Calcium and Vitamin D: New Recommendations

Transcription

1 Calcium and Vitamin D: New Recommendations Adapted from Spotlight on Nutrition Issues with permission from Dairy Farmers of Canada August 2011 Key Messages Dietary Reference Intakes (DRI) for calcium and vitamin D were recently revised. These recommendations are for the generally healthy population. The review committee found strong evidence to support the relationship between calcium, vitamin D and bone health. Other research for their role in the prevention of chronic disease was not strong and was inconsistent or conflicting. The populations at risk of not getting enough calcium and vitamin D were identified. It is important for nutrition educators to note these groups. More is not better. Intake of excessive amounts of calcium and vitamin D, generally found with supplement use and not food and beverage intake, could have adverse health effects. Introduction Vitamin D and calcium are wellknown key nutrients for bone health. The Dietary Reference Intakes (DRIs) for these nutrients set by the Institute of Medicine (IOM) in 1997 were recently reviewed as a result of the consensus that there was enough new relevant research to merit a re-evaluation of the recommended intakes for vitamin D. Calcium was included as part of the vitamin D review process because of the two nutrients interdependent relationship, especially for bone health. 1 The American and Canadian governments sponsored the review process. The review committee s mandate was to: evaluate the scientific evidence for health outcomes associated with vitamin D and calcium and identify which outcomes are confirmed by a sufficient quality and quantity of evidence determine what intake of these nutrients is required to support the identified health outcomes determine how much intake is too much 2 This issue of Nutrition File for Health Educators provides an overview of the 2010 revised DRIs for vitamin D and calcium and highlights key issues relevant to the practice of Canadian health professionals. What Are Dietary Reference Intakes? Established for vitamins, minerals, macronutrients and energy, DRIs provide guidance for health professionals, educators, researchers and policy makers for assessing and planning the diets of healthy people. For example, DRIs were used in the development of Eating Well with Canada s Food Guide to help Canadians choose appropriate foods that provide sufficient nutrients to optimize health, prevent disease and reduce the risk of harm from consuming too much of any nutrient. 3 Calcium: What s it For? The chief function of calcium is to form bones and teeth. While calcium is also a vital intracellular messenger throughout the body, 98% of the body s calcium is found in the skeleton. 2 The new DRIs for calcium are based on evidence from calcium balance (the difference between calcium intake and urinary and fecal excretion, a proxy for bone mass) studies supporting calcium s role in bone health for those one

2 to 50 years of age, and on bone mineral density and fracture data for those over What if We Don t Get Enough or Get Too Much? Chronic calcium deficiency compromises bone health because calcium is resorbed from the skeleton to ensure that a normal blood calcium level is maintained. This demineralization can lead to reduced bone mass, osteopenia (reduced bone density and mass), osteoporosis and an increased risk of fracture. 2 A calcium-poor diet in conjunction with very low levels of vitamin D can also lead to rickets in children and osteomalacia in adults. 2 Did you know? New research findings about calcium A recent meta-analysis of randomized controlled trials noted a 27% to 31% increased incidence of myocardial infarction among groups taking a calcium supplement of more than 500 mg per day (without vitamin D) compared with groups taking a placebo. 4 The authors concluded that the suggested increased risk of myocardial infarction associated with calcium supplementation merits a reassessment of the role of calcium supplements in managing osteoporosis, given its modest effects on bone density and fracture. A follow-up review study from these authors suggests that the coadministration of vitamin D does not lessen these adverse effects. 5 In response to the initial research, Osteoporosis Canada issued a public statement that until further research is available, everyone should be careful not to consume calcium in excess of the dietary recommendations. 6 Research shows that excess calcium intake can lead to the development of kidney stones. 2 Interestingly, it is specifically the use of supplements that may be of concern when it comes to the risk of harm from excessive intake of calcium. 2 Studies of post-menopausal women suggest that the increased risk of kidney stones with excess intake of calcium is due to calcium intake from supplements and not from dairy sources. These studies are the basis of the revised (lowered from 2500 to 2000 mg) Tolerable Upper Intake Level (UL) for calcium for those over age For those under 50, the UL for calcium varies by age category (Table 1). Vitamin D: What s it For? The best-known function of vitamin D is the hormonal regulation of calcium and phosphorus concentration in the blood, which is critical to the provision of these minerals for the mineralization or building of bone. 2 The active or hormonal form of vitamin D (1,25-dihydroxyvitamin D, synthesized in the kidneys and other tissues) stimulates the absorption of calcium and phosphorus from the intestine, the reabsorption of calcium in the kidneys and the resorption of calcium from the skeleton to maintain blood calcium levels. It is through this support of calcium and phosphate levels in the blood that vitamin D promotes bone growth and maintenance and strong teeth. 2 Emerging research suggests that vitamin D also plays a role in other health outcomes, including some cancers, cardiovascular disease and hypertension, diabetes and metabolic syndrome, falls, certain immune responses, autoimmune disorders Table 1. Daily Dietary Reference Intakes for Calcium (mg) men women pregnant/ lactating pregnant/ lactating RDA UL

