Can PUFA Intakes Affect Body Composition in Young Children?
Adequate intakes of fat are important in the diets of infants and young children. The World Health Organisation gives advice regarding the role of fat in the diet: fats provide around half of the energy in the diets of infants aged up to 6 months, and should thereafter decline to providing around one quarter to one third of energy in adolescents. Fats are divided into three general categories based on their chemical composition, and each category contains a number of different types of fatty acids. The most nutritionally important fats are mono-unsaturated fatty acids (MUFA) and poly-unsaturated fatty acids (PUFA), while saturated fatty acids (SFA) should generally be limited in the diet. Two PUFAs, linoleic acid and alpha-linolenic acid are essential in the diet. Docosahexanoic acid (an omega-3 PUFA) is also recognized as being critical for the normal development of the brain and retina. Some research has shown that PUFA intake is associated with reduced risk of the metabolic syndrome and may affect body composition by reducing waist circumference and body fat percentage. Is there also a link in children?
Cardel and colleagues recently investigated how dietary intake of PUFAs were related to body composition in a racially diverse population of children aged 7 to 12 years of age. They divided the children into two groups for analysis based on their intake of PUFA from two 24-hour dietary recalls: the low-PUFA group consumed less than the median PUFA intake (5.84% of energy intake) and the high-PUFA group consumed more than then median intake. In total, low-PUFA children consumed 10 g PUFA per day compared to 17 g per day for the high-PUFA children. The median PUFA intake of 5.84% of energy intake was less than the recommended range for this age group of 6% to 11%. The children in the low-PUFA group therefore all had PUFA intakes were lower than recommended.
There were some differences in the diets between the low-PUFA and high-PUFA groups. The children in the high-PUFA group had greater intakes of all other types of fats, as well as greater total energy intakes, and they also had greater physical activity levels. There were no significant differences in demographic categories except for a higher percentage of African American children in the high-PUFA group.
The researchers measured body composition via DEXA scans and used multivariate linear regression to adjust for confounders and see if there was an effect of PUFA. The researchers found that the percent PUFA of energy, total PUFA, omega-3 and omega-6 fatty acid, and the ratio of PUFA to SFA were all associated with higher lean mass, and the percent PUFA of energy, total PUFA, the ratio of PUFA to SFA, and the omega-6 to omega-3 ratios were all associated with reduced fat in the abdominal area. The bottom line was that greater PUFA intake appeared to be related to more muscle and less tummy fat in children.
The authors suggest some possible mechanisms for this relationship. For example, Smith and co-workers found an increase in muscle protein synthesis in a clinical study. PUFA (and MUFA) appear to stimulate fat oxidation and diet-induced thermogenesis compared to SFA (Krishnan). This study is observational, however, and it is possible that other factors are responsible for this apparent relationship between PUFA intake and body composition.
The finding that median PUFA intakes are lower than recommended are a concern, and parents should pay attention to PUFA intakes in their children. PUFA is found in vegetable oils, nuts and seeds, oily fish, and some vegetables such as avocado, and in small quantities in beans and green leafy vegetables.
Michelle Cardel, Dominick J Lemas, Kristina Harris Jackson, Jacob E Friedman, and José R Fernández. Higher Intake of PUFAs Is Associated with Lower Total and Visceral Adiposity and Higher Lean Mass in a Racially Diverse Sample of Children. J. Nutr. jn212365; first published online August 12, 2015. doi:10.3945/jn.115.212365
Bender N, Portmann M, Heg Z, Hofmann K, Zwahlen M, Egger M. Fish or n3-PUFA intake and body composition: a systematic review and meta-analysis. Obes Rev. 2014 Aug;15(8):657-65. doi: 10.1111/obr.12189. Epub 2014 May 29. http://www.ncbi.nlm.nih.gov/pubmed/24891155
Krishnan S, Cooper JA. Effect of dietary fatty acid composition on substrate utilization and body weight maintenance in humans. Eur J Nutr. 2014 Apr;53(3):691-710. doi: 10.1007/s00394-013-0638-z. Epub 2013 Dec 22. http://www.ncbi.nlm.nih.gov/pubmed/24363161
Smith GI, Atherton P, Reeds DN, Mohammed BS, Rankin D, Rennie MJ, Mittendorfer B. Omega-3 polyunsaturated fatty acids augment the muscle protein anabolic response to hyperinsulinaemia-hyperaminoacidaemia in healthy young and middle-aged men and women. Clin Sci (Lond). 2011 Sep;121(6):267-78. doi: 10.1042/CS20100597. http://www.ncbi.nlm.nih.gov/pubmed/21501117