Fatty acid profile of human saliva: a possible indicator of dietary fat intake

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Summary

Objective:

Since conventional food questionnaires are not precise in assessing the dietary fatty acids, the purpose of this study was to determine the relationship between the salivary fatty acid profile and the alimentary habits of two different groups in an attempt to develop a more reliable way to determine the lipidic intake.

Design:

Twenty adults of both sexes, with mixed (M) or vegetarian (V) diets were studied. Data about the fat intake were obtained by means of a Food Frequency Questionnaire (FFQ) and the presence of the main salivary fatty acids was determined by gas chromatography.

Results:

A greater salivary concentration of alpha-linolenic acid (18:3 n-3) (2.82) was found in V than in M subjects (1.65) (p = 0.001), whilst arachidonic acid (20:4 n-6) was lower in V (3.93) than in M (4.52) (p = 0.045). The same difference regarding arachidonic acid was observed in the dietary fatty acid intake, also showing a significant correlation between its dietary and salivary levels in vegetarian subjects.

Conclusions:

These results show that salivary arachidonic acid, relevant for their eicosanoid production related to the tumourigenesis process and cardiovascular diseases, is influenced by dietary fats.

Introduction

The main target in nutritional epidemiology is the study of diet as a quantifiable determinant in disease occurrence. Considering the difficulty in getting reliable intake estimations through questionnaires, it is important to find adequate biochemical markers of certain nutrients like lipids in accessible body fluids.1

Saliva is a complex secretion whose composition is modified by a variety of factors such as its flow rate, collection time, and diet.2 Saliva constitutes a biological fluid useful for diagnosis and prognosis of certain diseases and it can be obtained by simple, non-invasive methods, an advantage over plasma.3, 4

Lipids in saliva were first described by Doubleday in 1909,2 then followed up by many researchers. However, references regarding humans are mostly restricted to lipid classification and quantification.

The total reported lipids have ranged from 0.9 to 8 mg/100 ml in submandibular saliva2, 5, 6 and from 0.24 to 7.6 mg/100 ml in parotid saliva.2, 5, 6, 7 These discrepancies among different researchers may be due to methodological variations, both in the sample collection and in the analytical techniques.

It was not possible to find published reports referring to the effect of diet on human salivary lipid composition. An experimental study carried out on monkeys showed that the quality of dietary lipids modifies the fatty acid profile of parotid and submandibular saliva.8 Alam and Shi have reported that essential fatty acid deficiency (EFAD) produces changes in the fatty acid composition of the three major salivary glands of rats, that are also reflected in lipids of plasma and whole saliva.9

Taking into account the importance of fat intake to human health and the fact that conventional food questionnaires are not precise in assessing the dietary fatty acids, the purpose of this study was to determine the relationship between the salivary fatty acid profile and the alimentary habits in the hope of developing a more reliable way to know the lipid intake.

Section snippets

Subjects

Twenty adult volunteers of both sexes, apparently healthy and with different alimentary habits were studied. The subject characteristics are described in Table 1. They were assigned to two groups according to their diets, mixed (M) and ovo-lacto-vegetarians (V). “Mixed” referred to the usual diet in Argentina, whilst under the vegetarian denomination, strict ovo-lacto-vegetarian adventists were included.

The criteria for inclusion in the study were:

  • (a)

    Age: 18–50 years old.

  • (b)

    Healthy condition

Food frequency questionnaire (FFQ)

A qualitative-quantitative FFQ, already tested for reproducibility and validity, was used to estimate the food consumption including total energy, fat as well as saturated, mono-unsaturated and polyunsaturated fatty acid intake.10, 11 Two well-trained interviewers applied the FFQ that contained 104 items, their nutrient composition obtained from regional studies and tables, and gathered information on daily, weekly and monthly food intake, emphasizing those rich in fat: dairy products and their

Characteristics of diets

Ovo-lacto-vegetarians: vegetable oils constituted the main source of fats. Dairy products, with the exception of cheese, were usually fat-free. Subjects had a high intake of eggs (five a week on average), and also of whole grains like wheat, rice and oats. The bakery products were home-made, with the addition of seeds and whole grain flours. A great variety of vegetables and fruits (both fresh and dried) were consumed daily.

The mean fatty acid composition of food consumed by this group,

Discussion

The vegetarian group (ovo-lacto-vegetarian) was shown to have higher levels of salivary alpha-linolenic acid (18:3 n-3) than the mixed group. This finding could be related to the significant intake of food rich in n-3 essential fatty acids, like legumes (soy in particular), dried fruits (mainly peanuts), sunflower and corn oils.

Even though arachidonic acid (20:4 n-6) may be derived from the metabolism of linoleic acid (18:2 n-6), present in almost all vegetable oils, the lower levels of

Acknowledgements

We thank the following persons: Dr. Johanna Lampe, from the Fred Hutchinson Cancer Research Centre, for her valuable recommendations; Casilda Rupérez and Patricia Bertolotto for their help in the statistical analysis; Prof. Dr. Alicia Navarro, for facilitating the use of Nutrio v.2 software and atlas; Biol. María Lantieri and Nélida Ramonda for their technical assistance; Dr. Paul D. Hobson, native English speaker, for critical reading of the manuscript.

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