Alpha-Linolenic Acid and Inflammatory Markers

Effect of Alpha-Linolenic Acid on Blood Markers of Inflammation

The optimal type of oil to prevent cardiovascular disease (CVD) is uncertain. In general, unsaturated oils with higher content of cis-monounsaturated fatty acids (MONO) or cis-polyunsaturated fatty acids (PUFA) are preferable over those rich in saturated fatty acids. However, unsaturated oils can vary in their relative contents of n-6 and n-3 fatty acids (specifically alpha-linolenic acid (ALA)). Some investigators advocate that oils rich in ALA are cardioprotective, while others suggest that optimal cardioprotective effects can only be obtained when oils are lower in n-6 fatty acids (mainly linoleic acid) in addition to being higher in ALA. It is hypothesized that increased ALA would result in beneficial effects on inflammatory markers. The objective of this trial is to establish definitively the biological effects of ALA with and without reductions in linoleic acid on inflammatory markers linked to CVD.

Study Overview

• Status: Completed
• Conditions: Cardiovascular Disease
• Intervention / Treatment: Dietary supplement: Flaxseed oil-Olive oil; Dietary supplement: Olive oil-olive oil; Dietary supplement: Flaxseed oil-sunflower oil; Dietary supplement: Olive oil-sunflower oil

Detailed Description

This study is a dietary trial that examines the effects of increasing ALA by 2 gr or 4 gr per day, with and without decreasing linoleic acid, on inflammatory markers linked to CVD. Trial participants (n=136), approximately 50% women, 50% men) are age 50 and older and living in the town of Montana, Bulgaria during the study. The study uses a double-blinded placebo-controlled, randomized cross-over design. Combinations of two oils that are considered healthy (sunflower and olive) and an ALA supplement containing either 2 or 4 gr of ALA (supplied as flaxseed oil) or placebo are consumed for 6 weeks each: sunflower-ALA (high linoleic-low ALA), sunflower-placebo (high linoleic-low ALA), olive-ALA (low-linoleic-high ALA) and olive-placebo (low linoleic-low ALA). The participants are indicated to keep their usual diet and physical activity through-out the study. The primary endpoints are plasma levels of inflammatory markers. Secondary endpoints include systolic and diastolic blood pressure, and plasma levels of LDL cholesterol, HDL cholesterol and triglycerides.

SPECIFIC AIMS

To determine the effect of increasing ALA by 2 or 4 gr per day in the context of a diet that that is high in linoleic acid (~13% energy) on inflammatory markers. The ALA effect will be tested by comparing ALA supplement vs. placebo while using sunflower oil for cooking at home. We hypothesize that ALA has favorable effects on inflammatory markers in the context of a diet that is high in linoleic acid.

To determine the effect of increasing ALA by 2 or 4 gr per day in the context of a diet that that is low in linoleic acid (~6% energy) on inflammatory markers. The ALA effect will be tested by comparing ALA supplement vs. placebo while using olive oil for cooking at home. We hypothesize that ALA has favorable effects on inflammatory markers in the context of a diet that is low in linoleic acid.

SECONDARY AIMS

To determine the effect of reducing linoleic acid from a high level (~13% energy) to a low level (~6% energy) while keeping ALA at a high level (2 or 4 gr per day) on plasma levels of inflammatory markers. The reduction in linoleic acid will be tested by comparing sunflower to olive oil while taking the ALA supplement. We hypothesize that reducing linoleic acid does not affect inflammatory markers when ALA intake is high.

To determine the effect of reducing linoleic acid from a high level (~13% energy) to a low level (~6% energy) while keeping ALA at a low level (placebo) on plasma levels of inflammatory markers. The reduction in linoleic acid will be tested by comparing sunflower to olive oil while taking the placebo. We hypothesize that reducing linoleic acid does not affect inflammatory markers when ALA intake is low.

To determine whether the intervention contrasts specified in the specific aims and secondary aims 1 & 2 affect plasma levels of LDL cholesterol, HDL cholesterol and triglycerides and blood pressure.

