Abstract
BACKGROUND: Only a limited number of studies have examined the vascular and postprandial effects of α-linolenic acid (ALA, C18:3n-3). Therefore, we performed a well-controlled trial focusing specifically on the effects of ALA on vascular function and metabolic risk markers during the fasting and postprandial phase in untreated (pre-)hypertensive individuals. METHODS: In a double-blind randomized, placebo-controlled parallel study, 59 overweight and obese adults (40 men and 19 women, aged 60 ± 8 years) with a high-normal blood pressure or mild (stage I) hypertension consumed daily either 10 g of refined cold-pressed flaxseed oil, providing 4.7 g ALA (n = 29), or 10 g of high-oleic sunflower (control) oil (n = 30) for 12 weeks. RESULTS: As compared with the high-oleic oil control, intake of flaxseed oil did not change brachial artery flow-mediated vasodilation, carotid-to-femoral pulse wave velocity, retinal microvascular calibers and plasma markers of microvascular endothelial function during the fasting and postprandial phase. Fasting plasma concentrations of free fatty acid (FFA) and TNF-α decreased by 58 μmol/L (P = 0.02) and 0.14 pg/mL (P = 0.03), respectively. No differences were found in other fasting markers of lipid and glucose metabolism, and low-grade systemic inflammation. In addition, dietary ALA did not affect postprandial changes in glucose, insulin, triacylglycerol, FFA and plasma inflammatory markers after meal intake. CONCLUSION: A high intake of ALA, about 3-5 times the recommended daily intake, for 12 weeks decreased fasting FFA and TNF-α plasma concentrations. No effects were found on other metabolic risk markers and vascular function during the fasting and postprandial phase in untreated high-normal and stage I hypertensive individuals.
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Key Points
Postprandial challenges may be used as tools to assess subtle changes in metabolic and vascular health following a high intake of ALA. In this 12-week randomized, double blind, placebo-controlled parallel study, effects of ALA (4.7 g per day, ~2% of energy intake) were assessed on a panel of vascular function markers and risk markers related to metabolic health during the fasting and postprandial phase. The well-controlled intervention study involved untreated overweight and obese adults with a high-normal BP or mild (stage I) hypertension, while using a high intake of ALA, about 3-5 times the recommended daily intake. Increasing daily ALA intake did significantly decrease fasting FFA and TNF-a concentrations. However, no effects were observed on other metabolic risk markers and vascular function during the fasting and postprandial phase when compared with the high oleic acid control. Circulating glucose and insulin, insulin sensitivity, and other lipids and lipoproteins were comparable between the two treatment groups. The study did not found differences for other plasma markers (i.e. IL-6, IL-8, CRP, SAA and MCP-1) between groups. No effects were found on other metabolic risk markers and vascular
function during the fasting and postprandial phase in untreated individuals with a high-normal blood pressure or mild (stage I) hypertension.