Impact of Egg Consumption on Carotenoid and Vitamin D Bioavailability in Pre- and Post-menopausal Women

The 2010 Dietary Guidelines for Americans emphasizes consumption of 4.5 cups of fruits and vegetables daily. However, US adults only consume on average 2.6 cups of fruits and vegetables daily. This low consumption may further result in the limited availability of fat soluble, health-promoting, phytochemicals such as carotenoids (CAT) from these foods. Dietary CAT have beneficial biological properties including antioxidant and anti-inflammatory effects and scientific research supports the protective effects of CAT against many degenerative diseases, including cardiovascular diseases, age-related macular degeneration, and some types of cancer. Therefore, either low intake or inefficient bioavailability of CAT from fruits and vegetables may reduce their potential effectiveness to retard or prevent disease. Recently completed randomized and crossover study found that co-consuming 150g (3 eggs) of scrambled whole eggs (SWE) which contains18g of lipid, increases overall CAT absorption from a mixed-vegetable salad >7-fold compared to a the same salad without eggs (3g of co-consumed lipid) in young healthy men. However, the occurrence of this benefit in women and older adults is unknown. Aging may affect CAT bioavailability due to age-induced physiological changes including reduced gastrointestinal tract function and modifications of chylomicron metabolism. Eggs are known to be a highly bioavailable source of CAT, presumably due to the presence of lipid and phospholipid in egg yolk. The highly bioavailable nature of CAT from eggs suggest that egg-derived factors may be leveraged to improve bioavailability of other CAT found in co-consumed vegetables. While promising, very limited data exist on the impact of a co-consumed food source of lipid to enhance CAT absorption in women or in older adults.

Vitamin D (VIT D) insufficiency is widespread with nearly 2/3 of Americans not meeting the current Institute of Medicine (IOM) recommendation for serum 25-hydroxyvitamin D (25(OH)D) concentration. VIT D has an essential function to regulate calcium homeostasis, including stimulating calcium's active intestinal absorption and renal excretion. Thus, maintaining adequate VIT D status is critical for overall skeletal health and the prevention of osteoporosis. Post-menopausal women are at high risk of having osteoporosis and this risk is reduced when adequate VIT D status is maintained. VIT D is fat-soluble and only a limited number of foods naturally contain it. Also, while VIT D absorption is enhanced by dietary lipid, the optimal amount of lipid required for maximal absorption has not been determined. A paucity of data exists regarding the effect of a co-consumed food source of lipid to enhance VIT D absorption and the impact of aging on VIT D bioavailability in women.

Inclusion criteria

• Pre- (regularly menstruating, aged 19-45y) and post-menopausal (aged 60+y) females
• weight stable (± 3 kg in the past 3 months)
• constant habitual activity patterns within last 3 months
• no acute illness
• not diabetic or have chronic diseases known to influence lipid or energy metabolism
• blood 25(OH)D>20 nmol/L
• non-smoking
• drinking no more than 2 alcoholic drinks per day
• not taking estrogen-based birth control or osteoporosis prevention or treatment medications in the past 3 months
• not taking lipid-lowering medications

Exclusion criteria

• Males
• age <19 or age >45y for pre-menopausal women and age <60y for post-menopausal women
• weight change>3 kg in the past 3 months
• exercising vigorously over the past 3 months
• intestinal disorders including lipid malabsorption or lactose intolerance
• abnormal liver or kidney function tests
• blood 25(OH)D<20 nmol/L
• fasting blood glucose>110 mg/dL
• smoking
• drinking more than 2 alcoholic drinks per day
• taking estrogen-based birth control or osteoporosis prevention or treatment medications in the past 3 months
• taking lipid-lowering medications affecting plasma cholesterol concentration