Safe & Unsafe Foods

There are many human foods which are safe for hamsters. As rodents, these animals are quite diverse and unique in their eating habits. Many people, including owners, breeders and rescues tend to unfairly compare hamsters’ nutritional needs to those of dogs and cats. However, rats are much closer biologically to hamsters, and as such, are better comparisons when it comes to what is and is not safe. For ease, this list has been divided into various categories. Any food items which have controversy surrounding them are located at the bottom of the list, supported by peer-reviewed scientific documents which support their position as safe, or unsafe.

When working with fresh food, a good “portion” guide is the size of your hamster’s ear.

Food Safety Chart

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Fruits

Fruits are a popular addition to an everyday hamster mix. Below is a fairly comprehensive list of some fruits that are safe for hamsters. Some may be addressed later on in our controversial area. Please note that fruits are perfectly acceptable to feed to all species of hamsters. While some species of dwarfs are diabetic prone they can still enjoy fruit in moderation. This article does a great job explaining why sugar in itself is not inherently bad, and how fruit can be an important part in a dwarfs’ regular diet.

Vegetables

Vegetables are a welcome treat for any hamster. Just like humans, your hamster may have some preferences. This list is based off people’s preconceived notions of what a “vegetable” is, so some items may in fact scientifically be fruits, but for ease of the reader are included here.

Proteins

Miscellaneous Foods

Controversial Foods

There are quite a few foods which get bad reputations in the hamster community because of our preconceived notions. Below are some of the most “controversial” foods that are in fact safe. Where applicable, peer-reviewed scientific sources are provided. Huge thanks to the ladies from the California Hamster Association for helping with many of these foods!

Some of the hamster community has confused human grade almonds with bitter almonds, which are not sold for human consumption and contain cyanide. If you can eat it, so can your hamster.

Based on research into the rat fancy, provided it does not include the pit or skin, avocado is safe. It is also recommended that you use flesh that is NOT touching the pit. It is very high in fat, something the owner should consider.

“This study investigated the impact of diets contain- ing various levels of avocado (5, 10 and 15%) on gut health in rats fed for six weeks. Avocado-fed rats had significantly higher food intakes while their body weights remained similar to the control diet-fed rats. No significant changes in intestinal bacterial populations (ileum, cecum and colon) were found in rats fed avocado diets compared to the control diet. Ileum and colon tissues of rats fed avocado diets showed significantly higher expression of genes (β-defensin 1, mucin 3 or mucin 4) and a greater number of mucin-producing goblet cells in the colon. The percentage of avocado in the diet had varying effects in altering the biomarkers, whereby diet containing 15% avocado was the more effective diet. This study delivers new knowledge on the role of avocado on gut health in rats.” https://www.ncbi.nlm.nih.gov/m/pubmed/28550342/

Chocolate is a very contested topic in small pet communities. Ultimately, chocolate is perfectly safe, however many owners still feel an initial knee-jerk reaction. Since the active ingredient in chocolate (theobromine) is toxic to dogs, many people push hamsters under this umbrella. It couldn’t be further from the truth - in fact, chocolate could mean the difference between life and death for a hamster or rat!

“Hamsters and mice were much more resistant to theobromine than were rats. A decrease in growth and in thymic weights occurred only at the highest dose levels of theobromine and testicular and thymic changes were completely absent in hamsters. “ http://www.sciencedirect.com/science/article/pii/0041008X79902850

“…more resistant than rats, while hamsters were almost completely resistant to the effects of high doses of theobromine (Tarka et al., 1979).” http://www.sciencedirect.com/science/article/pii/0041008X80903609

“Theobromine shows moderate acute toxicity and the dog is more susceptible than rodents.” http://www.efsa.europa.eu/en/efsajournal/doc/725.pdf The use of theobromine (the active chemical in chocolate) as a bronchodilator:

“Suprisingly, accumulating evience suggests that dark chocolate can carry antitussive effects. Although mechanisms remain unknown, it is thought that theobromine, a methylxanthine intrinsic to dark chocolate, might potentially suppress cough.” http://dx.doi.org/10.3816/SCT.2007.n.006

Further Reading: http://dmd.aspetjournals.org/content/12/2/154.short

Owners have cautioned against the use of citrus fruits for years citing they are “too acidic”. However, there is no scientific evidence that supports this. Instead, science points to citrus fruits being beneficial. We advise owners use their better judgement, and stick to “sweeter” citrus fruits, such as tangerines and mandarins.

