Review Articles Emphasize Nutrition for Health over Deficiency Prevention
Two new reviews were published this week. Barnes and colleagues review nutrients with a role in maintaining cognitive function. Whitehead and colleagues conducted a meta-analysis of randomized, placebo-controlled studies (RCTs) using ≥ 3 g oat beta glucan daily.
Both reviews focus on nutrient intakes required to optimize health. As Barnes et al state in the introduction, recommended dietary intakes (RDAs) are set to prevent frank nutritional deficiency in most of the population. The RDAs do not address nutrient intakes needed to maintain nutritional status at levels required to maintain brain health.
Barnes and colleagues hypothesized that vitamin supplementation would prevent cognitive decline or improve cognitive function in elderly individuals who have low intake or biochemical indications of insufficiency in these nutrients. They searched the literature using the following search terms: elderly, cognition, vitamin B12, folate, folic acid, vitamin E, and malnutrition. The strongest evidence found was for folate and vitamin E. Not surprisingly, the benefit was in those with low vitamin status.
Dietary fiber is another shortfall nutrient. Most people do not consume the recommended 10-25 g of soluble fiber daily. Oat β-glucan, a water-soluble fiber, has approved cholesterol-lowering health claims. Based on a meta-analysis of 28 RCTs using ≥3 g oat β-glucan daily, Whitehead and colleagues report an overall reduction of low-density lipoprotein (LDL-C) and total cholesterol (TC) relative to control of 0.25 mmolL and 0.30 mmol/L, respectively. They conclude that a cholesterol-lowering effect can be achieved with the minimum dose of 3g daily; a dose considered effective by many regulatory agencies. The 28 RCTs were diverse, including healthy subjects as well as individuals with hypercholesterolemia and type 2 diabetes from Europe, North America, Asia and Australia. The oat β-glucan was consumed in a myriad of food forms: rolled oats, whole oat flour, oat bran, bread, muffins, muesli, breakfast cereals, cereal bars and biscuits. Because of the diversity of subjects and range of food forms, the authors conclude the cholesterol-lowering benefits of 3 g/d oat β-glucan are applicable to the general population.
Both review articles reinforce the importance of adequate nutrient intakes to maintain health. When the intake of a nutrient is too low, deficiency diseases may occur. However, achieving nutrient intake levels targeted to prevent deficiency is not synonymous with optimizing human health.
Yesterday was World Food Day, a reminder of our responsibility to help the 1.2 billion who live in extreme poverty, nutrition insecurity, and at risk of nutrient deficiency. However, human nutritionists should aspire to achieve more than preventing nutrient deficiencies. We should adopt the philosophy of our colleagues in animal nutrition who set nutritional requirements for optimal growth and health in addition to age and life stage.
Barnes JL, Tian M, Edens NK, Morris MC. Consideration of nutrient levels in studies of cognitive decline. 2014 Nutr Rev doi: 10.1111/nure.12144
Whitehead A, Beck EJ, Tosh S, Wolever TMS. Cholesterol-lowering effects of oat β-glucan: a meta-analysis of randomized controlled trials. 2014 Am J Clin Nutr doi: 10.3945/ajcn.114.086108
Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults: Executive Summary of the Third Report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection. 2001 JAMA doi: 10.1001/jama.285.19.2486