It has been said that most nutrition scientists are far more familiar with rats than with humans. - Park, 2019.
Many nutrition studies are about 70- 80 years old, while humans have been around for a few thousand years at least. And if we go by what our ancestors ate, fats were always a major component of our diets. So what’s with the exclusion of fats that we see around us?
Let’s begin from the beginning and understand the significance of dietary fats for our health and well-being. What are fats? What are their types? Once that’s clear, it is easy to understand which type of fats are an absolute must, which are to be consumed with restrain and which types of fats are to be avoided completely.
Functions of fats:
- Fats are the fuel reserves of our body.
- Protein sparing action: fats prevent the body from using proteins as energy source, thus ensuring proteins are available for body building and immunity.
- Vehicles for fat-soluble vitamins i.e. Vitamin A,D,E & K.
- Fats beneath the skin provide insulation against cold.
Non calorie roles of fats:
- BUILDING BLOCKS AND STRUCTURAL COMPONENT
The brain is composed mainly of fats (60%),called DHA.
At the cellular level, the membranes that separate the inside from the outside of the cell are mainly made of phospholipids, triglycerides and cholesterol.
2. ESSENTIAL FATTY ACIDS
These are mainly derived from vegetable fats and are involved in important bodily functions such as blood clotting, wound healing, inflammation, digestive processes,lung health and reproduction.
3. PRECURSOR OF HORMONES
Cholesterol is the primary building block for Vit D, sex hormones and hormones produced by the adrenals.
INDIAN COUNCIL OF MEDICAL RESEARCH (ICMR) is absolutely unambiguous about the requirement of fats in our diet.
It explains the concept of visible and invisible fats and lets us know the optimal dietary fat intake for Indian body type.
Visible fats - fats that are separated from their natural source. It is easy to estimate their intake in a daily diet. E.g. ghee from milk, cooking oils from seeds and nuts.
Invisible fats - fats that are not visible to the naked eye. They are present in almost every article of food,hence difficult to estimate their intake. e.g. cereals, pulses, nuts, milk eggs etc.
The reason why there is confusion regarding consumption of fats is that there are so many types of fats and also because most dietary sources contain mixed types of fats. The main fats consumed by us are in the form of various oils and fats.
Differences in dietary fats are based on their chemical structure. Let’s dive a bit deeper and understand fats based on their chemical composition.
Chemical structure of these fats do not have double bonds between fatty acids. These are solid at room temperature. Saturated fats may cause an increase in LDL levels, but there is no clear causative link between high consumption of saturated fats and heart disease.
Sources of saturated fats are :
1. fatty portion of meat, pork and chicken
2. Dairy products such as cream, butter, cheese, ghee
3. Coconut and palm oils
When it comes to saturated fats, it's best to restrict their consumption to a minimum though it's not necessary to eliminate them completely from diet.
These have double bonds in their chemical structure thus they are loosely packed hence they are liquid at room temperature. They are further divided into Monounsaturated fats (MUFA) and Polyunsaturated fats (PUFA).
MUFA : oils such as olive oil, groundnut oil,most nuts, most seeds
PUFA : these are called the essential fatty acids as they are entirely derived from diet (body cannot produce this type of fat).
These are further divided into
a. Omega-3 fatty acids:
Sources : fatty fish, such as sardines, tuna, salmon, trout, mackerel, and herring, ground flax and flaxseed oil, Soybeans, oysters, walnuts, sunflower seeds, chia seeds, hemp seeds.
b. omega-6 fatty acids:
Sources : canola oil, safflower oil, soybean oil, sunflower oil, walnut oil
While it’s certain that omega-3 fatty acids are beneficial to our body, studies are still being conducted to ascertain the exact usefulness of omega-6 fatty acids. For example canola oil, though unsaturated, is highly refined. Hence it can cause negative effects on health.
TGs are the transport form of the fats consumed. Liver converts excess calories, alcohol or sugar in the body into TGs which are then stored throughout the body. High levels of triglycerides along with high LDL is the main cause of fat build up in the arteries of heart and brain leading to organ dysfunction.
However, there are other factors too which can lead to elevated TGs levels-
- Cigarette smoking
- Alcohol addiction
- Certain medicines
- Thyroid disorders
- Poorly controlled type 2 diabetes
- Liver or kidney disorders
Some of the salient features of this type of fats are as follows
- found exclusively in animals.
- helps in transport of fatty acids to the liver.
- Important component of lipoprotein complex which transports lipids in body.
