Why fat is necessary in our diets
Despite the trendiness of low-fat diets, fat IS a necessary part of our diets.
Fat offers a fuel source, helps distribute fat soluble vitamins (example Vitamin D, Vitamin E), and becomes part of the cell membrane. Two fats are essential for humans because:
- we aren’t able to make them
- they are necessary for health
The two essential fatty acids (EFAs) for humans are linoleic acid (LA) and alpha-linolenic acid (ALA). I know you want me to skip to the point and just say WHY they’re essential, but we need to cover some basics first, so the answer to that burning question is going to have to wait a few sections.
Defining Fats
Fats are a category of molecules that include cholesterol, phospholipids, and triglycerides.
We ALL know about cholesterol.
Phospholipids
What is a phospholipid?
Phospholipids are a class of molecules that include a phosphate group. The phosphate group is hydrophilic (water loving) and is usually referred to as the phospholipid head and accounts for the phospho part of the molecule. The lipid part of the molecule is made up of a hydrocarbon chain double tail and this tail is hydrophobic (water fearing).
Figure 1. Structure of a phospholipid. The phosphate head and the lipid tails (Reference 1).
Why are phospholipids important?
Do you remember from high school biology that phospholipids are important for cell membranes?
Forming the cell membranes of every cell in our body are two layers of phospholipids that orient themselves so that the lipid hydrophobic (water fearing) tails point towards each other and the phosphate hydrophilic (water loving) heads point outwards either into the extracellular space (space between cells) or inwards into the intracellular space (space within cells).
The phospholipid bilayer forms the bulk of the cell membrane.
Figure 2. The cell membrane of every cell in our body is composed mostly of a phospholipid bilayer (Reference 2).
Figure 3. The rest of the story: cholesterol and proteins are dispersed throughout the phospholipid bilayer of the cell membrane (Reference 3).
We’re going to circle back around to phospholipids later in this post, but for now, let’s move on and talk about triglycerides.
Triglycerides
What is a triglyceride?
Triglycerides are composed of a glycerol backbone with 3 fatty acids attached to the glycerol backbone.
Figure 4. The structure of glycerol, fatty acids, and triglyceride (Reference 4).
Why are triglycerides important?
Triglycerides serve several functions in our body:
- Triglycerides are the main form of fat stored by our bodies.
- Triglycerides allow transfer of fat AND blood glucose to and from the liver (the liver breaks down the triglyceride molecules into fatty acids and glycerol (which the liver then converts to glucose), so it’s important to be able to move triglycerides to and from the liver as needed). Glucose is a major fuel source for our brains.
- Triglycerides are a main component of skin oils and make up about 40% of sebum
Triglycerides are found in a variety of foods. Triglycerides aren’t absorbed whole from the intestines. They’re broken down into their fatty acid and glycerol components so they can pass through the intestines into the bloodstream. The liver regenerates triglycerides from glycerol and 3 fatty acids.
Speaking of fatty acids…
Fatty Acids
The body can create most of the fatty acids it needs by converting carbohydrates to short chain fatty acids and then adding more and more carbons onto the fatty acid chain to create palmitic acid, which is a saturated fatty acid containing 16 carbons. Here’s the structure of palmitic acid.
Figure 5. Palmitic Acid (Molecular Formula: C16H32O2).
Interpreting Molecular Drawings
Let’s pause here and talk about what we’re looking at. In organic chemistry, it’s very common to draw a chemical structure as shown in this figure. Each line of the zig-zag represents a connection between two carbon atoms, so essentially, the point of each zig or zag represents a carbon atom.
Atoms that are not carbons are labeled as “O” for oxygen and “OH” for an oxygen atom bound to a hydrogen atom. Each carbon atom can have a total of four bonds (each line leaving a point is one bond, a double line represents two bonds to an adjacent atom).
The bonds not shown in the figure are the bonds between carbon atoms and hydrogen atoms, and it just gets too messy to show ALL those bonds.
Fatty acids that the body can make from carbohydrates and short chain fatty acids
Figure 6. The body can make omega-9 fatty acids on a fat restricted diet using carbohydrates as the starting material, but the body cannot make omega-3 and omega-6 fatty acids from carbohydrates (Reference 5).
