will continue to be needed to address these and other issues.
When available, this section emphasizes evidence from authoritative reviews and recommendations regarding the role of micronutrient supplements. The information comes from the US Preventive Services Task Force (USPSTF), Cochrane Reviews, meta‐analyses, and practice guidelines based on the best available information. Created in 1984, the US Preventive Services Task Force is an independent, volunteer panel of national experts in prevention and evidence‐based medicine. The Task Force works to improve the health of all Americans by making evidence‐based recommendations about clinical preventive services such as screenings, counselling services, and preventive medications. All recommendations are published on the Task Force’s website and/or in a peer‐reviewed journal.15 Cochrane Reviews are systematic reviews of primary research in human healthcare and health policy and are internationally recognized as among the highest standard of evidence‐based healthcare for prevention, treatment, and rehabilitation.16
To illustrate some of the better‐known relationships of specific antioxidant nutrients, vitamins, and minerals with selected diseases, conditions, and outcomes, several of those most relevant to older adults are summarized in the following sections. The chronic diseases and outcomes addressed include bone health and fracture risk, mild cognitive impairment and dementia, age‐related eye disorders, and cancer and cardiovascular disease, as well as the potential role of nutrient intake (focusing on zinc) in pressure ulcer injury healing. The section that discusses pressure ulcer injuries provides an example of a complex clinical condition in which malnutrition clearly plays a role but for which the causal relationships of specific nutrients are difficult to disentangle from the effects of other comorbidities and conditions. It also shows the challenge presented when a highly reliable biomarker for a given nutrient has not been identified, as is the case for zinc and several other micronutrients.
Bone health, fractures, vitamin D, and calcium
While not all osteoporotic fractures are directly attributable to deficiencies in vitamin D or calcium, these nutrients are essential for skeletal integrity and represent important modifiable factors associated with bone health.17 Vitamin D and calcium play a critical role in the prevention and treatment of osteopenia and osteoporosis. Along with other key determinants such as hormonal changes, these micronutrients must be present in adequate amounts for therapies with pharmacologic and nonpharmacologic treatments to be optimally effective. However, the potential benefits of these nutrients, which are very commonly under‐consumed from dietary sources, must be balanced with the potential risks of using supplemental forms.
Prevention of fractures in high‐risk populations
In a recent Cochrane Review, fracture outcomes were reported from 53 RCTs or quasi‐randomized trials of supplementation of vitamin D and/or calcium in postmenopausal women or men over age 65 from community, hospital, and nursing‐home settings and 22 trials of primarily participants with established osteoporosis in settings of institutional referral clinics or hospitals.17 Several forms of vitamin D were examined, including vitamins D2 and D3 (typically in foods and over‐the‐counter supplements) and activated forms of vitamin D (that are activated in the liver and/or kidney: calcidiol, alfacalcidol, and calcitriol). Vitamin D alone was not associated with preventing fractures, while vitamin D with additional calcium supplements reduced the risk of hip fractures and other fractures. Mortality risk was not increased from vitamin D and calcium supplements. However, an increased risk of other adverse effects was noted, such that it was recommended that those with kidney stones, kidney disease, high blood calcium, or gastrointestinal disease or those at risk of heart disease should seek medical advice before taking these supplements.18
Prevention of fractures in healthy populations
The use of supplements for primary prevention of osteoporosis‐related fractures in healthy populations lacks sufficient evidence to be recommended. An evidence review of 11 RCTs of vitamin D supplementation alone or with calcium found no association with reduced fracture incidence among community‐dwelling adults without known vitamin D deficiency, osteoporosis, or prior fracture (‘healthy populations’).17 With regard to potential risk of harm, supplementation with vitamin D alone, or in combination with calcium, did not increase all‐cause mortality, cardiovascular events, or cancer risk; and supplementation with calcium alone did not increase the incidence of kidney stones. However, supplementation with both vitamin D and calcium was associated with an increase in the incidence of kidney stones. USPSTF conclusions and recommendations in 2018 were as follows19:
The current evidence is insufficient to assess the balance of the benefits and harms of vitamin D and calcium supplementation, alone or combined, for the primary prevention of fractures in community‐dwelling, asymptomatic men and premenopausal women. (Insufficient ‘I’ statement.)
The current evidence is insufficient to assess the balance of the benefits and harms of daily supplementation with doses greater than 400 IU of vitamin D and greater than 1000 mg of calcium for the primary prevention of fractures in community‐dwelling, postmenopausal women. (Insufficient ‘I’ statement.)
Recommends against daily supplementation with 400 IU or less of vitamin D and 1000 mg or less of calcium for the primary prevention of fractures in community‐dwelling, postmenopausal women. (Discourage ‘D’ statement.)
These recommendations do not apply to people with a history of osteoporotic fractures of increased risk for falls, or a diagnosis of osteoporosis or vitamin D deficiency.
Summary
Vitamin D and calcium are required for bone development and health throughout life. The RDA in the US for calcium and AI for vitamin D for older people are 1000–1200 mg calcium daily and 600 IU (15 μg) vitamin D daily and can be obtained from a combination of foods and supplements.3 Recommended intakes for other countries are summarized elsewhere.10 Consumption of two cups (16 ounces, 473 ml) of vitamin D fortified milk (and/or yoghurt) daily provides at least 600 mg calcium and 200 IU (5 μg) vitamin D. The remainder can be obtained from dietary supplements and the smaller amounts in other foods, such as some fish for vitamin D. For individuals without vitamin D deficiency, the UL for vitamin D is 4000 IU (100 μg) daily in the US, Canada, and Europe.10
Guidelines for treating vitamin D deficiency and/or maintaining vitamin D status among those with osteoporosis are available.10 For vitamin D deficiency in adults, oral 6000 IU (150 μg) daily for eight weeks followed by 1500‐2000 IU (37.5–50 μg) daily has been recommended.10 Recommendations for those with osteoporosis are generally 600–800 IU (15–20 μg) daily, which is similar to recommendations for the general population.10 There are reports that intermittent high‐dose vitamin D supplementation can increase the risk of falls and fractures,10 so daily oral supplementation is preferable.
Mild cognitive impairment and dementia
Mild cognitive impairment (MCI) describes cognitive changes that are serious enough to be noticed by the affected individual and their associates but not sufficiently severe enough to affect the ability to carry out regular daily activities. Those with MCI are at a greater risk of developing Alzheimer’s disease, the most common dementia.20 However, MCI does not always lead to dementia. It can be reversible, as in the case of a medication side effect, or it can remain stable or even return to normal over time.
Because MCI can precede dementia, it has been the target of experimental interventions to delay conversion to dementia. Many factors are involved in dementia prevention, such as risk factor reduction and management of cardiovascular disease, stroke, and diabetes, as well as diet, exercise, cognitive engagement, and genomics.20 Cohort studies suggest an important role for dietary patterns and specific foods and nutrients for the prevention of MCI and dementia21; however, evidence on the specific benefits of vitamin and mineral supplements is limited.
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