↑ Lecture by Prof Salim Yusuf, world renowned cardiologist at a recent cardiology meeting.
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| http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(17)32252-3/abstract |
The Prospective Urban Rural Epidemiology (PURE) study is a large, epidemiological cohort study of individuals aged 35–70 years (enrolled between Jan 1, 2003, and March 31, 2013) in 18 countries with a median follow-up of 7·4 years (IQR 5·3–9·3). Dietary intake of 135 335 individuals was recorded using validated food frequency questionnaires. The primary outcomes were total mortality and major cardiovascular events (fatal cardiovascular disease, non-fatal myocardial infarction, stroke, and heart failure). Secondary outcomes were all myocardial infarctions, stroke, cardiovascular disease mortality, and non-cardiovascular disease mortality. Participants were categorised into quintiles of nutrient intake (carbohydrate, fats, and protein) based on percentage of energy provided by nutrients. We assessed the associations between consumption of carbohydrate, total fat, and each type of fat with cardiovascular disease and total mortality. We calculated hazard ratios (HRs) using a multivariable Cox frailty model with random intercepts to account for centre clustering
Carbohydrates, Fats, and CVD in the PURE Study
Carbohydrate intake was divided into quintiles. Those in Q5 consumed most, and those in Q1 consumed least. As can be seen from the slide below, presented by Dr. Yusuf, using the lowest carbohydrate intake (Q1) as a reference, there is an increased risk of CVD with increasing carbohydrate consumption.
Dr. Yusuf pointed out that earlier dietary guidelines “said reduce fats and compensate for it by carbohydrates. So essentially we’ve increased carbohydrate intake in most Western countries, and this is likely damaging.”
Furthermore, Yusuf said: “We were in for a big surprise. We actually found that increasing fats was protective. Now, these are all fats. So this very first slide challenges the WHO and the AHA guidelines on diet.”
With regards to carbohydrates as a percentage of daily energy consumption, he also said: “once you get past about 40% or about 55% of carbohydrate intake as percent energy, there is a steep increase in the risk of CVD. The WHO guidelines say that up to about 75% of carbohydrates is ok. But that is wrong.”
Then he adds:
“Again, total fats, if anything, is protective. And the reasons for this are twofold. Too low fat is inadequate, too high fat is probably bad. And the original studies from Finland was at extremely high fat levels, not the usual fat levels that populations consume.
Does the Type of Fat Matter?
Current dietary guidelines recommend that we limit the intake of saturated fats and replace them by mono- and polyunsaturated fats. Low-fat dairy products are recommended for the purpose of avoiding saturated fats. Vegetable oils should be used instead of butter.
As Dr. Yusuf points out, these recommendations are not supported by data from the PURE study:
“Then if you look at the types of fats, saturated fats, you will see there is not really a clear pattern of anything. Within the normal range, saturated fats are not harmful. May even be slightly beneficial. But there is no harm.
With monounsaturated fatty acids which are in olive oil, canola oil, and are part of the key to the Mediterranean diet, you get a clear benefit. Polyunsaturated fatty acids which are largely from vegetable oils, and remember that is processed oil, is largely neutral.
So, fundamentally, our fat story is: some fats are good, some fats may be neutral but it is carbohydrates that are the worst thing.”
“The other thing is; in the US there is this big swing to reduce milk consumption, and even if you consume milk, they want you to consume 2% or 1% of fat. What is the evidence? A big zero. Absolutely no evidence that low-fat milk is better for you. If anything, if you look at dairy sources of saturated fats, it is protective.
If you look at meat sources of fat, saturated fats, it’s neutral. And if you look at white meat such as chicken and fish, there is a trend towards benefit. So, red meat in moderate quantities is not bad and white meat may be moderately beneficial. But dairy fats such as cheese are probably good for you, and milk, there is really no data at all to reduce the fat content of milk.”
Saturated Fats, LDL-Cholesterol, and CVD
Dr. Yusuf says:
“Now, why did we go wrong. We went wrong because of surrogate end-points.
The story on saturated fats vs. LDL is consistent. Our data shows that as you increase the amount of saturated fats, your LDL goes up. But first, look at how much LDL goes up. This is a 150 thousand people in the analysis – from about 2.85 (108 mg/dL) to just under 3 (116 mg/dL). About 0.1 mmol/L (3.9 mg/dL) increase over a huge range of percentage of saturated fat (consumption).
But CVD shows exactly the opposite end-point.
Macronutrients and the ApoA/ApoB Ratio
Dr. Yusuf also addresses the effects of carbohydrate intake on more advanced lipoprotein measurements:
“Now, what about carbohydrate intake? If you look at LDL, there will be an inverse relationship. But if you look at ApoB/ApoA ratio, which today we know is the most sensitive marker for risk prediction there is a steep increase – from about 0.72 to nearly 0.85 with increasing carbohydrate intake. But with saturated fats, if anything, it is neutral or tending to go down.”
Final Remarks
Dr. Yusuf’s final remarks include these words:
“Contrary to common beliefs, the current recommendations to reduce saturated fats have no scientific basis. I’m not the only one saying this. You must have heard of the book called ‘The Big Fat Surprise’ by Nina Teicholz. She shook up the nutrition world, but she got it right.
Did you know that the seven countries studies that actually had a straight line between fat intake and CVD is fudged. I’m using the word fudged because 23 countries participated in that study and they took the seven best that fitted that line, and that’s what’s there. If you go through the literature, you will find that they chose the seven that fitted the line. The nutrition field has been distorted.”
So, is there a time for a reappraisal of public recommendations regarding the relationship between diet and heart disease following the presentation of the PURE date on macronutrients.
Obviously, this is a rhetorical question. Let’s get to work.
Time to change. period