3 and infectious diseases, neuropsychological functioning, preeclampsia, and physical performance. 2 However, the IOM review committee concluded that current evidence for the role of vitamin D in these health outcomes is not strong, is inconsistent or is conflicting. Therefore, the new DRIs for vitamin D are based solely on evidence supporting its role in bone health. 2 What if We Don t Get Enough or Get Too Much? Vitamin D deficiency results in poor mineralization of bones or in bone demineralization. This can lead to rickets in children and osteomalacia (bone softening) and osteoporosis (reduced bone density: porous, spongy, fragile bones) in adults. 2 At very high intakes (above IU/day), vitamin D is known to cause kidney and tissue damage. Epidemiological data also reveal an association between high blood levels of vitamin D (specifically 25-hydroxyvitamin D, measured as serum 25OHD) and an increased risk of allcause mortality, cardiovascular disease and pancreatic cancer. The increased health risk associated with high levels of serum 25OHD is the basis of the new Tolerable Upper Intake Limit of 4000 IU of vitamin D set for all people nine years and older. 2 For children younger than nine, the UL for vitamin D is lower and varies by age category (Table 2). How Much Vitamin D and Calcium Do We Need? The Recommended Dietary Allowance (RDA) for calcium and vitamin D are the amounts your individual clients should be striving to consume in their diet every day. It is the average daily nutrient intake sufficient to meet the nutrient requirements of nearly all (97 98%) healthy individuals in a particular life stage and gender group. 2 The Tolerable Upper Intake Limit is the highest average daily nutrient intake likely to pose no risk of adverse health effects to almost all individuals in the general population. 2 Tolerable Upper Intake Level: More is Not Better A common misconception is that the Tolerable Upper Intake Level of a nutrient is an intake amount to strive for, the rationale being that if the RDA is good for health then more is better. 2 But more is not better. Not only is there a risk of harm with an intake above the UL, the IOM review committee stated that evidence does not reveal any increased health benefit at intake levels above the RDA for either calcium or vitamin D. 2 Individuals can meet their RDA for calcium and vitamin D from food and beverages; nutrition experts agree that getting nutrients from food is best. Because the need for vitamin D increases after age 50, however, everyone over 50 should also take a daily vitamin D supplement of 400 IU. 7 What About Vitamin D and Calcium DRIs for Infants? DRIs for Vitamin D and Calcium for infants are expressed as Adequate Intakes (AI), the recommended daily average intake assumed to be adequate based on observed or experimentally determined estimates of nutrient intake by groups of apparently healthy people. 2 The AI for calcium for infants aged one to six months is 200 mg per day, based on the calcium content of breast milk. For ages seven to 12 months the AI is 260 mg per day, based on average intakes from breast milk and solid foods. The AI for vitamin D for infants is 400 IU per day. 2 Table 2. Daily Dietary Reference Intakes for Vitamin D (IU). 2 Age in Years pregnant/lactating RDA UL

