A Closer Look at Trace Elements

Only required in minute quantities, trace elements are relatively easy to get sufficient amounts and to meet your requirements from food alone.

Chromium

The trace element chromium's primary function is to potentiate the action of the hormone insulin in helping to regulate blood sugar levels. It is also involved in the metabolism of lipoproteins, maintaining nucleic acid structure and in gene expression.

Chromium is lost in urine, sweat, bile and hair, excessive physical exercise or tissue injury may also deplete tissue chromium levels. Adults require 23µg per day. Chromium deficiency is characterized by insulin resistance, raised blood sugar levels and blood cholesterol abnormalities. However, deficiency is rare other than in severe illness, malnutrition or long term parenteral nutrition.

When complexed with organic compounds, chromium is more efficiently absorbed than as an inorganic salt. Milling grains and processing foods considerably lowers chromium content. Foods cooked with acid-based sauces in stainless steel pans may obtain additional chromium from some types of cookware.

Chromium picolinate is a popular supplement marketed to help fat loss, however research does not support claims that it helps weight loss, build muscles or decrease body fat. However, chromium supplementation has been found to improve glucose tolerance in elderly adults who have low blood chromium levels as tissue chromium depletion occurs with age.

Dietary sources of chromium are listed below, but many foods have not been analyzed for chromium, so the list below does not include all possible sources.

Brewer's yeast (source of organic chromium complexes)
Whole grains
Wheat germ
Potatoes
Beef
Liver
Eggs
Chicken
Turkey
Seafood
Oysters
Green peppers
Apples
Bananas
Spinach
Broccoli
Cheese
Black pepper
Butter

Cobalt

Cobalt is a trace mineral but is only essential for humans as part of the structure of vitamin B12 and requirements of both micronutrients are closely linked. The amount of cobalt we consume is dependant on vitamin B12 intake as well as the soil and conditions where crops are grown and animals are reared.

Cobalt is widespread in our diet. Good food sources of cobalt include:

Fish
Red meat
Liver
Oysters
Milk
Nuts
Green leafy vegetables
Wholegrain cereals
Oats

Copper

The trace element copper is a component of many enzyme systems involved with a number of processes including synthesis of peptides, formation of red blood cells, bone building and as antioxidants. Deficiency of copper in children includes low white blood cells, increased susceptibility to infections and fragile bones. In adults deficiency is mainly defects in heart function.

We absorb between 35 and 70% of dietary copper, though the elderly absorb less. Adults should aim for 1.2mg of copper per day.

Good food sources include:

Seafood, eg oysters, squid, lobster, mussels, crab
Organ meats, i.e. liver, kidney, heart
Nuts especially cashews, macadamia, pecans, almonds and pistachios
Nut butters
Peanuts
Soya beans
Lentils
Whole grains
Fortified breakfast cereals
Dark leafy green vegetables
Mushrooms
Tomatoes
Potatoes
Sweet potatoes
Bananas
Grapes
Avocados
Dried fruits, eg prunes
Chocolate and cocoa
Black pepper
Yeast

Fluoride

Organic fluorine is a trace element required in very small amounts and is found in a number of foods; it forms calcium fluorapatite in tooth and bone and is involved in the mineralisation of bone and the prevention of dental caries.

Ionic fluoride is added to drinking water at 1mg/kg (1 ppm) and has drastically improved dental health. It is also added to toothpastes to help improve dental health.

Although there is no figure for the amount of fluorine which is required in the diet as there is no clinical deficiency, the effects on improved dental health demonstrate that some is needed. However, it's important that not too much fluoride is ingested, especially in children, as this can cause tooth mottling with crumbling enamel.

Main sources of fluorine come from fluoridated tap water, fluoride-fortified toothpastes and from the following food sources:

Tea & green tea
Kelp / seaweed
Mussels and other shellfish
Wine
Carbonated soft drinks

Iodine

The amount of iodine which adults require each day is around 140µg, and in the West most intakes are in excess of this and deficiency is rare. Iodine's principle role in the body is as part of the hormones thyroxine (T4) and triiodothyronine (T3) which are involved in the maintenance of metabolic rate and deficiency could lead to metabolic disturbances with weight gain and tiredness.

Iodine is abundant in our diet, and the major sources are dairy products. The following foods are particularly significant sources of iodine in our diets:

Seaweed / kelp (50g) - 415µg
Cod (100g) - 120µg
Pot of yoghurt (150g) - 88µg
Glass of skimmed milk (190ml) - 59µg
Beef liver (85g) - 36µg
Prawns (85g) - 35µg
Potatoes (110g) - 34µg
Turkey breast (85g) - 34µg
Tuna (85g) - 29µg
Egg (medium, whole) - 24µg
Bread (average, 1 slice – 25g) - 23µg
Strawberries (1 cup) - 13µg
Oats (70g) - 16µg
Mozzarella cheese (25g) - 10µg

Manganese

The trace element manganese is a component of a number of enzymes some of which act as antioxidants. It's not clear how much is absorbed or how it is regulated, but intakes seem to be related to iron intake. Deficiency hasn't been observed, but there would be possible reduced antioxidant function with low dietary manganese. Adults should aim for 1.4mg per day.

Although it is abundant in our diet, particularly rich dietary sources of manganese include:

Nuts
Seeds
Wheat germ
Whole grains
Seaweed
Spinach and other green leafy vegetables
Broccoli
Peas
Beans
Lentils
Pineapple
Oranges
Blueberries
Raisins
Egg yolk
Tea

Many herbs also contain manganese, such as alfalfa, burdock root, chamomile, dandelion, fenugreek, ginseng, hops, horsetail, lemongrass, parsley, peppermint.

