Are You Learning Nutrition as a Consumer, Scientist or Policy Maker?
Food is part of daily life. TalkingNutrition regularly summarizes newly published nutrition studies. Because people are interested in nutrition and health, peer-reviewed nutrition-related articles are often reported by the media. Is media coverage of nutrition research relevant to everyone – consumers, researchers and policy makers? Let’s discuss an example.
Marchetta and colleagues examine the relationship between natural food folate intake and blood folate concentrations. A 10% increase in natural folate intake is predicted to increase serum/plasma and red blood cell (RBC) folate concentrations by 6-7%. They recommend women of child-bearing age consume 450 µg dietary folate equivalents (DFE) to maintain ‘optimal’ RBC concentrations during pregnancy.
Folate is a water-soluble B vitamin found in dark green leafy vegetables, legumes, some fruit and liver. Folate deficiency is defined as a serum/plasma folate concentration < 10 mmol/L or a red blood cell concentration < 340 nmol/L. The term folate encompasses natural folate and folic acid. Because folate is required for nucleic acid (RNA and DNA) synthesis, consuming sufficient amounts of folate to maintain adequate folate status is particularly important during pregnancy. For women of child-bearing age, RBC folate concentrations ~1,000 mmol/L are recommended to prevent neural tube defects during pregnancy.
Scientists and policy makers want to know nutrient-status relationships (requirements), i.e. 450 DFE to maintain RBC folate ~ 1,000 nmol/L, to make population dietary intake recommendations: Estimated Average Requirement (EAR), Recommended Dietary Allowance (RDA) and Upper Limit (UL). RDAs are the average dietary intake needed to meet nutrient requirements of nearly all (97-98%) of healthy individuals. To assess populations, nutrition scientists and policy makers use EARs. For accuracy, scientists and policy makers want to understand the impact of different folate sources (natural folate vs folic acid) on folate status. They want to identify the best indicator of folate status: serum, plasma or RBC. By understanding relationships such as body weight with serum and RBC folate concentrations, dietary guidance with respect to folate intake can be refined. These insights can be used to adjust policy, e.g. fortification, and improve population health.
People seek comfort in knowing their dietary choices are meeting their body’s requirements. We don’t usually think in terms of population averages. Health and nutrition is personal. For the most part, people do not spend a lot time thinking about biological differences between folic acid and natural folate.
By the way, for any who think natural, organic food forms are nutritionally superior, this is incorrect. The folate form, i.e. folic acid, used in fortifying foods and dietary supplements is superior because it increases serum and red blood cells more than the folate forms found naturally in foods.
Few of us desire to read ingredient labels to learn if a food contains natural folate or folic acid. Upon reading a label, what is the likelihood that awareness of differences between folate forms will lead to different food choices? Frankly, who cares to know the best biological indicator of folate status? The truth is, it would be wonderful to have a trusted source (medical doctor or health professional) capable of interpreting and providing perspective on the results (laboratory value) from a personal sample (blood sample). While I may think my dietary choices are better than average, a blood folate measurement is needed to validate my belief - or warn of an extreme (low or high folate status).
Pregnant women should be told if their folate status isn’t adequate. When RBC folate concentrations are measured below 1,000 nmol/L, they should be counseled to increase folate intake. Some women will choose to eat more liver. Some may consume more spinach and oranges. Others may choose a combination of food and dietary supplements. In all cases, the measurement of RBC folate status empowers people to make informed choices to improve/maintain/decrease folate status.
Circling back, today’s main citation gives consumers, especially young women, targets for folate intake and RBC folate concentrations. The paper provides policy makers with information relating dietary intake with status assessment. In both cases, the best assessment of folate status requires a blood sample.
Marchetta CM, Devine OJ, Crider KS, Tsang BL, Cordero AM, Qi YP, Guo J, Berry RJ, Rosenthal J, Mulinare J, Mersereau P, Hamner HC. Assessing the association between natural food folate and blood folate concentrations: A systematic review and Bayesian meta-analysis of trials and observational studies. 2015 Nutrients doi: 10.3390/nu7042663
Institute of Medicine (US) Standing Committee on the Scientific Evaluation of Dietary Reference Intakes. "Its Panel on Folate, Other B Vitamins, and Choline. Dietary Reference Intakes for thiamin, riboflavin, niacin, vitamin B6, folate, vitamin B12, pantothenic acid, biotin, and choline." The National Academies Collection: Reports Funded by National Institutes of Health (1998).
World Health Organization. Serum and Red Blood Cell Folate Concentrations for Assessing Folate Status in Populations; World Health Organization: Geneva, Switzerland, 2013. WHO/NMH/NHD/EPG/12.1
Crider KS, Devine O, Hao L, Dowling NF, Li S, Molloy AM, Li Z, Zhu J-H, Berry RJ. Population red blood cell folate concentrations for prevention of neural tube defects: Bayesian model. 2014 BMJ doi: 10.1136/bmj.g4554
Bird JK, Ronnenberg AG, Choi S-W, Du F, Mason JB, Liu Z. Obesity is associated with increased red blood cell folate despite lower dietary intakes and serum concentrations. 2014 J Nutr doi: 10.3945/jn.114.199117