We know that dietary fat can help us absorb vitamins, but is this the case for all vitamins and does the kind of fat matter?
Firstly, it depends on the vitamin. There are fat-soluble vitamins (A, D, E, K) and water-soluble ones (C and the Bs).
Recent research has also found that eating fresh vegetables with a little fat, such as oil-based salad dressings or cheese, helps the body absorb valuable nutrients found in vegetables, such as lycopene and and beta-carotene, which have been found to have antioxidant effects and may also protect against cancer.
Now, a study published in September has confirmed the importance of fat for helping the body to absorb vitamin D.
The study, by Tufts University researchers, took 50 healthy adults and assigned them a daily dose of vitamin D3 either a fat-free breakfast consisting of egg whites, fruit, toast and cranberry juice or a breakfast including either a monounsaturated (olive oil) and polyunsaturated (corn oil) fatty acids (MUFA:PUFA), to see if one type of fat has a different effect.
The participants were also provided with lunch and dinner containing a similar ratio of fat/carbohydrate and protein as their breakfast while the researchers took blood samples throughout the day.
The groups who had fat with their breakfast had a 32 per cent higher absorption rate of the vitamin D than the fat-free participants.
"The presence of fat in a meal with which a vitamin D-3 supplement is taken significantly enhances absorption of the supplement, but the MUFA:PUFA of the fat in that meal does not influence its absorption," the authors concluded.
Interestingly however, and separate to this study, while vitamin D3 is necessary for calcium absorption, fat is not and does not help the absorption rate.
Calcium is not fat-soluble, so it is not aided by the bile stimulated in the small intestine, when we eat fat, which helps to break down the fat and fat-soluble vitamins. Previous studies have shown that calcium is absorbed better with a meal of some description though.
As for how much fat to have with your meal to optimise absorption of fat-soluble nutrients, there is no magic number.
And generally speaking, calcium and vitamin D aside, scientists suggest trying not to get your nutrients for supplements in the first place.
"If you have a varied, nutritious diet, none of this should be a concern, unless you have a medical condition that affects nutrient absorption," advises Berkeley University.
"As for supplements, we generally don't recommend them (with the exception of calcium and vitamin D for many people). Supplements are usually overkill anyway, supplying 100 per cent or more of the RDA of nutrients, so it hardly matters if absorption is reduced."