Molybdenum

Molybdenum is a trace element mineral required in minute amounts in our diet. It is essential for enzymes involved in metabolism of nucleic acids and sulphites and is abundant in our diets. However, there is one tiny region in northern China called Linxian which has very low quality soil that is lacking in a number of essential minerals, including molybdenum. This poor quality soil is reflected in the diets of the inhabitants and mineral deficiencies are prevalent. Symptoms of molybdenum deficiency are cancer related, and it has been linked to stomach and oesophageal cancer. Other symptoms can be racing heart rate, irritability, impotence and poor vision.

Although there is no recommended intake of molybdenum, because inadequate levels can lead to a deficiency, it is suggested that adults get 75 - 250 µg/day.

There are many foods that contain high amounts of molybdenum. Plant sources are high, although the amount will depend on the soil that the plant grows from.

Legumes - peas, beans, lentils
Liver
Kidney
Spinach
Cabbage
Wholegrain bread
Brown (unpolished) rice
Nuts
Milk
Hard tap water

Nickel

Nickel is an essential trace nutrient, albeit in a minor and undefined way. Deficiency results in reduced growth and slower formation of red blood cells. Nickel also influences the amount of iron we absorb from food.

Nickel is believed to be involved in the activation of some enzymes and hormones. It may also be involved in the structure of cells. Human requirements are met at just 5µg per day, and intakes in the West are well above this, thus natural deficiency is unheard of.

Up to 10% of people in the UK may have an allergy to nickel that causes dermatitis. This is usually caused by jewellery or coins that contain nickel, but nickel in food or supplements can also cause a rash if you have this allergy.

Nickel is abundant in our diets, although absorption from food is only about 1%, but as it's so plentiful, this is still more than adequate. Up to 27% is absorbed from water. Absorption is influenced by the amount of food, the acidity of the gut and the presence of phytate or competing minerals such as iron, magnesium, zinc and calcium.

Animal foods are poorer sources of nickel. Particularly important sources of nickel include:

Oats
Beans
Peas
Nuts
Chocolate
Water

Selenium

Selenium is a trace element mineral which is acts with vitamin E as a non-specific antioxidant involved in keeping free radical damage at bay, specifically as part of an enzyme called glutathione peroxidase. With an adequate intake of selenium, vitamin E requirements are more easily met.

Adult males should aim for 75µg of selenium per day and females 60 µg per day. Between 55-65% dietary selenium is absorbed. Deficiency in the West is rare, but soils across the World vary hugely in their selenium concentration, therefore selenium intakes can be low in some regions, e.g. North East China, where a type of heart disease, called Keshan disease, is prevalent due to selenium deficiency.

The following foods are significant sources of selenium in the Western diet, though the actual selenium content does vary depending on the soil concentration:

Brazil nuts
Brewer's yeast
Broccoli
Brown (unpolished) rice
Cabbage
Celery
Chicken
Corn
Cucumbers
Dairy products
Fish
Garlic
Kelp
Liver
Mushrooms
Onions
Liver
Kidney
Oysters
Nuts
Salmon
Seafood
Sesame seeds
Tuna
Vegetables
Wheat bran
Wheat germ
Wholewheat products

Silicon

Silicon is an essential trace mineral, but only required in minute amounts. Requirements are so low, so there is no recommended amount and it is widely distributed in our diet.

Silicon is essential for the proper functioning of connective tissue, nerve cells and the synthesis of thiamin. Deficiency of silicon may lead to increased cold sensitivity, soft brittle nails, wrinkles, thinning or loss of hair or poor bone development.

Whole grains are a rich source of absorbable silicon. Other main food sources of silicon are:

Apples
Oranges
Cherries
Raisins
Almonds
Peanuts
Raw cabbage
Onions
Carrots
Pumpkin
Celery
Cucumber
Fish
Honey
Corn
Brown rice
Seafood

Sulphur

Sulphur is present in a number of tissues, for example as chondroitin sulphate in cartilage. It is also involved in the detoxification of alcohol and other chemicals in the body. It is present in the two sulphur-containing amino aids cysteine and methionine which are abundant in our diet, meaning there is no specific requirement for sulphur. Protein rich foods are excellent sources of sulphur.

Particular good sources to note include:

Red meat
Organ meats
Poultry
Fish
Dairy products
Eggs
Beans
Lentils
Soya beans
Brussels sprouts
Cabbage
Cauliflower
Brussel sprouts
Garlic
Horseradish
Onions
Turnips
Watercress
Wheat germ

Vanadium

Vanadium is widely found in nature and is a trace mineral needed by the body in small amounts. It is active in many chemical reactions which occur in the body. Vanadium plays a role in cellular metabolism, the formation of bones and teeth, reproduction and growth. It also inhibits cholesterol synthesis. Vanadium is involved in maintaining blood glucose levels with the hormone insulin and lipid metabolism; it has significant insulin-mimetic properties in pharmacological doses.

Vanadyl sulphate is a popular nutritional supplement reported to help blood glucose control, although evidence is weak. Vanadium from the diet or from supplements is poorly absorbed; as little as 5%.

Particularly good food sources:

Vegetables
Seafood
Black pepper
Mushrooms
Parsley
Soya
Corn
Olives
Olive oil
Gelatin