So today I’m going to talk a bit about the big C word – Cancer. And more importantly how you could help reduce the likelihood of cancer in your pet (and yourselves) – Chemoprevention.
Cancer is one of the leading causes of death in dogs, with around 1 in 3 domestic dogs estimated to develop cancer. This statistic is similar to the stats for men, and worse than that for women. In both humans and dogs, as average length of life increases, so do cancer incidence rates. Female dogs seem to have an increased incidence of cancer compared to male dogs. Certain dog breeds are predisposed to higher rates of cancer than others, such as Flat Coated Retrievers and Boxers. Various other factors have been found to influence cancer rates, including diet, neutering status (see previous blog on neutering for more info), chemical exposure, lifestyle, etc.
Diet is one of the most commonly discussed life factors that could help minimise the risk of cancer. Most people just think this means “eating a healthy diet”; but what does that even mean? It is super hard to work out when it comes to human nutrition, but with dog food there is such a wide range of varied advice given out by different vets and animal professionals that it becomes almost a minefield. Even within the ‘natural feeding’ community there is so much variety – Should I feed a prey model? Should I include fruits and veggies? Should I cook it or feed raw? Should I make my own or buy a balanced complete pre-made one? What is the best?!?!
Well I think the answer to this is that there is no ‘best’ way to feed your pets, or yourselves, but there may be a ‘best’ way for your specific dog, or for you. As you know we recommend feeding a natural, Biologically Appropriate Raw (ideally!) Food diet (BARF diet). Many raw feeding experts and vets, on discussion of the inclusion of fruit and veg in raw food, agree that it isn’t necessarily ‘essential’ to do so, but it may well help improve health and supply some extra nutrients that are deficient in modern day foods. In the current farming climate foods contain lower levels of key nutrients, likely because animals are often sub-optimally farmed and soils are commonly deficient in nutrients from over-use of the land, poor crop rotation, or use of chemicals. It is also known that it is easiest to have a halting or reversing effect on cancers in the very earliest stage of development – where a normal cell turns into a pre-neoplastic cell. So this is where diet can get involved in chemoprevention.
Studies in humans have shown that approximately 20-40% of cancer incidents are preventable by consuming more fruits and vegetables, with this one action potentially preventing about 200,000 cancer-related deaths annually. In epidemiological studies, certain populations consuming diets rich in specific phytochemicals (plant-derived substances that have a biological effect in the body) have lowered incidence of heart disease, cancer and osteoporosis. Now dogs obviously aren’t humans and there are more studies on diet and cancer in humans than in dogs, but there is some evidence available in animals for the benefits of fruits and vegetables too. For example, Scottish terriers were found to have a reduced risk of developing Transitional Cell Carcinomas if they consumed vegetables at least 3 times a week. There are also many studies on experimental animals showing that dietary phytochemicals found in plant products can inhibit oncogenesis (tumour formation) and/or exhibit biological actions against the progression of various cancers. Other studies have found that a lean body condition, restricted calories and feeding in ‘meals’ rather than grazing can increase the lifespan of Labradors by up to 2 years. Terriers were found to have a reduced risk for the development of tumours and a lower incidence of pancreatitis, diabetes mellitus, and bone or joint diseases if kept at their ideal body weight. (See the earlier blog post on obesity for more info on how allowing your dog to stay chubby could be compromising their health)
So what can you do for your dog?
1 – Don’t feed a high heat processed canned, extruded or pelleted food!
Ever heard of Maillard Reaction Products (MRPs)? I hadn’t either until I read a few studies about them recently. MRPs are produced when food is browned, made golden or even burnt – it is known as a nonenzymatic browning reaction. They are known to increase palatability in human and animal foods because they have a nice taste (think perfectly cooked toast vs. warm bread). MRPs are formed by the Maillard reaction which reduces the bioavailability of amino acids such as Lysine. MRPs and other by-products of the Maillard reaction have been found in human studies to be carcinogenic to the point where human nutrition courses now advise therapists to recommend bread is only warmed and never properly toasted (how tragic!). Now back to how this affects dogs (and cats!). The key ‘wake-up’ study for me on this topic was looking at quantities of MRPs in commercially available pet foods (J Agric Food Chem 2014 van Rooijen et al. if you’re interested). The authors found that the average daily intake of one of these specific MRPs was 122 times higher for dogs, and 38 times higher for cats, than the average intake for adult humans. One Hundred and Twenty Two Times Higher! As if 38 times higher wasn’t bad enough! The authors conclude that as commercial pet foods are often the sole source of food for most pets that future research should focus on the long term health implications of these in our pets. If you look at previous, similar health extrapolations between humans and pets I think it’s likely these will be found to be carcinogenic for dogs and cats, as well as humans. MRPs aren’t the only bad thing about this browning process. A well-known by-product of the Maillard reaction is Acrylamide, which is a known carcinogen in small animals and classed as a group 2A carcinogen in humans.
