Caveman fad diet

Behind the Headlines

Friday May 9 2008

Caveman in cave

Volunteers ate a "caveman diet" including lean meat, berries and unsalted fish

“Eat like a caveman for a healthy heart”, is the headline in The Daily Telegraph today. It and several other newspapers report on a new study which claims that a “paleolithic” or caveman diet of berries, nuts, lean meat and fish “could help to reduce the risk of developing heart disease”.

The story is based on a small, short study of 20 young healthy volunteers which had a 30% drop out rate, with complete data for only six people available. However, these six people reduced their calorie intake by about 900 calories to about 1500 calories a day and the whole group of 14 who managed to stick with the study, lost on average 5lbs (2.3kg) in three weeks. There was no control group, so it is not possible to say whether there is anything about a caveman diet compared with any other low calorie diet that produces the weight loss or the other changes noted.

 

Where did the story come from?

Dr Magnus Österdahl and colleagues from the Karolinska Institute in Stockholm, Sweden carried out this research. The study was funded by grants from the Stockholm County Council and was published in the peer-reviewed: European Journal of Clinical Nutrition.

 

 

What kind of scientific study was this?

This was an uncontrolled observational study. The researchers say that they did not intend to copy stone-age eating habits but wanted to eliminate the harmful aspects of modern diets. They recruited 10 men and 10 women aged between 20 and 40 via a medical students’ association. They only included healthy people with a body mass index (BMI) of less than 30, who did not need hospital care, were not on prescription drugs, did not have an eating disorder or were already eating a special diet. Five of the 10 men and one of the 10 women did not complete the study either because of illness, an inability to complete the diet or they broke the study protocol for other reasons.

 

The average weight of the 14 volunteers who completed the study was 10stone 3lb (65.2kg) with a BMI of 22.2, so they were not overweight at the start of the study. The researchers measured a range of other factors, such as blood pressure and heart rate and took blood tests for haemoglobin, glucose, cholesterol and other markers of inflammation or clotting in the body such as plasminogen activator inhibitor-1 (PAI-1). PAI-1 protein is involved in the pathways that cause clotting within blood vessels. These tests were run on three occasions over 21 days.

There were strict instructions about what volunteers were allowed to eat freely, eat in restricted quantities and foods that were prohibited. They were allowed to eat fresh or frozen fruit, berries or vegetables, lean meat, unsalted fish, canned tomatoes, lemon or lime juice, spices and coffee or tea without milk or sugar, for three weeks. All dairy products were banned as well as beans, salt, peanuts, pasta or rice, sausages, alcohol, sugar and fruit juice. However, participants were allowed up to two potatoes a day and were also given some dried fruit, cured meats and a portion of fatty meat as a weekly treat.

“Short-term intervention with a paleolithic diet in healthy volunteers showed some favourable effects on cardiovascular risk factors.”

Magnus Österdahl, lead author

All volunteers were asked to record and, if possible, weigh everything they ate, but were given approximate weights of things they could not weigh. The researchers report that, unfortunately, there was a computer error when this food registration data was entered and only the data for one man and five women was available for analysis.

 

What were the results of the study?

There were significant reductions in five of the 19 parameters measured. Average weight decreased by 5lb (2.3kg), body mass index by 0.8, waist circumference by 0.2in (0.5cm), systolic blood pressure by 3mmHg and PAI-1 by 72%.

 

The researchers also note that energy intake decreased by 36% and that they observed other favourable effects such as a reduced fat composition of the diet and improved antioxidant content. However, they also point out the unfavourable effect on calcium intake – calcium levels in the blood fell by more than 50% (from 851mg to 395mg).

 

What interpretations did the researchers draw from these results?

The researchers say “this short-term intervention showed some favourable effects on diet, but that further studies, including control group, are needed”.

 

 

What does the NHS Knowledge Service make of this study?

“Fad diets” are often promoted as a method of improving health, however they should be subject to appropriate scientific investigation by well designed and conducted, preferably randomised and, at least, controlled studies. There are several limitations to this study which mean that readers should not draw too many conclusions from it.

