Biomedical subjects
Publications and source records attributed to M B Katan.
It was recently suggested that the intake of salicylates from food may have contributed to the decline in cardiovascular mortality in the United States. However, a normal mixed diet provides far too few salicylates to have an effect on disease risk.
Dietary fiber came into its own more than two decades ago. Unlike other dietary fads, however, research has continued to bear out the fact that fiber plays an important role in health promotion.
Coffee beans and some types of coffee brew-not the regular types of coffee prepared with a paper filter or with soluble coffee granules-contain the diterpenes cafestol and kahweol. Cafestol and kahweol raise the serum concentration of cholesterol and triglycerides in humans, and they also appear mildly to affect the integrity of liver cells. Both effects are transient after withdrawal of the diterpenes, and it is as yet unsure whether these effects are associated. Patients at increased risk of heart disease who drink large amounts of coffee should be advised to select brews low in diterpenes.
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OBJECTIVES: Ginger (Zingiber Officinale Roscoe) has been claimed to exert an anti-thrombotic effect in humans as ginger extracts inhibit cyclo-oxygenase activity of platelets in vitro. Effects of ginger consumption on ex vivo platelet function, however, are contradictory. We therefore investigated whether daily consumption of raw or cooked ginger decreases platelet cyclo-oxygenase activity as assessed by ex vivo maximally stimulated platelet thromboxane B2 production. DESIGN: We carried out a randomized placebo-controlled cross-over study of 3 x 2 weeks. SUBJECTS: Eighteen healthy volunteers aged 22 +/- 3 y (mean +/- s.d.) participated in the study; there were no dropouts. INTERVENTIONS: Subjects consumed 15 g of raw ginger root, 40 g of cooked stem ginger, or placebo daily for two weeks. We took fasted venous blood samples and measured thromboxane B2 production in maximally stimulated platelet-rich plasma at days 12 and 14 of each treatment period. RESULTS: Mean decrease in thromboxane production relative to placebo was 1 +/- 9% for ginger root, and -1 +/- 8% for stem ginger, with no effect of treatment order (P = 0.984). CONCLUSIONS: We cannot confirm the putative anti-thrombotic activity of ginger in humans.
OBJECTIVE: Intake of alpha-linolenic acid may have a beneficial effect on coronary heart disease, but little information is available on the intake and sources of alpha-linolenic acid (C18:3 n-3) in populations. We therefore assessed intake and sources of alpha-linolenic acid in Dutch elderly men. DESIGN AND SUBJECTS: Dietary histories were obtained from participants of the Zutphen Elderly Study, a Dutch cohort study. Food consumption data were available from 876 men in 1985 and from 541 of the same men in 1990. Daily intakes of alpha-linolenic acid were assessed using a food table developed for this purpose. Alpha-linolenic acid content of edible fats, seafood and some commonly eaten dishes were mainly derived from chemical analyses of Dutch foods, and other values were obtained from published food tables. RESULTS: Alpha-linolenic acid provided 0.5 +/- 0.1% of energy intake (mean +/- s.d.) or 1.30 +/- 0.46 g/day in 1985, and 1.21 +/- 0.52 g/day in 1990. The Pearson correlation coefficient for intake of alpha-linolenic acid in 1985 and 1990 was 0.34. Margarines were the main source (25.4%), followed by meat and the fats used in cooking meat (10.8%), bread (9.8%) and vegetables (7.8%). CONCLUSIONS: An increase in intake of alpha-linolenic acid, is most easily realized by the use of unhydrogenated oils rich in alpha-linolenic acid such as rapeseed and soybean oil, and of margarines and other fats containing such oils.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
The average diet may provide some 8-10 g/day of unsaturated fatty acids with a trans double bond. Previous studies showed that dietary trans fatty acids may simultaneously raise low-density lipoprotein (LDL) cholesterol and reduce high-density lipoprotein (HDL) cholesterol. Human plasma contains a protein (CETP) which transfers cholesterylesters from HDL to lipoproteins of lower density. We hypothesized that CETP could play a role in the effect of trans fatty acids on lipoproteins and measured the activity levels of CETP in serum samples from a 9-week study in which 55 volunteers were fed three controlled diets with different fatty acid profiles. Mean activity was 114 (% of reference serum) after consumption of a high trans fatty acid diet, as opposed to 96 after linoleic acid and 97 after stearic acid (P < 0.02). We conclude that the increased activity of CETP may contribute to the rise in LDL cholesterol and the fall in HDL cholesterol seen on diets with high contents of trans fatty acids.
