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Review finds low-carb eating benefits wide range of health markers

Posted Aug 22 2012 3:15pm

I’m a long-time advocate of diets that are generally lower in carbohydrate than those encouraged by most Governments, health agencies and health professionals. I’m not very prescriptive about it, and prefer not in my talks or writings to give specific carbohydrate ‘targets’ e.g. no more than 50 g of carbohydrate a day. I do, however, advise those wanting to optimise their health and weight to avoid or limit foods with added sugar (sometimes even foods that are naturally sugary too), as well as reining in starchy carbohydrates such as bread, potatoes, rice, pasta and breakfast cereals.

Just this change in dietary tack will very often bring significant improvements in terms of weight and general wellbeing. The underlying mechanisms are probably various. But it occurs that this sort of eating regime will help to stabilise blood sugar levels, which so often seems to impact positively on things like energy levels, mood and sleep. Another thing is that many of the foods de-emphasised on this approach may have quite-toxic effects on the body. Many grains (particularly wheat), for instance, have the capacity to induce problems related to food intolerance that can cause problems such as fatigue and gastrointestinal symptoms. Grains aren’t particularly nutritious either, so losing a bunch of them is unlikely to lead to problems with nutrition status (despite what some health professionals would have us think).

Of course, not everyone is enthused by low-carb approaches, and some will publish articles or studies which are broadly critical of them. In one such study , it was claimed that the low-carb phenomenon is putting Swedish people in perilous danger. However, even a cursory glance at the design of the study reveals it’s simply not fit for purpose. It is my opinion that the authors are less motivated by a desire to get to the truth, and perhaps more motivated to produce whatever they can (however poor the science) to justify and support their biases against this dietary approach.

One of the reasons I say this is because it is widely recognised that the best judge of any approach (dietary or otherwise) is not the sort of junk ‘epidemiological’ science they churned out, but clinical studies. Studies where the approach is actually tried in real, live human beings.

My eye was caught today by a paper published yesterday which reviews the impact of low-carbohydrate eating on a range of health markers. The review amassed data from 17 studies in the form what is called a ‘meta-analysis’ [1]. This sort of review study is not necessarily ideal, at least in part because it included approaches utilising different carbohydrate intakes over different lengths in sometimes quite different demographics of people. Also, another problem is that in studies of this nature people are usually ‘free living’, and this means that adherence to the ‘diet’ is not assured and tends to drop off over time too.

Nevertheless, the broad results from this review make interesting reading in that, overall, low carbohydrate eating was found, on average to bring statistically significant benefits in several measures including:

  • Body weight (average loss of 7 kg)
  • Abdominal circumference (average reduction of 5.74 cm = 2.26 inches)
  • Systolic blood pressure (average reduction of 4.81 mmHg)
  • Diastolic blood pressure (average reduction of 3.10 mmHg)
  • HbA1c – also known as glycosylated haemoglobin and a measure of blood sugar control over the preceding 3 months or so (average reduction 0.21 per cent)
  • Reduction in blood insulin levels
  • C-reactive protein reduction (an inflammatory marker – inflammation being something that has the capacity to drive disease process)
  • Increase in levels of supposedly ‘healthy’ HDL cholesterol

No overall effect was seen on levels of supposedly ‘unhealthy’ LDL cholesterol. Though, we know from research that low carbohydrate diets tend to lead to lead to increases in the size of LDL particles and reduce the number of ‘small, dense’ LDL – changes that are believed to be desirable in terms of cardiovascular disease risk reduction [2].

Taken as a whole, these effects can only really be seen as a sign that low-carb eating has broadly beneficial effects across just about every health markers it’s been judged with.

None of this, I suspect, will come as too much of a surprise to those who employ this strategy in practice, or to many people who have used it on themselves, in that similar results to those found in the studies will often stare us in the face. What is perhaps more surprising is how often doctors and health professionals seem unaware of the evidence for low-carb eating (or perhaps just choose to ignore it).

References:

1. Santos FL, et al. Systematic review and meta-analysis of clinical trials of the effects of low carbohydrate diets on cardiovascular risk factors. Obesity Reviews epub 21 Aug 2012

2. Volek JS, et al. Modification of lipoproteins by very low-carbohydrate diets. J Nutr. 2005;135(6):1339-42

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