My belief is that the SACN report is based upon the World Health Organisation (WHO) Guidelines: Sugar Intake for Adults and Children which I covered in my previous blog post.
The Science Behind SACN’s review contains the 'evidence' on page 15-18 and it makes for an interesting read. For the full review click the link above.
SACN’s claim the review was comprehensive and includes systematic reviews of the literature in order to identify 'relevant' studies.
Their 'objective was to identify the best quality evidence' so they restricted it to 'evidence from randomised controlled trials (which have the potential to demonstrate a causal relationship, e.g. between an aspect of diet and a risk factor for disease) and prospective cohort studies (which reveal associations, e.g. between an aspect of diet and a disease risk factor or endpoint) as these are considered the most robust study designs for diet and health research.'
Here are a few gems taken from this comprehensive review about the dangers of sugar. I'll leave you to draw your own conclusions about the quality of evidence upon which Mr Oliver has based his latest campaign.
'Very few studies on the effects of individual sugars, such as glucose, fructose or sucrose, met the inclusion criteria. There was also insufficient evidence of appropriate quality to draw conclusions on the impact of sugars intake on the majority of cardio- metabolic outcomes in adults, including body weight.
Few trials on fructose met the inclusion criteria for the SACN report because many were either not randomised or they were of insufficient duration. No studies specifically investigating the effects of high fructose corn syrup were identified that met the inclusion criteria. However, as concern has been expressed around fructose consumption and its implications for cardio-metabolic health, evidence from trials that did not meet the inclusion criteria for SACN’s report were considered. It was concluded that, on balance, there was insufficient evidence to demonstrate that fructose intake, at levels consumed in the normal UK diet, leads to adverse health outcomes independently of any effects related to fructose’s presence as a component of total and free sugars.'
'There was a lack of evidence to assess the impact of sugars intake on oral health in adults; evidence for a relationship comes from studies in children and adolescents. Most of the evidence on sugars and on sugars-sweetened foods and beverages considered in SACN’s report is derived from prospective cohort studies.'
'Prospective cohort studies are observational in nature rather than involving an intervention and so cannot demonstrate a causal relationship, only an association. Generally, evidence from three or more such studies was used to judge whether an association existed, where possible supported by a meta-analysis of the combined data.'
'Expert judgement was also applied and where an association appeared to exist, the evidence was graded as adequate, moderate or limited (details of the evidence grading system used by SACN can be found in Annex 2 of the SACN report).'
The evidence for a relationship between sugars intake and tooth decay comes from mainly prospective cohort studies and some trials, conducted in children and adolescents. Studies that adjusted results for tooth brushing frequency were given more weight during the assessment because oral hygiene practices may have affected results. SACN concluded that decreased consumption of free sugars would help to lower the risk of dental decay, which continues to be a problem in the UK.
In children and adolescents:
Cardiovascular disease, colorectal cancer and type 2 diabetes
The findings from prospective studies were:
- there is insufficient evidence to enable conclusions to be drawn in relation to cardiovascular disease risk factors or endpoints (events) (see paragraphs 6.6-6.17 of the SACN report)
- sugars or sugars-sweetened beverage intake are not associated with the incidence of colorectal cancer (see paragraphs 6.38-6.39 of the SACN report)
- there is no association between the incidence of type 2 diabetes and total or individual sugars intake (see paragraphs 6.23-6.34 of the SACN report)
but a greater risk of type 2 diabetes is associated with a higher intake of sugars- sweetened beverages. This finding was not supported by the limited evidence from randomised trials, which showed no effect of diets differing in sugars content on blood sugar and insulin levels or on insulin resistance (see paragraphs 6.25-6.28 of the SACN report)
SACN comments that the reason for this discrepancy with type 2 diabetes, between the results of prospective studies and randomised controlled trials, is not clear. Presumably the increased risk might reflect higher energy intakes among those with higher intakes of sugars-sweetened drinks. In a meta-analysis of prospective (observational) cohort studies, incidence of type 2 diabetes increased by 23% for each additional 330ml/day of sugars- sweetened drinks consumed (see paragraphs 6.35-6.37 of the SACN report).
Randomised controlled trials
Although most of the evidence available that met SACN’s inclusion criteria came from prospective, observational cohort studies, some randomised controlled trials also met the inclusion criteria. Randomised controlled trials can provide evidence of causal relationships rather than associations. Generally, there needed to be three or more randomised controlled trials to determine whether or not there was evidence of an effect. Where an effect appeared to be present, the evidence was graded by SACN as adequate, moderate or limited.
Randomised controlled trials examining cardiovascular risk factors, body weight, inflammatory markers and risk factors for type 2 diabetes demonstrate no effects of increasing sugars intake.
There is also insufficient evidence to assess the link between individual sugars and sugars-sweetened foods and drinks and cardio-metabolic outcomes.
I'm not totally against Jamie's desire to shift people towards a more wholesome diet, but his demonisation of sugar in drinks whilst continuing to sell sweet desserts ironically leaves me with a bitter taste in my mouth. As I've stated before, sugar is neither toxic (unless consumed in massive doses, which applies to most substances) or addictive. It is essential, (especially for brain function it would appear) and pretty disgusting if consumed alone (take the sugar challenge and see how many spoonfuls of table sugar you want to consume). I admit that when food processors get their hands on sugar and fat they are able to induce sometimes uncontrollable cravings, but as a chef surely that is Jamie's role? To create dishes that entice our tastebuds and leave us desiring more?
So is it a 'courageous, forward-thinking' document with evidence for action.....or a cowardly, backward-thinking attack with action without evidence that Jamie doesn't fully understand?