Last week we discussed the effects that certain foods
have on the risk of type 2 diabetes mellitus (T2 DM). High protein intakes were
found to increase the risk of T2 DM by up to 67%, while a high dietary fibre
intake of about 35 g per day reduced T2 DM by 34%. These findings are based on
meta-analyses of results obtained with multiple investigations and very large
combined study populations.
In this article we will look at some of the other
dietary factors that may play a role in lowering the risk of developing T2 DM,
as reported in the insightful lecture Dietary
Factors for the Prevention of Diabetes Mellitus presented by Prof Renée
Blaauw at SASA’s “Nutrition in NCD Prevention Roadshow” held in Pretoria
earlier this year.
Milk and dairy products such as yoghurt, cheese and
amazi/maas are often blamed for a variety of ills, and many people have told me
that they are cutting out dairy to improve their health! Where this erroneous
attitude comes from is a mystery as dairy products contain the highest quantity
of easily absorbable and utilisable calcium in the human diet.
Read: Dairy diary: the lowdown and the heads-up
The meta-analysis of 7 studies that probed the effect
of dairy products on the risk of developing T2 DM, showed that individuals who
had the highest intake of milk and dairy products were 14% less likely to
develop T2 DM compared to people who consumed very little dairy.
Further analysis of the data obtained with the
combined studies, identified a difference in effect depending on the
fat-content of the dairy products that were studied. The total positive effect
of dairy products produced a reduction in risk of 14% as mentioned above, but
low-fat dairy products (low-fat milk, yoghurt, amazi, cottage cheese) reduced
the risk by up to 18%. In general, risk of T2 DM was lowered by 10% for every
extra serving of low-fat dairy per day.
Gao and co-authors, concluded from their study that “a
modest increase in daily intake of dairy products such as low fat dairy, cheese
and yoghurt may contribute to the prevention of T2 DM”. They caution that these
results need to be confirmed with randomised controlled trials.
Tong and his team suggest that calcium, vitamin D and
whey proteins in dairy products may help to reduce the risk of T2 DM. For
example, there is some evidence that whey proteins can increase insulin
Omega-3 Fatty Acids
One would expect protective compounds such as omega-3
FAs, to be useful in preventing T2 DM, but a meta-analysis conducted by Wu and
co-authors at the Harvard School of Public Health, Boston, USA, was not able to
identify either a negative or a positive effect of fish consumption
(fish/seafood are rich sources of omega-3 FAs) on T2 DM. The basic results of
the meta-analysis appeared to be neutral. However, the results did show that
alpha-linolenic acid (ALA), an omega-3 FA derived from plants which is found
in linseed and flax oils, may possibly slightly lower the risk of T2 DM.
Read: Omegas explained
Considering that T2 DM is associated with chronic,
low-grade inflammation, particularly in fat tissue and that signals from the
chronically inflamed tissue prevent insulin from working efficiently, it is
feasible to expect that anti-inflammatory compounds like omega-3 FAs would
counteract inflammation and thus help to reduce the risk of T2 DM. More
in-depth research may help to clarify the role of omega-3 FAs and
fish/seafood/omega-3-rich plants as sources of EPA, DHA and ALA (omega-3 FAs)
in reducing the risk of T2 DM.
The Coffee Saga
Coffee has been blamed for years as a cause of a
variety of human conditions including insulin-dependent diabetes and T2 DM.
More recently however, research has begun to exonerate this maligned beverage!
Much more positive findings have emerged about coffee lately and this also
applies to the role that coffee may play in the development of T2 DM.
Researchers at Harvard University combined the results
of more than 1,1 million study participants, including 45,335 people with T2
DM, to determine if caffeinated coffee or decaffeinated coffee increases or
decreases the risk of this disease.
Read: Coffee? Go for it!
Coffee consumption was found to be inversely
associated with the risk of T2 DM, which means that the more coffee the
subjects consumed, the lower their risk of developing T2 DM. This was true for
both caffeinated and decaffeinated coffee. One cup of coffee a day reduced the
risk of T2 DM by 8% and 6 cups of coffee per day reduced the risk by 23%. It is
important to keep in mind that none of the studies determined what effect
adding milk or sugar to coffee may have on coffee’s protective effect.
The authors of this study suggest that compounds such
as chlorogenic acid, a phenolic compound found in coffee, may be responsible
for the positive effect, because chlorogenic acid reduced blood glucose
concentrations in studies using experimental animals. Other bioactive
components of coffee like lignans, quinides and trigonelline may also be implicated.
Because it appears that the protective effect exerted
by coffee on the risk of T2 DM is not linked to its caffeine content, it is
prudent not to consume more than 6 cups of caffeinated coffee a day. Increasing
caffeine intake may cause a variety of other physiological effects, which are
not positive, including increased heart rate or palpitations, increased blood
pressure, insomnia, tremors and jitteriness, to name but a few. The
recommendation is, therefore, to consume coffee in moderate quantities of not
more than 6 cups a day. Both caffeinated and decaffeinated coffee can apparently
protect us against the risk of developing T2 DM.
Thanks to the excellent lecture present by Prof Blaauw
and the meta-analyses conducted by the various researchers mentioned in her
talk, our understanding of dietary factors that can reduce the risk of T2 DM
has expanded to include low-fat dairy products and moderate quantities of
caffeinated or decaffeinated coffee.
Omega-3 FAs as found in fatty fish or seafood, did not
have a significant protective effect against Type 2 diabetes mellitus, but this
finding should not detract from the other protective roles played by omega-3
FAs in cardiovascular disease and other inflammatory conditions.
Less protein and more fibre may prevent type 2 diabetes
Study explains omega 3's benefits
Pro Tip: Have a cuppa
- Blaauw R (2015). Dietary Factors for the Prevention of
Diabetes Mellitus. Lecture presented on 12 February 2015, at the SASA Nutrition
in NCD Prevention Roadshow, Pretoria.
- Ding M et al (2014). Caffeinated and decaffeinated
coffee consumption and risk of type 2 diabetes: a meta-analysis of cohort
studies. Diabetes Care, 37(2):569-86.
- Gao D et al (2013). PloS One, 2013 Sep 27, 8(9):
- Tong X et al (2011). Dairy consumption and risk of
type 2 diabetes: a systematic review and a dose-response meta-analysis.
European Journal of Clinical Nutrition, 65(9):1027-31.
- Wu JH et al (2012). Omega-3 fatty acids and incident
type 2 diabetes: a systematic review and meta-analysis. British Journal of
Nutrition, June, 107, Suppl. 2:S214-27.
Image: Stop diabetes from Shutterstock
Dr Ingrid van Heerden is a registered dietician and holds a doctoral degree in Nutrition and Biochemistry. She believes that "we are what we eat" and offers free nutrition and weight loss advice via her DietDoc service on Health24.com. Read more of her articles.