Cut the Sugar in Children’s Diets to Prevent Heart Attacks?

Could reducing dietary sugar have benefits for heart health?

A study published in the journal ‘Atherosclerosis’ is making headlines this week (1).  According to press articles (the original article isn’t available for public viewing yet), substituting starchy carbohydrates for sweet ones can improve some of the key markers for heart disease in children in just 9 days (2).

As someone who makes a living from enabling people to be free of sugar, and someone who has written about the alarming level of sugar in children’s diets previously,  you would think this article would make me feel that all my birthdays had come at once.  However, much as l love encouraging people to be free, I am rather fond of science too, so I feel that it’s important to discuss the limitations of the article as well as its potential.

Author, Author
The first thing to note is that that this trial is part-authored by Robert Lustig, who has become well-known for his crusade against fructose.  I am a fan of Robert Lustig. I have been lucky enough to attend one of his lectures, and was impressed. He has amassed a great deal of clinical knowledge over the years.  Much of what he says makes a great deal of sense if, like me, you struggle to lose weight; reading his book was a bit of a ‘lightbulb moment’.  However, it would not be in his interests to publish an article that showed no benefit from reducing fructose, so it’s only right to question whether a conscious or unconscious bias is at play here.

Could replacing sweet foods with other carbohydrates protect children from heart disease?

Testing, Testing
The test group was a group of children aged 9-18 with metabolic syndrome.  This is obviously a very specific, albeit a very important group of subjects; the results may not be applicable to the wider population.  There was no control group, i.e. children who remained on their original diet, so it is impossible to see how far the beneficial effects could be attributed to just being in a trial, or to some other unknown factor.  It is also important to note that changes in the children’s diet were based on what they said they ate.  This is a notoriously problematic way of assessing someone’s diet, and even more so with children.  This could be seen as being in the study’s favour, however; if my experience is anything to go by, children are likely to under-report the amount of sugar they eat, so if reducing only a part of the sugar in their diet has such positive results, removing it altogether might be even more beneficial.

Time, Gentlemen, Please
This study was conducted over a ten-day period.  That means that any claims that are made about its ability to reduce disease cannot possibly be substantiated, and there is no way of knowing whether the benefits could be sustained over a longer period.  The paper itself does not make such claims, but inevitably press articles do.  That is misleading.  In order to know whether these dietary changes would, in fact, prevent disease, one would have to follow these children for several decades and they would have to remain on the diet.  There are not many children who would sign up to reducing sugar radically for the number of years needed for the study, and even fewer who would stick to it!

When working with children, consider the ethics of asking them to commit to anything long-term!

Two Scientists, Three Opinions
The impressive thing about this study was not that the children lost weight; they didn’t.  It was that biological markers which are considered risk factors for heart disease improved even though the children didn’t lose weight.  What I believe the researchers are trying to say is that you don’t have to lose weight to improve the health of your heart.  I personally applaud this sentiment, but not everyone agrees, and not all the evidence produces similar outcomes to this trial.  For example, a meta-analysis involving 1369 adults showed that low carbohydrate diets actually raised LDL cholesterol (3) – the form that doctors tell us is ‘bad’.  A separate analysis of trials involving 447 adults agrees (4).  Furthermore, an analysis of 32 studies about the effects of high-fat versus low-fat diets for markers of heart disease in overweight and obese adults concluded that neither diet was better than the other (5).

Squaring the circle?
How might this difference be accounted for?  Firstly, the latest trial involved children.  It may be that dietary change is more effective the younger you are, which would hardly be surprising. Indeed, in children under 12, fizzy drinks have been associated with increased cholesterol, more inflammation and larger waist measurements (6).  It should also be noted that the study was not testing low-carbohydrate diets as such; rather the foods containing sucrose (table sugar) were replaced with other forms of carbohydrate.  When you look at reducing sucrose or fructose specifically, the picture changes.  One study looked at the effect of consuming different concentrations of sugar in fizzy drinks over a 3 week period.  The more fructose was in the drinks, the higher the markers for heart disease rose (7).  Some scientists believe that sugar only causes these problems if subjects gain weight (8), but a meta-analysis involving 1660 patients showed that the effect of sugar was most noticeable when compared with diets in which there was similar calorie intake in the high and low sugar diets (9). In fact we do not know for certain, because we would need to establish whether, and at what level, eating sugar (or a particular type of sugar) over several years would a) make a difference to markers for heart disease and b) actually increase the rate of heart disease.

