There has been an increasing number of voluntary recalls from pet food companies due to excess Vitamin D. Increased awareness and accountability are responsible for the recall frequency more than an actual increase in incidents. The recalls have applied to virtually all animals at one time or another, including dogs, cats, livestock, guinea pigs, birds, primates and fish. Unfortunately, pet parents aren’t usually provided with details about the dangers and symptoms of excess Vitamin D.
There is also an increasing number of pet parents opting to make their own pet food. Vitamin D deficiency is a concern in homemade pet diets and supplementation is common. It’s important that pet parents be aware of the dangers of over-supplementation so they will monitor intake accordingly.
The problem with Vitamin D
Vitamin D is a fat soluble vitamin, which means excesses are not excreted and hypervitaminosis will occur if too much is ingested.
The threat of Vitamin D overdose is minimal through a natural, balanced diet and adequate light exposure. The highest risk comes from synthetic Vitamin D supplementation, either through pet food or from vitamin supplements administered by pet parents. Natural fish oil and liver supplements may also pose a danger in very high doses. The safe range may be up to 10 times the daily recommendation and short term excesses may not have any negative impact unless extreme. The most common concern over elevated levels of Vitamin D in pet food is due to the long term effects (more than a couple of months).
The level of Vitamin D toxicity is subject to the type of Vitamin D. For example, Vitamin D3 (used in rodenticides) has been proven to be more toxic than Vitamin D2 in many species. Toxicity is also increased when Vitamin E is combined with elevated levels of dietary phosphorus and calcium, and reduced with lower levels of phosphorus and calcium.
There is an increased danger to certain pet species that are prone to Vitamin D toxicosis, such as Macaws and some other avian species. Pet fish and other aquatic pets with diets based largely on whole fish may be at a higher risk Vitamin D toxicosis from synthetic supplementation. This is especially true in manufactured fish food that typically over-fortifies to compensate for vitamin loss in the water column. Growing and senior animals are also more vulnerable.
When excess Vitamin D is consumed it results in ‘hypervitaminosis D’. It can have a variety of negative effects associated with high concentration of calcium in the blood from bone resorption and increased absorption of calcium in the intestines. The pathological effect is soft tissue calcification, cellular degeneration and inflammation. Deaths in cats and dogs caused by hypervitaminosis D is most commonly due to chronic renal failure.
Hypervitaminosis D specifically effects the:
- Bones & Joints
- Heart & Arteries
- Digestive system
- Muscular system
- Lymph Glands
- Parathyroid Glands
Symptoms of Vitamin D toxicosis and consequential conditions in pets may include loss of appetite, notable weight loss, increased water intake & urination, diarrhea (may be bloody), vomiting, bone & joint pain, lameness, irregular heartbeat, and depression. Blood tests will show low phosphate and high calcium in the blood. Symptoms in pet fish may include slow growth, dark coloration, lethargy, and loss of appetite.
Unless a veterinarian recommends synthetic supplements, natural sources of Vitamin D are the safest option. Sunlight, oily fish, egg yolk and seaweed are all natural sources of Vitamin D.
If you suspect Hypervitaminosis D, see your veterinarian immediately.
Kahn, Cynthia. The Merck Veterinary Manual. 2010.
Michael Stanford, BVSc, MRCVS. The Effect of UV-B Lighting Supplementation in African Grey Parrots. Avian 2004.
DSM Nutritional Products
Halver, J.E. Fish Nutrition. Second ed. Academic Press, San Diego, CA, USA. 1989.
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