Download Starchy carbohydrates with every meal is good

Debate
‘Starchy carbohydrates with every meal
is good advice’
For
Dr Trudi Deakin, X-PERT Health (registered charity), Hebden
Bridge, West Yorkshire, UK
Carbohydrates consist of sugars, starches and fibres.
Their primary role is to provide glucose to cells in the
body. Glucose is the main energy source for the brain,
central nervous system and red blood cells, which are the
only carbohydrate-dependent cells. Glucose also can be
stored as glycogen in liver and muscle.1
The role of carbohydrates has been the source of
much public and scientific interest. This includes the
relationship of carbohydrates with health outcomes,
including cardiovascular disease (CVD), type 2 diabetes,
bodyweight, and dental caries. However, no detrimental
effects of carbohydrates as a source of calories on these
or other health outcomes have been reported. In fact, a
moderate body of evidence suggests that dietary fibre is
essential for optimal digestive health, helps provide
satiety, promotes healthy laxation and protects against
CVD, obesity, type 2 diabetes and other long-term
conditions.2–4 The energy value of digestible carbohydrates is generally accepted as four calories per gram.
Research suggests that high-fibre diets can aid in
weight control through lower energy yield.5 Few
studies have linked carbohydrates to obesity. Indeed,
successful weight loss and maintenance are linked to
low-fat, high-carbohydrate diets in people with6 and
without diabetes.7
Requirement of carbohydrate
The minimal amount of carbohydrate is determined by
the brain’s requirement for glucose. A recommended
dietary allowance (RDA) for carbohydrate of 130g/day
for adults and children aged one year and older has
been established.Í
The acceptable macronutrient distribution range
(AMDR) for carbohydrate is 45–65% of total calories.8 It
is recommended that the majority of carbohydrate is
derived from fibre-rich starchy food.9 A comparison of
the RDA to the AMDR shows that the recommended
range of carbohydrate intake is higher than the RDA.
For example, if an individual with a caloric intake of
2000kcal/day consumes 55% of calories as carbohydrate,
1100kcal would be from carbohydrate. This equates to
275g carbohydrate, well above the RDA of 130g/day
needed for brain function.
Guideline daily amounts (GDAs) translate science
into consumer-friendly information. All values are based
on the recommendations of the UK COMA (Committee
on Medical Aspects of Food Policy) report on Dietary
Reference Values.10 GDA values are broadly consistent
between the UK, Europe and internationally. The GDA
for total carbohydrates is calculated using 47% energy
from carbohydrate.11
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PRACTICAL DIABETES VOL. 30 NO. 4
Carbohydrates in the diet of people with diabetes
Diabetes is viewed as a disorder of carbohydrate metabolism due to its impact on hyperglycaemia. Blood glucose
concentration following a meal is determined by absorption of glucose in the blood stream and its clearance.12
Carbohydrate is the only macronutrient that has a direct
impact on blood glucose. Nutritional recommendations,
integral in diabetes management, have been an area of
persistent controversy, particularly regarding the proportions and types of carbohydrate.
