Dietary fat and risk of breast and colon cancer

Lignans and human health

This review focuses on the possible role in human health of the consumption of lignan-rich foods. Most of the plant lignans in human foods are converted by the intestinal microflora in the upper part of the large bowel to enterolactone and enterodiol, called mammalian or enterolignans. The protective role of these compounds, particularly in chronic Western diseases, is discussed. Evidence suggests that fiber- and lignan-rich whole-grain cereals, beans, berries, nuts, and various seeds are the main protective foods. Many factors, in addition to diet, such as intestinal microflora, smoking, antibiotics, and obesity affect circulating lignan levels in the body. Lignan-rich diets may be beneficial, particularly if consumed for life. Experimental evidence in animals has shown clear anticarcinogenic effects of flaxseed or pure lignans in many types of cancer. Many epidemiological results are controversial, partly because the determinants of plasma enterolactone are very different in different countries. The source of the lignans seems to play a role because other factors in the food obviously participate in the protective effects. The results are promising, but much work is still needed in this area of medicine.

Implementation of a 4-y, high-fiber, high-fruit-and-vegetable, low-fat dietary intervention: results of dietary changes in the Polyp Prevention Trial

BACKGROUND

The Polyp Prevention Trial (PPT) was a multicenter randomized clinical trial designed to determine the effects of a high-fiber (4.30 g/MJ), high-fruit-and-vegetable (0.84 servings/MJ), low-fat (20% of energy from fat) diet on the recurrence of adenomatous polyps in the large bowel.

OBJECTIVE

Our goal was to determine whether the PPT intervention plan could effect change in 3 dietary goals and to examine the intervention's effect on the intake of other food groups and nutrients.

DESIGN

Participants with large-bowel adenomatous polyps diagnosed in the past 6 mo were randomly assigned to either the intervention (n = 1037) or the control (n = 1042) group and remained in the trial for 4 y. Three dietary assessment instruments were used to measure dietary change: food-frequency questionnaires (in 100% of the sample), 4-d food records (in a 20% random cohort), and 24-h dietary recalls (in a 10% random sample).

RESULTS

Intervention participants made and sustained significant changes in all PPT goals as measured by the dietary assessment instruments; the control participants' intakes remained essentially the same throughout the trial. The absolute differences between the intervention and control groups over the 4-y period were 9.7% of energy from fat (95% CI: 9.0%, 10.3%), 1.65 g dietary fiber/MJ (95% CI: 1.53, 1.74), and 0.27 servings of fruit and vegetables/MJ (95% CI: 0.25, 0.29). Intervention participants also reported significant changes in the intake of other nutrients and food groups. The intervention group also had significantly higher serum carotenoid concentrations and lower body weights than did the control group.

CONCLUSION

Motivated, free-living individuals, given appropriate support, can make and sustain major dietary changes over a 4-y period.

Moderate to mild malnutrition in African children of 10-12 years: roles of dietary and non-dietary factors

In all Third World populations, among preschool and schoolchildren, low weight- and height-for-age, i.e. below the 5th centile of US NCHS reference standards, are common, affecting 10-50%. Orthodoxly, shortfalls are attributed largely to insufficiency of food. In an attempt to throw more light on the situation regarding African schoolchildren, studies have been made on series of pupils, aged 10-12 years, at three rural schools in North West Province, South Africa. Of 396 pupils, 126 (31.8%) were below, and 270 (68.2%) above the 5th centile. Enquiries were made on each pupil's diet and meal pattern, their class position and games aptitude, and, regarding home characteristics, their family size, Parent(s) working, and the latter's interest in education. With minor exceptions, no significant differences in odds ratios were found between respective groups below and above the 5th centile. Evidently, there are multiple influencing factors. Hence, among children of school-age, there must be caution against overblaming undernutrition, and of overrating the health disadvantages from mild to moderate malnutrition. For definition clarification, long-term observations are necessary.

Diet in the prevention of cancer: what are the chances of avoidance?

