My blog last Friday questioned the wisdom of recent advice dished out to us on how to prevent cancer. The crux of this issue is that such recommendations are based on so-called ‘epidemiological’ studies which may show associations between things (e.g. obesity and cancer) but cannot be used to prove that one is causing the other.
The only way to know for sure whether advice to, say, eat less red meat and fat and eat more fruits and vegetables, is beneficial is to get individuals to make relevant changes to their diet, and compare their health outcomes to those who did not make such changes. Such ‘intervention’ studies are expensive and difficult to do, and are therefore a rare breed compared to the much more plentiful epidemiological study. However, intervention studies do exist, and when they do, the provide the best opportunity we have for assessing the relevance and likely effectiveness of conventional nutritional advice.
One of the biggest dietary intervention trial is known as the Women’s Health Initiative Dietary Modification Randomized Controlled Trial (WHI trial). The trial was initiated in 1993, and recruited a total of almost 50,000 post-menopausal women and followed them for an average of about 8 years. About 60 per cent of these women were allowed to continue on their normal diet (the control group). The remaining 40 per cent of women were instructed to make their diet ‘healthier’ but reducing total fat to 20 per cent of calories, to eat at least 5 portions of fruits and vegetables a day, and to eat 6 or more portions of wholegrains a day. This group ” the intervention group ” received frequent group sessions designed to educate these women about healthy eating and support them in their quest.
It’s one thing telling people to do things, it’s another thing them doing it. In studies of this nature there is always going to be a bit of ‘slippage’. However, over the course of the study, there appeared to be very real differences in the average diet between the two groups.
Notably, compared to the control group, the intervention group ended up eating:
22 per cent less fat
23 per cent less saturated fat
20 per cent less cholesterol
25 per cent less trans fats
17 per cent more fibre
an additional serving of fruit or vegetables each day
an additional ½ a serving of grains each day
Taken as a whole, most health professionals, dieticians and nutritionists would view such differences as an indication that the intervention group ate a significantly healthier diet than the control group.
The results of this mammoth and expensive ($ 415 million) study are now in the public domain. The most recent appraisal of the data appeared last month in the Journal of the National Cancer Institute and focused specifically on cancer outcomes.
Previous analyses, published last year, had shown not reduced risk of either breast cancer or colon cancer in the intervention group [2,3]. In the latest study, the scientists involved in this project extended their analysis to more than 20 other cancers. And what the results showed is this:
The ‘healthy’ eating group were not found to be at a reduced risk of any of these cancers (NONE of them)
The logical interpretation from this is that this study singularly failed to demonstrate that ‘healthy eating’ reduces the risk of cancer.
Now, have a read through the ‘results’ and ‘conclusions’ from the abstract (summary) of the study.
RESULTS: Ovarian cancer risk was lower in the intervention than in the comparison group (P = .03). Although the overall ovarian cancer hazard ratio (HR) was not statistically significantly less than 1.0, the hazard ratio decreased with increasing intervention duration (P(trend) = .01). For the first 4 years, the risk for ovarian cancer was similar in the intervention and control groups (0.52 cases per 1000 person-years in the intervention group versus 0.45 per 1000 person-years in the comparison group; HR = 1.16, 95% confidence interval [CI] = 0.73 to 1.84); over the next 4.1 years, the risk was lower in the intervention group (0.38 cases per 1000 person-years in the intervention group versus 0.64 per 1000 person-years in the comparison group; HR = 0.60, 95% CI = 0.38 to 0.96). Risk of cancer of the endometrium did not differ between the groups (P = .18). The estimated risk of total invasive cancer was slightly lower in the intervention group than in the control group (HR = 0.95, 95% CI = 0.89 to 1.01; P = .10).
CONCLUSIONS: A low-fat dietary pattern may reduce the incidence of ovarian cancer among postmenopausal women.
What these results highlight is the fact that in the second half the study, the risk of ovarian cancer was statistically lower than in the intervention group (compared to the control group).
Actually, though, over the whole course of the study, the risk for ovarian cancer was not lower in the intervention group. So it seems what has gone on here is some ‘data dredging’ ” the practice of looking at the data long and hard enough and enough different ways to finally turn up something ‘positive’.