“To investigate the molecular mechanism based chemopreventive efficacy of hesperetin on 7,12-dimethylbenz(a)anthracene (DMBA) induced hamster buccal pouch (HBP) squamous cell carcinoma (SCC). The oral tumour was provoked by painted with 0.5% DMBA on left buccal pouch thrice a week for 10 consecutive weeks developed well-differentiated SCC and tumour formation was 100% in DMBA alone. We evaluated the chemopreventive potential of hesperetin by assessing the lipid peroxidation (LPO) by-products, status of enzymatic, non-enzymatic antioxidants, detoxifying agents etc. Moreover, modulating expression of apoptotic and cell proliferation markers were observed in HBP SCC experimental hamsters. Oral administration of hesperetin (20 mg/kg b.w.) to DMBA painted hamsters significantly reversed the stages of oral SCC. Our findings indicate that hesperetin possesses a chemopreventive effect in DMBA-induced oral SCC by exerting anti-carcinogenic property.” https://www.ncbi.nlm.nih.gov/pubmed/28457144

“The results of this study suggest that lemon peels and the waste stream of the lemon peels are as effective in lowering plasma and liver cholesterol in hamsters as the pectin extracted from the peels and that also compounds other than pectin are probably responsible for the cholesterol lowering effect of the citrus peels.” https://www.ncbi.nlm.nih.gov/pubmed/11990004

“The data show that 4 flavonoids (hesperetin, neohesperidin, tangeretin, and nobiletin) were inactive. The results with naringin and naringenin show that both of these flavonoids significantly lowered tumor number [5.00 (control group), 2.53 (naringin group), and 3.25 (naringenin group)]. Naringin also significantly reduced tumor burden [269 mmm3(control group) and 77.1 mmm3(naringin group)]. The data suggest that naringin and naringenin, 2 flavonoids found in high concentrations in grapefruit, may be able to inhibit the development of cancer.” https://www.ncbi.nlm.nih.gov/pubmed/18444138

Additional Reading:

Recently, some studies have come out about cilantro and the mint family that indicate it might not be a great option for your hamster. Owners will need to rely on their own judgement when feeding cilantro. The problem with mint is not cut and dry–which is one reason we caution against it. While the animal is able to eat it and appear fine and healthy, it’s impossible to know what’s going on inside. The following study uses different concentrations of peppermint extract and oil to study the effects of mint overall. You’ll notice they do have to kill the test subjects and perform necropsies to see the damage done, which is something we just can’t do on pets until it’s too late.

While mint does admittedly have some positive effects on rodents, the big concern is that over time, it causes “Cystlike spaces scattered in the white matter of the cerebellum” of the test subjects. In other words, feeding mint regularly is associated with brain damage and we know very little about how this affects them throughout their lifespan. https://www.ncbi.nlm.nih.gov/pubmed/11766133

Cucumber and watermelon both get a bad reputation as more watery fruits. They are perfect foods for providing hydration especially on long journeys. As well, a hamster will simply moderate their water intake to make up for it. When worried, just remind yourself that we allow our animals free access to water… which is arguably much waterier than cucumber or watermelon!

Unlike many other animals, hamsters are not lactose intolerant. This means they can consume dairy and dairy products without any issue.

Hamsters also demonstrated the highest levels of lactose consumption. […] The hamster’s pregastric pouch is similar in both structure and function to the rumen of herbivores. It is likely that the ruminant type microorganisms residing in the pregastric pouch, like those of the rumen of herbivores, rapidly attack and digest water soluble carbohydrates such as lactose, thereby minimizing the amount of ingested lactose that reaches the small intestine intact and sparing hamsters the negative consequences of lactose ingestion that are typically experienced by monogastric animals such as rats. Voluntary Lactose Ingestion in Gerbils, Rats, Mice, and Golden Hamsters, David DiBattista, Physiology and Behaviour, Vol. 52, pp 59-63, 1992.

