Lipid Factor III transFatty Acids and Other Unidentified Factors in Oils

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Nutritional values of vegetable oils have been evaluated primarily based on their FA composition. However, we began to realize that factors other than FAs (TG) influence animal physiology significantly at doses comparable to human intakes. Some kinds of vegetable oils and partially hydrogenated oils shortened the survival of stroke-prone SHR (SHRSP) rats unusually as compared with others. The free FA fractions derived from canola oil and hydrogenated-soybean oil exhibited no or significantly reduced activities, indicating the presence of minor components other than FAs (TG) [Huang et al., 1997; Rat-nayake et al., 2000].

On the other hand, trans-FAs in hydrogenated oils have been regarded as a risk factor of CHD (related to elevated cholesterol levels), and movements to exclude them from our food environment are rapidly in progress, although epidemiological evidence is not clear enough as summarized in the earlier part of this section. Here, we take into account the possible involvement of factors other than phytosterols and trans-FAs that influence animal physiology. Those vegetable oils with antinutritional factors cause kidney lesion, decrease mega-karyocyte counts in the bone marrow, reduce blood platelet counts and shorten survival in SHRSP rats [Okuyama et al., 1996; Ohara et al., 2005]. De creased platelet number by canola oil-containing milk replacer is detected in piglets as well [Innis et al., 1999]. Their potential implication in human nutrition is briefly summarized in the latter part of this section.

Fig. 83

Intake of FAs and Risk of CHD in a cohort of Finnish men - Data for trans-FA

Data taken from Pietinen et al. [1997].

p = 0.044

H

p = 0.145

CZ

_

p = 0.004

p = 0.032

p = 0.770

[

p = 0.118

p = 0.767

L

EPA/DHA Chol

0 0.5 1.0 1.5 2.0 0 Multivariate relative risk (RR)

EPA/DHA

0.5 1.0 1.5 2.0 RR adjusted also to other factors

Male smokers (n = 21,930) aged 50-69 years were followed for 6.1 years. Major coronary events (n = 1,399) and coronary deaths (n = 635) were noted. After controlling for age, supplement group, several coronary risk factors, total energy and fiber intake, the authors observed a significant positive association between trans-FA intake or LA intake and the risk of coronary deaths. In the multivariate model, the intakes of trans-FA and «3 FAs from fish were directly related to the risk of coronary deaths. There was no association between intakes of saturated or cis-monounsaturated FAs, LA or ALA, or dietary cholesterol and the risk of coronary deaths. All the associations were similar but somewhat weaker for all major coronary events.

Concluding remarks: The selective nature of this cohort (middle-aged, smoking men eating a diet high in fat) warrants relatively cautious extrapolation to other populations.

Our comments: The intake of LA was positively associated with the risk of coronary events, but the association became non-significant when adjusted to other FAs. The intake of trans-FAs was highly positively associated with risk in a multivariate analysis (p = 0.004) but no data were given for its association after adjustment to other FAs. When adjusted to other FAs, ALA («3) intake was inversely and fish «3 FA intake was positively associated with the risk of coronary events. The authors discussed the problems of mercury pollution of local freshwater fish in this area.

Fig. 84

Dietary intake of trans-FAs and systemic inflammation in women - From Nurses' Health Study I and II

Data taken from Mozaffarian et al. [2004].

sTNF-RI (p = 0.002) sTNF-R2 (p < 0.001) IL-6 (p = 0.40) CRP (p = 0.40)

sTNF-RI (p = 0.002) sTNF-R2 (p < 0.001) IL-6 (p = 0.40) CRP (p = 0.40)

Quintile of BBEInBFA intake

In 823 generally healthy women in the Nurses' Health Study I and II, concentrations of soluble tumor necrosis factor-a receptors 1 and 2 (sTNF-R1, sTNF-R2), interleukin-6 (IL-6), and C-reactive protein (CRP) were measured. Usual dietary intakes assessed from 2 semiquantitative food-frequency questionnaires were averaged for each subject.

Results: In age-adjusted analyses, trans-FA intake was positively associated with sTNF-R1 and sTNF-R2 (p for trend < 0.001 for each): sTNF-R1 and sTNF-R2 concentrations were 10% (+108 pg/ml) and 12% (+258 pg/ml) higher, respectively, in the highest intake quintile than in the lowest. These associations were not appreciably altered by adjustment for body mass index, smoking, physical activity, aspirin and NSAID use, alcohol consumption, and intakes of saturated fat, protein, «6 and «3 FAs, fiber, and total energy. Adjustment for serum lipid concentrations partly attenuated these associations, which suggests that they may be partly mediated by effects of trans-FA on serum lipids. trans-FA intake was not associated with IL-6 or CRP concentrations overall but was positively associated with IL-6 and CRP in women with higher body mass index (p for interaction = 0.03 for each).

