Video of my presentation starts at 14:28, and lasts until 1:29:00+!
Linoleic acid (C18:2, n-6) is an essential fatty acid that must be obtained from the diet, because our body can’t make it. How much linoleic acid should we eat every day for optimal health? To answer this question, I’ll investigate the association between circulating levels of linoleic acid with all-cause mortality risk, followed by identification of a corresponding dietary intake. Let’s have a look!
First, are circulating levels of linoleic acid associated with all-cause mortality risk? 4 studies have investigated this issue:
- In a 15-year study of 1,551 middle-aged men (average age, 52y), increased circulating linoleic acid was associated with significantly reduced all-cause mortality risk in 3 of the 4 multivariable-adjusted models (Laaksonen et al. 2005).
- In a 15-year study of 4,232 older adults (60y) elevated circulating linoleic acid was associated with significantly reduced all-cause mortality risk in men, but not women (Marklund et al. 2015).
- In a 34-year study of 2,009 middle-aged men (average age, 50y) increased circulating linoleic acid was associated with significantly decreased risk of all-cause mortality (Warensjö et al. 2008). For example, shown below is the association between the risk of death from cardiovascular-related disease with the circulating linoleic acid concentration. At both 20 and 30 years after study onset, subjects that had circulating linoleic values above the median had approximately half of the mortality risk from CVD, when compared with below-median values for linoleic acid.
- In a 13-year study that included both older men and women (average age, 74y), and, more subjects (2,792) than the studies of Laaksonen and Warensjöet combined, plasma phospholipid percentages of linoleic acid greater than ~21-24% were associated with significantly reduced all-cause mortality risk:
Colectively, these 4 studies show that increased circulating levels of linoleic acid are associated with reduced all-cause mortality risk. How much linoleic acid should we eat to achieve optimal circulating values? In other words, what dietary intake of linoleic acid corresponds to 21%+ of plasma phospholipid linoleic acid? Based on the data below, dietary intakes of linoleic acid that are greater than 14% of total calories are associated with circulating linoleic acid values of 21% (Wu et al. 2014).
On my ~2300 calorie diet, that translates into 322 calories (36g) from linoleic acid. I get a significant amount of dietary linoleic acid from one of the best linoleic acid food sources, walnuts, which contain 5.8 grams of linoleic acid per 100 calories (see Lipids, C18:2, http://ndb.nal.usda.gov/ndb/foods/show/3690?fg=&man=&lfacet=&count=&max=&qlookup=&offset=&sort=&format=Full&reportfmt=other&rptfrm=&ndbno=&nutrient1=&nutrient2=&nutrient3=&subset=&totCount=&measureby=&_action_show=Apply+Changes&Qv=.152&Q6919=1&Q6920=1&Q6921=1&Q6922=1&Q6923=1&Q6924=1).
Just using walnuts alone, I’d need ~700 calories per day to reach 14% dietary linoleic acid! Although I’m always interested in dietary strategies that may reduce all-cause mortality risk, allocating ~30% of my daily calories to only walnuts is not ideal for my high-fiber approach to health (https://michaellustgarten.wordpress.com/2015/07/17/on-a-paleo-diet-not-if-you-fiber-intake-is-less-than/), nor would it satiate me, as high-volume vegetable meals are best for that. A more reasonable dietary linoleic acid target (for now) is ~8%, the point at which plasma linoleic acid mostly plateaus (see the plot above). 8% on my 2300 calorie diet translates into 20 grams of linoleic acid per day. I should note that I also get a good amount of linoleic acid (6.4 grams) from the 30 grams of sesame seeds that goes into my giant salad’s dressing, which I eat 2-3x per week. When combined with ~300 calories from walnuts/day, that gets me to at least 8% of my daily calories from linoleic acid.
Laaksonen DE, Nyyssönen K, Niskanen L, Rissanen TH, Salonen JT. Prediction of cardiovascular mortality in middle-aged men by dietary and serum linoleic and polyunsaturated fatty acids. Arch Intern Med. 2005 Jan 24;165(2):193-9.
Marklund M, Leander K, Vikström M, Laguzzi F, Gigante B, Sjögren P, Cederholm T, de Faire U, Hellénius ML, Risérus U. Polyunsaturated Fat Intake Estimated by Circulating Biomarkers and Risk of Cardiovascular Disease and All-Cause Mortality in a Population-Based Cohort of 60-Year-Old Men and Women. Circulationz 2015 Aug 18;132(7):586-94.
Warensjö E, Sundström J, Vessby B, Cederholm T, Risérus U. Markers of dietary fat quality and fatty acid desaturation as predictors of total and cardiovascular mortality: a population-based prospective study. Am J Clin Nutr. 2008 Jul;88(1):203-9.