4 Since breast milk is not a good source of vitamin D, breastfed infants require a daily 400 IU vitamin D supplement until one year of age or until other food and beverage sources provide sufficient amounts of vitamin D. 8 In Canada, fortification of all infant formula with vitamin D is mandatory; however, if small or premature infants consume less than one litre of formula per day vitamin D supplementation should be considered. Who s at Risk of Not Getting Enough? Calcium. The DRI review committee reported that girls aged nine through 18 years and women over 50 are at risk of not consuming adequate calcium from their food. 2 But it should be noted that there is some concern that postmenopausal women taking calcium supplements may actually be consuming too much calcium. 2 Those who exclude dairy products (for example, vegans, non-lacto vegetarians) may also be at risk of not getting enough calcium. 2,9,10 Dairy products such as milk, yogurt and cheese are the main food sources of calcium for Americans and Canadians 2,11 and data from the 2004 Canadian Community Health Survey indicates that a substantial share of every age group is not consuming the minimum recommended number of milk product servings (as per the pre-2007 Food Guide). 12 Vitamin D. Subgroups who may be at risk of not getting enough vitamin D (owing to low dietary intake or limited sun exposure) include the elderly living in institutions, those with dark skin, breastfed infants (since breast milk is low in vitamin D) 2 and those with certain medical conditions that affect vitamin D absorption (such as, Crohn s disease, cystic fibrosis, celiac disease, surgical removal of part of the stomach or intestines, and some forms of liver disease). 13 Certain prescription medications also affect the metabolism of vitamin D. 2 Those who exclude milk, which is fortified with vitamin D, or fortified soy beverage as an alternative, may also be at risk of consuming inadequate vitamin D. 2,10 According to Canadian Health Measures Survey data, non-white racial background and low milk consumption (less than once per day) are both associated with lower blood levels of vitamin D. Furthermore, those of non-white racial background who also drink milk less than once per day have an average blood level of vitamin D below that deemed sufficient for good bone health. 2,14 Health Canada has promised a quick turnaround on its review of the impact of the new DRIs on dietary guidance for Canadians 15 ; stay abreast of reports from Health Canada on this matter. In the meantime continue to follow current dietary guidelines such as Canada s Food Guide. Of key importance is being aware of which subgroups of individuals may be at risk of insufficient intake of calcium or vitamin D. Did you know? When skin is exposed to a sufficient amount and strength of sunlight (specifically ultraviolet B rays), it is able to make vitamin D. A number of factors limit this process, however, including clothing, dark skin pigmentation, distance from the equator, season, time of day and the recommended use of sunscreen to prevent skin cancer. As a result of public health concerns about the increased risk of skin cancer associated with sun exposure, the DRIs for vitamin D assume individuals have minimal sun exposure and that all vitamin D must come from food, beverages or supplements. 2 4