 

  • The researchers suggest that the high drop out rate of six people in 20 (30%) has caused the study to be underpowered, that is, they were unable to detect a significant effect for some measures. However, it is also possible that they did not detect a significant effect in some measures because they were not there or because the effect was harmful. More importantly, a high dropout rate suggests that there is something about the diet that makes six out of 20 people disinclined to complete a three-week study.
  • At least one of the dietary components of a “healthy diet” changed unfavourably during the study. Calcium content fell by more than 50% (from 851mg to 395mg) and this, over a long period of time, could have had harmful effects on bone strength.
  • A control group is important in this sort of study for a number of reasons. One important statistical error that can show up in uncontrolled trials is known as “regression toward the mean”. This refers to the fact that those with extreme scores on any measure at one point in time will, for purely statistical reasons, probably have less extreme scores the next time they are tested. This research is unable to exclude this effect.
  • It is not possible to say which part of this diet contributed to the reduction PAI-1, though reduction in weight on its own is thought to effect blood levels of this protein.
  • It is not clear if maintaining this diet for longer than three weeks is possible, or if it results in long term benefits or harms.

Low calorie, low salt diets are expected to have an effect on weight and blood pressure in people who are overweight or have high blood pressure. This somewhat extreme 1500 calorie diet in healthy young volunteers appears hard to tolerate. It is not clear if a “caveman diet” has any specific advantage beyond the modest weight loss. By excluding calcium it may also be harmful for some people too.

 

Sir Muir Gray adds...

Another bit of advice is to eat nothing your great grandmother would not have been able to recognise; less food, less animal food, more grains and vegetables, and more walking, the cavemen had no car.

 

Links to the headlines

Eat like a caveman for a healthy heart. The Daily Telegraph, May 9 2008

'Caveman diet' lowers the risk of heart disease, new research shows. Daily Mail, May 9 2008

Eat like Fred Flinstone to stay healthy. Metro, May 9 2008

Was a caveman’s diet the secret of Raquel’s figure? Daily Express, May 9 2008

Stone-age diet may lower risk of heart disease. The Guardian, May 9 2008

Study hails 'caveman diet' benefits. Channel 4 News, May 9 2008

Links to the science

Österdahl M, Kocturk T, Koochek A, Wändell PE. Effects of a short-term intervention with a paleolithic diet in healthy volunteers. Eur J Clin Nutr 2008; 62:682–685

Further reading

Hooper L, Bartlett C, Davey Smith G, Ebrahim S. Advice to reduce dietary salt for prevention of cardiovascular disease. Cochrane Database Syst Rev 2004, Issue 1

Pirozzo S, Summerbell C, Cameron C, Glasziou P. Advice on low-fat diets for obesity. Cochrane Database Syst Rev 2002, Issue 2

Ratings

How helpful is this page?

Average rating

Based on 20 ratings

All ratings

Add your rating

Comments

The 5 comments posted are personal views. Any information they give has not been checked and may not be accurate.

CaloriesAndFat said on 05 June 2013

The hypocracy of this article is clearly lost on the NHS. From a prue scientific point of view the challenges the NHS raises with respect to this study are valid - if only they applied the same rigour to their own recommendations!! None of which have any basis in science.

By way of example, there have only ever been 2 double blind randomised control trial investigating the effect of reducing saturate fat on heart disease. Nether found any effect. Other RCTs (although not double blind) have found similar results.

I could go on - whether it is "base your diet on starchy foods, eat 5 a day. minimise intake of fatty foods. None of these have any support in robust science.

Report this content as offensive or unsuitable

Jez0 said on 13 March 2013

In case anybody has doubts on this article, evolutionary biologist Marlene Zuk has written a book which debunks the "science" behind the paleo diet: http://www.salon.com/2013/03/10/paleofantasy_stone_age_delusions/

Report this content as offensive or unsuitable

RustyFish said on 21 May 2012

Unlike most "fad diets", this one is supported by an admittedly very simple scientific and evolutionary logic which adds to its appeal. The NHS needs to provide more information regarding the pros and cons of dairy and cereal products and more research needs to be done in general. It is unsurprising that people fall head over heels for these diets when we are becoming more intolerant of the foods which form a large part of our diet.

Report this content as offensive or unsuitable

woodgod said on 07 December 2011

Seems that more and more people are buying into this. It get's a bit annoying having people tell me to completely avoid all dairy and bread.

Report this content as offensive or unsuitable

User363614 said on 17 December 2010

Sir Muir seems to have missed the point. Cavemen did not eat grains unless they were starving. They ate animals because they are more satisfying and provide key nutrients that are sadly lacking from many 'Western' diets; omega-3, protein and B-vitamins.

Report this content as offensive or unsuitable

Analysis by Bazian

Edited by NHS Choices