Jun 30, 2020

Prostate cancer – Supplements which could harm

Nutritional supplements can be a convenient way of correcting dietary deficiency or boosting the intake of specific foods which have healthy properties. Some have been tested in well conducted national randomised trials [Thomas], but most have not.

Unlike drugs, supplements do not need a medical licence. Health claims are governed by the European Food Standards agency (EFSA) who do allow some marketing claims. However, unscrupulous sellers try to bend the rules by using names of brands which imply a benefit for a specific organs or disease such as Prost or immune boost. The worse culprits are those adding words such as “Research” in their company titles in a ploy to mislead customers despite conducting no clinical studies at all.

Many Institutes have actually conducted studies on supplements and as a general rule, the ones showing most promise involve concentrated whole foods rather than specific chemicals extracted from foods [Thomas]. These studies have shown us that some ingredients are beneficial, some have no effect, but of most concern some have been linked to harm or potential harm.

This blog highlights three more notable examples:


Cloves and spearmint extracts.

clovesThese contain very high levels of phytochemicals and can be direct antioxidants [Gülçin]. There is little research in humans and absolutely none involving men with prostate cancer. Clove oil has been investigated as an anaesthetic and euthanizing agent for fish species [Holloway].  Spearmint has been investigated for hirsutism and could affect androgen levels in a negative way [Akdogan].

In one of the worse examples of the ugly face of an unregulated supplement industry sellers have thrown these ingredients into blends which have been tested for safety in well conducted randomised studies. Their inclusion has no logical rational, their effects on biological pathways, drug interactions or whether they could counter balance the positive effects of the other ingredients is completely unknown [Brownlee]. If this was not unethical and dangerous enough, sellers then use terms such as improved, updated, new research, or scientifically tested trying to deceive customers in believing comparative research has occurred. You have to wonder, with this level of morality, what other quality assurance issues could be in jeopardy in manufacturers expected to exert a great deal of trust and self- governance.




Vitamin A & E supplements

Vitamin  A deficiency still commonly effects children in developing countries causing  blindness. Vitamin E deficiency syndromes are rare but low levels have been shown to increase the susceptibility or carcinogens. In the west, however, vitamin A and E deficiencies are is rare, but suboptimal levels should be avoided with a good diet of nuts, fruit, carrots, sweet potatoes but not with regular supplements unless correcting a known deficiency.

Unlike polyphenols which promote a natural adaptive increase in anti-oxidant enzymes in times of oxidative stress, direct anti-oxidants (vitamin A and E) can actually block this process. So, in the long term, this leads to greater oxidative stress. Excess oxidative stress can mitigate other health benefits of exercise, increase damage to DNA, impede joint and tissue repair [Teixeira, Avery, Poljsak, Eder, Peternelj].

Vitamins A & E can also block keap1 which signals nrf2 to reduce the anti-oxidant levels. As such they cause anti-oxidant enzymes to remain elevated, even when the oxidative stress subsides [Eder]. Combined with their direct antioxidant properties this can result in the mopping up of too many ROS directly that can lead to a state called anti-oxidative stress. This is a recently recognised concern, especially amoung individuals who regularly take antioxidant supplements [Poljsak].

These biological process explain why intervention studies have reported that long term intake of vitamin A and E supplements is linked to an increased cancer risk [Thomas, Poljsak]. For example, the ATBC showed a higher incidence of lung cancer [Albanes]; The Women’s Health Study involving  patients with diabetes or cardiovascular disease showing a higher incidence of heart disease [Richardson]; The Queensland skin cancer study which reported a higher rate of recurrent skin cancers. The SELECT study showing a higher incidence of prostate cancer [Klein]. the CARET Study showing an increased risk of both lung and prostate cancer [Omenn].



