Assessing Omega-3 Fatty Acid Status with Dietary Intakes vs Biologic Measures 18 Feb 2013
The omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are known to affect inflammatory pathways, brain and cognitive function, cardiovascular health, vision, and more. The children of women with higher omega-3 status during pregnancy have a lower risk of being autistic. For these reasons, many people are trying to eat more oily fish and seafood, choose omega-3 fortified foods and beverages, and often take an omega-3 supplement. The questions become: how much DHA and EPA is enough? And how do I know if my omega-3 status is optimal?
The most common estimate of nutrient status is to estimate intakes with dietary records. People are asked to record the types and amounts of foods consumed. Then experts apply food composition tables to calculate nutrient intakes. Unfortunately, estimating dietary status from food records is fraught with errors ranging from over- and under-reporting to incomplete nutrient composition databases.
Wallingford and associates examined the correlation between food frequency questionnaires (FFQ) and biological samples in 72 adult British women. The average EPA, DHA, and α-linolenic (ALA) intakes were 171±168, 236±243, and 850±260 mg/d, respectively. The majority of women were consuming less than the recommended 300-500mg of EPA and DHA daily. The strongest correlation of FFQ was with red blood cell (RBC) EPA (r = 0.57, p<0.0001), followed by DHA (r = 0.50, p<0.0001) and the total sum of EPA+DHA+ALA (r = 0.27, p<0.03). RBC are more representative of long term omega-3 fatty acid intake because of their 90d lifespan. And almost ¾ of the total fatty acid (3.56 of 4.9) content of RBC was DHA. This compares to US women 40-59y with 236μmol/L of total omega-3 fatty acids (sum of 64.2μmol ALA/L, 43.9μmol EPA/L , and 128μmol DHA/L) with DHA representing ~54% of the total omega-3 pool according to the 2012 CDC Second Nutrition Report.
The facts are: 1. Most people are not consuming recommended amounts of long-chain omega-3 fatty acids. 2. It is difficult to predict nutritional status from dietary intakes. 3. More research is needed using biological samples to ascertain nutrient status. -mm-
Wallingford SC, Pilkington SM, Massey KA, Al-Aasswad NMI, Ibiebele TI, Hughes MC, Bennett S, Nicolaou A, Rhodes LE, Green AC. Three-way assessment of long-chain n-3 PUFA nutrition: by questionnaire and matched blood and skin samples. 2013 Br J Nutr http://dx.doi.org/10.1017/S0007114512001997