Vitamin D for people over 50: Background

1. Issue

The amount of vitamin D provided by the food intake pattern recommended in the revised Food Guide does not meet the Adequate Intake (AI) established by the Institute of Medicine of the National Academies for individuals over 50 years of age. Meeting the Adequate Intake for those 51 years and over through food sources alone is almost impossible without recommending unrealistic daily amounts of some foods. 

Thus, Health Canada recommends that in addition to following Canada's Food Guide, all adults over the age of 50 should take a daily vitamin D supplement of 10 micrograms (400 IU).

2. Role of Vitamin D

Vitamin D is involved in bone health. The major role of vitamin D is the maintenance of serum calcium and phosphate concentrations within the normal range (IOM, 1997). Improved muscle strength, reduced fracture rates, and reduced rates of falling have been associated with higher levels of vitamin D in the body (Bischoff et al., 2003; Bischoff-Ferrari et al., 2004a, 2004b, 2005).Vitamin D may also play a role in the prevention of some cancers and offer a protective effect against certain autoimmune diseases (Munger et al., 2004; Gorham et al., 2005; Harris, 2005; Garland et al., 2006).

Vitamin D deficiency impairs normal bone metabolism, leading to rickets in children and osteomalacia (undermineralized bones) or osteoporosis (porous bones) in adults (IOM, 1997).

Vitamin D overdose is manifested by hypercalcemia (elevated calcium level in the blood). Prolonged exposure to excess vitamin D can lead to calcification of the kidney and other soft tissues including the heart, lungs and blood vessels (IOM, 1997).

3. Dietary Reference Intakes for Vitamin D

The Dietary Reference Intakes (DRIs) are a set of scientifically based nutrient reference values for healthy populations.  DRIs are based on indicators of good health and the prevention of chronic disease, as well as possible adverse effects of excess intakes of nutrients.  There are several different types of reference values, each with different uses (see Appendix for definitions).

Table 1 shows the Adequate Intake for vitamin D for men and women 19 years and over, as well as the Tolerable Upper Intake Level, as established by the Institute of Medicine (IOM) of the National Academies.

Table 1. Dietary Reference Intakes for Vitamin D (IOM, 1997)

Age groups	Adequate Intake (AI) (for men and women)	Tolerable Upper Intake Level (UL) (for men and women; chronic exposure)
19-50 years	5 μg (200 IU) per day	50 μg (2000 IU) per day
51-70 years	10 μg (400 IU) per day
>70 years	15 μg (600 IU) per day

Since the publication of the DRIs for vitamin D in 1997, there has been a large body of research published that indicates that vitamin D needs may be even higher than the AIs listed above.

4. Sunlight and Vitamin D

Vitamin D is synthesized in the skin upon exposure to ultraviolet B (UVB) radiation. However, this synthesis is affected by latitude, season, time of day, age, sunscreen use, and skin pigmentation (IOM, 1997). In Canada, vitamin D synthesis in the skin is absent during the winter months (October to March), and for an even greater part of the year in far northern latitudes. This means that for a significant portion of the year, Canadians must rely on dietary intake of vitamin D to maintain adequate levels of vitamin D in the body.

5. Sources of Vitamin D in the Canadian Food Supply

The major sources of vitamin D are fortified foods. In Canada, cow's milk and margarine must be fortified with vitamin D. Goat's milk, fortified plant based beverages (ex. fortified soy beverages), and some calcium-fortified orange juices are permitted to be fortified with vitamin D. Cheese and yogurt can be made with vitamin D-fortified milk, however, the final product does not contain as much vitamin D as fluid milk alone. The only natural sources of vitamin D in the Canadian food supply are fatty fish and egg yolks.

Because it is a commonly-consumed food, fluid milk is a major dietary source of vitamin D.

6. Vitamin D Content of the Revised Food Guide

The Food Guide's healthy eating pattern was developed through a process called modelling. In modelling, different combinations and amounts of food are tested until a nutritionally adequate pattern is found.

Canada's Food Guide recommends 3 servings of Milk and Alternatives each day for adults over the age of 50. It is also recommended for all ages to "Have 500 mL (2 cups) of milk every day for adequate vitamin D."

The results of modeling showed that even when following these recommendations, the food intake pattern does not meet the AI for vitamin D for men and women aged 51 to 70 and 71 and older.

Trying to increase the vitamin D content of the modelled diets through food sources was deemed impractical because it would require consuming large amounts of specific foods on a daily basis.

7. Addressing the Vitamin D Shortfall in the Revised Food Guide

Meeting the AIs for vitamin D for those 51 years of age and older is almost impossible without recommending unrealistic daily amounts of some foods. Supplements containing vitamin D can be used as a complement to foods to achieve the recommended levels of dietary vitamin D intake.