So our advice is to ideally feed a raw diet, and so avoid all ‘browning’ products. If this isn’t possible then a lightly cooked, or low heat processed food, is better than a high heat processed food. Keep MRPs to a minimum!
2) Feed fresh vegetables (and fruits) at least 3 times a week
Pretty straight forward hey? Some of you may already be doing this but are there vegetables and fruits that are better for chemoprevention than others? Of course there are! Otherwise I wouldn’t be writing anything in this section. Before we look at those though we should find out how phytochemicals can help prevent cancer right? Here’s a little bit of the science, hopefully simplified for better understanding (I know we vets can sometimes revert to science speak, which isn’t always easy to follow!):
The ability of any single phytochemical to be chemopreventive, and so reduce tumour formation, doesn’t come from a single biological response, but is rather the result of a combination of various, specific intracellular effects – I know, nothing is ever straight forward! Here are some of the molecular and cellular activities regulated or affected by chemopreventive phytochemicals: Cell proliferation, differentiation and apoptosis – this is the normal cell cycle where cells are formed, differentiate into their specific type with their specific jobs, and then when they are old or become abnormal they are destroyed; Cell cycle progression – if the cell cycle halts then the likelihood of abnormal cells is higher, and they won’t be destroyed as they should be; Angiogenesis – the formation of new blood vessels, which in cancer feed the tumour; DNA repair – because cancer cells form from mutated normal cells, or damaged DNA; Carcinogen activation/detoxification by metabolic enzymes – if the carcinogens are not activated, or can be successfully removed before they cause damage then cancer is minimised; Metastasis – the spread of the cancer around the rest of the body; Hormonal and growth factor activity – both hormones and growth factors can have either promoting or suppressing effects on neoplastic cells; Expression and functional activation of oncogenes or tumour-suppressor genes – these are present in cellular DNA and under certain circumstances can transform a cell into a cancerous cell or suppress this formation, respectively; Oxidative stress – oxidation leads to the formation of free radicals which steal electrons from neighbouring cells leaving them damaged; Inflammation – like oxidative stress this damages cells making them more likely to start on the path to pre-neoplastic and neoplastic cell formation.
So here’s a little list of some of the best fruit and vegetable additions to your dogs’ diets, I have included a few medicinal herbs and mushrooms for interest sake. Vegetable and fruits are easy to add to your dogs’ diets - chopped finely, grated, lightly steamed or blended with a little water. (For advice on how to include herbs and spices in your pets’ diets see previous blog on herbs):
Spices & herbs: Turmeric, Ginger, Garlic (care with dose as too much can be toxic), Chilli peppers (obvious care required with these too!), Parsley, Rosemary, Thyme, Oregano, Peppermint, Sage
Fruits: Berries – cherries, blueberries, raspberries, blackberries, cranberries, etc., Apples, Tomatoes, Plums (no stones!)
