Nutrition Advice for Residents of Lake Wobegon
In describing the residents of Lake Wobegon, Garrison Keillor writes it is a community where “all the women are strong, all the men are good-looking, and all our children are above average”. The belief that we are unique, and certainly not average, may partially explain dietary and lifestyle behaviors. When the 2015 Dietary Guidelines Advisory Committee (DGAC) writes that the majority of Americans are not consuming recommended amounts of 8 essential nutrients, we probably think, “glad that doesn't apply to me”. This is an unfortunate misperception for two reasons.
First, convention dictates that population-based studies, e.g. those reviewed by the 2015 DGAC committee, use Estimated Average Requirements (EAR) – an intake to meet requirements for the average person – when assessing dietary intake. By definition, the EAR isn’t enough for half the people in an age range. It isn't a very high bar to only meet the needs for half the population. Individuals should consume the Recommended Dietary Allowance (RDA) for their age (and sex) to be confident of meeting nutrient requirements. So when the 2015 DGAC concludes there are nutrients with serious shortfalls in our diet using the EAR, the chances that an individual is consuming adequate amounts of vitamins A, C, D, E, folate, calcium, magnesium, fiber or potassium aren’t good. In fact, there is a less than 50:50 chance that an individual is consuming the amount of a nutrient their body needs. Sad but true.
Jungert and Neuhauser-Berthold measured plasma vitamin C concentrations in elderly subjects (72 y). The volunteers were independently living seniors participating in an ongoing cohort study on nutrition and health in Germany. The study focused on understanding causes for differences in plasma concentrations between males and females. Some important insights into the lower plasma vitamin C concentrations observed in men than women (other than lower vitamin C intake among men) are discussed.
Median plasma vitamin C concentrations were 62 and 76 µmol/L for the men and women, respectively. Only 8% of women and 18% of men had plasma vitamin C levels <50 µmol/L. Compare this to the most recent nationally representative US data where 8% of all Americans are below a much lower cutoff (28 µmol/L) – the concentration used by doctors to give a clinical diagnosis of scurvy.
Second, volunteers for nutrition studies appear to be recruited from Lake Wobegon. Why do I write this? Because volunteers tend to be more health conscious than the average person. Medical doctors volunteering for the Physicians Health Study were much healthier and less likely to die than those who did not. Dietary supplement users are also a group who exhibit healthier lifestyles. So it is possible that nutrition intervention and cohort studies are not very representative of the general population.
If are from Lake Wobegon (and obviously above average, maybe even in the top 2-5%), then you definitely need to consume the RDA. The EAR is for the average person and according to the DGAC report, the average person is missing many essential nutrients from their diet.
Jungert A, Neuhauser-Berthold M. The lower vitamin C plasma concentrations in elderly men compared with elderly women can partly be attributed to a volumetric dilution effect due to differences in fat-free mass. 2015 Br J Nutr doi: 10.1017/S0007114515000240
Sesso HD, Gaziano JM, VanDenburgh M, Hennekens CH, Glynn RJ, Buring JE. Comparison of baseline characteristics and mortality experience of participants and nonparticipants in a randomized clinical trial: the Physicians’ Health Study. 2002 Controlled Clin Trials doi: 10.1016/S0197-2456(02)00235-0
Dickinson A, MacKay D. Health habits and other characteristics of supplement users: a review. 2014 Nutr J doi: 10.1186/1475-2891-13-14