Table 2 shows the approximate amount of vitamin D provided by the revised Canada's Food Guide for men and women aged 51 and over, as well as the extra vitamin D needed to meet the AI.

Table 2. Meeting Needs for Vitamin D

Age groups	Adequate Intake(AI) μg (IU)	Approximate Vitamin D provided by revised Food Guide (assuming 500 ml/2 cups of fluid milk)	Extra vitamin D needed to meet AI μg (IU) (for men and women)
51 -70 y	10 (400)	5 (200)	5 (200)
71 y +	15 (600)	5 (200)	10 (400)

8. Recommended Amount of Supplemental Vitamin D

The recommended amount is 10 μg (400 IU) of supplemental vitamin D daily. In addition to following the Food Guide, a 10 μg (400 IU) supplement will ensure that individuals over 50 years of age will meet the AI for vitamin D. It is recognized that a supplement of 10 μg (400 IU) will provide 5 μg (200 IU) more than the AI for people 51-70 years. However, daily intake of vitamin D will still be well under the UL of 50 μg (2000 IU). In addition, recommending a consistent amount of 10 μg (400 IU) for all ages over 50 years makes for ease of messaging.

9. Conclusions and Recommendations

The need for vitamin D increases after age 50. It is difficult to meet the vitamin D recommendations for people over 50 years of age without recommending unrealistic daily amounts of some foods.

The amount of vitamin D provided by Canada's Food Guide does not meet the Adequate Intake (AI) established for individuals over 50 years of age. 

Adequate vitamin D is important for bone health and helps to reduce the risk of fractures in older adults. 

Therefore the following message recommending the use of supplements to achieve adequate intakes of vitamin D is included on the Food Guide:  

10. References

Bischoff HA, Stähelin HB, Dick W, Akos R, Knecht M, Salis C, Nebiker M, Theiler R, Pfeifer M, Begerow B, Lew RA, Conzelmann M. 2003 Effects of vitamin D and calcium supplementation on falls: a randomized control trial. J Bone Miner Res 18:343-51.

Bischoff-Ferrari HB, Dawson-Hughes B, Willett WC, Staehelin HB, Bazemore MG, Zee RY, Wong JB. 2004 Effect of vitamin D on falls a meta-analysis. JAMA 291:1999-2006.

Bischoff-Ferrari HA, Dietrich T, Orav J, Hu FB, Zhang Y, Karlson EW, Dawson-Hughes B. 2004b Higher 25-hydroxyvitamin D concentrations are associated with better lower-extremity function in both active and inactive persons aged 60 y. Am J Clin Nutr 80:752-8.

Bischoff-Ferrari HA, Willett WC, Wong JB, Giovannucci E, Dietrich T, Dawson-Hughes B. 2005 Fracture prevention with vitamin D supplementation A meta-analysis of randomized control trials. JAMA:295 2257-64.

Garland CF, Garland FC, Gorham ED, Lipkin M, Newmark H, Mohr SB, Holick MF. 2006 The role of vitamin D in cancer prevention. Am J Pubic Health 96:252-61.

Gorham ED, Garland CF, Garland FC, Grant WB, Mohr SB, Lipkin M, Newmark HL, Giovannucci E, Wei M, Holick MF. 2005 Vitamin D and prevention of colorectal cancer. J Steroid Biochem & Molecular Biol 97:179-94.

Harris SS. 2005 Vitamin D in type 1 diabetes prevention. J Nutr 135:323-5.

IOM. (Institute of Medicine) 1997. Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D and Fluoride. Washington DC: National Academy Press.

Munger KL, Zhang SM, O'Reilly E, Hernán MA, Oleh MJ, Willett WC, Ascherio A. 2004 Vitamin D and incidence of multiple sclerosis. Neurol 62:60-5.

Appendix: Dietary Reference Intakes

Estimated Average Requirement (EAR) - the amount of a nutrient that is estimated to meet the requirement of half of all healthy individuals in a given age and gender group. This value is based on a thorough review of the scientific literature.

Recommended Dietary Allowance (RDA) - the average daily dietary intake of a nutrient that is sufficient to meet the requirement of nearly all (97-98%) healthy persons. This is the number to be used as a goal for individuals. It is calculated from the EAR.

Adequate Intake (AI) - only established when an EAR (and thus an RDA) cannot be determined because the data are not clear-cut enough; a nutrient has either an RDA or an AI. The AI is based on experimental data or determined by estimating the amount of a nutrient eaten by a group of healthy people and assuming that the amount they consume is adequate to promote health.

Tolerable Upper Intake Level (UL) - the highest continuing daily intake of a nutrient that is likely to pose no risks of adverse health effects for almost all individuals. As intake increases above the UL, the risk of adverse effects increases.