Two other things are noteworthy about how this study has been ‘spun’. Firstly, the authors of the study appear to have swept under the carpet the stunning failure of ‘healthy’ eating to reduce the risk of cancer. And, secondly, it looks like have actually attempted to present these dismal results in a positive light – .not just with regard to ovarian cancer, but cancer in general. Note again the part of the last line of the ‘results’ section of the abstract reads: The estimated risk of total invasive cancer was slightly lower in the intervention group than in the control group.
Note also, though, the rest of this line reads: (HR = 0.95, 95% CI = 0.89 to 1.01; P = .10). What this means is that the ‘slightly lower’ incidence of cancer in the intervention group was not statistically significant, and therefore is most likely due to chance. I’m wondering if such positive spin and misrepresentation of the facts doesn’t border on the unethical.
And here’s another thing, one major goal of healthy eating advice has to do with weight. The idea here is that cutting back on fat (particularly heart-stopping saturated fat and cholesterol) will promote weight loss or aid maintenance of a healthy weight. Other data from the WHI trial has showed that the average weight difference between the intervention and control groups was 0.4 kg (about a pound) after 7½ years [4]. Imagine all that potential sacrifice and deprivation for years and years to find that, in terms of weight, it’s got you precisely nowhere.
How was this other failing of ‘healthy eating’ summarised? The ‘conclusion’ from this study reads: A low-fat eating pattern does not result in weight gain in post-menopausal women. That’s a funny way of putting it.
References:
1. Prentice RL, et al. Low-fat dietary pattern and cancer incidence in the Women’s Health Initiative Dietary Modification Randomized Controlled Trial.
J Natl Cancer Inst. 2007;99(20):1534-43 [Epub Oct 9 2007]
2. Beresford SA, et al. Low-fat dietary pattern and risk of colorectal cancer: the Women’s Health Initiative Randomized Controlled Dietary Modification Trial.
JAMA. 2006;295(6):643-54.
3. Prentice RL, et al. Low-fat dietary pattern and risk of invasive breast cancer: the Women’s Health Initiative Randomized Controlled Dietary Modification Trial.
JAMA. 2006;295(6):629-42.
4. Howard BV, et al. Low-fat dietary pattern and weight change over 7 years: the Women’s Health Initiative Dietary Modification Trial.
JAMA. 2006;295(1):39-49.
here is a similar one just published:
http://www.ajcn.org/cgi/content/abstract/86/5/1445?etoc
Hi John,
What does a ‘normal diet’ mean in the context of this study – “About 60 per cent of these women were allowed to continue on their normal diet (the control group).”
From reading this it almost feels like it doesn’t make any difference to our health what we eat, yet we know that not all food is created equal. I would be interested to know what the ‘normal’ diet consisted of. Presumably not KFC and fanta?
Mel
John. This study seems to be about fat, not nutrition. There are so many nutrients that need to be taken into account. As we both know it is not just about fat. They needed to look at a whole range of antioxidants, magnesium, all vitamins, how food is cooked, how much raw food was in the diet, how processed the food was. Some researchers think that they can just separate out parts of a diet like fat and see what happens. Nutrition is too complicated for that. It is extremely difficult to do studies on nutrition but a prospective study like this one should have been better. How you analyse the data is always important. THe intervention group just had one extra piece of fruit a day so eiter the control group had a good diet ( Ex group told to eat 5 pieces) or the ex group did not eat what they were told.
As far as I am concerned and there are loads of studies diet is paramount for health but knowing what diet to eat is the difficult thing for people. A low fat diet can be good or bad depending on what they eat. I knew a vetetarian who ate no fruit and no vegetables! Hilda
Mel
Take a look at this link:
http://jama.ama-assn.org/content/vol295/issue6/index.dtl
It will take you to the edition of JAMA from last year which published 3 studies (1st 3 studies under ‘Original Communications’) regarding the findings of the WHI trial . These studies are ‘free to access’, and contain considerable detail about what the women in the intervention and ‘control’ groups ate in this study.
