In his rebuke of Denise Minger Campbell makes a valid point that univariate analysis is fraught with danger.
What he means is analysing one variable to an effect can be misleading as other variables may be playing a part.
For example he cites that with wheat there is a predisposition for higher wheat consuming regions to be lower green plant eating regions. This would tilt the results somewhat if we accept that green plant is protective.
Indeed there are 23 regions where wheat exceeds grenn plant consumption and 41 where green plant exceeds wheat.
Looking at wheat alone and comparing it with average consumption of wheat across all regions, when it is above average heart disease stands at a high 23.24
But what would we expect to happen if wheat was greater than average wheat consumption but so too was green plant greater than average green plant consumption. Would we expect HD to be below 23.24 ?. Well it comes in at 26.33 from 7 regions
Wheat greater than average but plant less than average HD = 21.8 from 15 regions
Wheat less than average but plant greater than average HD = 8.91 from 19 regions
I have been taking a look at the raw China Study data and in particular with regard to wheat. I loaded the data up into Excel and tidied up the data to do a simple check on wheat and Heart Disease.
The average incidence of heart disease across all regions is 20.38 (HEART DISEASE AGE 35-69 (stand. rate/100,000)
The average intake of wheat is 130.08 grams per day
Now if we look at the numbers for heart disease when the wheat consumption is below average we get heart disease at 15.32
However for heart disease when wheat is above the average of 130.08 we get heart disease at 28.56
As we increase wheat to >140.08 we get HD at 29.49
Wheat > 150.08 HD 29.68
Wheat > 170.08 HD 30.6
The other interesting feature is that if you lower wheat consumption below average HD does not drop it remains fairly constant suggesting that there is a level in which when exceeded HD starts to take off. That levels appears to be 210 grams per day, above that and HD starts to take off. In summary the numbers tend to suggest that eating up to 210 grams per day of wheat is not a big deal but after that HD kicks in. Note I am simply relaying the figures here, sure maybe low wheat eaters are non smokers or whatever
Now finally with regard to wheat V Rice. There were 51 regions with data for rice and wheat. Not surprisingly there were 35 where rice eclipsed wheat consumption whilst wheat was greater than rice in only 16 regions. The average Heart Disease figure for the rice consuming regions was 10.4 whilst for the regions consuming more wheat than rice it came in at a whopping 24.6
Another bagel please waiter !
Looking at the World Health Organisation data on average total cholesterol levels for men aged 25+ and then marrying that with the highest risk countries for heart disease and the lowest risk countries for heart disease one would expect, if the the doctors are correct, to see a glaring message. Well you decide. Which group do you think is the top risk group and bottom risk group for heart disease based on the countries average total cholesterol shown to the right.