We’re officially less than 24 hours away from Thanksgiving and people are clearly excited by the thought of going into tryptophan-induced turkey comas*. Another nutrient found in turkey that is involved in tryptophan metabolism is vitamin B6. And did you know that, according to the CDC, vitamin B6 deficiency is the most common nutrient deficiency in the United States?
It seems like the only nutrition-related topic in the news this week is Thanksgiving, and rightfully so! We’ve all heard the story about how the tryptophan in turkey makes us sleepy because it supports the production of the neurotransmitter serotonin, which is involved in the brain’s regulation of sleep. But did you know that tryptophan can actually be used to produce the B-vitamin niacin in the body?
Vitamin E is an essential antioxidant vitamin and the most abundant fat-soluble antioxidant in the body. Vitamin E helps maintain the integrity of cell membranes, including the brain, and plays a vital role in many physiological processes such as cell signaling. Despite the importance of Vitamin E, more than 90% of Americans do not consume enough Vitamin E as α-tocopherol (the only form maintained in the body) to meet the estimated average requirements.
Vitamin E supplementation is important for brain health in older populations; helping to slow the progression of Alzheimer’s Disease. A recently published study by Kitajima and colleagues illustrates the importance of Vitamin E for brain health earlier in life as well.
Compared to full-term infants, low birth weight infants have higher requirements for Vitamin E, but lower storage, intake and poorer absorption of Vitamin E (Greer, 2005). This means that low birth weight infants have lower Vitamin E levels and much greater risk of Vitamin E deficiency.
In Japan where the study by Kitajima and colleagues was carried out there are recommendations but no clear requirements for Vitamin E supplementation in extremely low birth weight infants (birth weight <1,000g). This enabled a ‘natural experiment’ whereby 259 school-aged children were divided into 3 groups based on the length of Vitamin E supplementation they received 8 years prior as extremely low birth weight infants; no supplementation, daily supplementation for less than 6 months, and daily supplementation for more than 6 months. Children who received Vitamin E supplementation for more than 6 months in infancy had the lowest likelihood of impaired mental development and the greatest performance IQ.
Although there is still much work to be done, it is exciting that something as “simple” as Vitamin E could help the long-term mental development of vulnerable infants.
Kitajima H, Kanazawa T, Mori R, Hirano S, Ogihara T, Fujimura M. Long-term alpha-Tocopherol supplements may improve mental development in extremely low birth weight infants. Acta Paediatr. Epub ahead of print Nov 8 2014. doi: 10.1111/apa.12854
Greer FR, Vitamin A, E, and K In: Tsang RC, Uauy R, Koletzko B, Zlotkin SH (eds). Nutrition of the Preterm Infant: Scientific Basis and Practical Guidelines 2nd edn. Digital Educational Publishing: Cincinnati, Ohio, 2005, pp 141–173
Henriksen C, Helland IB, Ronnestad A, Gronn M, Iverson PO, Drevon CA. Fat-soluble vitamins in breast-fed preterm and term infants. Eur J Clin Nutr. 2006;60:756-62.
Chan DK, Lim MS, Choo SH, Tan IK. Vitamin E status of infants at birth. J Perinat Med. 1999;27:395-8.
Winter may not officially begin for another month, but much of the United States and Canada had snow and below freezing temperatures this week. Whether or not you are snowed in, the shorter days mean less sunshine. Sun exposure is an important source of vitamin D, especially since few foods naturally contain Vitamin D. As a result, at northern latitudes, serum concentrations of serum 25-hydroxyvitamin D concentrations are significantly lower in the winter than the summer (McKenna MJ, 1992).
Regular readers of Talking Nutrition will be familiar with the wide range of health problems associated with lower serum vitamin D, which has been the topic of many posts. However, with observational studies, where there is no intervention, it can be unclear whether low serum Vitamin D is the cause or the result of poor health. Afzal and colleagues assessed low serum 25-hydroxyvitamin D concentrations in 95,766 Danish adults in relation to risk of death. The twist was that the risk of death was compared between two groups: people with genetic variants known to decrease serum vitamin D concentrations (Wang et al, Ahn et al) and people without these variants. Genetically low serum Vitamin D was associated with 30% increased risk of mortality and 40% increased mortality from cancer. This provides compelling evidence that lifelong low vitamin D has a causal relationship with mortality.
As researchers continue to discover links between vitamin D and health, the importance of meeting the dietary reference intakes (DRIs) for adequacy is apparent. When sun exposure is low, both food and supplemental sources should be considered.
Afzal S et al. Genetically low vitamin D concentrations and increased mortality: mendelian randomisation analysis in three large cohorts. BMJ 2014; epub ahead of print
MJ McKenna. Differences in vitamin D status between countries in young adults and the elderly. The Am J of Med. 1992;93,69-77
Wang TJ, et al. Common genetic determinants of vitamin D insufficiency: a genome-wide association study. Lancet. 2010;376:180-8
Ahn J, et al. Genome-wide association study of circulating vitamin D levels. Hum Mol Genet. 2010;19:2739-45
Dietary guidance encourages the consumption of fruits, vegetables, whole grains, fat-free and low-fat dairy products, and seafood. Why? Because far too many people are not consuming recommended amounts of dietary fiber, calcium, magnesium, vitamin D and vitamin E. As discussed yesterday, most people need to increase their consumption of omega-3 fatty acids to balance n-3:n-6 fatty acid levels in the body. These food groups provide these nutrients.
The membranes of cells in our bodies require long-chain polyunsaturated fatty acids (LCPUFA) to function normally. Based on typical dietary patterns, recommendations are to increase intake of LCPUFA and limit saturated and trans fatty acids.
With the exception of coconut and palm kernel oil, vegetable fats tend to be richer sources of LCPUFA then saturated fatty acids. There are two families of LCPUFA : the omega-3s and omega-6s.
The Food and Agriculture Organization (FAO) is holding its Second International Conference on Nutrition this week in Rome. In their Declaration on Nutrition, the Ministers and Representatives reaffirm the right of everyone to adequate food and fundamental right of everyone to be free of hunger. Malnutrition, including undernutrition, micronutrient inadequacies, overweight and obesity, affect individual well-being. They limit human potential and reduce productivity of individuals.
Following the scientific literature on the relationship between plasma homocysteine and health has been something of a roller coaster ride over the last few years. The brief introduction is that elevated homocysteine levels have been associated with an increased risk of health conditions such as stroke, heart disease, and cognitive decline – yet randomized controlled trials (RCTs) have had mixed results. So what’s going on here?