Conclusions: trans-FA intake is positively associated with markers of systemic inflammation in women. Further investigation of the influences of trans-FAs on inflammation and of implications for coronary disease, diabetes, and other conditions is warranted.

Our comment: Despite the deduced conclusion and high degree of statistical significance (very low p values), the data shown in this figure are not convincing enough; relative marker concentrations (the highest quintile to the lowest quintile) of 1.09 (sTNF-R1) and 1.12 (sTNF-R2) were significant (p < 0.002) but those of 0.87 (IL-6) and 0.82 (CRP) were not (p = 0.40).

Fig. 85

Relative risk of total myocardial infarction according to quintiles of dietary S, cholesterol, LA, ALA and Keys' score - Data for trans-FAs

Data taken from Health Professionals Follow-Up Study in the USA [Ascherio et al., 1996].

Average intake of BBEInBfatty acids (g/day) (quintile)

Health professionals (45-75 years old, n = 43,757) were followed for 6 years from 1986. Figures are relative risks. Details are described in the legend to table 3.

Conclusion: These data do not confirm the strong association between intake of saturated fat and risk of CHD seen in international comparisons. However, they do fit the hypothesis that saturatedfat and cholesterol intakes affect the risk of CHD as predicted by their effects on TC concentration. They also support a specific preventive effect of ALA intake.

Our comments: Among health professionals in the USA, trans-FA intake was apparently positively associated with MI. However, the association became weaker after multivariate analysis, and insignificant when adjusted further to dietary fiber intake.

Fig. 86

Dietary fat intake and risk of CHD in women - trans-FA and LA

Data taken from 20 Years of Follow-up of the Nurses' Health Study [Oh et al., 2005].

Quintile

Quintile

The association of dietary fat and specific types of fat with risk of CHD was examined among 78,778 women initially free of CVD and diabetes in 1980. The association between intakes of PUFAs and trans-fat with CHD risk was most evident among women younger than age 65 years. Multivariate relative risk was adjusted for age, body mass index, smoking, alcohol intake, parental history of MI, history of hypertension, menopausal status, hormone use, multivitamin use, vitamin E supplement use, physical activity, and energy, protein and cholesterol intake, and intakes of saturated (Sat), monounsaturated (Mono), polyunsaturated (PUFA), trans-fat (Trans); ALA; marine «3 FAs; cereal fiber and fruits and vegetables.

Conclusion: Findings continue to support an inverse relation between polyunsaturated fat intake and CHD risk, particularly among younger women. In addition, trans-fat intake was associated with increased risk of CHD, particularly for younger women.

Our comments: The relative risk of trans-fat was 1.33 (p = 0.01) in this study compared with 1.21 (p = 0.20) in the Health Professionals Study (fig. 87) . Highly positive association between trans-FA and CHD has been noted in Costa Rican adults for whom relative risks were 2.94 (all trans-FAs) and 5.05 (18:2 trans-FAs) [Baylin et al., 2003], but not in the industrialized countries. We point out the problems of statistical treatments; the choice of factors for adjustments may influence the outcome greatly.

As to the effects of dietary LA on CHD, the relative risk of PUFA (mostly LA) for the highest vs. the lowest quintile was 0.75 (p = 0.004) in the Nurses' Health Study while it was 1.04 (p = 0.89) in the Health Professional Study (table 3; fig. 87), which is far from the value to account for severalfold difference in CHD mortalities among different populations (e.g. fig. 12, Seven Countries Study). Although a protective effect of LA in CHD mortality has been continuously shown by this group, it is difficult to accept that increasing the intake of LA is beneficial for the prevention of atherosclerosis. The LA may be a surrogate marker of vegetable oil containing anti-thrombotic (apoplexy-accelerating) factors leading to decreased platelet number. One of such factors in hydrogenated oils may be dihydro-vitamin K1 and related compounds (fig. 88).

Relative risk of total myocardial infarction according to quintiles of dietary S, LA and ALA

Data taken from Health Professionals Follow-Up Study in the USA [Ascherio et al., 1996].

Quintile

A part of table 3 (multivariate analysis adjusted for dietary fiber) was shown here to compare with figure 86. See details in table 3.

Our comments: Two epidemiological studies performed in the USA (fig. 86, 87) differ in gender proportion of the selected subjects, but adjusted relative risks shown in these figures are relatively similar. However, the conclusions derived from these two studies are quite different because of the difference in p values. One factor to be considered is a possible difference in the degrees of health consciousness; nurses may have paid special attention to energy balance, physical exercise, choice of fats and oils and other potential protective factors compared with health professionals, which brought about a small difference in the outcome. An important fatty acid, ALA, is not included in figure 86. Regardless of the difference in conclusions from these studies, the impact of dietary LA and trans-FAs on CHD is very small, if any, compared with several-fold difference in CHD mortality among different populations (fig.12-15).

Nutritional values of fats and oils estimated by the survival rates of SHRSP rats

Data taken from Okuyama et al. [1996] and Ratnayake et al. [2000].

