Despite all the food we consume, we would think we are getting all the nutrients we need, but its not so. Below are the vitamins you're most likely short on, plus easy ways to boost your intake.
Vitamin B6
This important vitamin helps the
body produce serotonin and norepinephrine, two chemicals that
facilitate communication between the brain and nerve cells, which is
crucial for keeping body processes like the immune system and metabolism
humming along. Some studies show that a B6 deficiency can cause
problems that affect the nerves, skin, and circulation; other research
shows supplementing can improve memory loss, diabetes, asthma, ADHD and
acne.
How to tell if you're lacking:
Deficiency is more common in alcoholics and people with liver and
kidney issues or an overactive thyroid. You're also more likely to lack
B6 if you're a vegetarian, vegan, or lactose-intolerant, as this vitamin
is found in poultry, lean meat, seafood, milk, and yogurt.
How much you need: Adults ages 19 to 50 need 1.3 milligrams every day; older women need 1.5 milligrams and older men need 1.7 milligrams.
Get more:
legumes, carrots, spinach, peas, potatoes, milk, yogurt, cheese, eggs,
fish, liver, meat, and fortified flour and cereal grains
Vitamin D
Known as the "sunshine vitamin,"
D is produced when the skin is exposed to the sun. Considering the
amount of vitamin D we get from food sources is minimal—and the amount
of time we're spending outside, without sunscreen, is at an all-time
low—it's no surprise that the Centers for Disease Control and Prevention
(CDC) has reported that 32% of both children and adults in the U.S. are
deficient. Experts are concerned about this, as too little D has been
linked to everything from increased risk of cancer and heart disease to
severe asthma in children.
How to tell if you're lacking:
Signs of too little vitamin D may include bone pain, muscle weakness
and feeling down (one study found that those who were low on vitamin D
were 11 times more likely to be depressed than those with normal
levels). Another sign, says Brown: Getting sick more often than usual.
"Vitamin D is a key player in a healthy immune system," she says.
How much you need:
A blood test is the best way to check your vitamin D levels, and the
target range is somewhere around 45 to 50 ng/mL; the amount you'll need
to supplement depends on how close or not you are to that target. While
the official recommendations are 600 IU for those age 1 to 70 and 800 IU
for those older than 70, many experts believe that recommendation
should be somewhere in the 1,000 IU to 6,000 IU range, so it's important
to work with your doctor on finding the right dose for you.
Get more: fatty fish (salmon, tuna, mackerel), beef liver, cheese, egg yolks, and vitamin D-fortified milk and orange juice
Vitamin C
This vitamin does double-duty as
an antioxidant: It helps block cell mutations triggered by dangerous
free radical molecules; C also aids wound healing, cartilage repair, and
the maintenance of strong bones and teeth. Research suggests it's a
powerhouse in battling the common cold. Studies show that people who
take vitamin C supplements on a regular basis have milder symptoms and
shorter colds. 
How to tell if you're lacking:
First signs tend to be fatigue, muscle and joint pain, and easy
bruising; dry skin, swollen or discolored gums, and poor wound healing
can also clue you in to a lack of C. Chronic deficiency (that lasts
three months or more) can lead to an illness called scurvy, which can
cause lethargy and in advanced cases, jaundice and fever.
How much you need: Women need 75 milligrams a day; men need 90 milligrams.
Get more:
citrus fruits, cantaloupe, kiwi, mango, papaya, pineapple, berries,
broccoli, Brussels sprouts, spinach, leafy greens, sweet potatoes, and
winter squash.
Vitamin B12
Like B6 and other B vitamins,
B12 plays an important role in keeping the metabolism humming. It's also
crucial in the formation of red blood cells and DNA, says Brown, as
well as supporting the health of the central nervous system.
How to tell if you're lacking:
Studies have shown that not enough vitamin B12 can lead to mental
disorders such as depression and anxiety, muscle weakness or stiffness,
incontinence, low blood pressure, and vision problems. Also, if you're a
vegetarian or vegan (or have simply scaled back on the amount of animal
products you eat for health reasons), there's a greater chance you'll
be deficient thanks to the fact that, like vitamin B6, most food-based
sources of B12 come from animal products. 
How much you need:
Those 14 years old and up need 2.4 micrograms a day; pregnant women
need 2.6 micrograms daily and breastfeeding women need 2.8 micrograms a
day.
Get more:
organ meats, shellfish, meat, poultry, eggs, milk, and other dairy
foods, some fortified breakfast cereals and nutritional yeasts
As we have seen, these vitamins are very essential to the function of the body. But our body lack these vitamins on regular basis, therefore we should replenish ASAP before they are completely used.