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Higher circulating α-carotene was associated with better cognitive function: an evaluation among the MIND trial participants.
Liu, X, Dhana, K, Furtado, JD, Agarwal, P, Aggarwal, NT, Tangney, C, Laranjo, N, Carey, V, Barnes, LL, Sacks, FM
Journal of nutritional science. 2021;10:e64
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Plain language summary
Diet has been identified as one of the important modifiable lifestyle factors in preventing Alzheimer’s disease. Carotenoids are potent antioxidants, naturally occurring pigments found in red, yellow, orange and dark green fruits and vegetables. Literature from epidemiological studies links fruit and vegetable consumption, and higher levels of carotenoids, with a lower risk of cognitive decline among older adults from different regions. The aim of this study was to examine (1) the association between dietary intakes of carotenoids and global/domain-specific cognition, and (2) how participants’ dietary patterns corresponded to their plasma levels of carotenoids. This study is an evaluation of baseline blood nutrients and cognition among the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) participants. Participants are predominantly Caucasian females with a mean age of 69⋅8 years. Results show that high levels of plasma α-carotene were associated with higher scores for global cognition, and episodic and semantic memory. The carotenoids lutein and zeaxanthin (combined) were positively associated with better scores for semantic memory. A dietary pattern that featured greater consumption of vegetables other than green leafy vegetables and fruits, corresponded to high α-carotene in blood which was associated with higher cognition scores. Authors conclude that blood nutrient levels as objective markers could characterise individuals’ dietary patterns, which could facilitate a targeted dietary intervention to prevent cognitive decline.
Abstract
There is emerging evidence linking fruit and vegetable consumption and cognitive function. However, studies focusing on the nutrients underlying this relationship are lacking. We aim to examine the association between plasma nutrients and cognition in a population at risk for cognitive decline with a suboptimal diet. The Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) trial is a randomized controlled intervention that examines the effects of the MIND diet to prevent cognitive decline. The primary outcome is global cognition. A multivariate linear model was used to investigate the association between blood nutrients and global and/or domain-specific cognition. The model was adjusted for age, sex, education, study site, smoking status, cognitive activities and physical activities. High plasma α-carotene was associated with better global cognition. Participants in the highest tertile of plasma α-carotene had a higher global cognition z score of 0⋅17 when compared with individuals in the lowest tertile (P 0⋅002). Circulating α-carotene levels were also associated with higher semantic memory scores (P for trend 0⋅007). Lutein and zeaxanthin (combined) was positively associated with higher semantic memory scores (P for trend 0⋅009). Our study demonstrated that higher α-carotene levels in blood were associated with higher global cognition scores in a US population at risk for cognitive decline. The higher α-carotene levels in blood reflected greater intakes of fruits, other types of vegetables and lesser intakes of butter and margarine and meat. The higher circulating levels of lutein plus zeaxanthin reflected a dietary pattern with high intakes of fruits, green leafy, other vegetables and cheese, and low consumption of fried foods. Objective nutrient markers in the blood can better characterize dietary intake, which may facilitate the implementation of a tailored dietary intervention for the prevention of cognitive decline.
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Improved antioxidant and fatty acid status of patients with cystic fibrosis after antioxidant supplementation is linked to improved lung function.
Wood, LG, Fitzgerald, DA, Lee, AK, Garg, ML
The American journal of clinical nutrition. 2003;77(1):150-9
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Plain language summary
Oxidative stress is elevated in patients with cystic fibrosis (CF). It has been hypothesised that supplementing with antioxidants reduces oxidative stress and therefore the rate of lung deterioration in CF patients. The aim of the study was to examine oxidative stress and antioxidant defences in CF patients after antioxidation supplementation in relation to fatty acid status, dietary intake and clinical status. Children with CF were given a high dose supplement containing 200mg vitamin E, 300mg vitamin C, 25mg beta-carotene, 90 micrograms selenium and 500 micrograms vitamin A for 8 weeks. The control group received low doses of vitamins A and E equal to the RDA, which is part of routine treatment for some CF patients. At the end of the study, the group taking the high dose antioxidant supplement showed significant increases in plasma concentrations of vitamin E, beta-carotene, selenium and glutathione peroxidase compared to the control group. Despite this, there were no significant differences in markers of lung function or wellbeing between the two groups. The researchers did however find correlations between both increased plasma fatty acids and antioxidant (beta-carotene and selenium) status and improved lung function, suggesting that antioxidant supplementation and high fat diets may be beneficial for CF patients. Since increased plasma fatty acids are linked to oxidative stress, the authors point out the importance of reducing oxidative stress in CF patients who are on a high-fat diet.
Abstract
BACKGROUND Oxidative stress, as measured by 8-iso-prostaglandin F(2)(alpha) (8-iso-PGF(2)(alpha)), and depleted antioxidant defenses were shown in stable cystic fibrosis (CF) patients. The plasma fatty acid status of CF patients was linked to oxidative stress after respiratory exacerbations. OBJECTIVE We examined changes in plasma 8-iso-PGF(2)(alpha), antioxidant defenses, plasma fatty acid status, and clinical markers resulting from short-term antioxidant supplementation. DESIGN Forty-six CF patients were randomly assigned to either group A [low dose of supplement (10 mg vitamin E and 500 micro g vitamin A)] or group B [high dose of supplement (200 mg vitamin E, 300 mg vitamin C, 25 mg beta-carotene, 90 micro g Se, and 500 micro g vitamin A)]. Plasma concentrations of 8-iso-PGF(2)(alpha), vitamins E and C, beta-carotene, zinc, selenium, and copper; plasma fatty acid composition; erythrocyte glutathione peroxidase (EC 1.11.1.9) and superoxide dismutase (EC 1.15.1.1) activities; lung function; and dietary intake were measured before and after 8 wk of supplementation. RESULTS Antioxidant defenses in group B improved, whereas those in group A did not: in groups B and A, the mean (+/- SEM) changes (Delta) in vitamin E were 10.6 +/- 1.5 and -1.9 +/- 0.9 micro mol/L, respectively (P < 0.001), (Delta)beta-carotene were 0.1 +/- 0.04 and -0.01 +/- 0.02 micro mol/L, respectively (P = 0.007), (Delta)selenium were 0.51 +/- 0.10 and -0.09 +/- 0.04 micro mol/L, respectively (P < 0.001), and (Delta)glutathione peroxidase activity were 1.3 +/- 0.3 and -0.3 +/- 0.6 U/g hemoglobin, respectively (P = 0.016). There were no significant differences between the groups in Delta8-iso-PGF(2)(alpha), (Delta)vitamin C, (Delta)fatty acid composition, (Delta)superoxide dismutase activity, (Delta)lung function, or (Delta)white cell count. Within group B, (Delta)beta-carotene correlated with (Delta)percentage of forced vital capacity (r = 0.586, P = 0.005), (Delta)selenium correlated with (Delta)percentage of forced expiratory volume in 1 s (r = 0.440, P = 0.046), and (Delta)plasma fatty acid concentrations correlated with (Delta)percentage of forced expiratory volume in 1 s (r = 0.583, P = 0.006) and Delta8-iso-PGF(2)(alpha) (r = 0.538, P = 0.010). CONCLUSIONS Whereas increased beta-carotene, selenium, and fatty acid concentrations are linked to improved lung function, increased plasma fatty acid concentrations are linked to oxidative stress. If oxidative stress is deemed to be important to the clinical outcome of CF patients, means of reducing oxidative stress while maintaining a high-fat, high-energy diet must be investigated.