Fats and oils that extend survival

Control oils

Fats and oils that shorten survival unusually

Perilla seed oil (ALA-rich) Soybean oil

Linseed oil (ALA-rich) Fish oil (DHA-rich) Butter Lard

Safflower oil (LA-rich) Sesame oil (LA-rich)

Canola

Rapeseed oil (erucic acid-rich) Olive oil Corn oil

Safflower oil (oleic acid-rich) Sunflower oil (oleic acid-rich) Evening primrose oil Hydrogenated soybean oil Hydrogenated canola oil

Our explanations: Stroke-prone, spontaneously hypertensive (SHRSP) rat strain was selected from Wistar/Kyoto strain through SHR strain, and develops hypertension and dies of cerebral bleeding in high frequency when NaCl solution was loaded as drinking water. Diets supplemented with 10% fat or oil were fed to SHRSP rats from weaning, and survival rates were estimated. The data combined from those of different laboratories and from different sets of experiments are classified into three groups as summarized above. It should be noted that all fats and oils were not estimated under the same conditions; hence this grouping is a rough measure of their effects on survival of SHRSP rats. Difference in mean survival times of soybean oil group and canola oil group was more or less 40% in the absence of NaCl loading.

Our comments: As the free fatty acid fractions derived from canola oil and hydrogenated soybean oil exhibited no or significantly reduced activity, the difference in the observed survival times was not accounted for by the difference in their fatty acid and phytosterol compositions. Efforts to identify the presumed minor components are in progress, but one of the factors in hydrogenated oils is likely to be dihydro-vitamin K (fig. 88).

Fig. 88

An antinutritional factor in hydrogenated vegetable oils, and unidentified nutritional factors in some vegetable oils

Booth et al. [2001], Sato et al. [2003] and Okuyama et al. [1998].

(CH2CH2CHCH2)3H Hydrogénation

Phylloquinone (Vitamin K,)

(CH2CH2CHCH2)3H Hydrogénation

Phylloquinone (Vitamin K,)

Conversion in brain, pancreas, testis, salivary gland, bone, arterial wall, kidney, liver

Dihydro-Vitamin K,

Suppression of PIVKA-II synthesis in liver: K, > dihydro-K,

(protein induced by vitamin K absence)

Osteocalcin synthesis: No activity [Booth et al., 2001]

Suppression of PIVKA-II synthesis in liver: K, > dihydro-K,

(protein induced by vitamin K absence)

Osteocalcin synthesis: No activity [Booth et al., 2001]

(CH2CH = C-CH2)4H x (not converted to MK4) [Sato et al., 2003]

(CH2CH = C-CH2)4H x (not converted to MK4) [Sato et al., 2003]

Menaquinone (Vitamin K2 MK4)

Our explanations: Vitamin K1 with one double bond in the four isoprenoid side chains is metabolized in our body to vitamin K2 (menaquinone 4 with four double bonds in the side chain), which appears to have physiological activities different from that of vitamin K1. Vitamin K1 is rich in vegetable oils such as soybean oil, canola oil and olive oil, and dihydro-vitamin K 1 is produced by hydrogenation, which is partially active for the formation of mature coagulation factors, but is ineffective for the production of osteocalcin involved in bone metabolism [Booth et al., 2001]. Matrix Gla (carboxylated glu-

tamyl) proteins are also produced by vitamin K-dependent enzymes and play roles in cellular proliferation. Inhibition of vitamin K-dependent reactions could cause decreased thrombotic tendency, increased bleeding tendency and altered physiology of other unraveling functions of different vitamin Ks. In this sense, dihydro-vitamin K1 at adequate doses maybe beneficial for the prevention of thrombotic diseases but anti-nutritional at higher doses.

Another reason to consider these unidentified factors in vegetable oils, exists in the periods before changes in dietary fats and oils exert significant effects on CHD in clinical trials. In the Helsinki Businessmen Study (fig. 10; table 4), the difference in the CHD mortalities of the control and intervention groups became clearer and greater after 10 years whereas in the Lyon Diet Heart Study the choice of canola and olive oil in the intervention group exerted significant preventive effects within 2 years (fig. 67). In spite of the 70% risk reduction within a few years found in the Lyon Diet Heart Study it appears to be too early to ascribe the observed effects to reduced intake of LA and increased intake of ALA and oleic acid. These oils may contain additional factors other than TG (FAs) that are anti-thrombotic at adequate doses as canola oil and olive oil, each at 10% (w/w) of diet, are known to accelerate cerebral bleeding in stroke-prone SHR rats, and the former is known to decrease platelet counts in rats and piglets compared with soybean oil [Ohara et al., 2005; In-nis et al., 1999].

Although a significant portion of this section needs further confirmation, we must keep our eyes open for the potential involvement of dihydro-vitamin K1 and other unidentified factors in vegetable oils when dietary FAs-CHD relationship is interpreted.

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