Abstract
This paper describes the effects of flaxseed and its components (flax oil, secoisolariciresinoldiglucoside [SDG], flax lignan complex [FLC], and flax fibers] on serum lipids (total cholesterol [TC], low-density lipoprotein-cholesterol [LDL-C], high-density lipoprotein cholesterol [HDL-C], and triglycerides [TG]) in animals and humans. Ordinary flaxseed reduces TG, TC, LDL-C, and TC/HDL-C levels in a dose-dependent manner in animals. In humans, it reduces serum lipids in hypercholesterolemic patients but has no effects in normocholesterolemic patients. Flax oil has variable effects on serum lipids in normo- and hypercholesterolemic animals. Flax oil treatment, with a dosage containing greater than 25 g/day of α-linolenic acid, reduces serum lipids in humans. Although FLC reduces serum lipids and raises serum HDL- C in animals, its effects on serum lipids in humans are small and variable. Flax fibers exert small effects on serum lipids in humans. Crop Development Centre (CDC)-flaxseed, which contains low concentrations of α-linolenic acid, has significant lipid lowering effects in animals. Pure SDG has potent hypolipidemic effects and raises HDL-C. In conclusion, flaxseed and pure SDG have significant lipid-lowering effects in animals and humans, while other components of flaxseed have small and variable effects.
Link to Full Text
Key Points
The effects of flaxseed and its constituents are variable, which may be due to variable doses and species variations. The small effects of flaxseed and its constituents may be due to small doses and frequency of administration. Large doses at frequent intervals may have significant effects on serum lipids. First, studies should be conducted in experimental animals with various doses of flaxseed, flax oil, SDG, FLC, and flaxseed fiber to determine optimal doses for improving serum lipid levels. With this approach, optimal dosage of flaxseed and its constituents can be determined. The present data suggest that flaxseed oil, FLC, and flaxseed fibers may not serve as therapeutic agents for lowering serum TC, TG, LDL-C, TC/HDL-c, and LDL-C/HDL-c, not even for elevating serum levels of HDL-C. They may be used as adjunctive therapeutic agents for treatment of hyperlipidemia. Flaxseed and SDG may serve as therapeutic agents for hyperlipidemia treatment. To date, the effects of SDG have not been tested in patients with normocholesterolemia nor hypercholesterolemia. SDG and FLC may be very useful in elevating serum levels of HDL-C. Flaxseed and its constituents may serve as preventive measures against hypercholesterolemia and familial hypercholesterolemia. Flaxseed reduced the serum levels of TC, LDL-C, and TG in a dose-dependent manner in rats, hypercholesterolemic rabbits, and ovariectomized golden Syrian hamsters. CDC-flaxseed markedly reduced serum TC, LDL-C, TC/HDL-C, and LDL-C/HDL-C in rabbits. Flaxseed reduced the serum levels of TC, LDL-C, and TG in hypercholesterolemic subjects but had no effects in normocholesterolemic subjects. Flaxseed oil has variable and small effects in animals but reduces the serum levels of TC, LDL-C, HDL-C, TG, Apo-A1, and Apo-B in humans. Pure SDG markedly and significantly reduces the serum levels of TC, TG, LDL-C, TC/HDL-C, and LDL-C/HDL-C in hypercholesterolemic rabbits, rats, and mice. FLC reduced the serum levels of TC, TG, and LDL-C, and increased the levels of HDL-C, in hypercholesterolemic rabbits. It did not, however, affect serum lipids in normocholesterolemic rabbits, with the exception of increasing HDL-C. The effects of FLC on serum lipids were very variable and small in subjects with or without hypercholesterolemia. Flaxseed fiber had mild effects on serum lipids in humans. In conclusion, flaxseed and pure SDG have significant lipid-lowering effects in animals and humans, while other components of flaxseed have variable and small effects.