What we can see from this figure is that our bodies CAN make omega-9 fatty acids using carbohydrates, but on a fat restricted diet, our bodies cannot make omega-3 or omega-6 fatty acids.
The arrows in the figure above show conversion from one fatty acid to another, and the names to the right of the arrows indicate the enzyme that the body uses to complete the step shown (Δ5-desaturase is an enzyme, so is elongase, and so are Δ6-desaturase and Δ9-desaturase). These are all enzymes our body uses to lengthen and desaturate fatty acids.
We’ll talk more in the next post about exactly what 18:3n-7 and 22:3n-9 in the figure above mean, but we don’t need to cross that bridge just yet.
Essential fatty acids
Our bodies need eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and arachidonic acid (AA) for a variety of functions that we’ll talk about in a minute.
You probably recognize EPA and DHA from fish oil. EPA and DHA are both omega-3 fatty acids that can be synthesized in our bodies from the omega-3 fatty acid, alpha-linolenic acid (ALA).
While our bodies can make omega-9 fatty acids, our bodies are not able to make omega-3 fatty acids, so we need to eat ALA to give our body the fuel it needs to make EPA and DHA.
We can also eat foods containing EPA and DHA directly, and this becomes more and more important as we grow older (and also if we’re on a vegetarian or vegan diet) but as long as we’re not lacking any of the desaturase enzymes and eating enough foods high in ALA, we’re providing our bodies the necessary nutrient to create EPA and DHA.
The same is true for arachidonic acid. Arachidonic acid can be made by our bodies from the omega-6 fatty acid, linoleic acid (LA). Arachidonic acid (AA) can also be ingested directly from a variety of food sources.
Here’s a diagram of how our bodies convert ALA to EPA and EPA to DHA and how our bodies convert LA to AA.
Figure 7. Why alpha-linolenic acid (omega-3) and linoleic acid (omega-6) are necessary nutrients in our diet (Reference 5).
But, WHY are these fatty acids essential for our health?
The omega-3 fatty acids are important for:
- Nerve health – numbness and tingling are reported in omega-3 deficient diets.
DHA in particular is important for neurological health aiding in neuron creation and growth (neurogenesis), communication between neurons (neurotransmission), and protecting neurons from oxidative stress (Reference 7).
DHA can be made in the body from either ALA or EPA.
- Brain development – Several papers show that stroke recovery is improved by supplementing a person’s diet with fish oil (high in EPA and DHA).
Literature also suggests that omega-3 fatty acids are important during pre-natal development and infancy for ensuring sufficient central nervous system (brain and nerve) development (Reference 7, Reference 9, Reference 10).
- Vision – blurred vision is a known side effect of omega-3 deficiency (Reference 6), AND higher omega-3 concentration in an infant at birth is associated with better visual development (Reference 7)
- There’s growing evidence that higher levels of DHA in our bodies are associated with reduced amyloid plaques in Alzheimer’s Disease (Reference 9).
Omega-3 and Omega-6 fatty acids are important for preventing:
- Skin Lesions – dry, flaky red inflamed skin results from deficiency in either omega-3 or omega-6 essential fatty acids
- Eczema – eczema is another skin condition linked to omega-3 and/or omega-6 essential fatty acid deficiency
- Severe Exfoliative Dermatitis – extremely dry and flaky skin (Picture 1 below) was healed by supplementing with omega-3 and omega-6 fatty acids
- Recurrent infection – in infants with essential fatty acid deficiency, repeated infections are common
Picture 1. Extreme dry skin (left) due to essential fatty acid deficiency, and resolution of condition upon supplementation with essential fatty acids (right) (Reference 8).
Fatty Acid Composition of Human Breast Milk
Human breast milk contains quite a bit of the omega-6 essential fatty acid, linoleic acid (LA). It also contains arachidonic acid (AA) and the omega-3 fatty acids: alpha-linolenic acid (ALA), EPA, and DHA.
Studies show that babies fed breast milk typically show a faster rate of cognitive growth and visual development compared with babies fed formula (Reference 11 and Reference 12).
Optimal Ratio of Omega-3 to Omega-6 Essential Fatty Acids
Our Western diets have a higher ratio of Omega-6 compared to Omega-3 fatty acid consumption. Estimates are on the order of about 15/1. It turns out an optimal ratio for cardiovascular health is closer to 4/1. That’s 4 grams or 4% Omega-6 per 1 gram or 1% Omega-3 consumed.
