Nutrition priorities for people living with cancer.
* In Australia, the number of cancer survivors has been estimated at 267000 and is increasing. Cancer survivors are at increased risk of other health problems after a diagnosis of cancer, including heart disease, diabetes and functional impairment, which may benefit from lifestyle intervention.
* There is evidence that weight management and physical activity will positively impact on quality of life, cancer recurrence and overall survival for cancer survivors.
* Evidence that dietary intakes of vegetables, fruit or related nutrients affect recurrence or survival is somewhat supportive but not conclusive. Further randomised controlled trials are required.
* Although dietary supplement use is very common among cancer survivors, there are very few studies of the effect of nutritional supplements on cancer recurrence and survival.
* Lifestyle interventions have shown promise for cancer survivors, in particular women with breast cancer. Further research is required to determine the efficacy and effectiveness of specific lifestyle interventions designed for both breast cancer survivors and survivors of other forms of cancer.
The role of lifestyle factors, such as nutrition, physical activity and a healthy weight, in improving survival rates for people with cancer is an emerging area of research. According to the American Cancer Society's expert committee, who reviewed the evidence on the impact of lifestyle factors on quality of life, cancer recurrence and overall survival, convincing data exist that obesity is associated with breast cancer recurrence, and evidence on obesity and prognosis is also accumulating for other cancers. (1) They also concluded that physical activity may be important for reducing the risk of recurrence and extending survival for some cancer survivors. (1)
The number of people surviving with cancer is on the rise due to the ageing population, increasing incidence of some types of cancers, improvements in early detection and treatment. In Australia, the number of cancer survivors has been estimated at 267 000. (2)
Although survivorship should be celebrated, it is important to acknowledge that the impact of cancer is significant and associated with several long-term health and psychosocial sequelae. (3) Cancer survivors may be at increased risk of weight gain, functional impairment, fatigue, other chronic diseases (osteoporosis, cardiovascular disease, diabetes), secondary cancers and death from non-cancer causes, which may be amenable to lifestyle intervention. There is evidence that cancer patients die of non-cancer causes at a higher rate than persons in the general population; the non-cancer relative hazards ratio has been estimated at 1.37, with almost half of the deaths being from cardiovascular disease. (4-7) This paper defines cancer survival and discusses lifestyle factors in the cancer survival context.
DEFINITION OF A CANCER SURVIVOR
For the purposes of this paper, a cancer survivor is defined as someone who has completed their active treatment phase and who is not undergoing palliative care. The nutritional and physical activity needs of most people with cancer change during their different phases of cancer treatment and recovery from treatment. The individual survivor's overall health and social circumstances should be considered before making any lifestyle changes.
LIFESTYLE HABITS OF CANCER SURVIVORS
Earlier research suggested that the practice of healthful behaviours was higher among cancer survivors than in the population at large, but many of these studies relied on modest-sized convenience samples and were limited in terms of length of follow up and heterogeneity of cancer type. (3,8) More recent reports using much larger data sets and assessing behaviours in longer-term cancer survivors indicate that few lifestyle differences exist between individuals diagnosed with cancer and the general population--a population marked by inactivity, overweight and obesity, and suboptimal fruit and vegetable consumption. (9,10) This marks a paradigm shift and the realisation that although some cancer patients make healthful lifestyle changes after diagnosis, these changes may not generalise to all populations of cancer survivors or may be temporary.
Therefore, some cancer survivors may experience the 'teachable moment' and change their lifestyle behaviours, but may slip back into unhealthy lifestyle practices over time and resume the very behaviours (e.g. smoking, being sedentary and overweight) that initially placed that them at increased risk. (3)
There have been some smaller randomised controlled trials (RCTs) examining lifestyle interventions for improving survival from prostate cancer. In a recently published RCT, men with early-stage prostate cancer who were undergoing watchful waiting, were randomised onto a strict vegan diet that contained only 10% of energy from fat, supplemented with soy, fish oil, selenium, and vitamins E and C. (11) The intervention also included regular exercise (30 min of walking 6 days a week), doing yoga or some other type of meditation, and participating in support groups. After one year, men in the diet and exercise intervention had decreased their prostate-specific antigen (PSA) levels by 4%, while those in the control group had increased PSA levels by 6%, which was just statistically significant. The study concluded that intensive lifestyle changes may affect the progression of early, low-grade prostate cancer in men. Further studies and longer-term follow up are required. (11)
Being overweight or obese has been associated with an increased risk for dying of cancer. (12) A large cohort study in the USA estimated that the current patterns of overweight and obesity could account for 14% of cancer deaths in men and 20% in women. (12)
Most of the existing literature for cancer survival outcomes is focused on breast cancer survivors.
Increased body mass index or body weight has been found to be a significant risk factor for breast cancer recurrence and decreased survival. (13) Studies have shown an up to five-times increased risk of death (30-540%) in heavier women with breast cancer compared with women in the healthy-weight range. (13) In 2005, results from the Nurses Health Study showed that large weight gains after breast cancer diagnosis were associated with a 64% greater risk of recurrence, compared with those women who maintained their weight. (14) Smaller weight gains were associated with smaller increases in risk. (14)
Being overweight or obese has also been associated with recurrence of colorectal cancer. (15,16)
Results from the Women's Intervention Nutrition Study (WINS) study, a RCT involving 2400 women (aged 48-79 years) with early-stage breast cancer, have further highlighted the importance of weight management for cancer survivors. In this RCT, the intervention group received group nutrition counselling to decrease their fat intake. After five years of follow up, the dietary fat intake of the intervention group was significantly lower (P < 0.001), corresponding with a significantly lower (P = 0.005) mean body weight in intervention participants. (17) The risk of recurrence was decreased by 24% in the intervention group compared with the control group, which was a statistically significant result (P = 0.034). (17) Further analysis is required to determine whether it was the decrease in fat intake, the change in fatty acid profile, increase in fibre intake or weight loss that was responsible for the benefits.