The picture is further complicated because of new thinking that LDL cholesterol is only harmful when it is ‘dense’, so lowering of LDL per se may not necessarily be helpful, and an increase may not necessarily be harmful.  Dense LDL cholesterol disappeared altogether during the study (2).  However, the implications of this for cardiovascular health are not yet known.

So can we draw any conclusions at all from this latest study?  For my money the study was too small too short I duration and too specific for us to make any statements about whether reducing sugar will reduce heart disease.  However, I think that the study is interesting enough to warrant further work, particularly as it is supported by evidence from other studies in young people.  There are probably at least 3 things that are indicated and supported by this study.

1. Table sugar and high fructose corn syrup unlikely to have any benefits for children, and are likely to be problematic, especially when combined with other less healthy dietary choices.

2. A sugar reduction programme may be more beneficial when started in childhood.

3. There are likely to be factors other than weight which influence heart health, and these can be improved even in the absence of weight loss.

These thoughts may not be eye-openers, but they do reinforce what is already known and that, after all, is a worthwhile objective of scientific research.

References:

1. Gugliucci, A.., Lustig, R.H., Caccavelo, R., Erkin-Cakmak, A., Noworolski, S.M., Tai, V.W., Wen, M.J., Mulligan, K., & Schwartz, J-M, (2016).  Short-term isocaloric fructose restriction lowers apoC-III levels and yields less atherogenic lipoprotein profiles in children with obesity and metabolic syndrome.  Obesity (Silver Spring), 24(2), 453-460.
2. http://universityofcalifornia.edu/news/cutting-sugar-causes-drop-heart-disease-risk-factors-among-obese-children. [Accessed 20 July 2016].
3. Mansoor, N., Vinknes, K.J., Veierod, M.B., & Rettersol, K., (2016).  Effects of low-carbohydrate diets v. low-fat diets on body weight and cardiovascular risk factors: a meta-analysis of randomised controlled trials.  British Journal of Nutrition, 115(3), 466-479.
4. Nordmann, A.J., Nordman, A., Briel, M., Keller, U., Yancy, W.S. Jr, Brehm, B.J., & Bucher, H.,C., (2006). Effects of low-carbohydrate vs low-fat diets on weight loss and cardiovascular risk factors: a meta-analysis of randomized controlled trials. Archives of Internal Medicine, 166(3), 285-293.
5. Schwingshackl, L., & Hoffmann, G., (2013).  Comparison of effects of long-term low-fat vs high-fat diets on blood lipid levels in overweight or obese patients: a systematic review and meta-analysis.  Journal of the Academy of Nutrition and Dietetics, 113(12), 1640-1661.
6. Kosova, E.C., Auinger, P., & Bremer, A.A., (2013).  The relationships between sugar-sweetened beverage intake and cardiometabolic markers in young children. Journal of the Academy of Nutrition and Dietetics, 113(2), 219-227.
7. Stanhope, K.L., Mieici, V., Bremer, A.A., Lee, V., Lam, H.D., Nunez, M.V., Chen, G.X., et al, (2015).  A dose-response study of consuming high-fructose corn syrup–sweetened beverages on lipid/lipoprotein risk factors for cardiovascular disease in young adults.  American Journal of Clinical Nutrition, 101(6), 1144-1154.
8. Wang, D., Sievenpiper, J.L., de Souza, R.J., Cozma, A.I., Chiavaroil, L., Ha, V., Mirrahimi, A., et al, (2014).  Effect of fructose on postprandial triglycerides: a systematic review and meta-analysis of controlled feeding trials. Atherosclerosis, 232(1), 125-133.
9. Morenga, L., Howatson, A.J., Jones, R.M., & Mann, J., (2014).  Dietary sugars and cardiometabolic risk: systematic review and meta-analyses of randomized controlled trials of the effects on blood pressure and lipids.  American Journal of Clinical Nutrition, 100, 65-79.