The diterpenes cafestol and kahweol are present in unfiltered coffee in oil droplets and floating fines. They elevate serum cholesterol and alanine aminotransferase (ALT). We measured fines in coffee brews, and examined diterpene availability from spent grounds in healthy volunteers. Turkish or Scandinavian boiled coffee contained 2-5 g fines/L and French press coffee contained 1.5 g fines/L. An intake of 8 g fine grounds/d for 3 wk increased cholesterol by 0.65 mmol/L (95% CI 0.41-0.89 mmol/L) and ALT by 18 U/L (95% CI 4-32 U/L) relative to control subjects (n = 7/group). In a crossover study (n = 15), mean serum cholesterol was 4.9 mmol/L after consumption of both fine and coarse grounds for 10 d (P = 0.43). Serum ALT activities were 29 U/L on fine and 21 U/L on coarse grounds (P = 0.02). Floating fines could contribute substantially to the hyperlipidemic and ALT-elevating effect of unfiltered coffee. Diterpene measurements in coffee brews should include the contribution of fines.
We examined the effect of the positional distribution of fatty acids within dietary triglycerides on serum lipoproteins. Sixty subjects consumed two diets of equal fatty acid composition for 3 wk each. In the palm oil diet 82% of palmitic acid was attached to the outer two carbon atoms of glycerol, and 18% to the middle carbon. In the diet rich in enzymatically modified palm oil these figures were 35% and 65%, respectively. On the modified-fat diet, average lipoprotein concentrations showed nonsignificant (P > 0.13) increases of 0.06 mmol/L for total, 0.03 mmol/L for HDL, and 0.04 mmol/L for LDL cholesterol compared with palm oil. The small increases in total and LDL cholesterol were statistically significant in the men (n = 23) but not in the women (n = 37). The ratio of HDL to LDL cholesterol and serum triglyceride concentrations were unchanged. Thus, a large difference in dietary fatty acid configuration had little effect on lipoprotein concentrations in humans.
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Variable amounts of olive oil rather than hard fats were used in classic Mediterranean diets. We review the effects of replacing hard fats with olive oils or starchy foods on blood lipoprotein concentrations. The saturated fatty acids lauric, myristic, and palmitic acids raise both low-density lipoprotein (LDL) and high-density lipoprotein (HDL) somewhat compared with oleic acid. If any fat is replaced by carbohydrates, fasting triglyceride values rise and HDL concentrations fall; effects on LDL depend on the type of fat that is being replaced. Trans isomers of oleic acid lower HDL and raise LDL and lipoprotein(a). The fatty acids in unhydrogenated fish oil potently lower triglycerides but may raise LDL somewhat. When body weight is forcibly kept constant, substitution of unsaturated oils such as olive oil for hard fats rich in saturated or trans fatty acids will produce a more favorable lipoprotein profile than replacement of fat by carbohydrates. However, high-oil diets might lead to obesity, which would undo their favorable effects.
Quercetin is a dietary antioxidant that prevents oxidation of low-density lipoproteins in vitro. Intake of quercetin was inversely associated with coronary heart disease mortality in elderly Dutch men. However, the extent of absorption of quercetin in humans is unclear. The aim of this study was to quantify absorption of various forms of quercetin. Nine healthy ileostomy subjects were studied, to avoid losses caused by colonic bacteria. They followed a quercetin-free diet for 12 d; on days 4, 8, and 12 they received a supplement of fried onions at breakfast (rich in quercetin glucosides) equivalent to 89 mg aglycone, pure quercetin rutinoside (the major quercetin compound in tea) equivalent to 100 mg aglycone, or 100 mg pure quercetin aglycone, in random order. Subsequently, participants collected ileostomy effluent and urine for 13 h. In vitro incubations of quercetin or its glycosides with gastrointestinal fluids showed minimal degradation. Absorption of quercetin, defined as oral intake minus ileostomy excretion and corrected for 14% degradation within the ileostomy bag, was 52 +/- 15% for quercetin glucosides from onions, 17 +/- 15% for quercetin rutinoside, and 24 +/- 9% for quercetin aglycone. Mean excretion of quercetin or its conjugates in urine was 0.5% of the amount absorbed; quercetin excretion in urine was negatively correlated with excretion in ileostomy effluent (r = -0.78, n = 27). We conclude that humans absorb appreciable amounts of quercetin and that absorption is enhanced by conjugation with glucose.
