To Fat or Not to Fat?
I’m sure many of you are aware of the term healthy fats, but what exactly does that mean? And does this therefore follow that there are unhealthy fats? Keep on reading for a brief history into how the public’s understanding of a ‘healthy diet’ got a little confused.
Why was a low-fat diet promoted in the past?
For a long time, fat consumption was synonymous with obesity and heart disease. The public were warned that eating too much fat will make you fat – makes sense, right? – However, cardiology experts, such as Dr Malhotra, now warn that the ‘low-fat is best’ mantra has paradoxically resulted in a rise in cardiovascular risks and obesity (1). So how is it that despite avoiding fatty foods we are now the third fattest nation in Europe?
The explanation starts with the scientific evidence. Epidemiological and animal research from way back in the 70’s suggested that high fat consumption, specifically saturated fat, resulted in increased levels of LDL (low-density lipoproteins) cholesterol which is linked to an increased risk of cardiovascular disease.
LDL transports cholesterol and other lipids to target tissues around the body. High quantities of LDL and LDL cholesterol are associated with increased risk for plaque build-up in the artery walls. This is why LDL cholesterol is often termed ‘bad’ cholesterol.
Plaque is the accumulation of fat, cholesterol and other substances. The presence of plaque can narrow the arteries resulting in restricted blood flow. If plaque continues to build it can completely block the artery. If that blocked artery supplies the heart, it will deprive the heart of oxygenated blood and ultimately result in a myocardial infarction (also known as, a heart attack).
This evidence informed the governments nutritional guidelines which urged people to avoid fatty foods in preference for a low-fat diet.
Replacing fat with sugar
Although we were reducing our fat consumption as a nation, we were also increasing our consumption of sugar and sugar sweetened, processed foods. This, according to Dr Malhotra, has worsened the risk of heart disease (1).
The consumption of sugar is now thought to be an independent risk factor for the development of metabolic syndrome – a combination of diabetes, obesity, and high levels of triglycerides and LDL cholesterol – which greatly increases a person’s risks of developing heart disease.
Dr Malhotra highlights that the subtype of LDL that is associated with cardiovascular disease is not the type that is shown to increase following saturated fat consumption. Saturated fat consumption increases large buoyant (type A) LDL particles. Whereas, recent evidence suggests that those associated with heart disease are the smaller, denser (type B) LDL particles.
This is a classic case of correlation does not equal causation. Just because saturated fat consumption was associated with increased levels of LDL doesn’t mean its consumption increases the risk of heart disease. This highlights why it’s really important to understand the quality of the evidence which nutritional guidelines are based on and how the development of research can deepen our understanding of nutrition and health.
Now it’s important to note here that much like fat, sugar has become the new demon of nutrition and removing all sugar from your diet (i.e. fruit) is not recommended. Remember we do not eat single nutrients; we eat whole foods! (but that will have to be another post for another day).
Why are fats important?
Fat is a vital component in the body and without fat we would not be able to function. Beyond providing cushioning and insulation to our bodies, fat literally makes up the membranes of our cells, and the brain is made of almost 60% fat!
It is an important source of energy and supports cells growth. Dietary fats, especially monounsaturated fats, also aid the absorption of specific nutrients. Lipid soluble nutrients do not dissolve in water and often require the co-consumption of dietary fats to be efficiently absorbed into our bodies.
For example, without fat, it is estimated from in vitro studies that only 50% of the beta-carotene (provitamin A) found in cooked carrots is absorbed into our blood stream. Whereas when co-consumed with dietary fats (the best being mono-unsaturated fats like olive oil) 80% is thought to be absorbed (2).
What fats should we be consuming?
The most up to date scientific evidence suggests mono and poly- unsaturated fatty acids (MUFAs and PUFAs) are the fats we should be consuming. When we look at the epidemiological evidence, those consuming diets high in these fats have a lower risk of developing cardiovascular disease.
Beyond epidemiology, randomised control trials (RCTs) suggest that these fats can improve lipid profiles. In other words, elevate our levels of ‘good’ cholesterol (HDL cholesterol) and reduce our levels of ‘bad’ cholesterol (LDL cholesterol) (3).
