Continuing the discussion from Essential Fatty Acids: Ratios versus Amounts:
Quoted is what I’ve determined is an accepted range of the EFAs. (If that can be disputed, please message me or comment to the linked thread!) However, while those numbers are great to have, determining the amounts in various foods has been the next challenge. Half of the ingredients on the DIY site contradict one another and the USDA database lipid breakdown seems to leave some ambiguity, particularly with the “18:3 undifferentiated” point.
My concern is this: For a given entry on the USDA database that does NOT specify individual isomers, but only lists “18:3” and “18:2” undifferentiated, etc, how can someone reliably break down the omega-3/6 fatty acids for a DIY ingredient entry?
Example: Masa Flour per 100g USDA Database
Fatty acids, total polyunsaturated: 1.724 g
18:2 undifferentiated: 1.672 g
18:3 undifferentiated: .052 g
No specific isomer breakdowns
According to the USDA SR27 doc pages 21-24 and SelfNutritionData Fatty Acids, “undifferentiated” is the sum of all specific isomers within a given lipid, with a common name given for the most typical found. In the case of 18:2, that is linoleic acid (LA), aka 18:2(n-6)c,c, aka Omega-6 PUFA. For a DIY recipe using 100g of Masa, I would put 1.67g of Omega-6 Fatty Acids, although I cannot be certain that is the specific isomer included.
Easy, right? Well… then we come to “18:3 undifferentiated” which includes both 18:3(n-3)[ALA - Omega 3] AND 18:3:(n-6)[GLA - Omega 6]! In other words - if I understand this correctly - this one point includes both Omega 3 and Omega 6 isomers! And often this is the only breakdown given, leaving me to guess which of the two omegas are actually included. I’d think this is fairly significant to understand to determine my Omega intake and ratios with any kind of accuracy. Often it may be obvious dependent upon the food source, but then again maybe not.
Should I just assume the remaining .052g of “18:3 undifferentiated” is also an Omega 6 source and add it to the total? Do I ignore it? Do I hedge my bets and add is an Omega-3 (doubtful)? I do not like this uncertainty!
When adding ingredients to a recipe using the USDA database, what does everyone look at specifically while compiling the omega serving sizes?
Essential Isomer Breakdown:
- ALA (alpha-linoleic acid) = 18:3(n-3) / plant sources
- EPA (eicosapentaenoic acid) = 20:5(n-3) / marine animal sources
- DHA (docosahexaenoic acid) = 22:6(n-3) / marine animal sources
- DPA (clupanodonic acid) = 22:5(n-3) / marine animal sources
- LA (linoleic acid) = 18:2(n-6) / vegetable oils
- GLA (gamma-linoleic acid) = 18:3(n-6) / vegetable oils
- AA (arachidonic acid) = 20:4(n-6) / meat sources
… Granted, this is going deeper than may be strictly necessary, but as I’ve been doing my research, the lipid numbers on the USDA kept popping up and I haven’t been fully confident on what it all meant. I’m hoping others with a chemistry background or more general knowledge can help me make sure I understand what to record to make my master ingredient list as accurate as possible.
Let’s have some dialogue! (I searched and doesn’t seem like this has been brought up specifically… probably for a reason. ;))