Cruciferous vegetables: Cabbages, Broccoli, Cauliflower, Kale, Brussell sprouts, Watercress, Bok choi, Rocket, Radishes
Yellow-Orange vegetables: Carrots, Sweet potatoes, Yellow Squash, Peppers
Mushrooms: Oyster, Maitake, Shiitake, Reishi, Lion’s mane, Coriolus, Cordyceps (these are the best and some are considered ‘medicinal’ but even everyday button mushrooms can have beneficial effects – it’s regular dietary intake that’s important)
Medicinal Herbs: Milk thistle, Echinacea, Panax ginseng, Baical skullcap, Astragalus
Miscellaneous: Green tea (care with caffeine content – use decaff or pour over boiling water, immediately pour away and then make the tea), Honey (high sugar content so again avoid too high a dose), Soya beans (care with allergies to soya in dogs)
Here is an extra little list of the exact and best known phytochemicals for some of these, included for the inner geek that I know will be inside some of you, and in case you would like to research further:
Curcumin in Turmeric; Polysaccharides in mushrooms; Epigallocatechin-3-gallate (EGCG) in Green tea; Quercetin in Apples, Tomatoes and Berries; Ursolic acid in Apples (especially the peel), rosemary, thyme, berries, mint, oregano, hawthorn; Isothyocyanates in cruciferous vegetables; Sulforaphane in Broccoli; Apigenin in Parsley; Perrilyl alcohol in Cherries, sage, perppermint; Lycopene in Tomatoes; Genestein in Soyabeans; Capsaicin in Chilli peppers; 6-Gingerol in Ginger; Indole-3-carbinol in Cabbages; Diallyl-sulphide in Garlic; Caffeic acid phenethyl ester in Honey.
[Included for human interest only: Resveratol in red grapes, and red wine you’ll be pleased to know. Obviously not appropriate for dogs but thought you’d like the perfect excuse for a glass of wine!]
3) Don’t leave chronic inflammation to run unchecked
It is estimated that about 25% of all cancers are linked to chronic inflammation, inflammation induced by environmental exposures, diet or infection of pathogens. Cancer is a complex disease and there are many avenues in its progression that phytochemicals can target. The easiest ones to help with diet and management are Oxidative stress (with antioxidant foods) and Inflammation (by avoiding inflammatory foods, feeding an appropriate diet and treating acute inflammation before it becomes chronic). We’ve talked about a fair few of the antioxidant rich foods in point 2 above, so what can we do about inflammation?
It’s amazing how many animals live with low level chronic inflammation, without their owners realising! This could include skin or ear inflammation, joint or muscle inflammation, gum inflammation, gut inflammation… Sometimes when a problem has always been there in a pet it becomes ‘normal’. The most common of these we see are gum and gut inflammation.
Some people think there is nothing you can do to keep your dogs’ teeth clean, and so their gums free of inflammation, except brush them which isn’t always a feasible solution. In fact it’s well accepted that over half of all dogs will have dental disease by 3 years old – that always enrages me as it is so unnecessary! If you’ve read our other blogs then you’ll know that the answer to this issue lies in an appropriate diet and some good old fashion chewing, ideally on a raw meaty bone (read our previous blog on bones for advice on dental health for bone eaters or otherwise). Some dogs may need a dental or extractions before dental health can be maintained, but often this can be avoided if your dogs’ dental disease hasn’t progressed too far.
Gut inflammation is the other common chronic problem so let me set it straight: It is not normal for your dog to do a solid poo in the morning and for it to get softer and softer as the day goes on. It is not normal for your dog to have extremely variable stools, soft one day and hard the next. It is not normal for your dog’s stool to commonly have a mucus (jelly-like) sheath on it. These are signs of chronic low grade gut inflammation! The right diet for your dog, and possibly short or long term herbal supplementation/support, should sort this out in no time.
Skin/ear and joint/muscle inflammation are more complicated and advice should be sought from your vet. Oftentimes though, with allergic skin and ear problems, finding the right diet for your dog can make a massive difference as it removes one potential allergen avenue from the mix, which could keep your dog below the allergy threshold, and so itch-free. Joint and muscle issues need a proper assessment, but can often be minimised in your dogs’ futures by ensuring that after any trauma or injury they are assessed for any spinal or joint misalignments by a Chiropractor (ideally McTimoney) or the like, and their diet is not pro-inflammatory. Supplements can also be added to their diet from middle age onwards to support joint health and mobility.
4) Avoid exposing your pets to unnecessary chemicals
This could include home or laundry cleaning products – use as natural a product as you can find; chemicals on recently sprayed fields – wait until at least after it rains before walking there; medications that aren’t necessary for maintaining health – over-vaccination, over-use of flea/worming treatments, unnecessary antibiotics…; etc.
So although Cancer is considered the big C-word, maybe we should be focusing instead on Chemoprevention as being the new big C-word. Everything has to die of something, and we all tragically know that our pets don’t live as long as we do, but there are things you can do to help your dog live as long and healthy a life as possible. We can’t stop cancer yet, but we might be able to slow it down.