Before the advent of insulin therapy, dietary management was the only form of therapy for diabetes.13 Dietary
prescriptions in that period emphasised strict restriction
of carbohydrate intake and an increased intake of dietary
fat.14,15 Later, as the serious cardiovascular complications
of diabetes became recognised, nutritional recommendations for diabetes were sharply revised to moderate consumption of fats and liberalisation of carbohydrates.16,17
Today, diabetes dietary advice continues to play an
important role, not only for the day-to-day control, but
also for the prevention of complications. One of the
most fundamental recent changes is the need for individualisation of nutrition prescription. Rather than prescribing a uniform proportion of fats and carbohydrates,
current recommendations recognise that there is little
evidence for the ideal macronutrient composition of the
diet in the management of hyperglycaemia,18 although it
has been shown that replacing saturated fat with starchy
carbohydrates achieved beneficial effects on dyslipidaemia in type 2 diabetes.19 Thus, greater flexibility and
consumption of macronutrients based on the GDA for
healthy eating are encouraged.20,21
When people with diabetes receive carbohydrate
awareness structured education and monitor carbohydrate consumption – whether by carbohydrate counting,
exchanges, or experience-based estimation – they manage to improve glycaemic control and lose weight.22,23
Daily consistency in carbohydrate intake is associated
with improved blood glucose control,24 although this
may not apply to people on intensified insulin therapy
who adjust their insulin dose based on their actual
carbohydrate intake.25
Concerns about omitting starchy carbohydrates
from meals
Humans can survive without an exogenous supply of
carbohydrate. However, adaptation to a fat and protein
fuel requires considerable metabolic adjustments. In
the absence of dietary carbohydrate, synthesis of glucose requires amino acids derived from the hydrolysis
of endogenous or dietary protein or glycerol derived
from fat.1
Reviews of lower-carbohydrate diets have shown that
weight loss is associated with the duration of the diet and
restriction of energy intake, but not with restriction of
carbohydrates.26 Reviews of people with diabetes have
COPYRIGHT © 2013 JOHN WILEY & SONS
Debate
‘Starchy carbohydrates with every meal is good advice’
demonstrated improvements in glycaemic control, fasting glucose, and triglycerides in the short term,27–30 but
a systematic review that only included randomised
controlled trials greater than 12 weeks, concluded that
there were no consistent differences in weight and
HbA1c over the longer term.31
There may be subtle, unrecognised and untoward
effects of a low-carbohydrate diet that only become
apparent when adopted by populations not genetically
or traditionally adapted to it. Of particular concern are
the long-term consequences of a chronic production of
β-hydroxybutyric and acetoacetic acids (ketoacids).
There is evidence that a diet low in carbohydrate, deficient in wholegrains, water-soluble vitamins and some
minerals, may result in nutritional deficiencies; arterial
plaques and stiffness; hypertension, dyslipidaemia and
insulin resistance; bone mineral loss; kidney, bladder,
and/or urethra stones; increased levels of homocysteine,
free fatty acids and non-esterified fatty acids.1,32–37 It may
also affect the development and function of the central
nervous system38 and adversely affect an individual’s
general sense of wellbeing.39
Conclusion
Regular consumption of quantity-controlled fibrous
carbohydrate is good advice. Because individuals with
diabetes have a two- to four-fold increase in CVD risk
compared to those without diabetes,40 it is even more
important that healthy eating principles are incorporated. Although carbohydrates have a direct impact on
glycaemia, there is no evidence that lowering glycaemic
load by eliminating starchy carbohydrates from
meals improves glycaemic control in the long term, and
Against
Dr David Cavan, DM, FRCP, Consultant Physician, Bournemouth
Diabetes and Endocrine Centre, Royal Bournemouth Hospital,
Bournemouth, UK
For many years, the standard advice for people with
diabetes has been to eat starchy carbohydrates with every
meal.1 Over the past few years, many people with diabetes
have queried the wisdom of this, and the official line has
now been softened. Although new guidance has removed
this requirement, many patients were educated in the
starchy carbohydrate era, and many documents and websites still quote it. As recently as last year, a spokesperson
for Diabetes UK tried to defend this approach in a radio
interview, with limited success.2
Diet has always been an important component of the
management of diabetes. Historical accounts suggest
that, as diabetes was associated with excess glucose, a lowcarbohydrate diet was deemed an appropriate treatment. Hence, until the 1930s, the recommended diet
derived only 15% of calories from carbohydrate.1 By the
1970s, however, concern was growing that a low-carbohydrate diet was necessarily high in fat, and fat was seen as
causing high cholesterol levels, heart disease and obesity.
A healthy diet was considered to be one which is low in
fat and high in carbohydrates, and it was felt people with
PRACTICAL DIABETES VOL. 30 NO. 4
eliminating starchy carbohydrate from meals is more
likely to result in the diet becoming deficient in health
promoting nutrients such as wholegrains and excessive
in atherogenic properties such as saturated fat.
