Vitamin A is important for vision, immune function, skin health, bone growth and reproduction. It is obtained in our diet from animal sources (as the retinol form) and plant sources (predominantly as beta-carotene in orange-red fruits and vegetables). After absorption, beta-carotene must be converted into active vitamin A, by the beta-carotene oxygenase 1 (BCO1) enzyme.

• BCO1 – encodes the BCO1 enzyme. Four common changes in BCO1 affect the activity of the enzyme and influence the availability of active vitamin A. Individuals that are slow converters (decreased BCO1 activity) are at risk of vitamin A deficiency, and it is important for these people to consume more animal-sourced vitamin A (retinol form).

Vitamin B6 is needed for carbohydrate metabolism, cognitive development, immune function, skin health and hemoglobin formation. It is found in high quantities in chickpeas, fish, beef liver, starchy vegetables and non-citrus fruits.

• NBPF3 – encodes a protein of unknown function. A variation in NBPF3 increases the risk of vitamin B6 deficiency

Vitamin B12 is necessary for the normal functioning of the brain and nervous system, and is required for DNA synthesis and the metabolism of fatty acids and amino acids. Fish, meat, poultry, eggs and milk are rich sources of vitamin B12.

• FUT2 – encodes part of a complex involved in host-microbe interactions. A variation in FUT2 distinguishes between “secretors” and “non-secretors”. Individuals with the “non-secretor” variant are protected from infection with H. pylori and are less likely to suffer from vitamin B12 deficiency.

Vitamin C is involved in the production of several critical biological molecules (e.g. collagen and neurotransmitters), immune response, wound healing, absorption of non-heme iron, and as an antioxidant to remove toxic byproducts. Foods that are high in vitamin C include dark leafy vegetables, citrus fruits, broccoli, berries and tomatoes.

• SLC23A1 – encodes a transporter that is important for maintaining healthy vitamin C levels. A variation in SLC23A1 reduces the absorption and distribution of vitamin C and increase the risk of deficiency.

Vitamin D is required to modulate cell growth, aid in immune functions, decrease inflammation and maintain normal bone growth and remodelling. Ultraviolet B radiation (from sunlight) triggers the synthesis of vitamin D in the body. Vitamin D can also be obtained from some foods, including fatty fish, fish liver oils and fortified foods (e.g. infant formula, milk and cereals).

• CYP2R1 – encodes an enzyme responsible for part of the conversion process of vitamin D into physiologically active calcitriol. Variants of CYP2R1 are associated with reduced enzyme activity and reduced levels of active vitamin D.
• GC – encodes a binding protein that is required to transport active vitamin D around the body and into the cells. Variations of GC reduce the efficiency of vitamin D transport and cellular uptake.

Vitamin E promotes the immune system, healthy eyes and skin, as well as a number of other metabolic processes. High levels of vitamin E are found in nuts, seeds and vegetable oils.

• APOA5 – encodes an apolipoprotein that helps control plasma triglyceride levels, high-density lipoprotein (HDL) maturation, cholesterol metabolism, and the transport of vitamin E into the cells. A genetic variant of APOA5 has been shown to influence vitamin E levels.

Folate is essential for proper growth and development, and is important for the conversion of the toxic homocysteine amino acid to methionine. Dark green vegetables and dried legumes are good sources of folate.

• MTHFD1 – encodes an important enzyme in the metabolism of folate, and variants in MTHFD1 have been linked to folate-related disorders.
• MTHFR – encodes an enzyme required for the activation of folate. Changes in MTHFR lead to lower levels of active folate circulating in the body.

Iron is required to make hemoglobin – an essential protein that transports oxygen around the body. Iron is obtained from both meat and plant sources and is transported by transferrin to other tissues around the body.

• TMPRSS6 – encodes part of the signalling pathway that controls iron absorption from the diet and iron release from stores within the body. Variants in TMPRSS6 disrupt this pathway and can increase the risk of iron deficiency.
• TF – encodes transferrin, the transporter of iron around the body. One particular variant of TF is associated with increased transferrin but less efficient binding to iron, so less iron is transported around the body, increasing the risk of iron deficiency.

Omega-3 fatty acids are important for normal, healthy metabolism. They are found in pant and fatty fish oil.

• NOS3 – encodes an enzyme required for the production of nitric oxide, a signalling molecule that plays a protective role in the cardiovascular system. A variant in NOS3 influences triglyceride levels and how effectively individuals respond to omega-3 supplementation.