Good dietary sources (4)
- Olive oil
- Rapeseed oil
- Corn Oil
- Sesame Oil
- Flax, sesame and sunflower seeds
- Wallnuts and pine nuts
- Oily fish (e.g. mackerel, trout and sardines)
So what about saturated fat? RCTs have shown that replacing saturated fats with mono and poly- unsaturated fats can improve lipid profiles which could in turn reduce cardiovascular risk. In line with these findings the UK government guidelines (the Eatwell Guide) suggest opting for unsaturated fats instead of saturated fats. It is recommended we consume no more than 30g for men and 20g for women of saturated fat per day. It’s important to note that although fat is an essential part of our diet it is calorie dense (9kcal/gram) compared to carbohydrates and protein (4kcal/gram). However, excess calories from any of these macronutrient sources will be converted into body fat.
What fats should we avoid?
The main fats we should be avoiding are trans fats. Although some trans fats naturally occur in fats of animal origins they can also be produced industrially and are added to many processed foods such as cakes, biscuits, cookies and pastries (e.g. pies, sausage rolls). Trans fats are the result of vegetable oils being hydrogenated to turn them from liquid to solid or semi-solid at room temperature. The food industry favours these fats because of their longer shelf-life.
Epidemiological data links trans-fat consumption with increased CVD risk and RCTs suggest that trans-fat consumption results in poor lipid profiles (increased LDL and decreased HDL) (4).
Following on from a preliminary determination in 2013 which stated that trans fats are no longer ‘Generally Recognised as Safe’, The American Food and Drug Administration (FDA) have since banned the addition of trans fats to all food products by manufacturers in the US.
However, the European Commission have not been as quick to ban trans fats but instead aim to cap trans fats (other than the small amounts naturally occurring in fats of animal origin) to 2g per 100g of fat by 2021.
Because of these legislative changes as well as the negative attention given to trans fats over present years, many retailers have reduced the levels of trans fats in their products.
Keep in mind when shopping that companies are not required to state the quantity of trans fats on the nutritional information printed on product packaging unless it exceeds 2% of fat. Hence, products with low levels of industrially produced trans fats will simply state ‘partially hydrogenated oils’ on the ingredients list.
1Malhotra, A., 2013. Saturated fat is not the major issue. Bmj, 347, p.f6340.
2Hornero-Méndez, D. and Mínguez-Mosquera, M.I., 2007. Bioaccessibility of carotenes from carrots: Effect of cooking and addition of oil. Innovative Food Science & Emerging Technologies, 8(3), pp.407-412.
3Baum, S.J., Kris-Etherton, P.M., Willett, W.C., Lichtenstein, A.H., Rudel, L.L., Maki, K.C., Whelan, J., Ramsden, C.E. and Block, R.C., 2012. Fatty acids in cardiovascular health and disease: a comprehensive update. Journal of clinical lipidology, 6(3), pp.216-234.
My go to breakfast (packed full of those healthy fats!)
The monounsaturated fatty acid (MUFA) content of avo’s is vital for the absorption of the carotenoids and other lipid soluble nutrients trapped inside fruit and veggies…(such as the tomatoes and mushrooms we just devoured)… there are some amazing antioxidant, anti-inflammatory and anti-cancer compounds in fruits and veggies that can be unlocked with co-consumption of fats (especially unsaturated)
We also added some of our home made garlic and rosemary infused olive oil for an extra MUFA boost!
Swapping saturated and trans-fat options such as cheese, butter, margarine etc. with unsaturated fat options like olive oil, avocado, nuts and seeds can reduce your risk of heart disease, improve cholesterol levels and reduce blood pressure! So, bring on the healthy fats!
1 large mushroom
6 cherry tomatoes
1tbsp balsamic vinegar
2 slices sourdough bread
Half an avocado
1tbsp olive oil (I used my home-made garlic and rosemary infused olive oil)
Salt and pepper to taste
- Pre-heat the oven to 180. Meanwhile, fry off the mushrooms in a little oil (I use Aldi’s rapeseed oil).
- Roast the tomatoes in the oven drizzled with a little oil and the balsamic vinegar for around 15-20 minutes.
- Mash the avocado in a bowl with the olive oil and then spread onto sourdough toast
- Pile on the mushrooms and tomatoes and you’re done!