- Precursor of bile acids, sex hormones and Vit D.
Dietary source: cheese, eggs, beef, pork, poultry and shellfish.
Also synthesised by liver.
The blood cholesterol level = (the absorption in the gut + production in the liver) - (the excretion via the faeces and the use of cholesterol by cells)
Cholesterol in the blood is carried by lipoproteins: LDL (low density lipoprotein) and HDL (high density lipoprotein). While cholesterol is a major component of both LDL & HDL, high concentration in LDL are considered as “bad fats”, while high concentration in HDL is considered “good fats”. LDL cholesterol builds up in the walls of arteries, making them narrow. These plaques cause further deposition of calcium and blood clot formation - blocks the blood supply to the organ leading to heart attack or brain stroke.
These are molecular complexes formed by lipids and proteins, functioning as transport vehicles for lipid components such as cholesterol and TGs. There are 5 major classes of lipoproteins-
2. VLDL (Very low density lipoprotein) : help in transport of TGs
3. LDL : transport cholesterol from liver to peripheral tissues, thus high LDL means more cholesterol getting deposited in various body organs.
4. HDL : help in transport of cholesterol from tissues to liver
5. Free fatty acids - albumin : produced by liver, important indicator of healthy liver function.
Thus higher the HDL : LDL ratio, lesser is the cholesterol deposition in our arteries and tissues; thus reducing the risk of developing cardiovascular diseases.
Trans fatty acids
They are formed by adding hydrogen to vegetable oils which causes oils to become solid at room temperature. This is an artificial process done to prevent foods from getting spoiled.
Trans fats increase LDL cholesterol,while decreasing the HDL cholesterol. Most restaurants and bakeries use trans fat while cooking their foods, which is the most common cause of increased trans fat in our diets. The World Health Organisation (WHO) is working to eliminate trans fat from the global food supply by 2023.
How does one consume fats?
All the information above makes one thing sure, that fats are definitely not our foes. So the question arises how do we befriend them? How do we consume fats to enable optimal balance and extract maximum benefits from them?
Vegetable oils are high in PUFA content. However they are very sensitive to heat. Repeatedly heating vegetable oils can decrease their antioxidant activity and increase free radical production, which may lead to poor health effects. Avoid overheating or burning of vegetable oils to keep their nutrient content. Some oils such as extra virgin olive oils, walnut oils etc are a big NO for Indian style of cooking where spices are tempered in really hot oil (tadka), though they are good for Mediterranean dishes where food is gently sautéed in warm oil or used as dressing in salads.
Saturated fats such as cheese and butter need to be consumed in moderation. Match the calorie intake with activity levels to avoid obesity. Also since these help in making foods tasty and give high levels of satiety, excluding them completely is not advisable. Just make sure these are derived from natural sources sans chemical additives and are unprocessed
The recommendations for trans fatty acids are to keep their intake less than 1% of total fat intake. If possible eliminate them completely from the diet. Vanaspati/dalda needs to be avoided.
Limiting consumption of red meat reduces the intake of saturated fats and cholesterol. Pork belly, chicken breast, beef etc are loaded with saturated fats. Occasional consumption will not harm, though the definition of ‘occasional’ means maximum once or twice a month. Fatty fishes like salmon, mackerel, and tuna are good substitutes as their fats are rich in essential fatty acids, without causing the fat overload as is seen from meats.
There is an increase in scientific studies confirming its health benefits, but more research is needed in this direction. Ghee (cow milk butter) is a rich source of vitamins, antioxidants and healthy fats. It contains butyrate, a fatty acid that has known anti-inflammatory properties. Ghee is a good source of fats for people who have dairy allergies as it's prepared after removing the milk solids. However since ghee is a saturated fat, moderation in its consumption is desirable. - reference
Since dietary cholesterol has minimal impact on blood cholesterol levels (baring those genetically predisposed to hypercholesterolemia), the common advice is to not exceed 300 mg/day cholesterol intake. An easier way to go about it would be to restrict consumption of saturated fats to once or twice a week.
Fats cause a plethora of medical diseases starting from obesity to cardiovascular disorders and certain cancers. And hence it's natural to be cautious about eating fats. However, it's the over consumption that should be avoided, not the fats themselves. Not to forget that certain types of fats are a definite no go e.g. trans fats.
Enjoy such homemade delicacies cooked in cold pressed oils and ghee during festivals without any guilt. And try to control the puff pastries and cookies bought over the counter throughout the year.
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