Mel . Please don’t reach that conclusion. In my job I see people making great steps in health just by changing their diet for a few months. We should eat what we were intended to eat. Buy one of Johns books and you’ll see. No KFC and fanta or margerine or other processed foods won’t do it. Hilda
I didn’t know that having a moderately healthy diet like that was supposed to prevent cancer – I thought it was supposed to prevent heart and related circulatory problems and other diseased related to being obese.
I think a lot of cancer is caused by all the chemicals we’re exposed to now whatever we eat.
Tiggy
Now we sit back & watch all the “experts” tell us why this study didn’t confirm their dearly held beliefs. As for the so called “healthy diet” by the time you finish consuming the huge amounts of carbs = sugar there is little wonder the body cell structure tends to break down & illness results. Send in all the fake foods made with soy & chemicals & it is little wonder the body breaks down. It is an amazing thing the body, but we do have to put a bit of effort into not polluting it with anti – nutrients & chemicals.
I’m struggling to get my head around diet right now.
I have metabolic syndrome, hypothyroid, high triglycerides, low HDL and moderate/high LDL and I’m doing ok with this approach. But….
I have MS and the ‘optimum’ diet for MS is low animal fat (or so Roy Swank and the Best Bet Diet originators claim) and no gluten or pulses.
Of the two approaches towards health management, the low-carb diet wins hands down for me. Keeping blood glucose levels even is important. Fatigue is a big problem with MS (and ME) and I am pretty sure that for those whose bodies don’t work as well as they should, that the blood glucose rollercoaster has a big part to play with this.
But….the Best Bet and Swank diets are adamant that animal fats are also bad guys.
More confusing is that information that Vitamin D (the wonder vitamin right now) is very important to help keep MS at bay, but one of the best sources for dietary vitamin D is lard.
Confused?
You bet I am.
How about the next stop for dietary researchers should be to find a great way of eating that helps people with chronic diseases to get the best from their diets.
Proper clinical research that is not funded by cereal manufacturers or any sort of lobbying group.
I did try to follow a 90% raw food diet for the first few months of this year. I felt great in the summer months, but it’s just not possible in winter. I didn’t feel good emotionally though. Rawfooders are mostly vegans and they regard food as some sort of evangelical religion.
I took great comfort from this…http://www.beyondveg.com/billings-t/vegan-pledge/vegan-pledge-1a.shtml
When I feel confused (often) I read this. It helps!
Haven’t seen Roy Swanks stuff, but Best Bet whilst being ” adamant that animal fats are also bad guys.” doesn’t offer any good evidence for this.
People tend not to be aware that for example, beef fat is as much monounsaturated fat as saturated. Plus a little Polyunsaturated. This probably varies with the animals diet however.
Yes, it is very confusing. The Swank results are anecdotal and not specific enough for me to buy into it wholeheartedly.
There’s a lot of pronouncements from ‘experts’ on MS, from the LDN doctors who say that beta-interferon drugs can’t be taken with LDN, despite the fact that there is not a shred of clinical evidence for this.
There’s also another doctor with an interest in MS, who says that no carbs should be eaten at all and that offal and brains should be consumed at least once per week (not sure about eating brains), along with a great deal of animal fats.
I think I agree with not eating legumes or grains and I have had the best year since diagnosis so far through all this, but what really, really bugs me about the approaches to handling MS, is that the ‘experts’ are so polarised. Certainly until this year, Ashton Embry who promotes the Best Bet Diet was anti-interferon use. Why?
The MS society won’t discuss diet.
It would appear that those people with an open mind are left feeling unsupported if they decide to try both diet and drugs as a way to help minimise MS.
as a post menstrual, weight gaining,woman I have been even more aware of my nutrutional needs. There is so much information but really no clear advice. Each ‘group’ or ‘research’ trying to sell its own beliefs.
I did spend some time the other day trying to make a list of what I should be eating each day / week. The results would have made me obese!!. Do the 3 brazil nuts count as one of my, at least, five a day, how many bottles of cod liver oil etc, how can I eat ALL those portions of oily fish, white meat or pulses.
It is a minefield.
One thing I have noticed though is that if I listen to my body I seem to have cut out red meat and eat no bread and I hadn’t even noticed I had