The Women's Healthy Eating and Living (WHEL) study is a RCT of over 3000 women, which is evaluating the effect of a reduced-fat diet and increased intake of fruits and high-fibre vegetables among both pre- and postmenopausal women with early-stage breast cancer. (18) The intervention in the WHEL study is delivered by telephone, whereas the WINS intervention was delivered by group counselling. Results are expected in 2008.
Evidence that dietary intakes of vegetables, fruit or related nutrients (e.g. beta carotene, vitamin C) affect recurrence or survival is somewhat supportive but not conclusive. (13) The effect on risk is likely to only be modest. In a review of eight studies that examined the effect of fruit and vegetable intake on breast cancer outcomes, three studies found a significant association between increased intakes of fruit and vegetables with a decreased risk of death in breast cancer cohorts, with the risk ratios ranging from 0.1 to 0.8. (13) One study found a trend for risk reduction that was not significant, and another study found a significant inverse association only in women with node-negative disease. (13)
For oral cancers, the consumption of vegetables, citrus fruit and orange juice has been associated with a better prognosis. (19) Fruit and vegetables are recommended for their important role as a low energy density source of nutrients (vitamins, minerals, phytochemicals and fibre) and their contribution to weight management, as well as for their probable cancer-protective effect.
Although there is a consistent body of evidence on the association between meat consumption and risk of colorectal cancer, (20-22) there is insufficient evidence of an association between meat consumption and cancer survivorship. There are no specific recommendations about meat consumption for people living with cancer; however, a moderate intake of meat (65-100 g of cooked red meat), three to four times a week, as specified in the Australian Dietary Guidelines and Australian Guide to Healthy Eating, would be applicable for cancer survivors. (23,24)
No studies have found a significant association between alcohol intake and cancer survival, despite the convincing evidence for alcohol being associated with the incidence of some types of cancer. (13,25)
EXERCISE AND PHYSICAL ACTIVITY
The benefits of exercise and physical activity for cancer survivors are becoming more apparent, especially in alleviating fatigue. (26-28) The proven benefits of exercise for cancer survivors include improved cardiovascular fitness, muscle strength, body composition, fatigue, anxiety, depression, self-esteem, and several components of quality of life (physical, functional and emotional). (27)
The Nurses Health Study was one of the first studies to show that physical activity improved breast cancer survival rate and not just quality of life, and showed that the greatest survival benefit occurred in women who performed moderate activity, such as the equivalent of walking three to five hours per week at an average pace, compared with those women who were sedentary. (29) There was a 26% to 40% improvement in survival outcomes (including death, breast cancer death and breast cancer recurrence) for those women who were more active compared with the least active women. (29)
It is currently not known what exercise prescription would be most beneficial for which types of cancer, at which stage of disease or treatment. Information is required on the best type, frequency, duration and intensity of exercise to recommend to cancer survivors. (30)
Although dietary supplement use is very common among cancer survivors, there are very few studies of the effect of nutritional supplements on cancer recurrence and survival.
Foods, like vegetables and fruits, are complex and contain many different types of nutrients and phytochemicals, which cannot always be replicated in a supplement form. The results from clinical trials using vitamin supplements (e.g. beta-carotene) to prevent cancer in particular high-risk groups have been disappointing. (31)
It is still prudent to encourage cancer survivors to obtain the potentially beneficial compounds from food. Nutritional supplements are rarely a replacement for a diet rich in vegetables and fruit and their complex mixture of phytochemicals. A daily multivitamin supplement in amounts equivalent to 100% of the recommended dietary intakes is a good choice for those cancer survivors who are not able to eat a healthy diet. The use of vitamin and mineral supplements in higher doses should be assessed and discussed on an individual basis. High doses of dietary supplements may be associated with toxicity.
Cancer patients undergoing active treatment are at risk of food-borne illness, particularly if they are undergoing immunosuppressive treatment. Cancer survivors may be at increased risk of immunosuppression compared with the general population, and therefore should be careful to avoid foods that may contain unsafe levels of pathogenic microorganisms. (1)
Lifestyle interventions for cancer survivors are an upcoming, but understudied area in Australia. As people with cancer are at high risk of other chronic diseases, other benefits besides reduced cancer recurrence may be realised with lifestyle intervention. Further RCTs are required to assess the efficacy of dietary and/or physical activity interventions and advice for cancer survivors. A better understanding of the enabling factors and barriers to cancer patients following dietary and physical activity advice is also required.
Recommendations for cancer survivors, which are supported by The Cancer Council NSW, include the following:
* Maintain a healthy body weight with a body mass index between 18.5 and 25 kg/[m.sub.2]
* Be physically active -- aim for at least 30 minutes of moderate activity daily
* Eat more fruit and vegetables -- aim for two serves of fruit and five serves of vegetables a day
* Limit or avoid alcohol -- no more than two standard drinks a day for men and no more than one standard drink a day for women
* Handle and prepare food safely
Most of these recommendations are consistent with advice to reduce the risk of cancer, and should be considered within the context of the individual survivor's overall health and social circumstances.
Kathy Chapman and The Cancer Council NSW provided an independent review of the evidence and did not accept payment from Meat and Livestock Australia Limited for this paper.
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The Cancer Council NSW, Sydney, New South Wales, Australia
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|Title Annotation:||Section 4: The role of red meat in the prevention and management of chronic disease|
|Publication:||Nutrition & Dietetics: The Journal of the Dietitians Association of Australia|
|Article Type:||Disease/Disorder overview|
|Date:||Sep 1, 2007|
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