Wu JH, Lemaitre RN, King IB, Song X, Psaty BM, Siscovick DS, Mozaffarian D. Circulating omega-6 polyunsaturated fatty acids and total and cause-specific mortality: the CardiovascularHealth Study. Circulation. 2014 Oct 7;130(15):1245-53
The stereotype about the Paleo diet is that it is meat heavy. How much meat Paleo era-eaters ate is debatable, but that they consumed large amounts of potassium rich, plant-based foods is not! When examining 159 Stone Age diets, the average daily potassium intake has been reported to be 400 meq/day (Sebastian et al. 2006), as shown below:
How much is 400 meq in milligrams (mg) of potassium? 1 meq = 39.1 mg of potassium, so to figure that out we multiply 400 *39.1, thereby yielding an average daily potassium intake of 15,640 mg/day! It’s important to note that this value is based on a 3000 calorie diet (Eaton et al. 1997). Dividing 15,640/3000 yields 5.21 mg potassium/calorie.
In contrast, as studied in 12,581 US adults, the average dietary potassium intake has been reported to be only ~2600 mg/day (Cogswell et al. 2012). Furthermore, only 1.4% of all subjects had potassium values greater than 4700 mg/day!
What’s my potassium intake? Shown below is my 7-day average intake from 8/29/2015-9/4/2015. The black rectangle in the lower right corner shows my average daily potassium intake to be 10,383 mg/day.
My average daily calorie intake during that week was 2193. In terms of mg potassium/calorie, my value is 4.73 (10,383/2193), which isn’t far from the reported average Paleo value. What’s yours?
For reference, shown below is a representative day during that week (Wednesday, September 2; 2251 calories) for what I ate.
Cogswell ME, Zhang Z, Carriquiry AL, Gunn JP, Kuklina EV, Saydah SH, Yang Q, Moshfegh AJ. Sodium and potassium intakes among US adults: NHANES 2003-2008. Am J Clin Nutr. 2012 Sep;96(3):647-57.
Eaton SB, Eaton SB 3rd, Konner MJ. Paleolithic nutrition revisited: A twelve-year retrospective on its nature and implications. Eur J Clin Nutr. 1997 Apr;51(4):207-16.
Sebastian A, Frassetto LA, Sellmeyer DE, Morris RC Jr. The evolution-informed optimal dietary potassium intake of human beings greatly exceeds current and recommended intakes. Semin Nephrol. 2006 Nov;26(6):447-53.
If your goal is optimal nutrition, would you choose grapes or raisins? To most, the obvious answer would be grapes, because they’re less calorie dense than raisins. Grapes contain 20 calories per ounce, whereas raisins contain 85 calories/ounce. But, what if I asked the same question, and you had 100 calories to spend on either grapes or raisins? Although they’re the same fruit-raisins are dehydrated grapes-is there a difference in nutrition, when normalized to calories?
Before delving into the nutritional comparison it is important to briefly discuss what happens during the dehydration process. The grape obtains energy through photosynthesis occurring in the green stem. Once the grape is removed from its stem, it still has an energy requirement that needs to be met. Since the stem is no longer providing this energy, the grape begins to use its own chemical processes to maintain energy demand. At the core of the difference between the raisin and the grape is that once the grape leaves the stem, it starts to break down its own energy stores (ATP) to maintain the cellular energy demand, a process that consumes water.
Are there nutritional differences between the grapes and raisins?
In the table we see that when normalized to 100 calories, there isn’t a difference in protein, fat or carbohydrate, when comparing grapes and raisins.
Among the minerals, Copper content is reduced by more than 40% in raisins when compared with grapes. Copper is a cofactor for the antioxidant enzyme, Copper-Zinc Superoxide Dismutase. That its content reduced in raisins indicates a diminished antioxidant response.
Antioxidant depletion in raisins is also evident when looking at the vitamin list. Vitamin C (95% reduced), β-Carotene (100%), Vitamin A (100%), Leutein + Zeaxanthin (100%), Vitamin E: α-Tocopherol (86%), and Vitamin E: γ-Tocopherol (90%) are all dramatically reduced in raisins, when compared with grapes. That raisins are depleted in antioxidants, when compared with grapes is confirmed by looking at their respective ORAC (Oxygen Radical Absorbance Capacity) values: 261 for grapes vs. 113 for raisins.
The B-vitamins riboflavin (59%), pantothenate (56%), and Vitamin B6 (54%), each of which are required for efficient energy metabolism are reduced in raisins.
Finally, both Vitamin K (94%) and choline (neurotransmitter, 54%) are also reduced in raisins, when compared with grapes.
So, if your interest is optimal nutrition, eat grapes, not raisins!
Reference values for raisins and grapes obtained from http://www.nal.usda.gov/fnic/foodcomp/search/
ORAC values for raisins and grapes obtained from w ww.ars.usda.gov/SP2UserFiles/Place/…/Data/ORAC/ORAC_R2.pdf