Oil from coffee beans contains the diterpenes cafestol and kahweol, which greatly elevate cholesterol in humans. Consumption of 0.03 g coffee oil (0.86 mg cafestol and 1.04 mg kahweol)/kg body wt raised serum cholesterol by 1.27 mmol/L in volunteers. We fed coffee oil from this same batch to cebus and rhesus monkeys. Two groups of eight cebus monkeys were fed a purified diet containing 0.5% coffee oil or placebo oil (sunflower plus palm oil, 3:2, wt/wt) for 2 x seven and a half weeks in a crossover design. The daily intake of the coffee oil was 0.18 g (5.13 mg cafestol and 6.21 mg kahweol)/kg body wt, or sixfold that in the human study. Coffee oil did not affect plasma cholesterol or triglyceride concentrations compared with the placebo oil. Two groups of three rhesus monkeys were fed a commercial diet containing either 0.5% coffee oil or 0.5% placebo oil for 2 x 6 wk in a crossover design. The daily intake of coffee oil was 0.20 g (5.70 mg cafestol and 6.90 mg kahweol)/kg body wt. Again, there was no effect of coffee oil on plasma cholesterol or triglyceride concentrations. Contrary to the findings in human studies, coffee oil had no impact on plasma alanine aminotransferase activity in nonhuman primates. The cholesterol-raising effect of diterpenes from coffee oil, present in boiled coffee, seems to be specific for human primates.
OBJECTIVES: The cholesterol-raising effect of boiled coffee is caused by diterpenes from coffee oil. In order to identify the diterpene responsible, we analysed the diterpene composition of oils from Arabica (Coffea arabica) and Robusta (Coffea canephora robusta) beans and their effects on serum lipids and thyroid function. DESIGN, SUBJECTS, AND INTERVENTION: During the first 3-week period of a randomized, cross-over trial, 11 healthy, normolipaemic volunteers received per day either 2 g of coffee oil (n = 5) or placebo oil (n = 6). After a 2-week wash-out, the reverse treatments were applied for another 3 weeks. Six subjects received Arabica oil, supplying 72 mg day-1 cafestol and 53 mg day-1 kahweol, and five received Robusta oil, which provided 40 mg of cafestol, 19 mg of 16-O-methyl-cafestol, and 2 mg of kahweol per day. Background diets were constant. RESULTS: The average serum cholesterol levels rose by 0.65 mmol L-1 (13%) on Arabica oil (P < 0.025; 95% CI, 0.21-1.09 mmol L-1) and by 0.53 mmol L-1 (13%) on Robusta oil (NS; 95% CI -0.36-1.42 mmol L-1). The triglycerides levels rose by 0.54 mmol L-1 (71%) on Arabica (P < 0.005; 95% CI, 0.22-0.76 mmol L-1) and 0.49 mmol L-1 (61%) on Robusta oil (P < 0.005; 95% CI, 0.30-0.68 mmol L-1). None of the effects on serum lipids or lipoprotein cholesterol levels was significantly different between Arabica and Robusta oil. Concentrations of serum total and free thyroxine (T4), triiodothyronine (T3), and thyroid-stimulating hormone (TSH) were largely unaffected. CONCLUSIONS: Both Arabica and Robusta oil elevated serum lipid levels; therefore, cafestol must be involved and kahweol cannot be the sole cholesterol-raising diterpene. The mode of action of coffee diterpenes does not involve induction of hypothyroidism.