Role of Hazelnut Consumption in Improving Micronutrient Status in Older Adults

Older adults are at increased risk of various chronic diseases where inadequate levels of vitamins and minerals may play a significant role, including cardiovascular disease, Alzheimer's disease, liver disease, and cancer. Older adults are increasingly more susceptible to vitamin and mineral deficiencies with changes in dietary preferences, changes in socioeconomic status, decreased consumption of a variety of foods, poor absorption in the gut, and an increased demand for many of these micronutrients with advanced age.

Epidemiological studies and recent clinical trials have shown that use of multivitamin/mineral or single nutrient supplements, such as vitamin E, have beneficial effects on disease risk, but many people are hesitant to use dietary supplements due to reports of ineffectiveness or potential negative effects. However, food sources of vitamin E and other key vitamins and minerals continue to show health benefits. As an alternative to mandating consumption of multivitamin and mineral supplements or food fortification, a dietary solution is to increase consumption of nutrient-dense foods, like hazelnuts.

Tree nuts, including hazelnuts, contain a wide variety of vitamins and minerals, and are particularly good source of vitamin E and magnesium, two "shortfall nutrients" that are lacking in the typical American diet. Over 90% of U.S. adults do not meet recommended intake levels of vitamin E, and 60% do not get enough magnesium. Tree nuts are also a good source of protein and fiber and are high in healthful unsaturated fatty acids and phytochemicals such as flavonoids and phytosterols.

Most clinical studies on the benefits of nut consumption have been conducted using almonds and walnuts, with hazelnuts used less frequently. However, the health benefits of consuming hazelnuts have been demonstrated in many clinical trials, including lower blood glucose levels, alterations in blood lipids, and declines in biomarkers of oxidative stress. Although several clinical trials have investigated nutritional impact of hazelnuts in adults, no clinical trials with hazelnuts have focused on examining micronutrient status and potential health benefits only in older (≥55 years) adults.

Determination of body status of many micronutrients can be difficult, especially so the evaluation of vitamin E levels when age is considered as a factor. Although serum α-tocopherol levels are generally higher in adults above the age of 50 compared to younger adults, the increased prevalence of hypercholesterolemia in older adults makes interpretation of circulating α-tocopherol levels difficult. Alternatively, urinary α- and γ-carboxyethyl hydroxychromanol (α- and γ-CEHC) is believed to be a biomarker of α- and γ-tocopherol status that changes with vitamin E intake. In particular, low α-CEHC excretion is considered a reliable marker of poor α-tocopherol status, while an increase in α-CEHC is indicative of adequate α-tocopherol status.

The objective of this study was to determine whether daily hazelnut consumption by healthy older adults for 16 weeks improves biomarkers of micronutrient status, especially vitamin E and magnesium. For a detailed assessment of vitamin E status, plasma α- and γ-tocopherol concentrations were determined together with urinary α- and γ-CEHC levels. In addition, a commercially available lymphocyte proliferation assay was utilized to evaluate the status of several other micronutrients. Since hazelnut consumption is reported to reduce blood lipids and improve glucose homeostasis, these biomarkers were also monitored in our study.