Cod liver oil and fish oils supplements

supplementsOmega 3, rich in oily fish are essential for a many important biological pathways. As Western diets are generally deficient – we certainly should be eating more seafood, mackerel, sardines and other oily fish. A fish oil supplement has always seemed a sensible option to boost intake but as studies emerge some concerns have been raised. Some oils have been found by the consumer watchdog consumerlab.com to contain dioxins and PCB, as they use fish from polluted seas or fish that are higher up the food chain. If exposed to heat, oxygen and light, fish oils are broken down into substances such as aldehydes which have carcinogenic properties.

Cod liver oil also has very high levels of vitamin A and  naturally contains vitamin E but extra amounts are often added as an antioxidant preservative. Clinical studies have reported that regular consumption probably does not help heart disease, stroke or overall death [Abdelhamid, Chawdury]. In terms of cancer, their prolonged intake consumed regularly may slightly increase prostate cancer risk although this may be relate to excess vitamin E intake [Klein, Brasky]. The court is still out but until this issue is resolved, many would  recommend avoiding fish oil supplement especially those with extra vitamin E instead concentrate on whole foods.




References – supplements harm prostate


Thomas R et al (2017). Phytochemicals in Cancer Management. Current Research in Compl and Alt therapy 105, 01.

Thomas R et al (2015) Phytochemicals in cancer prevention and management? BJMP 8( 2), 1-8.

Thomas R, et al (2014). A double-blind, placebo-controlled randomised trial evaluating the effect of a polyphenol-rich whole food supplement on PSA progression in men with prostate cancer-the U.K. NCRN Pomi-T study. Prostate Cancer and Prostate Diseases 17(2):180.

Omenn G et al. (1996) Effects of a combination of β carotene and vitamin A on lung cancer and cardiovascular disease. The New England Journal of Medicine. p.;334(18):1150–1155.

Albanes D et al. (1996) Alpha-tocopherol and beta-carotene supplements and lung cancer incidence in the alpha-tocopherol, beta-carotene cancer prevention study effects of base-line characteristics and study compliance. J Natl Cancer Inst 88: 1560-70.

Gupta-Elera G et al (2012) The role of oxidative stress in prostate cancer. Eur  J Cancer Prev. 21(2):155-162.

Teixeira V  et al (2009) Antioxidants do not prevent post exercise peroxidation and may delay muscle recovery. Medicine & Science in Sports & Exercise: 41( 9); 1752-60.

Avery N et al (2003) Effects of vitamin E supplementation on recovery from repeated bouts of resistance exercise. J Strength Cond Res. Nov;17(4):801-9.

Eder K et al (2002) Excess dietary vitamin E lowers the activities of antioxidative enzymes in erythrocytes of rats fed salmon oil. J Nutr. 132:3400–4.

Poljsak B (2012) The Neglected Significance of “Antioxidative Stress” Oxid Med Cell Longev. 480895.  doi: 10.1155/2012/480895

Klein E et al (2011). Vitamin E and the risk of prostate cancer: the Selenium and Vitamin E Cancer Prevention Trial (SELECT). JAMA. 2011;306(14):1549-56.

Brownlee T et al (2018). Drug Interactions between Enzalutamide and Complementary Medications – Patient with Prostate Cancer: The Canadian J of Hosp pharmacy. 71,4 276-81.

Gülçin I et al (2010). Antioxidant activity of clove oil. Arabian J of Chemistry.  5 (4).489-499

Holloway A et al (2004), Effects of clove oil on blood hormone profiles in fish Aquaculture Research, 35: 1025-1030.

Akdogan M et al (2007) Effect of spearmint (Mentha spicata Labiatae) teas on androgen levels in women with hirsutism. Phytotherapy Research. 21 (5), 444-49

Abdelhamid A et al (2018). Omega 3 fatty acids for the primary and secondary prevention of cardiovascular disease. Cochrane Database of Systematic Reviews 2018, Issue 7. Art.

Brasky T et a (2013). Plasma phospholipid fatty acids and prostate cancer risk in the SELECT trial. J Natl Cancer Inst.105(15):1132-41.

Chawdury R et al (2014). Association of Dietary, Circulating, and Fatty Acids With Coronary Risk. A Systematic Review and Meta-analysis Annals of Internal Medicine 160 (6), 398-40



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