[5A] Lipids

excess macronutrients not used for energy immediately can be? Are excess proteins stored?

stored as glycogen or triglycerides

no

AMDRs as a % of energy for 1-3yrs, 4-18yrs, and ≥19yrs

1-3yrs: 30-40%

4-18yrs: 25-35%

≥19 yrs: 20-35%

key for growth and development

Which essential fatty acids are particularly important to obtain in adequate amounts for a healthy diet?

Omega-6 (linoleic acid) and omega-3 (α-linolenic acid)

examples of foods high in fat

Oil (highest), sunflower seeds, almonds, eggs, dairy (cheese)

Do fruits and vegetables of high fat

Generally no

Foods that contain cholesterol VS foods that do not

Significant cholesterol only in animal origin foods

Grains, vegetables, legumes, fruits provide almost no chol

Fatty acids are ____ acids with

carboxylic acids

aliphatic chain of variable length

Describe what triglycerides are

one glycerol mol + 3 fatty acid tails

Describe what phospholipids are

phosphate head group + two fatty acid tails

Phosphate is ++ polar with aliphatic nature

Describe steroid structure

Four fused rings arranged in a specific configuration (A, B, C, D)

3 roles of fatty acids in the body

1. Energy metabolism (through beta-oxidation (beta bond broken) > krebs)

2. Component of triglycerides (fat storage molecules)

3. Component of phospholipids (cell membranes)

How do biochemical properties and biological roles in lipids vary (4)

• Chain length (typically 14 to 22 carbons; longer = more solid)

• Number of C=C bonds (saturated vs. unsaturated [mono- or poly-])

• Location of C=C bond(s) (omega)

• Structure of C=C bonds (cis- or trans-)

How to classify fatty acids: 1. saturated/unsaturated 2. mons/poly, 3. omega, 4. cis/trans

1. saturated: no double C bonds, unsaturated: 1 or more double C bonds

2. (done if unsaturated) monounsaturated: 1 double C, polyunsaturated: >1 double C

3. omega: location of first double C from methyl (back tail, no O) group

4. cis: Hs on same side of double C, tend to have kink in chain. trans: Hs on opposite side of double C, more similar to saturated fats then cis

3 types of saturated fatty acids with examples, overall where are saturated fatty acids found

Palmitic acid (palm oil, red meat, butter, cheese)

Myristic acid (dairy, coconut oil)

Stearic acid (animal meats, some grains, cocoa butter)

Abundant in animal foods (e.g., meat, dairy) as well as some plant sources (e.g., palm and coconut oils)

Since saturated fats lack double C bond, how do they behave

Solid at room temp

Resistant to rancidity (harder to spoil with oxidation) > last longer

Since unsaturated fats have double C bond(s) how do they behave

Melt at lower temps

More likely to break down, the more double bonds sometimes the more vulnerable

Commonality of cis vs trans fatty acids

Cis are most common naturally occurring

Trans are rare naturally (mostly during partial hydrogenation processing)

Examples of omega 3 (3)

Alpha-linolenic acid (vegetable oils)

Eicosapentaenoic acid (EPA)

Docosahexaenoic acid  (DHA) found in fish oils

Examples of omega 6 (2)

Linoleic acid (corn and safflower oils)

Arachidonic acid (meat and fish)

Are omega 3 and 6 essential nutrients?

Yes we need to get them through our diet

Omega-3 and omega-6 fatty acids are essential because humans are unable to synthesize fatty acids with C=C at these positions

omega 3 vs 6 in Canadian diet overall

Omega 6 is plentiful in Canadian diet, Omega 3 is usually lacking

Omega 3 and omega 6 fatty acids are used in

formation of the phospholipids and to synthesize regulatory molecules (eicosanoids)

What are eicosanoids and describe their role

Hormone-like

Regulatory work in body (makes sure processes are at good baseline, not too high/low)

control processes such as inflammation, blood clotting, BP (via smooth m. contractility), gene expression (glucose and fatty acid metabolism), and immune function

Recommended ratio of omega6 to omega3 and why

5-10 omega-6 : 1 omega-3

affects types and amounts of eicosanoids produced

Compare the pathways and major roles of omega-6 and omega-3 fatty acids, what do elcosanoids do from omega-6 vs omega 3

Omega-6:

Linoleic acid → Arachidonic acid →

- Normal brain development

- Produces eicosanoids that: Promote inflammation and clotting

Omega-3:

α-Linolenic acid (ALA) → EPA + DHA (can also get from eating fish)

EPA (eicosapentaenoic acid):

- Produces eicosanoids that: suppresses inflammation and clotting

DHA (docosahexaenoic acid):

- Important for normal brain development

Why you need both omega 3 and 6 because they have different roles in the balance

What nutrients are essential? (3)