People with diabetes should receive structured education so that they may identify and incorporate fibrous
starchy carbohydrate into their meals but ensure that
carbohydrate is not eaten to excess. Consumption needs to
be appropriate for bodyweight, physical activity levels and
glycaemic control (usually between the RDA, 130g, and
the GDA, 230g for women and 300g for men). Food
choices should be kept as easy and simple, and every effort
should be made to increase, not restrict, the variety and
flexibility in food choices. In determining diabetes nutrition-related education priorities, individuals need to know:
• Which foods contain carbohydrate.
• Appropriate portion sizes for carbohydrate foods.
• Carbohydrate servings (or grams) they should choose
to eat for meals or snacks.
By using these principles, food records and, if necessary,
blood glucose monitoring data, it can be determined if
blood glucose goals are being met. If not, food intake or
medications should be reviewed to determine what
adjustments are required.41
Declaration of interests
The author is Chief Executive of the charitable not-forprofit organisation, X-PERT Health.
References
References are available online at www.practical
diabetes.com.
diabetes should follow such a diet, rather than focus on
reducing carbohydrates. Protein was also considered less
safe, for fear it might be associated with renal problems.
As a result, the recommended carbohydrate intake
increased first to 40%, and then to over 50% of all
calories1 – not necessarily because carbohydrates were
good, but because fat and protein were bad.
In the 1970s, people with type 1 diabetes were treated
with fixed doses of insulin (usually once or twice a day)
and in order to avoid their glucose levels falling to too
low, they were very sensibly recommended to eat carbohydrate-containing snacks between each meal, and to eat
carbohydrates with every meal. However, there was little
distinction in recommendations between type 1 and type
2 diabetes, and this advice became the norm for everyone with diabetes. With the move away from ‘diabetic
diets’, people with diabetes were advised to follow
national guidelines for a healthy diet, which also recommended starchy carbohydrates with every meal, as
exemplified by the eat-well plate. On the Diabetes UK
website, this advice is repeated for people with type 1
diabetes3 (see extract shown in Table 1) – despite
the major advances in insulin management of type 1
diabetes, which made the 1970s-era advice obsolete.
How effective is this kind of advice? A few months ago,
a lady came to see me in clinic and expressed
concern that her blood glucose the previous evening had
COPYRIGHT © 2013 JOHN WILEY & SONS
165
Debate
‘Starchy carbohydrates with every meal is good advice’
Food groups and
what's in a portion
How many
portions do you
eat in a day?
How many
portions should
you eat in a day?
Bread, cereals, rice,
pasta and potatoes
One portion is equal
to:
• 2–4 tbsp cereal
• 1 slice of bread
• Half a small chapati
• 2–3 crispbreads or
crackers
• 2–3 tbsp rice, pasta,
cous-cous, noodles
or mashed potato
• 2 new potatoes or
half a baked potato
I eat...
7–14
Include starchy
foods at all meals
Table 1. Extract reproduced from Diabetes UK’s chart for eating well with
type 1 diabetes. (www.diabetes.org.uk/Guide-to-diabetes/Food_and
_recipes/Eating-well-with-Type-1-diabetes/A-healthy-balance/Getting-thebalance-right/)
gone up to 26mmol/L. When I asked what she had eaten,
she said she always kept to the right diet, and had eaten a
baked potato. Let’s assume she followed the advice in
Table 1 and had half a baked potato – this could equate to
50g of carbohydrate, which in itself could cause her
glucose to rise by 15mmol/L or more.
It is now well-recognised that complex carbohydrates
can have a similar effect on blood glucose levels as that
of sugars, with baked potato and white rice having a glycaemic index of 85 and 98 respectively4 as they are, after
all, quickly broken down to glucose. So, eating starchy
carbohydrates with every meal risks pushing glucose levels
up and up. Which begs the question – why treat diabetes,
which is essentially an intolerance to glucose, with glucose?
Yet this has been the received wisdom for many years.
