Dietary Lipids, Health Implications, and Recommendations

Posted on Sep 4, 2024 in Biology

Lipids in the Diet

Broad group of naturally occurring molecules including fats, waxes, sterols, fat-soluble vitamins (A, D, E, and K), monoglycerides, triglycerides, phospholipids, and others.
Main biological functions: energy storage, structural components of cell membranes, and signaling molecules.

Lipids enter the body through the mouth and pass to the stomach, largely unaffected by its acidic environment.
Absorption primarily occurs in the small intestine, where bile salts emulsify lipids and lipases hydrolyze them into fatty acids and glycerol.
Hydrolyzed lipids enter the bloodstream and are transported to organs like the liver for metabolism.
Fatty acids can be degraded to CO2 and water for energy production.

Found in animal products (butter, cheese, meat) and some vegetable sources (coconut oil, palm oil).
Have a strong hypercholesterolemic effect.

Primarily found in vegetable oils, nuts, seeds, and fish.
Monounsaturated Fats (e.g., olive oil) – May reduce LDL cholesterol and increase HDL cholesterol.
Polyunsaturated Fats (Essential Fatty Acids) – May decrease the risk of depression, hypertension, and ADHD.
- Omega-3 (algal oil, fish oil, fish, seafood) – May lower the risk of heart attacks.
- Omega-6 (sunflower oil, safflower oil) – May reduce the risk of cardiovascular disease.

Found in margarines, French fries, and other processed foods.
Created by hydrogenating liquid vegetable oils.
Increase LDL cholesterol, decrease HDL cholesterol, and may contribute to heart disease, diabetes, and other chronic conditions.

Functions:
- Major component of cell membranes.
- Required for the synthesis of sex hormones, bile acids, and vitamin D.
- Precursor to steroid hormones produced by the adrenal cortex and gonads.
Sources: Found only in animal-derived foods (meat, fish, poultry, eggs, dairy products).
The body synthesizes and metabolizes more cholesterol than is typically consumed in the diet.
In healthy individuals, dietary cholesterol intake has little correlation with blood cholesterol levels.
High intakes of saturated fat increase blood cholesterol, while linoleic acid and fiber can lower it by reducing absorption and increasing excretion.

Fats are an important energy source (1g = 9kcal) and should comprise approximately 25-30% of total energy intake.
Total fat should be >15% of energy to ensure adequate essential fatty acid intake, energy provision, and absorption of fat-soluble vitamins.
Recommended Dietary Allowance (RDA) for fats is approximately 70g/day (infants: 4.5g/kg, adults: 1.5g/kg).
Usual intake is approximately 130g/day.
Fat is the major energy store in the body; adipose tissue has 7-8 times the energy content of glycogen or protein-containing tissues.
During the first 6 months of life, dietary total fat should contribute 40-60% of energy for growth and tissue deposition.
From 6-24 months, fat intake should gradually reduce to ~35% of energy, depending on the child’s physical activity.

Reducing total fat intake to less than 30% of total energy helps prevent unhealthy weight gain in adults.
Strategies to reduce fat intake:
- Change cooking methods: remove fatty parts of meat, use vegetable oil instead of butter, and boil, steam, or bake instead of frying.
- Avoid processed foods containing trans fats.
- Limit consumption of foods high in saturated fats (e.g., cheese, ice cream, fatty meat).