Which Fats Should You Be Eating?
Here’s the good news: you can totally eat fats.
But there’s a bunch of small print. Turns out can’t eat all of the fats, all of the time. Or something like that.
Experts say, when it comes to weight loss and health, it’s important we learn to choose the right kinds of fats (and, equally, that we don’t pig out on them).
The low-fat myth?
Global recommendations for carbs (as a percentage of your daily food intake) can fall anywhere between 40% and 75%; ranges for protein are between 10%-35%, and between 20%-35% for fat. This means that there’s a pretty wide allowance for safely including fat and protein (depending on your individual health, medical history, taste preferences and even your budget).
The food-based dietary guidelines issued by South Africa’s Department of Health clearly state that fats should “never be completely excluded from our diet”, but caution that a high intake of fats is linked to “being overweight, high cholesterol levels, cardiovascular heart disease, diabetes and certain cancers” [see more on this, below]. The Department of Health also states that South Africans “eat sufficient and often too much meat, chicken and eggs”, but that our consumption of fish and milk tends to be low. The official caution to “eat fats sparingly” should be seen in this context and not as an advisory to cut out fats all together.
It’s not a fat free-for-fall
There are two reasons public health departments and public and private human nutrition experts advise caution when it comes to your fat consumption.
1. Fats are very energy dense, so it’s potentially easier to consume a greater number of calories with smaller portions. For example a cup of cooked regular (brown or white) rice has less than 250 calories. A cup of macadamia nuts? Try close to 1000 calories . 100g of carrots will give you just over 40 calories; but the same weight in cheddar cheese equals ten times that…
2. High fat intake is linked to a number of non-communicable diseases including cardiovascular disease, diabetes and cancer. This is where most of the debate begins, around how much total fat and which types of fats are good or bad for you. There are hundreds of peer-reviewed studies that attempt to evaluate the role or risk of high dietary fat consumption, and the effects of different types of fats. Sometimes the volume of research can appear to produce mixed messages – particularly when new studies are converted into dramatic media headlines.
Fancy names for “fat”
The terms “saturated”, “monounsaturated” and “polyunsaturated” refer to the chemical structure of the fatty acids that make up fats. Most foods contain a mixture of fatty acids, but some foods contain more of one kind than another.
Animal fats (excluding fish) contain a high percentage of saturated fatty acids.
Plant oils (excluding coconut and palm oils) contain more mono- and polyunsaturated fats.
Cholesterol is a form of fat called a lipid, which is found naturally in our blood and in animal tissue – and in the food we eat (but, says the Department of Health, the amount of cholesterol in food is not strongly linked to cholesterol levels in the blood). There are “good” (HDL) and “bad” (LDL) forms of cholesterol.
What does the study say?
In March 2014 a team of researchers, led by Cambridge University’s Dr Rajiv Chowdhury, published a paper that studied links between fatty acids and coronary disease.
The researchers, who evaluated data from numerous other studies involving over half-a-million people, found no associations between total saturated fatty acid consumption and coronary risk; the same paper also indicated no comparative (heart) benefit for the high consumption of polyunsaturated fatty acids. The finding attracted a lot of attention, because what it suggested pretty much flew in the face of all the recommendations (generally to cut down on saturated animal fats; and include heart-healthy mono- and poly-unsaturated fats) made by major public heart health organisations.
While some media outlets ran stories suggesting that “almost everything you’ve been told about unhealthy foods is wrong”, Dr Chowdhury’s study was not a license to eat as much bacon (or chicken fat) as we want.
This particular study was a data review and not a clinical trial itself. What Dr Chowdhury stated, in interviews following publication, was that his findings indicated more research and large-scale clinical trials were required.
The review itself was not without potential flaws, and came under serious criticism from other human nutrition experts, including the head of Harvard University’s Department of Nutrition, who wrote that the paper:
‘… is bound to cause confusion. A central issue is what replaces saturated fat if someone reduces the amount of saturated fat in their diet. If it is replaced with refined starch or sugar, which are the largest sources of calories in the U.S. diet, then the risk of heart disease remains the same. However, if saturated fat is replaced with polyunsaturated fat or monounsaturated fat in the form of olive oil, nuts and probably other plant oils, we have much evidence that risk will be reduced.”
Harvard’s Dr Willett pointed out two key “foods” that Dr Chowdhury also singled out as having an adverse effect on our health: sugar and refined carbohydrates. This message is, again, consistent with all of the “conventional” expert nutritional advice received by Men’s Health as part of the magazine’s extensive review of low-carb, high-fat practices. Are carbs bad for you? No (again, everything in moderation). Are refined carbs and added sugar bad for you? Yes.
The response from Harvard University also indicated that there was “much evidence” that a [balanced] diet high in mono- and polyunsaturated fats had significant heart benefits. One of the most important recent studies confirming this approach – a study that was not included in the Cambridge meta data review – is the Predimed Study published in the New England Journal of Medicine in 2013. This study, which followed nearly 7 500 subjects for nearly five years, found that “a Mediterranean diet supplemented with extra-virgin olive oil or nuts reduced the incidence of major cardiovascular events.”
Nearly two years prior, Dr Chowdhury was also lead author on another meta-study that found eating more oily fish could help ward off stroke (omega oil supplements, according to his recent paper, do not appear to offer the same benefits).
Numerous studies have also found clear links between high dietary intake of total fats and/or saturated fats with increased risks for other non-communicable diseases – including inflammatory bowel disease, certain types of breast cancer, and even asthma.
As research and clinical trials produce more data fields, we should be able to better map out the complex interplay between single macronutrients and our broader “diet” and behaviours – what we eat isn’t, on its own, a predictor of health; we need to take other factors into account like exercise, smoking, alcohol, our family histories.