Following the UK dietary guidelines increases risk factors for heart disease
Guest Article by Martin MacDonald
I've had this article written for a while and it originally started with this:
"Well… wow. Can't believe I've never seen this study! I'm gutted I can't get the full text… if you can, please would you send it to me! Here is a link to the full text website: LINK"
I have now got the full text and I thought I would share the technique that allowed me to get it – You can read our article on effective searching using PubMed HERE.
Research like this demonstrates why the Mac-Nutrition Facebook and Twitter pages do so well because people are realising how much bad dietary advice is out there. This article is also, as the title says, just a research update; I have focused on just one area and in the future will write something more extensive on the guidelines as a whole, including the premature information on salt and cholesterol intake in particular.
It is very easy to say "look at the nation, we're still becoming fat and diabetic despite reducing fat intake" but it would be reckless to base firm conclusions on such observational data… 😉
Instead, research like this shows just one area of how the UK Dietary Guidelines are perhaps a little premature. So, below I have given an overview of the research with a few extra comments to help explain some of the more complicated stuff. Needless to say, the easy conclusion here is; Don't increase your carbohydrate intake and reduce your fat intake thinking this is necessarily a healthy thing to do! Or more succinctly, don't follow the Dietary Guidelines.
[Note, when I use ‘significant’ below it means p<0.05. In instances where it is more significant, I have stated it]
Dietary guidelines advice: Increase carbohydrate intake and reduce fat intake.
Concern: Raised blood triglycerides (TG) are a known risk factor in coronary heart disease (CHD). TGs are perhaps a stronger indicator than cholesterol levels for risk of CHD. Carbohydrate intake is generally correlated to blood TG levels.
To evaluate the effect of advice to increase carbohydrate intake to 50% of energy intake as part of advice to follow current dietary guidelines on the dietary profile, including dietary glycaemic index (GI) and plasma lipids in healthy post-menopausal women.
- Twelve healthy post-menopausal women with average age 56 years (+/- 6.5 years)
- Habitual diet was assessed by a 7-day weighed intake
- Based on this food diary, subjects were advised to increase their carbohydrate intake to comply with current dietary guidelines
- Subjects were asked to follow this diet for 4 weeks, in a free-living situation.
- Fasting blood samples were obtained at baseline and after 1 and 4 weeks.
[So what we are getting from these methods is that this research is aiming to see what happens in the REAL world when a woman goes to a dietitian, gets nutritional advice and then aims to follow that advice. We do not know at this point whether the advice is followed…]
- There was a significant decrease in body mass index (BMI) after 4 weeks [i.e. the women lost weight].
- There was a significant increase in blood TG concentrations after 1 week [that’s a bad thing].
- High-density lipoprotein (HDL) cholesterol concentration was significantly decreased after 1 and 4 weeks [that’s also a bad thing].
- The subjects significantly increased their percentage of energy from carbohydrates and starch (p < 0.05 and p < 0.01, respectively) after 1 week, and their percentage of energy from starch after 4 weeks [So they are managing to follow the advice they have been given].
- Dietary GI was significantly increased after 1 and 4 weeks [This is inevitable with increased carbohydrate intake and reduced fat intake. Even swapping butter for sweet potato will increase the dietary GI].
- Fruit and vegetable intake was significantly increased after 1 week (p < 0.01), as was fruit intake alone [the advice has led to an increased fruit and vegetable intake so the increase in carbohydrate has been partly from what most would agree are good sources].
- There was a significant increase in the 'antioxidant power' of blood plasma [most probably due to the increase in fruit and vegetable].
In post-menopausal women, following the UK dietary guidelines resulted in changes in the lipid profile that were more likely to favour an increased risk of coronary heart disease (CHD), as TAG concentrations were increased and HDL cholesterol concentrations were reduced.
One thing to draw attention to here is the fact that the women in this study lost weight. Now, over the four weeks this means the women were most likely in a net calorie deficit and you might say they were on a 'diet' or if you feel so inclined 'a healthy eating plan to lose weight'. When weight loss occurs in your average person, whether their BMI is 22, 27 or 33, you will generally find an improvement in various health markers simply because of the weight loss and the fact that the body has been in a semi-fasted state [fasting is very good at fixing many of the negative effects of poor diet]. So, what makes this even more interesting is that these woman lost weight and got more unhealthy!? What if they followed these rules for longer, and maintained their weight!? We could almost guarantee the results would be even less favourable than seen here!
Another final note, often the argument against lowering carbohydrate intake is that it will 'limit the intake of vegetables and fruit' however this is rubbish. Reducing the intake of bread, pasta and potatoes leaves plenty of room for vegetables and fruit whilst still maintaining a reduction in total carbohydrate intake. In fact, what a study that would be!
Mac-Nutrition's Methods: Subjects kept their carbohydrate intake constant but simply swapped ALL starchy carbohydrates for fruit and vegetables.
We hope you have enjoyed this article and hopefully it will make people think twice about blindly following guidelines in both professional practice and daily life.