In most western populations, cancer causes about a fifth of all deaths, and in developing populations, 5-15%, with the likelihood of further rises. Diet is considered responsible for about a third of cases of cancer and smoking another third. Dietarily, for cancer avoidance, recommendations made include eat less, eat much less fat especially saturated fat, and eat more plant foods, i.e. cereals, but very particularly vegetables and fruit. However, only high consumptions of the latter are consistently associated with a lower risk of cancers, notably of the digestive and respiratory tracts. For each change urged, meaningful compliance will be very difficult, due largely to conservativeness as well as to the higher cost of a 'prudent' diet. Notwithstanding, urges to make dietary changes, particularly relating to plant foods, must be continued, especially with regard to persons familially susceptible and, additionally, with the recognition that the measures recommended also serve to lessen susceptibility to cardiovascular diseases. Compliance, even by a small proportion, could result in large numbers benefiting due to the universality of the burden from cancer.

Is breast cancer avoidable? Could dietary changes help?

In the US, the life time odds of developing breast cancer has reached one in eight, with an incidence rate of 85 per 100,000 world population. The rate is half or less in women in some Mediterranean countries. At the extreme are rural African women whose rate is approximately 5-10 per 100,000. In African, compared with White women, protective factors include (1) reproductive behaviour, namely, slower growth before and after puberty, later age at menarche, high teenage pregnancy, high parity and long periods of lactation and amenorrhoea and (2) a diet of relatively low energy intake and of low-fat and high-fibre contents. In the Mediterranean setting, major dietary protective factors include a relatively low intake of saturated fat and high intakes of monounsaturated fat and of vegetables and fruit. Among White women, a reversion to protective reproductive behaviour is out of the question. Only in respect of diet, could significant avoiding action be taken. Adoption of an African type diet is wholly impracticable. Moreover, even conformation to a former Mediterranean diet, which is already changing, would be difficult, requiring reorientation of fat composition and large rises in intakes of vegetable and fruit. However, with resolution, were such changes made, at least by the very vulnerable, they would help, additionally, to protect against other diet-related cancers, especially colon cancer and against coronary heart disease.

Nutrition evaluation of dietary fat substitutes

In response to US dietary guidelines and health goals, the food industry has introduced a variety of innovative food products designed to help the American public lower its fat intake. The physical characteristics and safety considerations of these products are reviewed, as well as their association with chronic disease prevention.

Lack of promoting effects of alpha-linolenic, linoleic or palmitic acid on urinary bladder carcinogenesis in rats

Potential promoting effects of alpha-linolenic, linoleic and palmitic acids were investigated in a two-stage urinary bladder carcinogenesis model. In experiment 1, male F344 rats were given 0.05% N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) in their drinking water for 4 weeks and then basal diet containing 10% alpha-linolenic, 10% linoleic or 10% palmitic acid along with 0.2% butylated hydroxyanisole (BHA) as an antioxidant for 24 weeks. The development of tumors in the urinary bladder was not increased by treatment with any of the fatty acids. In experiment 2, male F344 rats were given 10% alpha-linolenic, 10% linoleic or 10% palmitic acid along with 0.2% BHA in their diet for 8 weeks without prior BBN treatment. The administration of fatty acids was not associated with any increase in the 5-bromo-2'-deoxyuridine labeling index of the urinary bladder epithelium. Serum and/or urine fatty acid levels increased in the cases of alpha-linolenic and linoleic acid treatments, but not with palmitic acid. Under the present experimental conditions neither the two polyunsaturated nor the one saturated fatty acid exerted any promoting effect on urinary bladder carcinogenesis.

Dietary advice: from folklore to present beliefs

Many countries have folklore beliefs about the use of foodstuffs to remedy ill health and to promote long life. Many of the beliefs and practices of the ancients and, more recently, "mothers's views of health" have a basic soundness and are in harmony with present-day advice on the attainment of a prudent diet and life-style.