppl. 1):S36
    –S46, 2004

  7. Warshaw HS, Power
    MA: A search for answers about foods with polyols (sugar alcohols).
    Diabetes Educ 25:307
    –321, 1999

  8. Warshaw H: FAQs
    about polyols. Today’s Dietitian. April2004
    , p. 37–44

  9. Warshaw HS,
    Bolderman KM: American Diabetes Association Practical Carbohydrate
    Counting: A How-to-Teach Guide for Health Professionals
    . Alexandria,
    Va., American Diabetes Association, 2001

  10. Powers MA:
    American Dietetic Association Guide to Eating Right When You Have
    Diabetes.
    Hoboken, N.J., Wiley and Sons,2003

  11. Burelle Y,
    Massicotte D, Lussier M, LaVoie C, Hillaire-Marcel C, Peronnet F: Oxidation of
    [13 C] glycerol ingested along with glucose during prolonged exercise.
    J Appl Physiol 90:1685
    –1690, 2001

  12. Institute of Medicine’s Dietary Reference Intakes for Energy,
    Carbohydrates, Fiber, Fat, Protein and Amino Acids. Washington, D.C., National
    Academy of Sciences, 2002

  13. Centers for Disease Control and
    Prevention
    : Trends in intake of energy and
    macronutrients—United States, 1971–2000.
    MMWR 53:80
    –82, 2004

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