5 Can We Meet Vitamin D Needs From Food and Beverages? The increase in the recommended intake for vitamin D (in contrast to little change in calcium recommendations) has raised the question of whether it is possible to consume sufficient vitamin D from food and beverages alone. Based on data from the Canadian Community Health Survey, intake of vitamin D from food and beverages does not meet the new DRI values. 2 However, a recent assessment of vitamin D status, measured as blood levels of 25-hydroxyvitamin D (25OHD) indicated that the average for Canadians aged between six and 79 years was 67.7 nmol/l. 14 This is higher than the threshold level of 50 nmol/l the IOM review committee specified is sufficient for bone health. 2 The apparent contradiction between insufficient vitamin D intake and healthy serum 25OHD levels suggests that vitamin D supplement intake, sun exposure or both are contributing to our vitamin D status. Recent analysis Did you know? The IOM report has identified a need for evidence-based guidelines for using 25-hydroxyvitamin D (25OHD) to screen for vitamin D deficiency, including the identification of groups for which these guidelines will be useful. 2 of Canadian data indicates widespread use of vitamin/ mineral supplements, especially in women over age 50, but mean daily intake of vitamin D from supplements has not yet been reported. 16,17 So while intake of vitamin D from food and beverages appears suboptimal, our measured vitamin D status indicates that the majority of Canadians are getting enough vitamin D from the combined sources of food, beverages, supplements and sun exposure. 2 How Does Canada s Food Guide Support Meeting DRIs? Canada s Food Guide supports a healthy eating pattern for the general Canadian population age two years and older. 18 The DRIs (1997 DRIs in the case of vitamin D and calcium) informed the development of Canada s Food Guide. In general, the combination of consuming the recommended number of servings and a variety of foods from the four food groups helps us consume the more than 50 nutrients we need in our diet every day. Specifically, foods from the Milk and Alternatives group are rich in calcium. Vitamin D intake is supported by these food guide recommendations: Every Canadian should drink 500 ml (2 cups) of milk every day (milk is fortified with vitamin D: each cup/250 ml contains 100 IU). We should eat at least two food guide servings of fish each week. All Canadians over 50 should take a 400 IU vitamin D supplement daily. 18 More on Canadians Vitamin D Levels Data indicates that over 10% of Canadians have blood levels of vitamin D below 37.5 nmol/l, the 1997 IOM threshold value determined to be sufficient for good bone health. 14 It is fair to say that an even greater percentage have blood levels below 50 nmol/l, the new threshold value deemed sufficient for maintaining healthy bones (especially among subgroups identified as at risk of low vitamin D levels). Analysis of data now needs to determine what percent of Canadians have vitamin D status insufficient for bone health given the new higher threshold value of 50 nmol/l. 5

6 Good Sources of Calcium Foods from the Milk and Alternatives group are the best sources of calcium (Table 3). Other foods containing a fair amount of calcium include certain greens and calciumfortified foods. In Canada, almost all packaged foods carry a nutrition facts table; consumers are encouraged to use that table to help them choose foods that have at least 15% of the Daily Value (% DV) for calcium per serving. 19 Three servings of foods labelled as providing 35% DV for calcium would provide adults with their RDA. Table 3. Good Sources of Calcium. 20 Milk and Alternatives Serving Size Calcium per Serving (mg) Milk, white or chocolate (skim, 1%, 2%, whole) 250 ml (1 cup) 300 Evaporated milk, undiluted (2%) 125 ml (1/2 cup) 367 Dry powdered milk, reconstituted with water (skim) 250 ml (1 cup) 300 Colby, Gouda, Edam or Swiss (Emmenthal) cheese 50 g (1 1/2 oz.) Yogurt, fruit-bottom (2 4% MF) or plain (1 4% MF) 175 g (3/4 cup) Ricotta cheese 125 ml (1/2 cup) Mozzarella cheese (23% MF) 50 g (1 1/2 oz.) 269 Soy beverage fortified with calcium Other Foods with Calcium 250 ml (1 cup) 320 Serving Size Calcium per Serving (mg)* 20 Tofu prepared with calcium 150 g (3/4 cup) sulphate Salmon or sardines, with bones (canned) 75 g (2 1/2 oz.) Orange juice fortified with calcium 125 ml (1/2 cup) 155 Turnip greens, spinach, collard greens, frozen (cooked) 125 ml (1/2 cup) Almonds, dried, blanched; dry roasted, unblanched 60 ml (1/4 cup) Beans, white, navy (cooked) 175 ml (3/4 cup) *Some values have been rounded up or averaged where specific foods or beverages have been reported as part of a group. Good Sources of Vitamin D Very few foods naturally contain vitamin D, but in general, fatty fish are the best food source of this nutrient. The mandatory fortification of milk with vitamin D in Canada in the 1970s was part of a national public health campaign to prevent vitamin D deficiency and virtually eliminated rickets in children. 21 Fortification of margarine (76 IU per tablespoon) and infant formula is also mandatory. Some soy beverages are also fortified with vitamin D 2 (Table 4). Conclusion New recommended intakes for vitamin D and calcium are based on the role of those nutrients in maintaining bone health. Blood levels of vitamin D indicate that the majority of Canadians aged six to 79 have sufficient levels to support good bone health. Since available data indicates that Canadians do not consume 6

