The purpose of this study is to determine if daily consumption of 2 oz of pecans compared to 3.5 oz pretzel snacks for 12 weeks will 1) contribute to the body's ability to protect itself from oxidative damage (caused by oxygen radicals created by ultraviolet (UV) B light) by evaluating skin resistance to UV light irritation, skin fats/oils degradation and "rusting", and oxidative damage to the skin genes; and 2) explore the mechanisms of how snack consumption may affect aging by analyzing blood markers of aging as well as the microbes living in the gut (gut microbiome).

Oxidative stress plays a significant role in the aging process. Antioxidant potential of tree nuts, including pecans, has been previously reported. However, very few studies have evaluated the antioxidant effects and their underlying mechanisms of nut consumption in the aging population. Skin is the largest organ and is the first body part to exhibit signs of aging. Human skin exposed to solar ultraviolet radiation (UVR) experiences a dramatic increase in production of reactive oxygen species (ROS) and inflammation. Moreover, skin aging is associated with increased levels of oxidative stress. Investigators previously showed that almond and pomegranate consumption can improve the antioxidant defense of skin by reducing UV-induced damage. In addition, the prebiotic properties of nuts and other bioactive-rich foods have been of great interest lately, current study team and others have reported the gut microbiome modulating effects of tree nut consumption. Based on this evidence and other published data, it is being proposed that pecans, due to their bioactive compound content, may have the potential to contribute to whole body antioxidant protection, modulate the gut microbiome and affect the aging process. The aim of this study is to evaluate the effects of incorporating 2 oz of pecans into diet compared to isocaloric pretzel snacks daily for 12 weeks 1) on whole body antioxidant capacity by evaluating skin resistance to UV irritation, lipid oxidation, and oxidative DNA damage; and 2) explore the mechanism of how pecan consumption affects aging by analyzing circulating biomarkers of aging as well as the gut microbiome. This will be a two-arm, randomized, placebo-controlled intervention study in 60 middle-aged and older generally healthy non-vegetarian/vegan women (age 55-75 years, Fitzpatrick's skin types II-IV). Investigating the effects of pecan consumption on skin antioxidant defense and systemic oxidative status will uncover valuable new insights into whether bioactive compounds in pecans can contribute to the total body antioxidant capacity and affect the aging process.

Inclusion Criteria:

• Female
• Generally healthy
• Aged 55-75 years
• BMI 18.5-34.9 kg/m2
• Fitzpatrick Skin type II-IV
• Consume a typical Western diet (low in polyphenols-rich foods and fiber)
• Willing to maintain habitual dietary and exercise patterns for the study duration
• Willing to maintain normal skin care products and pattern for the duration of the study
• Willing to come to study visits without any makeup and skin products on
• Subjects must read and sign the Institutional Review Board-approved written informed consent prior to the initiation of any study specific procedures or enrollment. A subject will be excluded for any condition that might compromise the ability to give truly informed consent.

Exclusion Criteria:

• Vegetarian/vegan
• Known nut allergy
• Skin-related prescription medication, supplements or non-prescription cosmeceutical agents
• Initiation of topical or oral prescription steroids and/or anti-inflammatory medications within 30 days prior to study enrollment
• Excessive exposure to either natural or artificial sunlight
• Screening laboratory values outside of the normal range that is considered clinically significant for study participation by the investigator
• Documented chronic disease
• Taking medications or supplements known to affect gut microbiota composition (antibiotics within the past 3 months, probiotics, fiber, etc.)
• Taking exogenous hormones (e.g. hormone replacement therapy)
• Recent weight fluctuations (>10% in the last 6 months)
• Smoker or living with a smoker
• Use of >20 g of alcohol per day
• Unable or unwilling to comply with the study protocol (including unwillingness to avoid nuts for the whole duration of the study)
• Unable to provide consent
• Pregnancy and/or lactation

Data analysis will be performed in-house.