Chances are you’ve already heard about vitamins being either fat or water soluble, but what does it mean and why do we need to know which is which?
Both fat- and water-soluble vitamins are absorbed into the body through the digestive tract, but it happens in very different ways. Water-soluble vitamins, including vitamin C and all of the B vitamins, slip easily through the intestinal wall during digestion and into the bloodstream, where they circulate freely through the body.
Fat-soluble vitamins, which include vitamins A, D, E and K, are absorbed with fatty foods that are broken down in the intestine, then packaged into tiny chylomicrons and transported in the lymphatic fluid before making their way to the bloodstream.
Because lipids play an important role in the absorption of fat-soluble vitamins, those on extreme low-fat diets can run the risk of deficiency. The Australian Dietary Guidelines recommend that most adults get 20-35% of their daily energy from fat, with saturated and trans fat contributing to no more than 10% of that energy.
Zinc is required by every cell and organ in the body. Find out more about why you need zinc.
Our bodies are very effective at storing fat-soluble vitamins, which are kept in the liver, fat cells and skeletal muscles until they’re needed. But that means they can build to potentially toxic levels. Carotenemia is a common condition that comes from eating excessive amounts of orange veggies like sweet potatoes and carrots. It often results in a yellow tint to the skin and has been linked to an increased risk of lung cancer in smokers.
By contrast, most water-soluble vitamins aren’t stored by the body (an exception is vitamin B12). Anything that’s not used is flushed out in your urine, so it’s important to get your RDI. But that doesn’t mean you can’t overdose on them. Too much vitamin C can cause diarrhoea, while excessive amounts of vitamin B6 can cause skin problems and nausea – and after a prolonged period, it may even cause nerve damage.
Thankfully, it’s unlikely that most of us will ever overdose on vitamins from food alone. However, take care when using supplements. Always stick to the recommended dosage and when in doubt, seek medical advice.
Talk to a Fernwood Food Coach about creating a tailored food plan to make sure you're getting all the vitamins and nutrients you need.
Cooking and processing
Water-soluble vitamins tend to be more vulnerable to heat and cooking, especially vitamin C. They can also leech out of vegetables into water, so steaming and microwaving is recommended over boiling for optimal nutrition content. Light, heat, oxygen exposure, juice pasteurisation, dehydration and canning can also deplete vitamin C levels. Even storage can take its toll, so keep veggies in your fridge’s crisper and try to eat them as fresh as possible.
The takeaway message? Eating a healthy, varied diet from all of the food groups every day is the best way to ensure you’re getting your vitamin needs – regardless of whether they’re fat or water soluble. Fresh food is best, but if you do need to take supplements, it’s always important to follow the correct advice from a professional.
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