7 sufficient vitamin D from food and beverages to meet the new higher recommended intake for this nutrient, it is likely that the use of vitamin D supplements and sun exposure are contributing to their vitamin D status. However, subgroups of people may be at risk of not getting enough calcium or vitamin D. Canadians should continue to look to Canada s Food Guide to support sufficient intake of vitamin D and calcium and should focus on foods and beverages that are good sources of these nutrients food is the best source of nutrients. Evidence does not support the idea that additional health benefits can be gained from getting more than the recommended intakes. Because of higher requirements, Canadians over 50, as well as breast-fed infants, should also take a vitamin D supplement of 400 IU per day. Health Canada is reviewing how the new intake recommendations could affect current and future dietary guidance for Canadians. This issue of Nutrition File for Health Educators was adapted from Spotlight on Nutrition Issues with permission from Dairy Farmers of Canada. It written by Leigh Underhill, MHSc, RD, Dairy Farmers of Canada. Reviewed by Dr. Stephanie Atkinson, Professor and Associate Chair, Research for the Department of Pediatrics at McMaster University. For a complete list of references, visit moreaboutmilk.com/educators.aspx. Table 4. Dietary Sources of Vitamin D. 20 Meat and Alternatives Salmon (Sockeye/red; baked or broiled) Salmon (Atlantic, Chum, Coho, Chinook; baked or broiled) Serving Size Vitamin D per Serving (IU) 75 g (2 1/2 oz.) g (2 1/2 oz.) Salmon with bones (pink, red; canned) 75 g (2 1/2 oz.) Herring, halibut, farmed trout (baked or broiled) Tilapia, lake Whitefish (baked or broiled) Tuna, yellowfin, albacore, ahi (baked or broiled) 75 g (2 1/2 oz.) g (2 1/2 oz.) g (2 1/2 oz.) 105 Egg, including yolk (boiled) 2 large 52 Milk and Alternatives Milk, white or chocolate (skim, 1%, 2%, whole) Serving Size Vitamin D per Serving (IU) 250 ml (1 cup) 104 Evaporated milk, undiluted (2%) 125 ml (1/2 cup) 108 Dry powdered milk, reconstituted with water (skim) Soy or rice beverage fortified with vitamin D 250 ml (1 cup) ml (1 cup) 88 The team of Alberta Milk registered dietitians are: Lee Finell, MHSA, RD Colinda Hunter, RD Debbie Pietsch, RD Cindy Thorvaldson, MSc, RD Jaclyn Chute, RD Nutrition File is a free quarterly research newsletter for health professionals, funded by the dairy producers of Alberta. If you are a new reader and would like to add your name to our mailing list, please contact Alberta Milk at: Phone: nutrition@albertamilk.com *Some values have been rounded up or averaged where specific foods or beverages have been reported as part of a group. 7

8 Calcium and Vitamin D: How Much Do You Need? Make no bones about it. Every day you need foods rich in calcium and vitamin D to maintain good bone health. How much do you need? Vitamin D per Day* Age in Years Recommended Dietary Allowance (IU) AIM FOR Tolerable Upper Intake Level (IU) STAY BELOW , pregnant/lactating IU = international units *For infant requirements consult your doctor or a registered dietitian. Calcium per Day* Age in Years Recommended Dietary Allowance (mg) AIM FOR Tolerable Upper Intake Level (mg) STAY BELOW , men , women , pregnant/lactating 19 50, pregnant/lactating mg = milligrams *For infant requirements consult your doctor or a registered dietitian. What if you don t get enough? Low-calcium diets can lead to osteopenia (weak bones), osteoporosis (very weak, brittle bones) and an increased risk of fractures. Low vitamin D can cause softening of the bones (rickets in children, osteomalacia in adults) and osteoporosis as well. More is not better. There is no extra health benefit to getting more than the Recommended Dietary Allowance (RDA) of calcium and vitamin D. But with supplement use there is a risk of harm from getting too much. Aim to meet the RDA and stay below the Tolerable Upper Intake Level (UL) to minimize the risk of harm from getting too much. Feed your bones. Nutrition experts agree that consuming nutrient-rich food and beverages is the best way to meet your nutrient needs. Following Canada s Food Guide can help you do this. Choose milk and alternatives. Foods from this food group are the best sources of calcium. They include milk, chocolate milk, yogurt and cheese. Drink your D. Canada s Food Guide recommends that all Canadians drink 500 ml (2 cups) of milk every day it is a major dietary source of vitamin D. Drink fortified soy beverages if you do not drink milk. Eat at least two servings of fish each week. Fatty fish such as salmon are excellent sources of vitamin D. Other fish which provide less vitamin D but are still good sources include halibut, herring, tilapia, trout, fresh tuna and whitefish. Want more information? Ask your doctor or consult a registered dietitian (RD). Find an RD in your area at aspx. Did you know? As we age, our bodies use vitamin D less efficiently. Health Canada recommends that all Canadians over age 50 take a vitamin D supplement of 400 IU daily. This is in addition to meeting the RDA for vitamin D from food and beverages Alberta Milk Permission granted to reproduce.