For reducing the risk of colon cancer and breast cancer, the optimal ratio is more like 2.5/1. So, 2.5 grams of Omega-6 per 1 gram of Omega-3 consumed (Reference 17).
Foods high in the essential fatty acids
If you’re wondering what to eat to boost your omega-3 and omega-6 intake, here’s a table for you that includes the % of the oil on a weight basis in each of the foods listed (Reference 13, Reference 14, Reference 15, Reference 16, and Reference 17).
|
Linoleic Acid (Omega-6) |
Alpha-Linolenic Acid (Omega-3) |
GLA (Omega-6) |
EPA & DHA (Omega-3) |
|
Chicken fat (~20%) |
|
|
Mackerel (0.59 g DHA & 0.43 g EPA per serving) |
|
Pecans (21%) |
|
|
Salmon (1.22 g DHA & 0.35 g EPA per serving) |
|
Pine Nuts (25%) |
Flax seeds (3.2 grams in 2 Tbsp.) |
|
Sardines (0.74 g DHA & 0.45 g EPA per serving of canned sardines) |
|
Walnuts (47%) |
Walnuts (38%) |
|
|
|
Pistachios (13%) |
Pistachios (13%) |
|
|
|
Brazil Nuts (24%) |
Brazil Nuts (24%) |
|
|
|
Extra Virgin Olive Oil (~10%) |
Brussel sprouts (44 mg per ½ cup raw) |
|
|
|
Sunflower Oil (~70%) |
Hemp seeds (21%) |
Blackcurrant Oil (~17.5%) |
Algal Oil (400-500 mg combined DHA & EPA) |
|
Borage Oil (38%) |
Perilla Oil (64%) |
Borage Oil (20%) |
|
|
Evening Primrose Oil (74%) |
|
Evening Primrose Oil (9%) |
|
|
Hempseed Oil (54%) |
Hempseed Oil (22%) |
|
|
|
Grapeseed Oil (75%) |
|
|
|
|
Flaxseed/Linseed (13%) |
Flaxseed/Linseed (53%) |
|
|
Aging and our body’s ability to convert LA to GLA and ALA to EPA and DHA
As we age, our ability to convert linoleic acid (LA) to gamma-linolenic acid (GLA) is reduced. The same thing happens with our ability to convert alpha-linolenic acid to EPA and EPA to DHA.
Unless we’re vegan, we don’t have to worry too much about loss of ability to convert GLA to arachidonic acid (AA) because AA is so abundant in our diets (it’s found in meat, eggs, and butter).
On the other hand, even in healthy adults, conversion of ALA to EPA and then finally to DHA is usually incomplete.
Only about 10% of the omega-3 essential fatty acid consumed is converted to DHA.
In the next post, we’re going to look at how our bodies use omega-3 and omega-6 fatty acids, and we’re also going to take a closer look at how we can improve our health (and our skin’s condition) by topically applying oils high in these fatty acids.
So, stay tuned for Topical Application of Essential Fatty Acids: How these EFAs can improve our skin’s condition and our health
References
Reference 1. Phospholipids. https://chem.libretexts.org/Bookshelves/Introductory_Chemistry/Book%3A_Introductory_Chemistry_(CK-12)/26%3A_Biochemistry/26.9%3A_Phospholipids
Reference 2. https://images.app.goo.gl/RrZDJMvayctU98ka6
Reference 3. Fluid mosaic model: cell membranes article. https://images.app.goo.gl/c5gYTcYhhy8oboKu8
Reference 5. https://www.tuscany-diet.net/tag/polyunsaturated-fatty-acids/
Reference 6 https://academic.oup.com/jn/article/128/2/427S/4724041
Reference 7. Omega 3 fatty acids on child growth, visual acuity and neurodevelopment. Cristina Campoy, Mª¯ Victoria Escolano-Margarit, Tania Anjos1, Hania Szajewska2 and Ricardo Uauy. British Journal of Nutrition (2012), 107, S85–S106 doi:10.1017/S0007114512001493
Reference 8. Essential Fatty Acid Deficiency in Human Adults During Total Parenteral Nutrition. MC Riella, JW Broviac, M Wells, and BH Scribner. Downloaded from http://annals.org / by Penn State University Hershey User on 09/19/2016.