Which then led him to further studies, which proved said hypothesis below.

It is surprising that adult golden hamsters, which resemble other animals in intestinal lactase nevertheless prefer lactose solutions to water over a wide range of concentrations and voluntarily ingest substanstial amounts of lactose […] the hamster’s unusually high level of voluntary lactose consumption depends upon its possession of a pregastric pouch that is similar in both structure and function to the rumen of herbivores […] In the golden hamster, ingested food first enters the pregastric pouch, where it remains for up to an hour or more, with volatile fatty acids being produced and absorbed into the bloodstream. Food then passes into the gastric pouch, which is similar to the glandular stomach of monogastric mammals such as rats, mice and gerbils. […] The microorganisms of the pre-gastric pouch allow hamsters to utilize nonprotein nitrogen sources, such as urea, and may play an important role in the digestion of plant material. Futhermore, those microorganisms, like those residing in the rumen of herbivores, would reasonably be expected to attack and digest water-soluble carbohydrates such as lactose, and thereby to minimize the amount of ingested lactose that reaches the gastric pouch and the small and large intestines. […] This experiment demonstrates that surgical removal of the hamster’s pregastric pouch causes a 40% reduction in voluntary lactose consumption. Surgical Removal of the Pregastric Pouch Reduces Voluntary Lactose Consumption in Golden Hamsters, David DiBattista and Michele Robillard in Physiology and Behaviour, Vol. 53, pp 425-429, 1993

Garlic has previously been thought as quite a dangerous food for hamsters. However, studies are showing that it actually has nutritional benefits! We still advise owners to not feed their hamsters raw garlic, or garlic on its own, however it is perfectly safe when cooked into other foods (ie. savoury baby food purees).

“The findings in this study further demonstrate that unlike most of the standard antileishmanial drugs, which require protracted parenteral therapy and are toxic, an agent derived from garlic can be administered either orally or intraperitoneally with similar effectiveness against Leishmania parasites.”” http://www.mrcindia.org/journal/issues/473160.pdf

“Administration of a combined dose of tomato and garlic significantly decreased the incidence of HBP carcinomas and mean tumor burden and the frequency of bone marrow micronuclei. . .The present study, an extension of our previous work, demonstrates the efficacy of the combina- tion in modulating xenobiotic-metabolizing enzymes and the increased frequency of bone marrow micronuclei. To- gether, these findings substantiate the antigenotoxic and anticarcinogenic effects of tomato and garlic reported by us and other workers.” https://www.ncbi.nlm.nih.gov/pubmed/15925298

“Administration of tomato and garlic, both alone and in combination, significantly decreased HBP tumor incidence and tumor burden. This was associated with modulation of lipid peroxidation and increase in GSH-dependent antioxidant enzyme activities and GSH/GSSG ratio in the buccal pouch, liver, and erythrocytes. From these results, we suggest that the enhancement of GSH and GSH-dependent enzymes by a tomato and garlic combination may be attributed to modification of the thiol status.” https://www.sciencedirect.com/…/pii/S0271531703002409

“The addition of garlic or onion facilitated lowering plasma lipid and enhanced the antioxidant function; suggesting that garlic had more effectiveness on lowering plasma lipids and inhibiting the accumulation of liver lipids, and suppress- ing antioxidative enzyme activities than onion.” https://www.atherosclerosis-journal.com/article/S0021-9150(97)84698-9/pdf

Similar to chocolate, since many dogs cannot tolerate grapes many hamster owners and keepers have deemed grapes unsafe. There is evidence to support grapes having health benefits.

“These findings suggested that consumption of wild grape WSCC might diminish the exposure of intestinal mucosa to toxic ammonia and other detrimental compounds and, hence exert, favorable effects on improving gastrointestinal milieu.” http://pubs.acs.org/doi/abs/10.1021/jf300942p

“This is the first time that chronic consumption of grape phenolics is shown to reduce obesity development and related metabolic pathways including adipokine secretion and oxidative stress.