Vitamins, some fatty acids, amino acids

Trace amounts of trans fats occur in some foods such as ____________ even though hydrogenated fats are banned in Canada

animal proteins (i.e. whole milk, ground beef)

Between saturated, monounsaturated, polyunsaturated, and trans fats which are healthier

Monounsaturated and polyunsaturated fats are healthier than saturated fats and trans unsaturated fats

Triglycerides, monoglycerides, diglycerides consist of

a glycerol molecule attached to three fatty acid tails via ester linkages (or one for mono, two for di)

Triglycerides are the ___________ for lipids in the body and will >

main storage molecule

accumulate within adipose cells

Triglycerides formed through

condensation reaction (removal of water) which occurs in intestinal cells

Are triglycerides soluble? How do they transport through blood

No

packed into lipoproteins

Triglycerides are __________ by lipases forming (2)

Hydrolyzed

Fatty acids and 2-monoacylglycerol

Phospholipids consist of

a glycerol molecule attached to two fatty acid tails via ester linkages + phosphate head group (phosphate takes up space that would have been occupied by third C tail)

Why are phospholipids unique amongst lipids

amphipathic (have polar and nonpolar regions)

Describe the characteristics of phospholipids heads vs tails

Phosphate head: hydrophilic, polar on either side allows membrane to be aqueous (body is aqueous environment)

Tails: hydrophobic core effective as barrier

Key biological roles of phospholipids (2)

forming plasma membranes and acting as emulsifiers of other lipids (lipoprotein membranes)

Sterols consist of? closely related to _____, which lack

four fused carbon rings (denoted A, B, C, and D) with a –OH group attached to C3 in the A ring

Steroids, which lack the -OH on C3 group

Cholesterol (4) roles

• Structural lipid that adds rigidity to cell membranes (mostly imbedded in inside nonpolar, amount of chol to maintain temp)

• Precursor for testosterone, progesterone, cortisol, aldosterone, vitamin D, other hormones.

• Bile salt synthesis (have polar and nonpolar region, micelle formation)

• Major component of LDL

Cholesterol is only present in ________, is it essential?

animal cells, can be synthesized by the body (not essential)

Functions of lipids (4)

• Providing structure to cell membranes

• Regulating biochemical processes (eicosanoids, hormone synthesis)

• ATP production (beta-oxidation)

• Fuel storage (triglycerides in adipose tissue)

Diets high in fat, saturated fat, and/or trans fat puts individuals more at risk for (7)

cancers, HTN, T2D, atherosclerosis, obesity, stroke, diverticulosis

Dietary lipids that promote heart disease (3)

• Cholesterol (=more LDL if cholesterol synthesis by the liver does not decrease in line with high dietary intake)

• Saturated fat (=higher circulating LDL due to increased LDL production and decreased LDL removal by tissues)

• Trans-fatty acids (=increased LDL levels and lower HDL levels; many also increased inflammation)

Dietary lipids that protect against heart disease (2)

• Omega-6 and omega-3 polyunsaturated fats (=lowers LDL when replacing saturated fats; may also increase HDL and promote synthesis of protective eicosanoids)

• Monounsaturated fats (=lowers LDL when replacing saturated fats, but this effect is more likely to be a whole-diet effect, e.g., Mediterranean diet, than effect  of MUFAS alone)

Why is promotion of eicosanoids important for protecting against heart disease

help regulate inflammation which is big part of atherosclerosis

Is calorie reduction the answer to reducing risk for health risks? explain

No.

All you do is switch out type of fat (switch calories from trans or sat > mono fats) (calories stay same just change where calories are coming from), whole grains over simple grains better

There is less evidence of this for cancer compared to CVD and neurodegenerative disease mortality

Dietary fat and cancer

Dietary fat may be a tumor promoter and/or initiator

Breast cancer relation with fat

Reduced incidence with the Mediterranean diet and diets high omega-3 fatty acids (fish, shellfish)

Studies on mice with implanted tumors: high-fat diets more likely to cause proliferation; but diets high in linoleic acid (omega-6) promote rapid tumour growth vs. diets high in saturated or omega-3 fatty acids

Colon cancer relation to fats

Higher incidence of colon and prostate cancer in diet high in saturated fats from red meat

Lower incidence of colon cancer with diets high in omega-3 fatty acids from fish

Potential mechanism: Gut bacteria metabolize excess fat and bile to produce tumor initiating compounds

Is there a relationship between dietary fat and body weight?

NO it is all about total Kcal***

calorie content is the issue (as long as fat content within reason)

Increasing prevalence of obesity is likely due to

increasing energy intake and decreasing energy expenditure, rather than increased fat intake alone

Biggest factor of obesity related to diet

Total Kcals