A diverse diet is essential for a healthy lifestyle. However, historically, dietary nutrients have often been studied individually, and our knowledge of their interactions is limited. Iron and vitamin A, which can come from provitamin A carotenoids, are among the most commonly deficient micronutrients globally, raising significant health concerns. Additionally, coenzyme Q10 is gaining attention for boosting energy and combating post-COVID fatigue. While emulsification and encapsulation can enhance the delivery of fat-soluble nutrients like carotenoids and coenzyme Q10, the effectiveness of the food-grade emulsifier phospholipid in improving bioaccessibility remains inconsistent. In relation to iron, novel electric processing has created an iron enriched kale, but its iron delivery compared to other iron sources is still unclear. Additionally, novel plant-based fortificant iron chlorophyll derivatives (ICDs) can enhance iron delivery to intestinal cells when co-digested with albumin. However, the impact of various food proteins, particularly plant proteins, on iron absorption requires further exploration.
In Objective 1, an in vitro digestion + Caco-2 intestinal cell model was used to evaluate the dose-response effect of phospholipid on carotenoid bioaccessibility and cell uptake, as well as whether liquid and powder forms of bioactive compounds encapsulated with phospholipid improve these parameters compared to a non-encapsulated control. Objective 2 examined the impact of novel electric treatment on the concentrations of antioxidants and carotenoids in kale. An in vitro digestion + Caco-2 model was used to determine if iron bioaccessibility and iron cell uptake from this kale surpass those from iron sulfate (the most common commercial iron supplement) and heme iron. For Objective 3, ICDs were digested alone and co-digested with whey, soybean, or pea protein isolates in vitro. A Caco-2 model was used to assess iron delivery. Metabolites in the digesta were profiled using liquid chromatography-mass spectrometry-based untargeted metabolomics.
A lecithin dose of 1 mg improved carotenoid bioaccessibility ~2x and led to increased Caco-2 cell uptake of the carotenes tested, but no change in xanthophylls tested, as compared to the control group. Doses of lecithin ≥ 3 mg did not improve carotenoid bioaccessibility or Caco-2 cell uptake and produced oil droplet aggregation. Encapsulation (by either VitaDry® or Vitasperse®, containing medium chain triglycerides + phospholipids) increased total astaxanthin bioaccessibility 2-2.4x and cell uptake by ~2x relative to control. Encapsulation also increased total lutein bioaccessibility by 3-5x and cell uptake 2.3x relative to control. There was no significant difference between VitaDry® and VitaSperse® products in regard to Caco-2 cell uptake. The Vita encapsulated CoQ10 was 1.4x more bioaccessible as compared to the control, with no difference between the VitaDry® and VitaSperse® products. The VitaDry® and VitaSperse® encapsulated CoQ10 was 6.0x and 5.5x better taken up by Caco-2 cells.
Following incubation with digesta, the combination moderate electric field-treated kale led to a 4x increase in cell ferritin relative to FeSO4 alone, with levels comparable to those seen with FeSO4+ascorbic acid (AA) and hemoglobin. In the highest amount of iron/100 g kale leaf, β-carotene and lutein were 3-4x lower, α-tocopherol was comparable, and AA was 3x higher, as compared to untreated kale. Notably, MEF-treated kale is an iron-rich source that demonstrates high iron delivery in vitro.
Whey protein isolate increased total iron bioaccessibility, while soybean and pea protein isolates decreased it, as compared to ICDs digested alone. All co-digested protein isolates reduced ICD bioaccessibility and cell ferritin formation compared to ICDs alone. With the addition of AA, the total iron and ICD bioaccessibility and Caco-2 cell ferritin formation following incubation with digesta containing ICDs+whey protein isolate were comparable to ICDs alone. However, bioaccessibility and ferritin formation following incubation with digesta containing ICDs+legume protein isolates were lower relative to ICDs. Ultra-high performance liquid chromatography-mass spectrometry metabolomics analyses revealed that ICDs+whey+AA digesta had increased glutamic acid and cysteine containing tri/dipeptides, which can chelate iron and potentially facilitate transport across the Caco-2 apical membrane, as compared to ICDs+whey. In contrast, the abundant trigonelline in legume digesta may have been responsible for inhibiting iron absorption, when ICDs were co-digested with plant proteins. However, more evidence is needed to verify these hypotheses.
These results guide bioactive nutrient pairings, which can help improve dietary strategies. Ultimately, we hope the findings will provide scientific insights that benefit human nutritional health.