n-3 fatty acids in human fat tissue aspirates are stable for up to 6 y.

OBJECTIVES: The content of n-3 (omega-3) polyunsaturated fatty acids in fat tissue is a valid indicator of their long-term consumption. We studied the stability of n-3 fatty acids in human subcutaneous fat microbiopsies after 6 and 11 y of storage. DESIGN: Microbiopsies were taken from a lump of human adipose tissue and stored at +20 and -80 degrees C. SETTING: Laboratory study. RESULTS: After 5.6 y at -80 degrees C the proportion of six out of seven highly polyunsaturated fatty acids varied between 91 and 102% (mean 97%) of their baseline values. Storage at +20 degrees C yielded recoveries between 82 and 105%. After 11 y at -80 degrees C the proportions in the original lump of tissue ranged from 88 to 101% (mean 94%). CONCLUSION: n-3 fatty acids in stored fat tissue aspirates are stable for 6-11 y, and are suitable markers of baseline diet in long-term epidemiological studies. SPONSORSHIP: Wageningen Centre for Food Sciences.

Effect of transgalactooligosaccharides on the composition of the human intestinal microflora and on putative risk markers for colon cancer.

BACKGROUND: Nondigestible oligosaccharides have been claimed to benefit the health of the colon by selectively stimulating the growth of bifidobacteria and by decreasing the toxicity of the colon contents. OBJECTIVE: We compared the effect of 2 doses of transgalactooligosaccharides and a placebo on the composition and activity of the intestinal microflora in 18 women and 22 men. DESIGN: Strictly controlled experimental diets were supplied to 3 intervention groups in a parallel design. The study was divided into 2 consecutive 3-wk periods during which each participant consumed a run-in diet followed by an intervention diet that differed only in the amount of transgalactooligosaccharides: 0 (placebo), 7.5, and 15 g/d. Breath samples and fecal samples were collected at the end of both the run-in and intervention periods. RESULTS: Apparent fermentability of transgalactooligosaccharides was 100%. The highest dose of transgalactooligosaccharides significantly increased the concentration of breath hydrogen by 130% (P < 0.01) and the nitrogen density of the feces by 8.5% (P < 0.05). The number of bifidobacteria increased after both placebo and transgalactooligosaccharides ingestion, but the differences between these increases were not significantly different. Transgalactooligosaccharides did not significantly affect bowel habits; stool composition; the concentration of short-chain fatty acids or bile acids in fecal water; the concentration of ammonia, indoles, or skatoles in feces; fecal pH; or the composition of the intestinal microflora. CONCLUSION: We conclude that transgalactooligosaccharides are completely fermented in the human colon, but do not beneficially change the composition of the intestinal microflora, the amount of protein fermentation products in feces, or the profile of bile acids in fecal water.

Effects of the flavonoids quercetin and apigenin on hemostasis in healthy volunteers: results from an in vitro and a dietary supplement study.

Intake of dietary flavonols and flavones was inversely associated with risk for cardiovascular disease in several epidemiologic studies. This may have been due to effects on hemostasis because flavonoids have been reported to inhibit platelet aggregation in vitro. We indeed found that 2500 micromol/L of the flavonol quercetin and the flavone apigenin significantly inhibited collagen- and ADP-induced aggregation in platelet-rich plasma and washed platelets by approximately 80-97%. However, lower concentrations, such as might occur in vivo, had no effect. To test this in vivo we fed 18 healthy volunteers 220 g onions/d providing 114 mg quercetin/d, 5 g dried parsley/d providing 84 mg apigenin/d, or a placebo for 7 d each in a randomized crossover experiment with each treatment period lasting 2 wk. Onion consumption raised mean plasma quercetin concentrations to 1.5 micromol/L; plasma apigenin could not be measured. No significant effects of onions or parsley were found on platelet aggregation, thromboxane B2 production, factor VII, or other hemostatic variables. We conclude that the antiaggregatory effects of flavonoids seen in vitro are due to concentrations that cannot be attained in vivo. Effects of dietary flavonols and flavones on cardiovascular risk are possibly not mediated by hemostatic variables.

Stability of n-3 fatty acids in human fat tissue aspirates during storage.

The content of n-3 (omega 3) polyunsaturated fatty acids in fat tissue is an indicator of their long-term consumption. Therefore, a method for determining n-3 fatty acids in human fat tissue microbiopsies was validated and the stability of n-3 fatty acids in biopsies was checked under various conditions of storage. Methyl esters were prepared from 25 to 35 mg adipose tissue and separated by capillary gas chromatography. Recovery of added eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) was 98-105%. The change after storage of fat samples at room temperature or at 4, -20, or -80 degrees C for 3 mo averaged +3.3% for EPA and +2.1% for DHA, with no effect of temperature. Storage at +20 or -80 degrees C for 7 mo yielded no perceptible change in EPA, DHA, or five other n-3 polyunsaturated fatty acids. EPA and DHA concentrations in adipose tissue aspirates are remarkably stable and deserve attention as biomarkers in epidemiological studies.

Effect of a lipid-rich fraction from boiled coffee on serum cholesterol.

Scandinavian-style boiled coffee, which raises serum cholesterol, was found to contain more lipid material than drip filter coffee, which does not. Ten volunteers consumed a lipid-enriched fraction from boiled coffee for six weeks: the supplement provided 77 g of water, 1.3 g of lipid, and 1.6 g of other solids per day. Serum cholesterol rose in every subject; the mean rise was 0.74 mmol/l after three weeks (range -0.09 to 1.48 mmol/l) and 1.06 SD 0.37 mmol/l or 23% after six weeks (range 0.48 to 1.52 mmol/l). The increase was mainly due to low-density-lipoprotein cholesterol, which rose by 29%, but very-low-density lipoprotein cholesterol was also raised, as evidenced by a 55% rise in triglycerides. High-density-lipoprotein cholesterol was unchanged. After supplementation had ended, lipid levels returned to baseline. Boiled coffee thus contains a lipid that powerfully raises serum cholesterol.