Prostate Cancer and Diet

My final year dissertation was a systematic review on how the dietary components cruciferous and allium vegetables, vitamin D, lycopene, dairy products, dietary fats and meats can either help or hinder the incidence and/or progression of prostate cancer. Seeing as my project amalgamated scientific evidence available on this topic up until April 2013, the evidence and dietary recommendations are very up to date and hopefully helpful for anyone at risk or suffering from prostate cancer, or those close to someone who is. I must note, that in no way am I saying diet can cure or completely prevent prostate cancer, but for some foods/dietary components there is evidence to show that they may slow/cease progression of cancer-cell development. However most of this evidence is in vitro or in vivo (isolated cells or in animals) as it is difficult/expensive/controversial (the list goes on) to test such things in humans, therefore it is difficult to assess how these components would work within a human post-metabolism. However there are also promising studies which have looked at patterns of disease/eating habits in populations which have shown a correlation between eating more/less of a certain thing which correlates with a larger/smaller incidence of prostate cancer as a whole. Some of the really interesting evidence like this are migration studies, which look at individuals moving from a low-risk country such as Japan to a high-risk country such as the UK, and usually the pattern (they look at a large amount of individuals migrating) is that their risk for prostate cancer rises greatly. Examples of these migration studies are by Maskarinec and Noh and Brawley et al.

Ok so for the evidence, my dissertation was around 12,000 words so I shall try and sum it all up concisely into recommendations!

Allium vegetables

These are vegetables such as garlic, onion, chives, shallots, leeks and scallions. Interestingly it has been proven in a study by Song & Milner that allowing garlic to stand for around 10 minutes after chopping/cutting is when the ‘magic’ happens. The enzymatic process following cell rupture has been found to take approximately ten-minutes, therefore for the needed anticancer effect this should be considered when cooking.

Epidemiological evidence for effect: Allium  ≥5 times a week and ≥5.5g garlic a week OR >2.14g garlic a day and >2.14g scallions a day

Target intake: ≥5 x 80g servings of Allium vegetables a week OR one clove of garlic a day

Good Source of (when cooking): One clove of garlic, 2.14g scallions, 80g other Allium

Advice: Take care if taking the medication Warfarin or Saquinavir (consult your GP if radically changing your diet)

Cruciferous vegetables

These are vegetables such as broccoli, Brussels sprouts, cabbage, cauliflower, collards, kale, celery, chinese cabbage, turnip, rape, wasabi, horseradish, watercress and radish (to name a few!)

Epidemiological evidence for effect: >3 servings a week (particularly broccoli, cauliflower and watercress) OR 5 servings of broccoli a week. Aim for a higher dose if post-diagnosis or advanced disease

Target intake: 3-5 80g servings a week (particularly broccoli, cauliflower and watercress). Choose a cruciferous vegetable as one of five a day, eat raw or steam.

Good source of: 80g any cruciferous vegetable

Advice: Due to these vegetables containing vitamin K (phylloquinone) it is advised that those taking Warfarin seek medical advice if drastically changing their diet.

Vitamin D

Vitamin D2 (calciferol) is present in some foods, added as a fortification, and also available in dietary supplements. Some of the main foods it can be found in are oily fish (herring, trout, mackerel, pilchards, salmon, sardines, tuna), sundried shiitake mushrooms, chanterelle mushrooms, margarine, fortified breakfast cereals and eggs. Vitamin D3 (cholecalciferol) is synthesised in the skin post-exposure to UVB radiation from sunlight or other sources such as sunbeds. It is difficult, especially with the Western diet of the UK, to consume adequate amounts from food alone, therefore sunlight exposure is needed. However this brings up the debate of the increased risk of skin cancer from prolonged sunlight exposure. Of which there is no absolute recommendation. Evidence was rather contradictory for this topic, and it would seem that individual genotype of the vitamin D receptor has a degree of risk/benefit associated with prostate cancer risk, however evidence is not yet conclusive enough. It seemed from evidence that it is the maintenance of adequate levels of serum vitamin D which reduces risk, rather than optimising levels to the full, however unfortunately the clinical level of optimal or adequate is not set! Recommendations were set after amalgamating results of no clinical detrimental effect.

The UK RNIs (recommended nutrient intake) have been disputed as being out of date, they have not been updated since 1991 and are far removed from other countries recommendations, such as the USA who updated their recommendations in 2010. For a person aged 4-64 the UK currently holds no RNI, however the USA recommends 15 ug daily. For people aged 65-70 the UK RNI is 10 ug/day, whereas the USA is double at 20 ug/day. Above 71 years the UK holds its recommendation of 10 ug/day, whereas the USA increases to 25 ug/day.

Those particularly at risk of a low serum level of vitamin D are the homebound elderly, people with highly pigmented skin, those covering their skin for religious or health reasons, institutionalised people and those living in areas where UVB radiation may be inadequate.

Epidemiological evidence for effect: Daily supplementation of up to 25ug (micrograms)

Target intake: 2-4 portions of oily fish a week (100-140g/portion). Supplementation 5-25ug (dependent on sunlight exposure, age and dietary intake).

Good source of: 100g oily fish

Lycopene

Lycopene is a member of the carotenoid family, which cannot be produced in the body and therefore must be obtained from the diet. The pigmentation is a deep red and can be found in foods such as tomatoes and tomatoes products, watermelon, pink grapefruit, apricot and pink-guava. It would seem from evidence (albeit rather mixed evidence) that cooked/processed tomato products contribute the most dietary lycopene. It is however unknown what the optimal dose of lycopene is, whether it works in isolation from its food-source or whether it is in combination with the food that it works, and whether or not it works best in combination with dietary fats in a mixed meal.

Target intake: ≥2 servings (80g) of cooked tomatoes or processed tomato products per week

Good source of: 80g cooked tomatoes or 1 serving tomato-product

Foods to eat in limited amounts – dairy products, meats and dietary fats (mainly saturated)

Advice:

  • Avoid direct exposure of meat to an open flame/hot metal surface
  • Avoid prolonged cooking times of meat, particularly at high temperatures
  • Remove charred portions of meat
  • Avoid making gravy from meat drippings
  • Continuously turn meat over on a high-heat surface
  • Limit saturated fat and omega-6 consumption
  • Limit consumption of high-fat dairy foods such as cheese, butter and full-fat milk
  • Increase omega-3 consumption with foods such as oily fish, eggs or flaxseed seeds/oil

I hope you found this interesting, please pass it on or recommend to anyone who may find the advice useful. Likewise if you would like anything clarified or have a question feel free to ask!

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