Reference 9. Neurobiology of Disease. A Diet Enriched with the Omega-3 Fatty Acid Docosahexaenoic Acid Reduces Amyloid Burden in an Aged Alzheimer Mouse Model. Giselle P. Lim, Frédéric Calon, Takashi Morihara, Fusheng Yang, Bruce Teter, Oliver Ubeda, Norman Salem Jr, Sally A. Frautschy and Greg M. Cole
Reference 10. Docosahexaenoic acid and human brain development: Evidence that a dietary supply is needed for optimal development. Journal of Human Evolution. Volume 77, December 2014, Pages 99-106. J. ThomasBrenna and Susan E.Carlson. https://www.sciencedirect.com/science/article/abs/pii/S0047248414000839
Reference 11. Koletzko B: Human Milk Lipids. Ann Nutr Metab 2016;69(suppl 2):27-40. doi: 10.1159/000452819.
Reference 12. J Thomas Brenna, Behzad Varamini, Robert G Jensen, Deborah A Diersen-Schade, Julia A Boettcher, Linda M Arterburn, Docosahexaenoic and arachidonic acid concentrations in human breast milk worldwide, The American Journal of Clinical Nutrition, Volume 85, Issue 6, June 2007, Pages 1457–1464, https://doi.org/10.1093/ajcn/85.6.1457
Reference 13. https://www.dietobio.com/dossiers/en/nuts/fats.html
Reference 14. Essential Fatty Acids in Vegetarian Nutrition. https://www.scienzavegetariana.it/medici/essentialfat.html
Reference 15. Plant Sources of Omega-3 Fatty Acids. https://www.healthline.com/nutrition/7-plant-sources-of-omega-3s#section2
Reference 16. Dietary Sources of DHA & EPA. https://www.medicalnewstoday.com/articles/323144.php#fish-sources-of-omega-3.
Reference 17. The importance of the ratio of omega-6/omega-3 essential fatty acids. https://www.ncbi.nlm.nih.gov/pubmed/12442909
Reference 18. February 2010. Vegetarian’s Challenge — Optimizing Essential Fatty Acid Status. By Brenda Davis, RD. Today’s Dietitian. Vol. 12 No. 2 P. 22. https://www.todaysdietitian.com/newarchives/020810p22.shtml
Additional References
https://medicaldetectivemd.com/2019/03/01/when-is-the-last-time-you-checked-your-oil-fish-oil/
Journal of Neuroscience 23 March 2005, 25 (12) 3032-3040; DOI: https://doi.org/10.1523/JNEUROSCI.4225-04.2005.
https://www.jneurosci.org/content/25/12/3032.short
Are Neurodegenerative Disorder and Psychotic Manifestations Avoidable Brain Dysfunctions with Adequate Dietary Omega-3? Letten F. Saugstad. First Published July 1, 2006 Research Article Find in PubMed. https://doi.org/10.1177/026010600601800302
https://journals.sagepub.com/doi/abs/10.1177/026010600601800302
Omega-3 for your eyes. https://www.health.harvard.edu/heart-health/omega-3-for-your-eyes
Fatty Acid Composition of Human Brain Phospholipids during Normal Development. https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1471-4159.1998.71062528.x
Journal of Lipid Research. Lipid composition of the normal human brain: gray matter, white matter, and myelin*. John S. O'Brien and E. Lois Sampson. October 1965. Volume 6, pages 537-544.
Fatty Acids and the Aging Brain. Alyssa Bianca Velasco, Zaldy S. Tan, in Omega-3 Fatty Acids in Brain and Neurological Health, 2014
Fatty Acid Composition of the Brain. https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/lipid-composition
https://www.sciencedirect.com/science/article/abs/pii/S0952327809001987
About the Author
Brandy's a formulation scientist and self-proclaimed health geek who loves hiking, gardening, bird-watching, and body boarding.
Her struggle with acne during her teens and 20s led to a holistic and healthy approach to skincare, embracing skin as an organ to be loved and cared for rather than a canvas to wage war on.
Since 2008, she's been developing all-in-one products for a simple routine at home, & Rain Organica started when her backpacking friends asked for a portable skincare routine to keep their skin healthy & happy on and off the trails.
You can try Rain Organica for yourself with The Essentials Kit, a complete skincare routine in just 3 steps.
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