Black et al (Low Fat Diet for Skin Cancer)

Hooper et al included this trial by Black et al as a reduced fat trial in their 2012 meta-analysis and as a reduced SFA trial in their 2015 meta-analysis

Studies Associated with the Trial

Effect of a Low-Fat Diet on the Incidence of Actinic Keratosis (1994) [1]

Evidence that a low-fat diet reduces the occurrence of non-melanoma skin cancer (1995) [2]

General guidelines for a low-fat diet effective in the management and prevention of nonmelanoma skin cancer (1997) [3]

Purpose

Ecological studies at the time and animal studies found a relationship between fat intake and the incidence of skin cancers and actinic keratosis (potentially precancerous tissue) [1] [2]

Methods

133 people with a previous diagnosis of skin cancer (define) were randomised to a low fat group or a control group.

The low fat group attended 8 weekly classes where they were advised to reduce fat intake to 20%, keep protein at 15% and increase carbohydrate to 65% and to avoid calorie deficit.  Foods containing sufficient vitamins and minerals to meet the recommended dietary allowances for adults were emphasized. The patients were taught behavioral techniques such as stimulus control, self-monitoring, and cognitive behavioral self-management to help them comply with the dietary regimen” [1] [2] [3].  “The primary strategy recommended for increasing carbohydrate intake was to increase consumption of grains, fruits, and vegetables. This strategy introduces an additional potential variable; i.e., a statistically significant inverse relationship has been reported between nonmelanoma skin cancer and high vegetable intake”. [3]

“The diet of the patients assigned to the control group was not changed” [1]

Results

Fat intake was maintained well at a little over 20% and despite advice to increase complex carbohydrates to maintain weight (which they did: 264.5g vs. 303.5g), the low fat group had a significant decrease in calorie intake and significant weight loss [1] [2] [3]

  

Consistent with the advice to consume more fruits, vegetables and grains, the low fat group increased their fibre and vitamin C intake, but not by much [3]

The low fat group had a significantly lower incidence of actinic keratoses [1] and total skin cancers [2] [3]

Hooper et al included this trial as a reduced fat trial in their 2012 meta-analysis and as a reduced SFA trial in their 2015 meta-analysis.  Similar to the other low fat trials, while it’s very appropriate to include this as a reduced fat trial, it is less appropriate to include this as a reduced SFA trial due to the simultaneous decreases in MUFA and PUFA as well.  Hooper et al reports the following results in their meta-analyses.  The incidence of CVD events and CVD mortality was not published, but it was reported that 1 person died in the low fat group and 2 people died in the control group.  They also flagged the trial as having high risk of ‘free of systematic difference in care’ and low risk of ‘free of dietary differences other than fat’ 

	Low Fat Group (N = 66)	Control Group (N = 67)
CVD Events	0	2
CVD Mortality	0	2
Total Mortality	1	2