The conventional nutritional approach for ‘heart health’ is a low-fat (specifically, low saturated fat), high-carbohydrate diet. For many reasons, this is not the sort of diet I would generally recommend to ward off heart disease. For more about this, click here.
One particular form of carbohydrate that has been vigorously promoted for its heart-healthy properties are the ‘wholegrains’ such as wholemeal bread and brown rice. The pushing of wholegrains appears to be backed by studies which allegedly find that those who eat more wholegrains tend to have a reduced risk of heart disease. However, these studies are epidemiological in nature, and by virtue of this can only really tell us about the association wholegrains have with heart disease, but in no way indicate that wholegrains actually reduce heart disease risk.
One major issues of studies of this nature is that they are prone to ‘confounding’. Essentially, the benefits associated with wholegrain consumption might not be due to wholegrain at all, but other things to do with wholegrain eaters. Wholegrains have been vigorously promoted as ‘healthy’ for ages now, and as a result, those who eat them are likely to be more health-conscious than those who don’t.
So, wholegrain eaters might, for example, exercise more, be less likely to be obese and smoke less than those who eat more refined grains. And it might be these factor that account for the apparent benefits of wholegrain eating.
One way to find out for sure whether wholegrains really are good for the heart is to conduct so-called intervention studies. What this would mean, in essence, would be to take a group of individuals, and randomise them to eating either a diet rich in wholegrain or a control diet (not rich in wholegrains), and then see over time if the wholegrain eaters ended up being protected from heart disease. I don’t believe such a study has ever been done.
The next best thing, perhaps, would be to do the same thing, but instead of monitoring heart disease risk, monitor ‘surrogate markers’ of heart disease instead. Surrogate markers for heart disease include factors include things like body weight and fatness, waist circumference, blood chemistry (e.g. glucose and insulin levels), inflammation, endothelial function (a measure of the health of the inside of the body’s arteries) and blood clotting. A recent study did just this [1].
In this study, 316 individuals aged 18-65 were randomised to one of three diets:
1. A diet which included 60 g of wholegrain each day for 16 weeks
2. A diet which included 60 g of wholegrain each day for 8 weeks, followed by 120 g of wholegrain for a further 8 weeks
3. A control diet (no dietary change, in which wholegrain consumption was less than 30 g per day) for 16 weeks
At the end of the study, there was no significant difference in any of the surrogate markers for heart disease tested.
Now, of course there are several potential explanations for these ‘disappointing’ findings including, perhaps, the fact that the study did not go on for long enough. However, four months is usually long enough to see quite dramatic changes in surrogate markers for cardiovascular disease, as long as the approach taken is correct.
It is perhaps the case that wholegrains and healthier than their refined counterparts. But they are still grains, and can still have relatively high glycaemic index (and glycaemic load) if eaten in quantity. As I have reported before, diets of relatively high GI and/or GL are associated with enhanced risk of cardiovascular disease. See here for more about this.
So, what might be better than adding wholegrain to the diet for reducing cardiovascular disease risk? I suggest taking grains out (or at least eating them in generally limited quantities). There is evidence that low-carb diets, compared to low-fat ones, lead to improvements in many surrogate markers of disease including serum glucose, measures of insulin resistance, triglyceride levels and high-density lipoprotein cholesterol levels [2].
And the other thing about low-carb diets is that they can really make a difference to body fatness, especially ‘abdominal obesity’. I had an email today from a fellow who had read my latest book (Waist Disposal), employed its advice, and promptly lost four inches (10 cm) off his waist in 5 weeks. I didn’t quiz him about precisely what he’s been eating, though I wouldn’t be surprised if the benefits he’s seen have been achieved without the ‘aid’ of wholegrains.
References:
1. Brownlee IA, et al. Markers of cardiovascular risk are not changed by increased whole-grain intake: the WHOLEheart study, a randomised, controlled dietary intervention B J Nutr 2010;104(1):125-134
2. Samaha FF, et al. Low-carbohydrate diets, obesity, and metabolic risk factors for cardiovascular disease. Curr Atheroscler Rep 2007;9(6):441-71