We hypothesize that ALA has favorable effects on plasma triglycerides and blood pressure compared to placebo regardless of whether linoleic acid is high or low.

We hypothesize that lowering linoleic acid has favorable effects on plasma HDL cholesterol but unfavorable effects on LDL cholesterol,regardless of whether ALA is high or low.

• Study Type: Interventional
• Enrollment (Actual): 130
• Phase: Not Applicable

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 50 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Age 50 or older at time of enrollment
• Willing to cook and eat foods prepared exclusively with the study oils and nothing else every day of the week at least 2 meals per day for 24 weeks
• Willing to eat no more than one meal per week prepared out of the home
• Willingness to take 4 or 8 capsules with ALA or placebo every day for 24 weeks
• Willingness to provide personal and next of kin address and phone number for follow-up visits to the home.
• Willingness to complete measurement procedures and blood draws.
• Ability and willingness to provide informed consent to be screened and to take part of the study.

Exclusion Criteria:

Medication Exclusions

• Unstable dose of medications during the past 2 months that raise or lower blood pressure, lipids or glucose. Unstable dose is a dose change in the past 6 months or less than 6 months of treatment.

Medical History Exclusions

• Active or prior CVD (stroke, MI, PTCA, CABG, congestive heart failure, symptomatic ischemic heart disease (angina), or CVD-related therapeutic procedure).
• Cancer diagnosis or treatment in past two years (however, persons with non-melanoma skin cancer, localized breast cancer, or localized prostate cancer can enroll if they did not require systemic chemotherapy)
• Active inflammatory bowel disease, malabsorption, or major GI resection
• Chronic renal disease
• Any serious illness not otherwise specified that would interfere with participation
• Stage 2 hypertension (SBP > 160 or DBP > 100 mmHg) based on the mean of 3 measurements on the screening visit, as well as a systolic BP > 170 or diastolic BP > 105 at any of the measurements

Other Exclusions

• Eat fish more than once per week including canned fish
• Significant oil preferences, intolerances, dietary habits, or dietary requirements that would interfere with adherence
• Planning to leave the area for more than two weeks prior to the anticipated end of participation
• Current participation in another study that manipulates diet or that will affect the outcome of this study
• Taking vitamin, vegetable oil, fish-oil, weight-loss, soy, mineral, or herbal supplements that cannot be stopped
• Unable to measure blood pressure (due to arm circumference > 50 cm)
• Investigator judgment (e.g. for concerns over adherence, or follow-up or for inappropriate behavior)

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Triple

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: High ALA-Low Linoleic	Dietary supplement: Flaxseed oil-Olive oil; 2 or 4 gr per day alpha-linolenic acid pill and olive oil used for cooking
Placebo Comparator: Low ALA-Low Linoleic	Dietary supplement: Olive oil-olive oil; 1 gr olive oil pill and olive oil used for cooking
Active Comparator: High ALA-High Linoleic	Dietary supplement: Flaxseed oil-sunflower oil; 2 or 4 gr per day alpha linolenic acid pill and sunflower oil used for cooking
Placebo Comparator: Low ALA-High Linoleic	Dietary supplement: Olive oil-sunflower oil; 1 gr olive oil pill and sunflower oil used for cooking

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
Markers of inflammation	6 weeks

Secondary Outcome Measures

Outcome Measure	Time Frame
Plasma lipids and blood pressure	6 weeks

Collaborators and Investigators

• Sponsor: Harvard School of Public Health (HSPH)

Study record dates

Study Major Dates

• Study Start: February 1, 2009
• Primary Completion (Actual): August 1, 2009
• Study Completion (Actual): August 1, 2009

Study Registration Dates

• First Submitted: August 27, 2009
• First Submitted That Met QC Criteria: August 27, 2009
• First Posted (Estimated): August 28, 2009

Study Record Updates

• Last Update Posted (Estimated): December 19, 2023
• Last Update Submitted That Met QC Criteria: December 13, 2023
• Last Verified: December 1, 2023

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Cardiovascular Diseases
• Other Study ID Numbers: P-16261-101