9 References NFFHE August Yetley EA et al. Dietary Reference Intakes for vitamin D: justification for a review of the 1997 values. Am J Clin Nutr 2009;89(3): Institute of Medicine. Dietary Reference Intakes for calcium and vitamin D. Washington, DC: National Academies Press, Institute of Medicine. Dietary Reference Intakes. The essential guide to nutrient requirements. Washington, DC: National Academies Press, Bolland MJ et al. Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis. BMJ 2010;341 c Reid IR et al. Cardiovascular effects of calcium supplementation. Osteoporosis Int DOI: /s Osteoporosis Canada. The potential link between calcium supplement intake and vascular events, April index.php/ci_id/7460/la_id/1.htm. 7. Health Canada. Eating well with Canada s food guide, hcsc.gc.ca/fn-an/food-guide-aliment/index-eng.php. 8. Health Canada. Vitamin D supplementation for breastfed infants: 2004 Health Canada recommendation. nutrition/infantnourisson/vita_d_supp-eng.php. 9. American Dietetic Association, Dietitians of Canada. Position of the American Dietetic Association and Dietitians of Canada: vegetarian diets. J Am Dietetic Assoc 2003;103(6): Craig WJ. Health effects of vegan diets. Am J Clin Nutr 2009;89(5): 1627S 1633S. 11. Johnson-Down L et al. Primary food sources of nutrients in the diet of Canadian adults. Can J Dietetic Pract Res 2006;67(1): Garriguet D. Nutrition: findings from the Canadian Community Health Survey. Overview of Canadians eating habits. Statistics Canada, Dietitians of Canada. Vitamin D: what you need to know, Vitamins/Vitamin-D--What-you-need-to-know.aspx. 14. Langlois K et al. Vitamin D status of Canadians as measured in the 2007 to 2009 Canadian Health Measures Survey. Statistics Canada Health Reports Mar. 2010;21(1). eng.pdf. 15. Health Canada. Vitamin D and calcium: updated Dietary Reference Intakes,

10 16. Garriguet D. Combining nutrient intake from food/beverages and vitamin/mineral supplements. Statistics Canada Health Reports Dec. 2010;21(4): Catalogue no XPE. 17. Vatanparast H et al. Socio-economic status and vitamin/mineral supplement use in Canada. Statistics Canada Health Reports Dec. 2010;21(4): Catalogue no XPE. 18. Health Canada. Eating well with Canada s food guide: a resource for educators and communicators, food-guide-aliment/educcomm/resource-ressource-eng.php. 19. Health Canada. Using the nutrition facts table: % daily value (fact sheet), cons/fact-fiche-eng.php. 20. Health Canada. The Canadian nutrient file, gc.ca/fnan/nutrition/fiche-nutri-data/cnf_aboutus-aproposdenous_ fcen-eng.php. 21. Health Canada. Food fortification in Canada: current practices, factsheet1-fiche1-eng.php.