Chardonnay grape seed procyanidin extract supplementation prevents high-fat diet-induced obesity in hamsters by improving adipokine imbalance and oxidative stress markers (PDF Download Available).” Available from: https://www.researchgate.net/publication/23499367_Chardonnay_grape_seed_procyanidin_extract_supplementation_prevents_high-fat_diet-induced_obesity_in_hamsters_by_improving_adipokine_imbalance_and_oxidative_stress_markers [accessed May 17, 2017].

Further Reading

Again, leeks are another commonly thought “dangerous” food. Studies show that they may have beneficial health impacts.

Persian leek is one of the most widely used herbal foods among Iranians. In this study, effects of oral administration of Persian leek on plasma and liver lipids were examined in hamster.Male Syrian hamsters were randomly divided into three groups: control (standard diet), high fat control (high-fat/high-cholesterol diet), Persian leek (high-fat/high-cholesterol diet + 1% per weight of diet from dried powdered Persian leek) for 14 weeks. High fat diet increased plasma and liver lipids as compared to standard diet. Adding Persian leek to the high-fat/high-cholesterol diet resulted in no significant changes in the concentration of the plasma lipids or liver cholesterol. However, liver triglycerides (TG), plasma Alanine aminotransferase and gene expression of tumor necrosis factor- α were decreased in hamsters fed high-fat diet containing Persian leek as compared to high-fat diet only. Persian leek might be considered as a herbal food that can reduce liver TG accumulation induced by high fat diets. https://www.ncbi.nlm.nih.gov/pubmed/27516982

Similar to garlic, onions have also shown that they’re safe, when cooked into other foods. We recommend owners only feed cooked onion, and when included in other food (like purees), as opposed to on its own.

“Onion has been shown to favorably modify the lipoprotein profile. However, research on its underlying mechanism is lacking. The present study investigated the interaction of dietary onion powder with the protein expression of key receptors and enzymes involved in cholesterol metabolism. Thirty-six male hamsters were randomly divided into three groups and fed a high-cholesterol control diet or the two experimental diets supplemented with 1% onion powder (OP-1) or 5% onion powder (OP-5), for a period of 8 weeks. It was found that onion dose-dependently decreased plasma total cholesterol (TC) level. The change in plasma lipoprotein profile was accompanied by a greater excretion of both fecal neutral and acidic sterols. Western blot analysis revealed that onion up-regulated sterol regulatory element binding protein 2 (SREBP-2), liver X receptor alpha (LXRα) and cholesterol-7α-hydroxylase (CYP7A1) with no effect on 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) and LDL receptor (LDL-R). It was concluded that the hypocholesterolemic activity of onion powder was mediated by enhancement of fecal sterol excretion and up-regulation of LXRα and CYP7A1.” http://pubs.rsc.org/en/Content/ArticleLanding/2010/FO/c0fo00036a#!divAbstract

“The addition of garlic or onion facilitated lowering plasma lipid and enhanced the antioxidant function; suggesting that garlic had more effectiveness on lowering plasma lipids and inhibiting the accumulation of liver lipids, and suppress- ing antioxidative enzyme activities than onion.” https://www.atherosclerosis-journal.com/article/S0021-9150(97)84698-9/pdf

The concern with peanut butter is simply it being sticky and gettting stuck in pouches. The best type of peanut butter to use is all natural. A small amount is perfectly fine, and a great way to encourage a picky hamster to take their medicine!

Similarly to grapes, raisins are often deemed unsafe because of their toxicity to some dogs. Raisins are perfectly fine and safe, and just like fruits, have good sugars in them that are fine even for diabetic species.

Tomatoes are often thought to be unsafe because they are “too acidic”. Fresh, their pH is 4.3-4.9. For reference, apples fall in the 3.2-4.0 range… so apples are more acidic based of pH. Tomatoes are perfectly fine as a treat.

Cucumber and watermelon both get a bad reputation as more watery fruits. They are perfect foods for providing hydration especially on long journeys. As well, a hamster will simply moderate their water intake to make up for it. When worried, just remind yourself that we allow our animals free access to water… which is arguably much waterier than cucumber or watermelon!

Dangerous Foods

As rodents, there are very few foods which are a hard no. Essentially they can eat just about anything humans can, but with some exceptions.