Is it any wonder, therefore, that many doctors treating
diabetes have lost confidence in the ability of patients to
achieve control of their diabetes by lifestyle changes, and
as a result hit the prescription pad? Is it any wonder that
people with diabetes – in their thousands – consult their
peers online for lifestyle advice that works? Like the
person who wrote the following on the Diabetes Support
Forum (http://diabetes-support.org.uk):
‘I'm type 2, diagnosed aged 62 in Nov 2009 and was
about 4 stone overweight. I did a diabetes education
course in March ’10. People were told at great length
about the fat and sugar content of various foods and told
to eat low-fat, starchy substitutes (7 to 14 units every day),
and “plenty of fruit and veg”. Fruit specifically included
bananas, grapes, and orange juice. After I found this
extremely helpful [internet] forum … I try to keep my
daily carbs below 100g. I maintain an HbA1c around 5.4%
[36mmol/mol] by diet and keeping active in various ways,
and so far need no medication. I have lost 3 stone in
weight and hope to lose another 7–14 lb.’
Type 2 diabetes is a condition of insulin resistance,
characterised by loss of control of hepatic glucose
output (causing hyperglycaemia), and inability to
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PRACTICAL DIABETES VOL. 30 NO. 4
manage ingested glucose.5 Increasing the latter will
further exacerbate hyperglycaemia. Net result: increased
insulin secretion (or injection), more insulin resistance,
and more hyperglycaemia. In type 1 diabetes, the
rediscovery of carbohydrate counting has enabled
patients to assess the effect of different foods on their
glucose levels. While, in theory, they can eat anything as
long as they inject the right amount of insulin, many
have learned that a lower carbohydrate load makes it
easier to manage glucose control, requires a lower
insulin dose, and encourages weight loss.6 They have
also learned to appreciate the freedom that comes from
having a carbohydrate-free meal; for example, when
eating out and not wishing to have to inject insulin.
There is evidence that low-carbohydrate diets can
be beneficial in type 2 diabetes,7 but these are often
dismissed as Atkins-type diets or as high-fat diets. However,
replacing carbohydrates with leafy vegetables, for example,
will not increase fat content and yet will have a significant
beneficial impact on glucose control. Even replacing a
bowl of branflakes with scrambled egg on toast reduces
calorie intake, despite a small increase in fat content – yet
with only 10g instead of 40g carbohydrate.
So abandoning the ‘starchy carbs with every meal’
slogan does not mean adopting a very low carbohydrate,
high-fat diet. It is my experience that people with diabetes
are finding it is possible to eat healthily and improve
diabetes control by restricting carbohydrate intake to
around 100g a day.
There is light at the end of the tunnel. The Diabetes
UK Nutrition Working Group in May 2011 issued new
guidance8 which stated: ‘There is no evidence for a recommended ideal amount of carbohydrate for maintaining
long-term glycaemic control in people with type 1 diabetes’, and that in type 2 diabetes: ‘The total amount of
carbohydrate consumed is a strong predictor of glycaemic
response.’ This would suggest that carbohydrate restriction
is beneficial to glycaemic control, yet the eat-well plate is
still used ubiquitously, which shows a third of the plate as
carbohydrates,9 and there is a lack of specific advice.
The Diabetes UK website now states: ‘Dietary management of diabetes depends more on eating regularly
and including starchy carbohydrate foods like pasta at
meals, and including more fruit, vegetables and pulses
in your everyday diet.’10 While not explicitly stating
‘starchy carbohydrates with every meal’ the choice of
words suggests something very similar – and that the
end of the tunnel is still some way off.
Conclusion
Starchy carbohydrate with every meal is not good advice,
and the diabetic professional community needs to
provide meaningful advice to help people with diabetes
make lifestyle changes that will help, not hinder, their
efforts at good control of their diabetes.
Declaration of interests
There are no conflicts of interest declared.
References
References are available online at www.practical
diabetes.com.
COPYRIGHT © 2013 JOHN WILEY & SONS
Debate
‘Starchy carbohydrates with every meal is good advice’
For
Dr Trudi Deakin, X-PERT Health (registered charity), Hebden
Bridge, West Yorkshire, UK
19.
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Against
Dr David Cavan, DM, FRCP, Consultant Physician, Bournemouth
Diabetes and Endocrine Centre, Royal Bournemouth Hospital,
Bournemouth, UK
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