Designing a Vitamin D Food Fortification Scheme: Bread, Juice or Milk?
Food fortification has been credited with helping to avoid widespread vitamin and mineral deficiencies in millions of people over the past decades. The reason why fortification is so effective is that it has the potential to increase the nutrient levels within an entire population without requiring any behavior change on the part of the individual. Fortification may be particularly helpful to increase the supply of nutrients that are only found in a limited number of foods, or restricted within a few food groups. Vitamin D has been added to milk in the United States and Canada since the 1940s, and the introduction of a carefully-planned fortification policy has been credited with eliminating rickets as a public health issue (the National Academies Press has a summary of fortification programs in the US and Canada here).
Other countries do not fortify with vitamin D. As vitamin D fortification is not allowed in Germany, yet the adult population appears to have generally low vitamin D levels compared to the US, Brown and colleagues have modeled the effect of fortifying various carrier foods with vitamin D to see the effect it would have on vitamin D levels. The aim is to prevent deficiency in the entire population while ensuring that people remain under upper limits for consumption. Three different carrier foods were investigated: orange juice, bread and milk. While there is considerable experience with the fortification of milk, some population groups do not consume milk due to lactose intolerance, and studies have shown that both orange juice (Tangpricha) and bread (Madsen) are suitable for vitamin D fortification. It is important to consider what proportion of the population consumes each type of food for the modeling process. As vitamin D levels typically fall in the winter time because the sun is not intense enough to stimulate vitamin D production in the skin, the authors also looked at seasonal fortification of these staple foods.
In Germany, bread appears to be the most suitable carrier for vitamin D fortification. This is due to the pattern of bread consumption. Almost all people in Germany consume bread (even at the 5th percentile, average intake was around 45 g per day), and the consumption of bread occurs within a fairly restricted range (people at the 95th percentile consumed around 300 g per day). Intakes in men were higher than for women. There is more variation in milk intakes; the 5th percentile consumes only a few teaspoons, whereas the 95th percentile consumes around 600 ml. The range in orange juice consumption was even higher, with the 5th percentile consuming no orange juice, and the 95th percentile consuming over one liter. Orange juice consumption also appears to be seasonal, with greater amounts consumed in summer. Bread, therefore, offers the best opportunity for the additional vitamin D to reach the greatest number of people yet avoid the risk of exceeding upper limits for fortification. It appears that there is a tradeoff between adding enough vitamin D to prevent vitamin D deficiency in people with low levels who consume little bread, and preventing excessive intakes in people with high vitamin D levels (and therefore do not benefit from vitamin D fortification) who consume large amounts of bread. From the article, it appears that even high consumers of all these foods are unlikely to reach blood levels of vitamin associated with toxicity. During the first years of implementation, it would be important to monitor the vitamin D status of the population to ensure that it is working properly.
Jonathan Brown, Arne Sandmann, Anita Ignatius, Michael Amling and Florian Barvencik. New perspectives on vitamin D food fortification based on a modeling of 25(OH)D concentrations. Nutrition Journal 2013, 12:151. doi:10.1186/1475-2891-12-151
Dietary Reference Intakes: Guiding Principles for Nutrition Labeling and Fortification (2003). National Academies Press. http://www.nap.edu/openbook.php?record_id=10872&page=46
International Osteoporosis Foundation. Vitamin D Status Around the World. 2013. http://www.iofbonehealth.org/facts-and-statistics/vitamin-d-studies-map
Madsen KH, Rasmussen LB, Andersen R, Mølgaard C, Jakobsen J, Bjerrum PJ, Andersen EW, Mejborn H, Tetens I. Randomized controlled trial of the effects of vitamin D–fortified milk and bread on serum 25-hydroxyvitamin D concentrations in families in Denmark during winter: the VitmaD study. Am J Clin Nutr. 2013 Aug;98(2):374-82. doi: 10.3945/ajcn.113.059469. http://www.ncbi.nlm.nih.gov/pubmed/23783292
Tangpricha V, Koutkia P, Rieke SM, Chen TC, Perez AA, Holick MF. Fortification of orange juice with vitamin D: a novel approach for enhancing vitamin D nutritional health. Am J Clin Nutr. 2003 Jun;77(6):1478-83. http://www.ncbi.nlm.nih.gov/pubmed/12791627